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128-475: GPO makes and sells four categories of products: medicines; antiretrovirals ; chemicals/test kits/natural products; and preventive medicines. Besides Thailand, it markets its products in Nigeria , Ghana , Bhutan , Somalia , Myanmar , Sri Lanka , Malaysia , Cambodia , and Vietnam . The GPO gives Thailand significant leverage in its price negotiations with foreign drug suppliers. As of 2018, GPO's chairman

256-462: A PI / NNRTI / INSTI ("base"). Initial regimens use "first-line" drugs with a high efficacy and low side-effect profile. The US DHHS preferred initial regimens for adults and adolescents in the United States, as of April 2015, are: Both efavirenz and nevirapine showed similar benefits when combined with NRTI respectively. In the case of the protease inhibitor based regimens, ritonavir

384-493: A long terminal repeat (LTR). Regions in the LTR act as switches to control production of new viruses and can be triggered by proteins from either HIV or the host cell. The Psi element is involved in viral genome packaging and recognized by gag and rev proteins. The SLIP element ( TTTTTT ) is involved in the frameshift in the gag - pol reading frame required to make functional pol . The term viral tropism refers to

512-567: A 69% increase in the risk of death. In 2015 the START and TEMPRANO studies both showed that patients lived longer if they started antiretrovirals at the time of their diagnosis, rather than waiting for their CD4 counts to drop to a specified level. Other arguments for starting therapy earlier are that people who start therapy later have been shown to have less recovery of their immune systems, and higher CD4 counts are associated with less cancer. The European Medicines Agency (EMA) has recommended

640-535: A cell by a virion can be called "cell-free spread" to distinguish it from a more recently recognized process called "cell-to-cell spread". In cell-free spread (see figure), virus particles bud from an infected T cell, enter the blood or extracellular fluid and then infect another T cell following a chance encounter. HIV can also disseminate by direct transmission from one cell to another by a process of cell-to-cell spread, for which two pathways have been described. Firstly, an infected T cell can transmit virus directly to

768-481: A cell surface. The unusual processing and high density means that almost all broadly neutralising antibodies that have so far been identified (from a subset of patients that have been infected for many months to years) bind to, or are adapted to cope with, these envelope glycans. The molecular structure of the viral spike has now been determined by X-ray crystallography and cryogenic electron microscopy . These advances in structural biology were made possible due to

896-414: A few tested specimens might provide inconclusive results because of a low quantity specimen. In these situations, a second specimen is collected and tested for HIV infection. Modern HIV testing is extremely accurate, when the window period is taken into consideration. A single screening test is correct more than 99% of the time. The chance of a false-positive result in a standard two-step testing protocol

1024-525: A high rate of baseline resistance, resistance testing is recommended before starting treatment; or, if the initiation of treatment is urgent, then a "best guess" treatment regimen should be started, which is then modified on the basis of resistance testing. In the UK, there is 11.8% medium to high-level resistance at baseline to the combination of efavirenz + zidovudine + lamivudine, and 6.4% medium to high level resistance to stavudine + lamivudine + nevirapine . In

1152-451: A human host cell when the newly formed virus particle buds from the cell. The viral envelope contains proteins from the host cell and relatively few copies of the HIV envelope protein, which consists of a cap made of three molecules known as glycoprotein (gp) 120 , and a stem consisting of three gp41 molecules that anchor the structure into the viral envelope. The envelope protein, encoded by

1280-574: A key step in the progression to AIDS. A number of studies with subtype B-infected individuals have determined that between 40 and 50 percent of AIDS patients can harbour viruses of the SI and, it is presumed, the X4 phenotypes. HIV-2 is much less pathogenic than HIV-1 and is restricted in its worldwide distribution to West Africa . The adoption of "accessory genes" by HIV-2 and its more promiscuous pattern of co-receptor usage (including CD4-independence) may assist

1408-534: A lasting effect. As a result, the standard of care is to use combinations of antiretroviral drugs. Combinations usually consist of three drugs from at least two different classes. This three drug combination is commonly known as a triple cocktail. Combinations of antiretrovirals are subject to positive and negative synergies , which limits the number of useful combinations. Because of HIV's tendency to mutate, when patients who have started an antiretrovial regimen fail to take it regularly, resistance can develop. On

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1536-613: A more stable conformation following the NC binding, in which both the DIS and the U5:AUG regions of the gRNA participate in extensive base pairing. RNA can also be processed to produce mature messenger RNAs (mRNAs). In most cases, this processing involves RNA splicing to produce mRNAs that are shorter than the full-length genome. Which part of the RNA is removed during RNA splicing determines which of

1664-477: A mutation in the CCR5 delta gene which results in a nonfunctional CCR5 co-receptor and in turn, a means of resistance or slow progression of the disease. However, as mentioned previously, this can be overcome if an HIV variant that targets CXCR4 becomes dominant. To prevent fusion of the virus with the host membrane, enfuvirtide can be used. Enfuvirtide is a peptide drug that must be injected and acts by interacting with

1792-447: A number of mechanisms, including pyroptosis of abortively infected T cells, apoptosis of uninfected bystander cells, direct viral killing of infected cells, and killing of infected CD4 T cells by CD8 cytotoxic lymphocytes that recognize infected cells. When CD4 T cell numbers decline below a critical level, cell-mediated immunity is lost, and the body becomes progressively more susceptible to opportunistic infections, leading to

1920-500: A psychoactive plant similar to opiates that is native to Thailand. A researcher at Chulalongkorn University has pointed out that Thailand has 200,000 Alzheimer's patients and 150,000 Parkinson's patients who could benefit from medical marijuana. Antiretroviral The management of HIV/AIDS normally includes the use of multiple antiretroviral drugs as a strategy to control HIV infection . There are several classes of antiretroviral agents that act on different stages of

2048-412: A range of views on this subject and the decision of whether to commence treatment ultimately rests with the patient and his or her doctor. The US DHHS guidelines (published April 8, 2015) state: The newest WHO guidelines (dated September 30, 2015) now agree and state: Baseline resistance is the presence of resistance mutations in patients who have never been treated before for HIV. In countries with

2176-464: A strain of SIV found in sooty mangabees. Since HIV-1 is derived from SIVcpz, and HIV-2 from SIVsm, the genetic sequence of HIV-2 is only partially homologous to HIV-1 and more closely resembles that of SIVsm. Many HIV-positive people are unaware that they are infected with the virus. For example, in 2001 less than 1% of the sexually active urban population in Africa had been tested, and this proportion

