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43-499: See text Herpesviridae is a large family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are also known as herpesviruses . The family name is derived from the Greek word ἕρπειν ( herpein 'to creep'), referring to spreading cutaneous lesions, usually involving blisters, seen in flares of herpes simplex 1, herpes simplex 2 and herpes zoster ( shingles ). In 1971,
86-422: A PI3K inhibitor is added to cells, the cytokine synthesis levels are significantly restored. The fact that cytokine levels are not completely restored indicates there is another pathway activated by cmvIL-10 that is inhibiting cytokine system synthesis. The proposed mechanism is that cmvIL-10 activates PI3K which in turn activates PKB (Akt). PKB may then activate mTOR , which may target Stat3 for phosphorylation on
129-401: A common origin. There are 4 orders, 47 families, 98 subfamilies, 1197 genera, 3601 species in the class. This makes Caudoviricetes the most populous class among viruses, accounting for approximately 30% of all recognized virus species and nearly half of all virus genera. Upon encountering a host bacterium, the tail section of the virion binds to receptors on the cell surface and delivers
172-587: A decrease in proliferation of PBMCs. This indicates that cmvIL-10 may lack the stimulatory effects that hIL-10 has on these cells. It was found that cmvIL-10 functions through phosphorylation of the Stat3 protein. It was originally thought that this phosphorylation was a result of the JAK-STAT pathway. However, despite evidence that JAK does indeed phosphorylate Stat3, its inhibition has no significant influence on cytokine synthesis inhibition. Another protein, PI3K ,
215-409: A flexible tail by a connector protein. The order encompasses a wide range of viruses, many containing genes of similar nucleotide sequence and function. However, some tailed bacteriophage genomes can vary quite significantly in nucleotide sequence, even among the same genus. Due to their characteristic structure and possession of potentially homologous genes, it is believed these bacteriophages possess
258-554: A lack of widespread consensus within the scientific community for extended periods. The continual publication of new data and diverse opinions plays a crucial role in facilitating adjustments and ultimately reaching a consensus over time. The naming of families is codified by various international bodies using the following suffixes: The taxonomic term familia was first used by French botanist Pierre Magnol in his Prodromus historiae generalis plantarum, in quo familiae plantarum per tabulas disponuntur (1689) where he called
301-401: A portal complex that allows entry and exit of DNA into the capsid. All herpesviruses are nuclear-replicating—the viral DNA is transcribed to mRNA within the infected cell's nucleus . Infection is initiated when a viral particle contacts a cell with specific types of receptor molecules on the cell surface . Following binding of viral envelope glycoproteins to cell membrane receptors,
344-516: Is analyzed to elucidate molecular mechanisms of latency. The avian infectious laryngotracheitis virus is phylogenetically distant from these two viruses and serves to underline similarity and diversity within the Alphaherpesvirinae . Research is currently ongoing into a variety of side-effect or co-conditions related to the herpesviruses. These include: Family (biology) Family ( Latin : familia , pl. : familiae )
387-499: Is commonly referred to as the "walnut family". The delineation of what constitutes a family— or whether a described family should be acknowledged— is established and decided upon by active taxonomists . There are not strict regulations for outlining or acknowledging a family, yet in the realm of plants, these classifications often rely on both the vegetative and reproductive characteristics of plant species. Taxonomists frequently hold varying perspectives on these descriptions, leading to
430-574: Is named after the computer program crAss, which was used to identify the first member of the Crassvirales order. The rest (including the proposed orders) infect archaea . Kirjokansivirales , Thumleimavirales , and Nakonvirales are named after mythological objects or deities; Methanobavirales and Magrovirales are named after archaic synonyms of the archaea they infect. Bacteriophages occur in over 1100 bacterial or archaeal genera. Over 6300 bacteriophages have been examined in
473-725: Is often accompanied by emergence of nonspecific symptoms , such as low-grade fever, headache, sore throat, malaise , and rash, as well as clinical signs such as swollen or tender lymph nodes and immunological findings such as reduced levels of natural killer cells . In animal models, local trauma and system stress have been found to induce reactivation of latent herpesvirus infection. Cellular stressors like transient interruption of protein synthesis and hypoxia are also sufficient to induce viral reactivation. The three mammalian subfamilies – Alpha -, Beta - and Gamma - herpesviridae – arose approximately 180 to 220 mya . The major sublineages within these subfamilies were probably generated before