2304-558: A target T cell via a virological synapse . Secondly, an antigen-presenting cell (APC), such as a macrophage or dendritic cell, can transmit HIV to T cells by a process that either involves productive infection (in the case of macrophages) or capture and transfer of virions in trans (in the case of dendritic cells). Whichever pathway is used, infection by cell-to-cell transfer is reported to be much more efficient than cell-free virus spread. A number of factors contribute to this increased efficiency, including polarised virus budding towards

2432-818: Is Dr Sopon Mekthon, who took over from Dr Nopporn Cheanklin. GPO's mission statement contains four objectives. One of them is to "To maintain price level of pharmaceutical products and medical supplies necessary for the Thai society to ensure people's accessibility." As an example, GPO will produce the antiretroviral drug efavirenz after receiving WHO approval. GPO's product costs 180 baht per bottle of thirty 600 mg tablets. The imported version retails for more than 1,000 baht per bottle. GPO will devote 2.5 percent of its manufacturing capacity to make 42 million efavirenz pills in 2018, allowing it to serve export markets as well as domestic. The Philippines alone will order about 300,000 bottles of efavirenz for 51 million baht. The GPO

2560-492: Is also important, with a planned Caesarian section having a lower risk than vaginal delivery or emergency Caesarian section. HIV can also be detected in breast milk of infected mothers and transmitted through breast feeding. The WHO balances the low risk of transmission through breast feeding from women who are on ART with the benefits of breastfeeding against diarrhea, pneumonia and malnutrition. It also strongly recommends that breastfeeding infants receive prophylactic ART. In

2688-460: Is an adaptation for repair of genome damage, and that recombinational variation is a byproduct that may provide a separate benefit. The final step of the viral cycle, assembly of new HIV-1 virions, begins at the plasma membrane of the host cell. The Env polyprotein (gp160) goes through the endoplasmic reticulum and is transported to the Golgi apparatus where it is cleaved by furin resulting in

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2816-516: Is bound with the CD4 protein, the envelope complex undergoes a structural change, exposing the chemokine receptor binding domains of gp120 and allowing them to interact with the target chemokine receptor. This allows for a more stable two-pronged attachment, which allows the N-terminal fusion peptide gp41 to penetrate the cell membrane. Repeat sequences in gp41, HR1, and HR2 then interact, causing

2944-402: Is complicated by the fact that many children who are born to mothers with HIV are given a single dose of nevirapine (an NNRTI) at the time of birth to prevent transmission. If this fails it can lead to NNRTI resistance. Also, a large study in Africa and India found that a PI based regimen was superior to an NNRTI based regimen in children less than 3 years who had never been exposed to NNRTIs in

3072-424: Is even lower in rural populations. Furthermore, in 2001 only 0.5% of pregnant women attending urban health facilities were counselled, tested or received their test results. Again, this proportion is even lower in rural health facilities. Since donors may therefore be unaware of their infection, donor blood and blood products used in medicine and medical research are routinely screened for HIV. HIV-1 testing

3200-464: Is high as the glycans shield the underlying viral protein from neutralisation by antibodies. This is one of the most densely glycosylated molecules known and the density is sufficiently high to prevent the normal maturation process of glycans during biogenesis in the endoplasmic and Golgi apparatus. The majority of the glycans are therefore stalled as immature 'high-mannose' glycans not normally present on human glycoproteins that are secreted or present on

3328-437: Is indeed within reach." In the same paper, he noted that an estimated 700,000 lives were saved in 2010 alone by antiretroviral therapy. As another commentary noted, "Rather than dealing with acute and potentially life-threatening complications, clinicians are now confronted with managing a chronic disease that in the absence of a cure will persist for many decades." The United States Department of Health and Human Services and

3456-399: Is initially done using an enzyme-linked immunosorbent assay (ELISA) to detect antibodies to HIV-1. Specimens with a non-reactive result from the initial ELISA are considered HIV-negative, unless new exposure to an infected partner or partner of unknown HIV status has occurred. Specimens with a reactive ELISA result are retested in duplicate. If the result of either duplicate test is reactive,

3584-454: Is intended for maintenance treatment of adults who have undetectable HIV levels in the blood (viral load less than 50 copies/ml) with their current ARV treatment, and when the virus has not developed resistance to certain class of anti-HIV medicines called non-nucleoside reverse transcriptase inhibitors (NNRTIs) and integrase strand transfer inhibitors (INIs). A separate argument for starting antiretroviral therapy that has gained more prominence

3712-590: Is intrinsically resistant to NNRTIs. Integrase inhibitors (also known as integrase nuclear strand transfer inhibitors or INSTIs) inhibit the viral enzyme integrase , which is responsible for integration of viral DNA into the DNA of the infected cell. There are several integrase inhibitors under clinical trial, and raltegravir became the first to receive FDA approval in October 2007. Raltegravir has two metal binding groups that compete for substrate with two Mg ions at

3840-555: Is its effect on HIV transmission. ART reduces the amount of virus in the blood and genital secretions. This has been shown to lead to dramatically reduced transmission of HIV when one partner with a suppressed viral load (<50 copies/ml) has sex with a partner who is HIV negative. In clinical trial HPTN 052 , 1763 serodiscordant heterosexual couples in nine countries were planned to be followed for at least 10 years, with both groups receiving education on preventing HIV transmission and condoms, but only one group getting ART. The study

3968-447: Is largely confined to West Africa . HIV is similar in structure to other retroviruses. It is roughly spherical with a diameter of about 120  nm , around 100,000 times smaller in volume than a red blood cell . It is composed of two copies of positive- sense single-stranded RNA that codes for the virus' nine genes enclosed by a conical capsid composed of 2,000 copies of the viral protein p24 . The single-stranded RNA

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4096-612: Is more likely, leading to immunodeficiency. Three groups of HIV-1 have been identified on the basis of differences in the envelope ( env ) region: M, N, and O. Group M is the most prevalent and is subdivided into eight subtypes (or clades ), based on the whole genome, which are geographically distinct. The most prevalent are subtypes B (found mainly in North America and Europe), A and D (found mainly in Africa), and C (found mainly in Africa and Asia); these subtypes form branches in

4224-429: Is no meaningful difference between abacavir-containing regimens and other NRTI-containing regimens. The evidence is of low to moderate quality and therefore it is likely that future research may change these findings. The goals of treatment for pregnant women include the same benefits to the mother as in other infected adults as well as prevention of transmission to her child. The risk of transmission from mother to child

4352-512: Is permitted to produce efavirenz and two other patented medications by having sought compulsory licensing (CL) under the provisions of the WTO agreement on intellectual property, the Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPs). Under a compulsory license, an individual or company seeking to use another's intellectual property can do so—for good reasons—without seeking

4480-561: Is present as both free virus particles and virus within infected immune cells . Research has shown (for both same-sex and opposite-sex couples) that HIV is not contagious during sexual intercourse without a condom if the HIV-positive partner has a consistently undetectable viral load . HIV infects vital cells in the human immune system, such as helper T cells (specifically CD4 T cells), macrophages , and dendritic cells . HIV infection leads to low levels of CD4 T cells through

4608-399: Is proportional to the plasma viral load of the mother. Untreated mothers with a viral load >100,000 copies/ml have a transmission risk of over 50%. The risk when viral loads are < 1000 copies/ml are less than 1%. ART for mothers both before and during delivery and to mothers and infants after delivery are recommended to substantially reduce the risk of transmission. The mode of delivery

4736-412: Is tightly bound to nucleocapsid proteins, p7, and enzymes needed for the development of the virion such as reverse transcriptase , proteases , ribonuclease and integrase . A matrix composed of the viral protein p17 surrounds the capsid ensuring the integrity of the virion particle. This is, in turn, surrounded by the viral envelope , that is composed of the lipid bilayer taken from the membrane of

4864-534: Is unknown how often such mixed packaging occurs under natural conditions. Bonhoeffer et al. suggested that template switching by reverse transcriptase acts as a repair process to deal with breaks in the single-stranded RNA genome. In addition, Hu and Temin suggested that recombination is an adaptation for repair of damage in the RNA genomes. Strand switching (copy-choice recombination) by reverse transcriptase could generate an undamaged copy of genomic DNA from two damaged single-stranded RNA genome copies. This view of

4992-446: Is used at low doses to inhibit cytochrome p450 enzymes and "boost" the levels of other protease inhibitors, rather than for its direct antiviral effect. This boosting effect allows them to be taken less frequently throughout the day. Cobicistat is used with elvitegravir for a similar effect but does not have any direct antiviral effect itself. The WHO preferred initial regimen for adults and adolescents as of June 30, 2013, is: In

5120-638: The African green monkey (SIVagm) and sooty mangabey (SIVsmm) are thought to have a long evolutionary history with their hosts. These hosts have adapted to the presence of the virus, which is present at high levels in the host's blood, but evokes only a mild immune response, does not cause the development of simian AIDS, and does not undergo the extensive mutation and recombination typical of HIV infection in humans. In contrast, when these strains infect species that have not adapted to SIV ("heterologous" or similar hosts such as rhesus or cynomologus macaques ),

5248-544: The CCR5-Δ32 mutation are resistant to infection by the R5 virus, as the mutation leaves HIV unable to bind to this co-receptor, reducing its ability to infect target cells. Sexual intercourse is the major mode of HIV transmission. Both X4 and R5 HIV are present in the seminal fluid , which enables the virus to be transmitted from a male to his sexual partner . The virions can then infect numerous cellular targets and disseminate into

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5376-469: The HIV life-cycle. The use of multiple drugs that act on different viral targets is known as highly active antiretroviral therapy ( HAART ). HAART decreases the patient's total burden of HIV, maintains function of the immune system , and prevents opportunistic infections that often lead to death. HAART also prevents the transmission of HIV between serodiscordant same-sex and opposite-sex partners so long as

5504-490: The World Health Organization (WHO) recommend offering antiretroviral treatment to all patients with HIV . Because of the complexity of selecting and following a regimen, the potential for side effects, and the importance of taking medications regularly to prevent viral resistance , such organizations emphasize the importance of involving patients in therapy choices and recommend analyzing the risks and

5632-445: The adsorption of glycoproteins on its surface to receptors on the target cell followed by fusion of the viral envelope with the target cell membrane and the release of the HIV capsid into the cell. Entry to the cell begins through interaction of the trimeric envelope complex ( gp160 spike) on the HIV viral envelope and both CD4 and a chemokine co-receptor (generally either CCR5 or CXCR4 , but others are known to interact) on

5760-421: The gag polyproteins still need to be cleaved into the actual matrix, capsid and nucleocapsid proteins. This cleavage is mediated by the packaged viral protease and can be inhibited by antiretroviral drugs of the protease inhibitor class. The various structural components then assemble to produce a mature HIV virion. Only mature virions are then able to infect another cell. The classical process of infection of

5888-514: The microtubule -based transport to the nucleus, the viral single-strand RNA genome is transcribed into double-strand DNA, which is then integrated into a host chromosome. HIV can infect dendritic cells (DCs) by this CD4-CCR5 route, but another route using mannose-specific C-type lectin receptors such as DC-SIGN can also be used. DCs are one of the first cells encountered by the virus during sexual transmission. They are currently thought to play an important role by transmitting HIV to T cells when

6016-403: The phylogenetic tree representing the lineage of the M group of HIV-1. Co-infection with distinct subtypes gives rise to circulating recombinant forms (CRFs). In 2000, the last year in which an analysis of global subtype prevalence was made, 47.2% of infections worldwide were of subtype C, 26.7% were of subtype A/CRF02_AG, 12.3% were of subtype B, 5.3% were of subtype D, 3.2% were of CRF_AE, and

6144-438: The α -chemokine receptor, CXCR4 , for entry. Dual-tropic HIV-1 strains are thought to be transitional strains of HIV-1 and thus are able to use both CCR5 and CXCR4 as co-receptors for viral entry. The α -chemokine SDF-1 , a ligand for CXCR4, suppresses replication of T-tropic HIV-1 isolates. It does this by down-regulating the expression of CXCR4 on the surface of HIV target cells. M-tropic HIV-1 isolates that use only

6272-427: The β -chemokine receptor, CCR5 , for entry and are thus able to replicate in both macrophages and CD4 T cells. This CCR5 co-receptor is used by almost all primary HIV-1 isolates regardless of viral genetic subtype. Indeed, macrophages play a key role in several critical aspects of HIV infection. They appear to be the first cells infected by HIV and perhaps the source of HIV production when CD4 cells become depleted in