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#1732765857062516-485: Is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy . It is classified between order and genus . A family may be divided into subfamilies , which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae , but that family
559-548: Is to encode viral proteins that detain the newly formed MHC in the endoplasmic reticulum (ER). The MHC cannot reach the cell surface and therefore cannot activate the T cell response. The MHCs can also be targeted for destruction in the proteasome or lysosome . The ER protein TAP also plays a role in MHC down regulation. Viral proteins inhibit TAP preventing the MHC from picking up a viral antigen peptide. This prevents proper folding of
602-481: The Genera Plantarum of George Bentham and Joseph Dalton Hooker this word ordo was used for what now is given the rank of family. Families serve as valuable units for evolutionary, paleontological, and genetic studies due to their relatively greater stability compared to lower taxonomic levels like genera and species. Caudovirales Caudoviricetes is a class of viruses known as
645-763: The International Committee on the Taxonomy of Viruses (ICTV) established Herpesvirus as a genus with 23 viruses among four groups. As of 2020, 115 species are recognized, all but one of which are in one of the three subfamilies. Herpesviruses can cause both latent and lytic infections. Nine herpesvirus types are known to primarily infect humans, at least five of which are extremely widespread among most human populations, and which cause common diseases: herpes simplex 1 and 2 (HSV-1 and HSV-2, also known as HHV-1 and HHV-2; both of which can cause orolabial and genital herpes ), varicella zoster (or HHV-3;
688-588: The Podoviridae as type C. He also divided his groups on the basis of head morphology: Within group A, A1 have small isometric heads; A2 have prolate heads; and A3 have elongated heads. Within groups B and C, numbers were similarly assigned: B1 and C1 have small isometric heads; B2 and C2 have prolate heads; and B3 and C3 have elongated heads. Because the "families" Myoviridae , Podoviridae and Siphoviridae were abolished for being polyphyletic, there are now many free-floating families, subfamilies, and genera in
731-463: The capsid , which is itself wrapped in a protein layer called the tegument containing both viral proteins and viral mRNAs and a lipid bilayer membrane called the envelope . This whole particle is known as a virion . The structural components of a typical HSV virion are the Lipid bilayer envelope, Tegument, DNA, Glycoprotein spikes and Nucleocapsid. The four-component Herpes simplex virion encompasses
774-529: The tailed bacteriophages ( cauda is Latin for "tail"). Under the Baltimore classification scheme, the Caudoviricetes are group I viruses as they have double stranded DNA (dsDNA) genomes, which can be anywhere from 18,000 base pairs to 500,000 base pairs in length. The virus particles have a distinct shape; each virion has an icosahedral head that contains the viral genome, and is attached to
817-477: The DNA into the cell by use of an injectisome-like mechanism (an injectisome is a nanomachine that evolved for the delivery of proteins by type III secretion ). The tail section of the virus punches a hole through the bacterial cell wall and plasma membrane and the genome passes down the tail into the cell. Once inside the genes are expressed from transcripts made by the host machinery, using host ribosomes . Typically,
860-457: The MHC and therefore the MHC does not reach the cell surface. Below are the nine distinct viruses in this family known to cause disease in humans. In addition to the herpesviruses considered endemic in humans, some viruses associated primarily with animals may infect humans. These are zoonotic infections: In animal virology , the best known herpesviruses belong to the subfamily Alphaherpesvirinae . Research on pseudorabies virus (PrV),
903-499: The S727 residue. Another one of the many ways in which herpes viruses evade the immune system is by down regulation of MHC I and MHC II . This is observed in almost every human herpesvirus. Down regulation of MHC I and MHC II can come about by many different mechanisms, most causing the MHC to be absent from the cell surface. As discussed above, one way is by a viral chemokine homolog such as IL-10. Another mechanism to down regulate MHCs
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#1732765857062946-416: The alphaherpesviruses may have been the earliest branch. The time of origin of the genus Iltovirus has been estimated to be 200 mya while those of the mardivirus and simplex genera have been estimated to be between 150 and 100 mya. Herpesviruses are known for their ability to establish lifelong infections. One way this is possible is through immune evasion. Herpesviruses have many different ways of evading
989-414: The causative agent of Aujeszky's disease in pigs, has pioneered animal disease control with genetically modified vaccines. PrV is now extensively studied as a model for basic processes during lytic herpesvirus infection, and for unraveling molecular mechanisms of herpesvirus neurotropism, whereas bovine herpesvirus 1 , the causative agent of bovine infectious rhinotracheitis and pustular vulvovaginitis ,
1032-476: The cause of chickenpox and shingles ), Epstein–Barr (EBV or HHV-4; implicated in several diseases, including mononucleosis and some cancers), and human cytomegalovirus (HCMV or HHV-5). More than 90% of adults have been infected with at least one of these, and a latent form of the virus remains in almost all humans who have been infected. Other human herpesviruses are human herpesvirus 6A and 6B (HHV-6A and HHV-6B) and human herpesvirus 7 (HHV-7), which are
1075-443: The cell (and thus the host) indefinitely. While primary infection is often accompanied by a self-limited period of clinical illness, long-term latency is symptom-free. Chromatin dynamics regulate the transcription competency of entire herpes virus genomes. When the virus enters a cell, the cellular immune response is to protect the cell. The cell does so by wrapping the viral DNA around histones and condensing it into chromatin, causing
1118-447: The cell-mediated immune response and natural killer cell response, respectively. The similarities between hIL-10 and cmvIL-10 may be explained by the fact that hIL-10 and cmvIL-10 both use the same cell surface receptor, the hIL-10 receptor. One difference in the function of hIL-10 and cmvIL-10 is that hIL-10 causes human peripheral blood mononuclear cells ( PBMC ) to both increase and decrease in proliferation whereas cmvIL-10 only causes
1161-503: The class without any preceding taxa before Caudoviricetes . There are currently 7 orders, 63 families, 109 subfamilies, 1360 genera, and 4079 species in the class. This article lists all official and proposed taxa of Caudoviricetes . (Note: quotation marks mean that the taxon is proposed and has not yet been ratified by the ICTV.) There are many unassigned taxa in Caudoviricetes as of ICTV (2022). Crassvirales infects bacteria and
1204-496: The double-stranded DNA genome into an icosahedral nucleocapsid. There is tegument around. Tegument contains filaments, each 7 nm wide. It is an amorphous layer with some structured regions. Finally, it is covered with a lipoprotein envelope. There are spikes made of glycoprotein protruding from each virion. These can expand the diameter of the virus to 225 nm. The diameters of virions without spikes are around 186 nm. There are at least two unglycosylated membrane proteins in
1247-524: The etiological agents for Roseola , and HHV-8 (also known as KSHV) which is responsible for causing Kaposi's sarcoma-associated herpesvirus . HHV here stands for "Human Herpesvirus". In total, more than 130 herpesviruses are known, some of them from mammals, birds, fish, reptiles, amphibians, and molluscs. Among the animal herpesviruses are pseudorabies virus causing Aujeszky's disease in pigs, and bovine herpesvirus 1 causing bovine infectious rhinotracheitis and pustular vulvovaginitis . Additionally,
1290-540: The family as a rank intermediate between order and genus was introduced by Pierre André Latreille in his Précis des caractères génériques des insectes, disposés dans un ordre naturel (1796). He used families (some of them were not named) in some but not in all his orders of "insects" (which then included all arthropods ). In nineteenth-century works such as the Prodromus of Augustin Pyramus de Candolle and
1333-419: The genome is replicated by use of concatemers , in which overlapping segments of DNA are made, and then put together to form the whole genome. Viral capsid proteins come together to form a precursor prohead , into which the genome enters. Once this has occurred, the prohead undergoes maturation by cleavage of capsid subunits to form an icosahedral phage head with 5-fold symmetry. After the head maturation,
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1376-460: The immune system. One such way is by encoding a protein mimicking human interleukin 10 (hIL-10) and another is by downregulation of the major histocompatibility complex II (MHC II) in infected cells. Research conducted on cytomegalovirus (CMV) indicates that the viral human IL-10 homolog, cmvIL-10, is important in inhibiting pro-inflammatory cytokine synthesis. The cmvIL-10 protein has 27% identity with hIL-10 and only one conserved residue out of