6400-536: The CCR5 receptor are termed R5; those that use only CXCR4 are termed X4, and those that use both, X4R5. However, the use of co-receptors alone does not explain viral tropism, as not all R5 viruses are able to use CCR5 on macrophages for a productive infection and HIV can also infect a subtype of myeloid dendritic cells , which probably constitute a reservoir that maintains infection when CD4 T cell numbers have declined to extremely low levels. Some people are resistant to certain strains of HIV. For example, people with

6528-405: The DIS (dimerization initiation signal) hairpin is exposed. The formation of the gRNA dimer is mediated by a 'kissing' interaction between the DIS hairpin loops of the gRNA monomers. At the same time, certain guanosine residues in the gRNA are made available for binding of the nucleocapsid (NC) protein leading to the subsequent virion assembly. The labile gRNA dimer has been also reported to achieve

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6656-419: The HIV env gene, allows the virus to attach to target cells and fuse the viral envelope with the target cell's membrane releasing the viral contents into the cell and initiating the infectious cycle. As the sole viral protein on the surface of the virus, the envelope protein is a major target for HIV vaccine efforts. Over half of the mass of the trimeric envelope spike is N-linked glycans . The density

6784-441: The HIV protein-coding sequences is translated. Mature HIV mRNAs are exported from the nucleus into the cytoplasm , where they are translated to produce HIV proteins, including Rev . As the newly produced Rev protein is produced it moves to the nucleus, where it binds to full-length, unspliced copies of virus RNAs and allows them to leave the nucleus. Some of these full-length RNAs function as mRNAs that are translated to produce

6912-570: The HIV virological synapse in vivo . The many dissemination mechanisms available to HIV contribute to the virus' ongoing replication in spite of anti-retroviral therapies. HIV differs from many viruses in that it has very high genetic variability . This diversity is a result of its fast replication cycle , with the generation of about 10 virions every day, coupled with a high mutation rate of approximately 3 x 10 per nucleotide base per cycle of replication and recombinogenic properties of reverse transcriptase. This complex scenario leads to

7040-538: The HIV-positive partner maintains an undetectable viral load. Treatment has been so successful that in many parts of the world, HIV has become a chronic condition in which progression to AIDS is increasingly rare. Anthony Fauci , former head of the United States National Institute of Allergy and Infectious Diseases , has written, "With collective and resolute action now and a steadfast commitment for years to come, an AIDS-free generation

7168-526: The LTR promoter acting by binding the TAR RNA element. The TAR may also be processed into microRNAs that regulate the apoptosis genes ERCC1 and IER3 . The rev protein (p19) is involved in shuttling RNAs from the nucleus and the cytoplasm by binding to the RRE RNA element. The vif protein (p23) prevents the action of APOBEC3G (a cellular protein that deaminates cytidine to uridine in

7296-468: The N-terminal heptad repeat of gp41 of HIV to form an inactive hetero six-helix bundle, therefore preventing infection of host cells. Nucleoside reverse-transcriptase inhibitors (NRTI) and nucleotide reverse-transcriptase inhibitors (NtRTI) are nucleoside and nucleotide analogues which inhibit reverse transcription. HIV is an RNA virus, so it can not be integrated into the DNA in the nucleus of

7424-569: The National Institute of Allergy and Infectious Diseases began recruiting patients for a trial examining the effects of a three drug combination of the protease inhibitor indinavir and two nucleoside analogs, illustrating the substantial benefit of combining two NRTIs with a new class of antiretrovirals, protease inhibitors , namely indinavir . Later that year David Ho became an advocate of this "hit hard, hit early" approach with aggressive treatment with multiple antiretrovirals early in

7552-537: The PARTNER study, which ran from 2010 to 2014, enrolled 1166 serodiscordant couples (where one partner is HIV positive and the other is negative) in a study that found that the estimated rate of transmission through any condomless sex with the HIV-positive partner taking ART with an HIV load less than 200 copies/ml was zero. In summary, as the WHO HIV treatment guidelines state, "The ARV regimens now available, even in

7680-433: The U.S.: Although IFA can be used to confirm infection in these ambiguous cases, this assay is not widely used. In general, a second specimen should be collected more than a month later and retested for persons with indeterminate western blot results. Although much less commonly available, nucleic acid testing (e.g., viral RNA or proviral DNA amplification method) can also help diagnosis in certain situations. In addition,

7808-535: The US, 10.8% of one cohort of patients who had never been on ART before had at least one resistance mutation in 2005. Various surveys in different parts of the world have shown increasing or stable rates of baseline resistance as the era of effective HIV therapy continues. With baseline resistance testing, a combination of antiretrovirals that are likely to be effective can be customized for each patient. Most HAART regimens consist of three drugs: Two NRTIs ("backbone")+

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7936-496: The US, the DHHS recommends against women with HIV breastfeeding. HIV The human immunodeficiency viruses ( HIV ) are two species of Lentivirus (a subgroup of retrovirus ) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. Without treatment,

8064-731: The United States there are both the International AIDS Society-USA (IAS-USA) (a 501(c)(3) not-for-profit organization in the US) as well as the US government's Department of Health and Human Services guidelines. In Europe there are the European AIDS Clinical Society guidelines. For resource limited countries, most national guidelines closely follow the World Health Organization (WHO) guidelines. The guidelines use new criteria to consider starting HAART, as described below. However, there remain

8192-409: The adaptive benefit of recombination in HIV could explain why each HIV particle contains two complete genomes, rather than one. Furthermore, the view that recombination is a repair process implies that the benefit of repair can occur at each replication cycle, and that this benefit can be realized whether or not the two genomes differ genetically. On the view that recombination in HIV is a repair process,

8320-423: The advent of AIDS. HIV-positive patients acquire an enormously broad spectrum of opportunistic infections, which was particularly problematic prior to the onset of HAART therapies; however, the same infections are reported among HIV-infected patients examined post-mortem following the onset of antiretroviral therapies. Thus, during the course of infection, viral adaptation to the use of CXCR4 instead of CCR5 may be

8448-403: The animals develop AIDS and the virus generates genetic diversity similar to what is seen in human HIV infection. Chimpanzee SIV (SIVcpz), the closest genetic relative of HIV-1, is associated with increased mortality and AIDS-like symptoms in its natural host. SIVcpz appears to have been transmitted relatively recently to chimpanzee and human populations, so their hosts have not yet adapted to

8576-497: The average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype . In most cases, HIV is a sexually transmitted infection and occurs by contact with or transfer of blood , pre-ejaculate , semen , and vaginal fluids . Non-sexual transmission can occur from an infected mother to her infant during pregnancy , during childbirth by exposure to her blood or vaginal fluid, and through breast milk . Within these bodily fluids, HIV

8704-592: The cell as new virus particles that will begin the replication cycle anew. Two types of HIV have been characterized: HIV-1 and HIV-2. HIV-1 is the virus that was initially discovered and termed both lymphadenopathy associated virus (LAV) and human T-lymphotropic virus 3 (HTLV-III). HIV-1 is more virulent and more infective than HIV-2, and is the cause of the majority of HIV infections globally. The lower infectivity of HIV-2, compared to HIV-1, implies that fewer of those exposed to HIV-2 will be infected per exposure. Due to its relatively poor capacity for transmission, HIV-2

8832-470: The cell types a virus infects. HIV can infect a variety of immune cells such as CD4 T cells , macrophages , and microglial cells . HIV-1 entry to macrophages and CD4 T cells is mediated through interaction of the virion envelope glycoproteins (gp120) with the CD4 molecule on the target cells' membrane and also with chemokine co-receptors . Macrophage-tropic (M-tropic) strains of HIV-1, or non- syncytia -inducing strains (NSI; now called R5 viruses ) use

8960-459: The collapse of the extracellular portion of gp41 into a hairpin shape. This loop structure brings the virus and cell membranes close together, allowing fusion of the membranes and subsequent entry of the viral capsid. After HIV has bound to the target cell, the HIV RNA and various enzymes, including reverse transcriptase, integrase, ribonuclease, and protease, are injected into the cell. During

9088-412: The course of the infection. Later reviews in the late 90s and early 2000s noted that this approach of "hit hard, hit early" ran significant risks of increasing side effects and development of multidrug resistance, and this approach was largely abandoned. The only consensus was on treating patients with advanced immunosuppression (CD4 counts less than 350/μL). Treatment with antiretrovirals was expensive at

9216-447: The development of AIDS. HIV is a member of the genus Lentivirus , part of the family Retroviridae . Lentiviruses have many morphologies and biological properties in common. Many species are infected by lentiviruses, which are characteristically responsible for long-duration illnesses with a long incubation period . Lentiviruses are transmitted as single-stranded , positive- sense , enveloped RNA viruses . Upon entry into

9344-585: The development of multi-drug resistant mutations. In contrast, antiretroviral combination therapy defends against resistance by creating multiple obstacles to HIV replication. This keeps the number of viral copies low and reduces the possibility of a superior mutation. If a mutation that conveys resistance to one of the drugs arises, the other drugs continue to suppress reproduction of that mutation. With rare exceptions, no individual antiretroviral drug has been demonstrated to suppress an HIV infection for long; these agents must be taken in combinations in order to have

9472-577: The development of stable recombinant forms of the viral spike by the introduction of an intersubunit disulphide bond and an isoleucine to proline mutation ( radical replacement of an amino acid) in gp41. The so-called SOSIP trimers not only reproduce the antigenic properties of the native viral spike, but also display the same degree of immature glycans as presented on the native virus. Recombinant trimeric viral spikes are promising vaccine candidates as they display less non-neutralising epitopes than recombinant monomeric gp120, which act to suppress

9600-470: The drug resistant strains to become dominant. This in turn makes it harder to treat the infected individual as well as anyone else they infect. One trial showed higher rates of opportunistic infections, cancers, heart attacks and death in patients who periodically interrupted their ART. There are several treatment guidelines for HIV-1 infected adults in the developed world (that is, those countries with access to all or most therapies and laboratory tests). In

9728-644: The drug. GPO produces cannabinoid medicines at its factory in Pathum Thani Province , where it also grows cannabis plants. The organisation is also seeking approval to build a three billion baht, 1,500- rai (240 ha; 590-acre), herb and marijuana facility in Chonburi Province . The GPO led an effort to convince the military government to approve marijuana research so that the GPO can market it for medical use. The move would make Thailand

9856-410: The ease with which they can be taken, which in turn increases the consistency with which medication is taken ( adherence ), and thus their effectiveness over the long-term. Although antiretroviral therapy has helped to improve the quality of life of people living with HIV, there is still a need to explore other ways to further address the disease burden. One such potential strategy that was investigated

9984-400: The enzyme; NNRTIs act as non-competitive inhibitors of reverse transcriptase . NNRTIs affect the handling of substrate (nucleotides) by reverse transcriptase by binding near the active site. NNRTIs can be further classified into 1st generation and 2nd generation NNRTIs. 1st generation NNRTIs include nevirapine and efavirenz . 2nd generation NNRTIs are etravirine and rilpivirine . HIV-2

10112-523: The first country in Asia to legalize medical cannabis. Dr. Nopporn Cheanklin, managing director of the GPO, said that, "The best strains of cannabis in the world 20 years ago were from Thailand, and now Canada has developed this strain..., we can't claim that ours is the best in the world anymore,...That's why we must develop our strain to...compete with theirs." The government's cabinet of ministers in May 2018 gave

10240-580: The first six months after infection HIV viral loads tend to be elevated and people are more often symptomatic than in later latent phases of HIV disease. There may be special benefits to starting antiretroviral therapy early during this acute phase, including lowering the viral "set-point" or baseline viral load, reduce the mutation rate of the virus, and reduce the size of the viral reservoir (See section below on viral reservoirs ). The SPARTAC trial compared 48 weeks of ART vs 12 weeks vs no treatment in acute HIV infection and found that 48 weeks of treatment delayed

10368-431: The generation of many variants of HIV in a single infected patient in the course of one day. This variability is compounded when a single cell is simultaneously infected by two or more different strains of HIV. When simultaneous infection occurs, the genome of progeny virions may be composed of RNA strands from two different strains. This hybrid virion then infects a new cell where it undergoes replication. As this happens,

10496-576: The generation of recombinational variation would be a consequence, but not the cause of, the evolution of template switching. HIV-1 infection causes chronic inflammation and production of reactive oxygen species . Thus, the HIV genome may be vulnerable to oxidative damage , including breaks in the single-stranded RNA. For HIV, as well as for viruses in general, successful infection depends on overcoming host defense strategies that often include production of genome-damaging reactive oxygen species. Thus, Michod et al. suggested that recombination by viruses