1419-412: The mammalian radiation of 80 to 60 mya. Speciations within sublineages took place in the last 80 million years probably with a major component of cospeciation with host lineages. All the currently known bird and reptile species are alphaherpesviruses. Although the branching order of the herpes viruses has not yet been resolved, because herpes viruses and their hosts tend to coevolve this is suggestive that
1462-486: The nine amino acids that make up the functional site for cytokine synthesis inhibition on hIL-10. There is, however, much similarity in the functions of hIL-10 and cmvIL-10. Both have been shown to down regulate IFN-γ , IL-1α , GM-CSF , IL-6 and TNF-α , which are all pro-inflammatory cytokines. They have also been shown to play a role in downregulating MHC I and MHC II and up regulating HLA-G (non-classical MHC I). These two events allow for immune evasion by suppressing
1505-552: The order Caudovirales , had lower taxa defined via morphology and contractile ability of their "tails". The Myoviridae had long tails that were contractile; the Podoviridae had short noncontractile tails; and the Siphoviridae had long noncontractile tails. Siphoviridae constitute the majority of the known tailed viruses. Bradley referred to what was known as the Myoviridae as type A, Siphoviridae as type B, and
1548-478: The outer envelope of the virion. There are also 11 glycoproteins. These are gB, gC, gD, gE, gG, gH, gI, gJ, gK, gL and gM. Tegument contains 26 proteins. They have duties such as capsid transport to the nucleus and other organelles, activation of early gene transcription, and mRNA degradation. The icosahedral nucleocapsid is similar to that of tailed bacteriophage in the order Caudovirales . This capsid has 161 capsomers consisting of 150 hexons and 11 pentons, as well as
1591-575: The seventy-six groups of plants he recognised in his tables families ( familiae ). The concept of rank at that time was not yet settled, and in the preface to the Prodromus Magnol spoke of uniting his families into larger genera , which is far from how the term is used today. In his work Philosophia Botanica published in 1751, Carl Linnaeus employed the term familia to categorize significant plant groups such as trees , herbs , ferns , palms , and so on. Notably, he restricted
1634-504: The species Iguanid herpesvirus 2 is currently unassigned to a genus and subfamily. See Herpesvirales#Taxonomy for information on taxonomic history, phylogenetic research, and the nomenclatural system. All members of the Herpesviridae share a common structure; a relatively large, monopartite, double-stranded, linear DNA genome encoding 100–200 genes encased within an icosahedral protein cage (with T=16 symmetry) called
1677-410: The tail is joined in one of two ways: Either the tail is constructed separately, and joined with the connector, or the tail is constructed directly onto the phage head. The tails consist of helix based proteins with 6-fold symmetry. After maturation of virus particles, the cell is lysed by lysins , holins, or a combination of the two. For most of virological history, Caudoviricetes which was known as
1720-549: The use of this term solely within the book's morphological section, where he delved into discussions regarding the vegetative and generative aspects of plants. Subsequently, in French botanical publications, from Michel Adanson 's Familles naturelles des plantes (1763) and until the end of the 19th century, the word famille was used as a French equivalent of the Latin ordo (or ordo naturalis ). In zoology ,
1763-418: The virion is internalized and dismantled, allowing viral DNA to migrate to the cell nucleus. Within the nucleus, replication of viral DNA and transcription of viral genes occurs. During symptomatic infection, infected cells transcribe lytic viral genes. In some host cells, a small number of viral genes termed latency-associated transcript (LAT) accumulate, instead. In this fashion, the virus can persist in
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1806-611: The virus to become dormant, or latent. If cells are unsuccessful and the chromatin is loosely bundled, the viral DNA is still accessible. The viral particles can turn on their genes and replicate using cellular machinery to reactivate, starting a lytic infection. Reactivation of latent viruses has been implicated in a number of diseases (e.g. shingles , pityriasis rosea ). Following activation, transcription of viral genes transitions from LAT to multiple lytic genes; these lead to enhanced replication and virus production. Often, lytic activation leads to cell death . Clinically, lytic activation
1849-571: Was also found to phosphorylate Stat3. PI3K inhibition, unlike JAK inhibition, did have a significant impact on cytokine synthesis. The difference between PI3K and JAK in Stat3 phosphorylation is that PI3K phosphorylates Stat3 on the S727 residue whereas JAK phosphorylates Stat3 on the Y705 residue. This difference in phosphorylation positions seems to be the key factor in Stat3 activation leading to inhibition of pro-inflammatory cytokine synthesis. In fact, when
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