10624-552: The genetic information that is transmitted from parental to progeny genomes. Viral recombination produces genetic variation that likely contributes to the evolution of resistance to anti-retroviral therapy . Recombination may also contribute, in principle, to overcoming the immune defenses of the host. Yet, for the adaptive advantages of genetic variation to be realized, the two viral genomes packaged in individual infecting virus particles need to have arisen from separate progenitor parental viruses of differing genetic constitution. It

10752-501: The granting of marketing authorizations for two new antiretroviral (ARV) medicines, rilpivirine (Rekambys) and cabotegravir (Vocabria), to be used together for the treatment of people with human immunodeficiency virus type 1 (HIV-1) infection. The two medicines are the first ARVs that come in a long-acting injectable formulation. This means that instead of daily pills, people receive intramuscular injections monthly or every two months. The combination of Rekambys and Vocabria injection

10880-546: The green light to amend the country's drug laws to allow research on medicinal marijuana. The bill is currently being debated in the National Legislative Assembly . Current Thai laws are tough on both the sale and use of marijuana. Possession of cannabis in Thailand could land its owner in jail for up to 15 years as the plant is a category-5 narcotic drug along with psychoactive mushrooms and kratom ,

11008-495: The host cell by blocking one of several targets. Maraviroc , enfuvirtide and Ibalizumab are available agents in this class. Maraviroc works by targeting CCR5 , a co-receptor located on human helper T-cells. Caution should be used when administering this drug, however, due to a possible shift in tropism which allows HIV to target an alternative co-receptor such as CXCR4 . Ibalizumab is effective against both CCR5 and CXCR4 tropic HIV viruses. In rare cases, individuals may have

11136-742: The human cell unless it is first "reverse" transcribed into DNA. Since the conversion of RNA to DNA is not naturally done in the mammalian cell, it is performed by a viral protein, reverse transcriptase , which makes it a selective target for inhibition. NRTIs are chain terminators. Once NRTIs are incorporated into the DNA chain, their lack of a 3' OH group prevents the subsequent incorporation of other nucleosides. Both NRTIs and NtRTIs act as competitive substrate inhibitors . Examples of NRTIs include zidovudine , abacavir , lamivudine , emtricitabine , and of NtRTIs – tenofovir and adefovir . Non-nucleoside reverse-transcriptase inhibitors (NNRTI) inhibit reverse transcriptase by binding to an allosteric site of

11264-415: The immune response to target epitopes. The RNA genome consists of at least seven structural landmarks ( LTR , TAR , RRE , PE, SLIP, CRS, and INS), and nine genes ( gag , pol , and env , tat , rev , nef , vif , vpr , vpu , and sometimes a tenth tev , which is a fusion of tat , env and rev ), encoding 19 proteins. Three of these genes, gag , pol , and env , contain information needed to make

11392-521: The integrated DNA provirus is transcribed into RNA. The full-length genomic RNAs (gRNA) can be packaged into new viral particles in a pseudodiploid form. The selectivity in the packaging is explained by the structural properties of the dimeric conformer of the gRNA. The gRNA dimer is characterized by a tandem three-way junction within the gRNA monomer, in which the SD and AUG hairpins , responsible for splicing and translation respectively, are sequestered and

11520-422: The metal binding site of integrase. As of early 2022, four other clinically approved integrase inhibitors are elvitegravir , dolutegravir , bictegravir , and cabotegravir . Protease inhibitors block the viral protease enzyme necessary to produce mature virions upon budding from the host membrane. Particularly, these drugs prevent the cleavage of gag and gag/pol precursor proteins. Virus particles produced in

11648-453: The other hand, patients who take their medications regularly can stay on one regimen without developing resistance. This greatly increases life expectancy and leaves more drugs available to the individual should the need arise. In 2000 drug companies have worked together to combine these complex regimens into single-pill fixed-dose combinations . More than 20 antiretroviral fixed-dose combinations have been developed. This greatly increases

11776-783: The past. Thus the WHO recommends PI based regimens for children less than 3. The WHO recommends for children less than 3 years: and for children 3 years to less than 10 years and adolescents <35 kilograms: US DHHS guidelines are similar but include PI based options for children > 3 years old. A systematic review assessed the effects and safety of abacavir-containing regimens as first-line therapy for children between 1 month and 18 years of age when compared to regimens with other NRTIs. This review included two trials and two observational studies with almost eleven thousand HIV infected children and adolescents. They measured virologic suppression, death and adverse events. The authors found that there

11904-410: The patient. Macrophages and microglial cells are the cells infected by HIV in the central nervous system . In the tonsils and adenoids of HIV-infected patients, macrophages fuse into multinucleated giant cells that produce huge amounts of virus. T-tropic strains of HIV-1, or syncytia -inducing strains (SI; now called X4 viruses ) replicate in primary CD4 T cells as well as in macrophages and use

12032-465: The phase of the retrovirus life-cycle that the drug inhibits. Typical combinations include two nucleoside reverse-transcriptase inhibitors (NRTI) as a "backbone" along with one non-nucleoside reverse-transcriptase inhibitor (NNRTI), protease inhibitor (PI) or integrase inhibitors (also known as integrase nuclear strand transfer inhibitors or INSTIs) as a "base". Entry inhibitors (or fusion inhibitors) interfere with binding, fusion and entry of HIV-1 to

12160-402: The poorest countries, are safer, simpler, more effective and more affordable than ever before." There is a consensus among experts that, once initiated, antiretroviral therapy should never be stopped. This is because the selection pressure of incomplete suppression of viral replication in the presence of drug therapy causes the more drug sensitive strains to be selectively inhibited. This allows

12288-472: The potential benefits. The WHO has defined health as more than the absence of disease. For this reason, many researchers have dedicated their work to better understanding the effects of HIV-related stigma, the barriers it creates for treatment interventions, and the ways in which those barriers can be circumvented. There are six classes of drugs, which are usually used in combination, to treat HIV infection. Antiretroviral (ARV) drugs are broadly classified by

12416-412: The presence of protease inhibitors are defective and mostly non-infectious. Examples of HIV protease inhibitors are lopinavir , indinavir , nelfinavir , amprenavir and ritonavir . Darunavir and atazanavir are recommended as first line therapy choices. Maturation inhibitors have a similar effect by binding to gag, but development of two experimental drugs in this class, bevirimat and vivecon ,

12544-406: The remaining 5.3% were composed of other subtypes and CRFs. Most HIV-1 research is focused on subtype B; few laboratories focus on the other subtypes. The existence of a fourth group, "P", has been hypothesised based on a virus isolated in 2009. The strain is apparently derived from gorilla SIV (SIVgor), first isolated from western lowland gorillas in 2006. HIV-2's closest relative is SIVsm,

12672-425: The reverse transcriptase, by jumping back and forth between the two different RNA templates, will generate a newly synthesized retroviral DNA sequence that is a recombinant between the two parental genomes. This recombination is most obvious when it occurs between subtypes. The closely related simian immunodeficiency virus (SIV) has evolved into many strains, classified by the natural host species. SIV strains of

12800-489: The rights holder's consent, and pays the rights holder a set fee for the license. This is an exception to the general rule under intellectual property laws that the intellectual property owner enjoys exclusive rights that it may license—or decline to license—to others. In the case of efavirenz, the patent owner, Merck , and the US Trade Representative , for years fiercely resisted allowing the GPO to produce

12928-650: The risk of HIV transmission from a person living with HIV who has been undetectable for a minimum of six months is negligible to non-existent, with negligible being defined as "so small or unimportant to be not worth considering". The Chair of the British HIV Association (BHIVA), Chloe Orkin , stated in July 2017 that 'there should be no doubt about the clear and simple message that a person with sustained, undetectable levels of HIV virus in their blood cannot transmit HIV to their sexual partners.' Furthermore,

13056-761: The risks of HIV treatment. Therapy during acute infection carries a grade BII recommendation from the US DHHS. HIV can be especially harmful to infants and children, with one study in Africa showing that 52% of untreated children born with HIV had died by age 2. By five years old, the risk of disease and death from HIV starts to approach that of young adults. The WHO recommends treating all children less than 5 years old, and starting all children older than 5 with stage 3 or 4 disease or CD4 <500 cells/ml. DHHS guidelines are more complicated but recommend starting all children less than 12 months old and children of any age who have symptoms. As for which antiretrovirals to use, this

13184-519: The single-stranded viral DNA and/or interferes with reverse transcription ). The vpr protein (p14) arrests cell division at G2/M . The nef protein (p27) down-regulates CD4 (the major viral receptor), as well as the MHC class I and class II molecules. Nef also interacts with SH3 domains . The vpu protein (p16) influences the release of new virus particles from infected cells. The ends of each strand of HIV RNA contain an RNA sequence called

13312-412: The site of cell-to-cell contact, close apposition of cells, which minimizes fluid-phase diffusion of virions, and clustering of HIV entry receptors on the target cell towards the contact zone. Cell-to-cell spread is thought to be particularly important in lymphoid tissues , where CD4 T cells are densely packed and likely to interact frequently. Intravital imaging studies have supported the concept of

13440-673: The specimen is reported as repeatedly reactive and undergoes confirmatory testing with a more specific supplemental test (e.g., a polymerase chain reaction (PCR), western blot or, less commonly, an immunofluorescence assay (IFA)). Only specimens that are repeatedly reactive by ELISA and positive by IFA or PCR or reactive by western blot are considered HIV-positive and indicative of HIV infection. Specimens that are repeatedly ELISA-reactive occasionally provide an indeterminate western blot result, which may be either an incomplete antibody response to HIV in an infected person or nonspecific reactions in an uninfected person. HIV deaths in 2014 excluding

13568-556: The structural proteins Gag and Env. Gag proteins bind to copies of the virus RNA genome to package them into new virus particles. HIV-1 and HIV-2 appear to package their RNA differently. HIV-1 will bind to any appropriate RNA. HIV-2 will preferentially bind to the mRNA that was used to create the Gag protein itself. Two RNA genomes are encapsidated in each HIV-1 particle (see Structure and genome of HIV ). Upon infection and replication catalyzed by reverse transcriptase, recombination between

13696-496: The structural proteins for new virus particles. For example, env codes for a protein called gp160 that is cut in two by a cellular protease to form gp120 and gp41. The six remaining genes, tat , rev , nef , vif , vpr , and vpu (or vpx in the case of HIV-2), are regulatory genes for proteins that control the ability of HIV to infect cells, produce new copies of virus (replicate), or cause disease. The two tat proteins (p16 and p14) are transcriptional transactivators for

13824-427: The target cell surface. Gp120 binds to integrin α 4 β 7 activating LFA-1 , the central integrin involved in the establishment of virological synapses , which facilitate efficient cell-to-cell spreading of HIV-1. The gp160 spike contains binding domains for both CD4 and chemokine receptors. The first step in fusion involves the high-affinity attachment of the CD4 binding domains of gp120 to CD4. Once gp120

13952-413: The target cell, the viral RNA genome is converted (reverse transcribed) into double-stranded DNA by a virally encoded enzyme, reverse transcriptase , that is transported along with the viral genome in the virus particle. The resulting viral DNA is then imported into the cell nucleus and integrated into the cellular DNA by a virally encoded enzyme, integrase , and host co-factors . Once integrated,

14080-610: The time to decline in CD4 count below 350 cells per ml by 65 weeks and kept viral loads significantly lower even after treatment was stopped. Since viral loads are usually very high during acute infection, this period carries an estimated 26 times higher risk of transmission. By treating acutely infected patients, it is presumed that it could have a significant impact on decreasing overall HIV transmission rates since lower viral loads are associated with lower risk of transmission (See section on treatment as prevention ). However an overall benefit has not been proven and has to be balanced with

14208-405: The time, ranging from $ 10,000 to $ 15,000 a year. The timing of when to start therapy has continued to be a core controversy within the medical community, though recent studies have led to more clarity. The NA-ACCORD study observed patients who started antiretroviral therapy either at a CD4 count of less than 500 versus less than 350 and showed that patients who started ART at lower CD4 counts had

14336-414: The two HIV envelope glycoproteins, gp41 and gp120 . These are transported to the plasma membrane of the host cell where gp41 anchors gp120 to the membrane of the infected cell. The Gag (p55) and Gag-Pol (p160) polyproteins also associate with the inner surface of the plasma membrane along with the HIV genomic RNA as the forming virion begins to bud from the host cell. The budded virion is still immature as

14464-484: The two genomes can occur. Recombination occurs as the single-strand, positive-sense RNA genomes are reverse transcribed to form DNA. During reverse transcription, the nascent DNA can switch multiple times between the two copies of the viral RNA. This form of recombination is known as copy-choice. Recombination events may occur throughout the genome. Anywhere from two to 20 recombination events per genome may occur at each replication cycle, and these events can rapidly shuffle

14592-557: The use of interleukin 2 as an add-on treatment to antiretroviral therapy for adults with HIV. Antiretroviral drug treatment guidelines have changed over time. Before 1987, no antiretroviral drugs were available and treatment consisted of treating complications from opportunistic infections and malignancies. After antiretroviral medications were introduced, most clinicians agreed that HIV positive patients with low CD4 counts should be treated, but no consensus formed as to whether to treat patients with high CD4 counts. In April 1995, Merck and

14720-570: The viral DNA into the host cell's genome is carried out by another viral enzyme called integrase . The integrated viral DNA may then lie dormant, in the latent stage of HIV infection. To actively produce the virus, certain cellular transcription factors need to be present, the most important of which is NF- κ B (nuclear factor kappa B), which is upregulated when T cells become activated. This means that those cells most likely to be targeted, entered and subsequently killed by HIV are those actively fighting infection. During viral replication,

14848-536: The virus in its adaptation to avoid innate restriction factors present in host cells. Adaptation to use normal cellular machinery to enable transmission and productive infection has also aided the establishment of HIV-2 replication in humans. A survival strategy for any infectious agent is not to kill its host, but ultimately become a commensal organism. Having achieved a low pathogenicity, over time, variants that are more successful at transmission will be selected. The HIV virion enters macrophages and CD4 T cells by

14976-425: The virus is captured in the mucosa by DCs. The presence of FEZ-1 , which occurs naturally in neurons , is believed to prevent the infection of cells by HIV. HIV-1 entry, as well as entry of many other retroviruses, has long been believed to occur exclusively at the plasma membrane. More recently, however, productive infection by pH -independent, clathrin-mediated endocytosis of HIV-1 has also been reported and

15104-463: The virus may become latent , allowing the virus and its host cell to avoid detection by the immune system, for an indeterminate amount of time. The virus can remain dormant in the human body for up to ten years after primary infection; during this period the virus does not cause symptoms. Alternatively, the integrated viral DNA may be transcribed , producing new RNA genomes and viral proteins, using host cell resources, that are packaged and released from

15232-403: The virus to evade the body's immune system. The reverse transcriptase also has ribonuclease activity that degrades the viral RNA during the synthesis of cDNA, as well as DNA-dependent DNA polymerase activity that creates a sense DNA from the antisense cDNA. Together, the cDNA and its complement form a double-stranded viral DNA that is then transported into the cell nucleus . The integration of

15360-410: The virus to mutate very rapidly, resulting in a high genetic variability. Most of the mutations either are inferior to the parent virus (often lacking the ability to reproduce at all) or convey no advantage, but some of them have a natural selection superiority to their parent and can enable them to slip past defenses such as the human immune system and antiretroviral drugs. The more active copies of

15488-449: The virus, the greater the possibility that one resistant to antiretroviral drugs will be made. When antiretroviral drugs are used improperly, multi-drug resistant strains can become the dominant genotypes very rapidly. In the era before multiple drug classes were available (pre-1997), the reverse-transcriptase inhibitors zidovudine , didanosine , zalcitabine , stavudine , and lamivudine were used serially or in combination leading to

15616-540: The virus. This virus has also lost a function of the nef gene that is present in most SIVs. For non-pathogenic SIV variants, nef suppresses T cell activation through the CD3 marker. Nef 's function in non-pathogenic forms of SIV is to downregulate expression of inflammatory cytokines , MHC-1 , and signals that affect T cell trafficking. In HIV-1 and SIVcpz, nef does not inhibit T-cell activation and it has lost this function. Without this function, T cell depletion

15744-475: The whole organism. However, a selection process leads to a predominant transmission of the R5 virus through this pathway. In patients infected with subtype B HIV-1, there is often a co-receptor switch in late-stage disease and T-tropic variants that can infect a variety of T cells through CXCR4. These variants then replicate more aggressively with heightened virulence that causes rapid T cell depletion, immune system collapse, and opportunistic infections that mark

15872-532: Was halted in 2010. Resistance to some protease inhibitors is high. Second generation drugs have been developed that are effective against otherwise resistant HIV variants. The life cycle of HIV can be as short as about 1.5 days from viral entry into a cell, through replication, assembly, and release of additional viruses, to infection of other cells. HIV lacks proofreading enzymes to correct errors made when it converts its RNA into DNA via reverse transcription . Its short life-cycle and high error rate cause

16000-710: Was likely to be suppressed. Pre-exposure prophylaxis (PrEP) provides HIV-negative individuals with medication—in conjunction with safer-sex education and regular HIV/STI screenings—in order to reduce the risk of acquiring HIV. In 2011, the journal Science gave the Breakthrough of the Year award to treatment as prevention. In July 2016 a consensus document was created by the Prevention Access Campaign which has been endorsed by over 400 organisations in 58 countries. The consensus document states that

16128-448: Was recently suggested to constitute the only route of productive entry. Shortly after the viral capsid enters the cell, an enzyme called reverse transcriptase liberates the positive-sense single-stranded RNA genome from the attached viral proteins and copies it into a complementary DNA (cDNA) molecule. The process of reverse transcription is extremely error-prone, and the resulting mutations may cause drug resistance or allow

16256-412: Was stopped early (after 1.7 years) for ethical reasons when it became clear that antiviral treatment provided significant protection. Of the 28 couples where cross-infection had occurred, all but one had taken place in the control group , consistent with a 96% reduction in risk of transmission while on ART. The single transmission in the experimental group occurred early after starting ART before viral load

16384-520: Was to add interleukin 2 as an adjunct to antiretroviral therapy for adults with HIV. A Cochrane review included 25 randomized controlled trials that were conducted across six countries. The researchers found that interleukin 2 increases the CD4 immune cells, but does not make a difference in terms of death and incidence of other infections. Furthermore, there is probably an increase in side-effects with interleukin 2. The findings of this review do not support

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