Gammaherpesvirinae
Encyclopedia
Gammaherpesvirinae is a subfamily of Herpesviridae
distinguished by reproducing at a more variable rate than other subfamilies of Herpesviridae. The Herpesviridae Study Group has proposed that the gammaherpesvirinae subfamily be subdivided into the following four genera
:
contains eight viruses that infect humans, is the most extensively studied group within this order and comprises three subfamilies, namely Alphaherpesvirinae
, Betaherpesvirinae
and Gammaherpesvirinae. Gammaherpesviruses belong to four separate genera: the
well-established genera Lymphocryptovirus
and Rhadinovirus
and the more recently defined genera Macavirus and Percavirus.
Gammaherpesviruses are of primary interest due to the two human viruses, EBV
and KSHV
and the diseases they cause.The gammaherpesviruses replicate and persist in lymphoid
cells but some are capable of undergoing lytic replication in epithelial or fibroblast
cells.
These viruses can be subdivided into two genera: lymphocryptoviruses (gamma-1) and rhadinoviruses (gamma-2). The lymphocryptoviruses (gamma-1) include Epstein-Barr virus
(EBV) or Human herpesvirus 4, Lymphocryptovirus
of rhesus monkeys and Herpesvirus papio of baboon
s, whereas the rhadinoviruses (gamma-2) include Herpesvirus saimiri (HVS), Kaposi's sarcoma-associated herpesvirus
(KSHV) or Human herpesvirus 8, Rhesus monkey rhadinovirus (RRV), Equine herpesvirus 2
and Mouse herpesvirus 68. The gammaherpesviruses, including HVS, EBV, KSHV, and RRV, are capable of establishing latent infection in lymphocytes.
Within this genus there are a number of unclassified viruses including cynomys herpesvirus 1 (CynGHV-1)
• Virus attachment and entry
• Viral DNA injection through nuclear
pore complex (NPC) into nucleus
• Assembly of nucleocapsids and encapsidation of viral genome
• Primary envelopment, invagination
s of nuclear membrane(s) and nuclear egress
• Tegumentation and secondary envelopment in the cytoplasm
• Egress
and extracellularvirions release
in these gammaherpesviruses have oncogenic potential, other viral genes may also play a role in viral transformation
. A striking feature of the four gammaherpesviruses is that they contain distinct ORFs involved in lymphocyte signaling events. At the left end of each viral genome are located ORFs encoding distinct transforming proteins.The Gammaherpes viral genes are capable of modulating cellular signals such that cell proliferation and viral replication occur at the appropriate times in the viral life cycle.
system especially must avoid being detected by host CD8+ cytotoxic T lymphocytes (CTLs). The gamma-herpesviruses are characteristically latent in lymphocytes and drive the proliferation that requires the expression of latent viral antigens. .The majority of gammaherpesviruses encode a specific protein that is critical for maintenance of the viral genome within latently infected cells termed the genome maintenance protein (GMP). GMPs are DNA-binding proteins that ensures that, as the host cell progresses through itosis, the viral episomes are partitioned to daughter cells. This provides continuous existence of the viral genome within the host cells.
Herpesviridae
The Herpesviridae are a large family of DNA viruses that cause diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word herpein , referring to the latent, recurring infections typical of this group of viruses...
distinguished by reproducing at a more variable rate than other subfamilies of Herpesviridae. The Herpesviridae Study Group has proposed that the gammaherpesvirinae subfamily be subdivided into the following four genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
:
- LymphocryptovirusLymphocryptovirusLymphocryptoviruses are a genus of herpesviruses that include the human Epstein-Barr virus as well as viruses that infect both Old World monkeys and New World monkeys...
- RhadinovirusRhadinovirusRhadinoviruses are a genus of herpesviruses that include the Human herpesvirus 8 , also known as Kaposi's sarcoma-associated herpesvirus , which causes Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman's disease. Other names for the Rhadinovirus genus include Rhadinoviridae...
- Macavirus
- Percavirus
Introduction
Herpesviruses represent a group of double-stranded DNA viruses distributed widely within the animal kingdom. The family Herpesviridae, whichcontains eight viruses that infect humans, is the most extensively studied group within this order and comprises three subfamilies, namely Alphaherpesvirinae
Alphaherpesvirinae
Alphaherpesvirinae is a subfamily of Herpesviridae primarily distinguished by reproducing more quickly than other subfamilies of Herpesviridae. In animal virology the most important herpesviruses belong to the Alphaherpesvirinae...
, Betaherpesvirinae
Betaherpesvirinae
Betaherpesvirinae is a subfamily of Herpesviridae distinguished by reproducing less quickly than other subfamilies of Herpesviridae.Betaherpesvirinae establish latency in leukocytes...
and Gammaherpesvirinae. Gammaherpesviruses belong to four separate genera: the
well-established genera Lymphocryptovirus
Lymphocryptovirus
Lymphocryptoviruses are a genus of herpesviruses that include the human Epstein-Barr virus as well as viruses that infect both Old World monkeys and New World monkeys...
and Rhadinovirus
Rhadinovirus
Rhadinoviruses are a genus of herpesviruses that include the Human herpesvirus 8 , also known as Kaposi's sarcoma-associated herpesvirus , which causes Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman's disease. Other names for the Rhadinovirus genus include Rhadinoviridae...
and the more recently defined genera Macavirus and Percavirus.
Gammaherpesviruses are of primary interest due to the two human viruses, EBV
EBV
EBV may refer to:* Epstein-Barr virus, a virus of the herpes family* EBV infectious mononucleosis, mononucleosis caused by the Epstein-Barr virus* Escuela Bella Vista, an American school located in Maracaibo, Venezuela...
and KSHV
KSHV
KSHV may refer to:* KSHV-TV, a television station licensed to Shreveport, Louisiana, United States* The ICAO airport code for the Shreveport Regional Airport* Kaposi's sarcoma-associated herpesvirus...
and the diseases they cause.The gammaherpesviruses replicate and persist in lymphoid
Lymphoid
Lymphoid is a term used to describe lymph or the lymphatic system.In the context of lymphoid leukemia, it refers specifically to lymphocytes Lymphoid leukemias and lymphomas are now considered to be tumors of the same type of cell lineage. They are called "leukemia" when in the blood or marrow and...
cells but some are capable of undergoing lytic replication in epithelial or fibroblast
Fibroblast
A fibroblast is a type of cell that synthesizes the extracellular matrix and collagen, the structural framework for animal tissues, and plays a critical role in wound healing...
cells.
These viruses can be subdivided into two genera: lymphocryptoviruses (gamma-1) and rhadinoviruses (gamma-2). The lymphocryptoviruses (gamma-1) include Epstein-Barr virus
Epstein-Barr virus
The Epstein–Barr virus , also called human herpesvirus 4 , is a virus of the herpes family and is one of the most common viruses in humans. It is best known as the cause of infectious mononucleosis...
(EBV) or Human herpesvirus 4, Lymphocryptovirus
Lymphocryptovirus
Lymphocryptoviruses are a genus of herpesviruses that include the human Epstein-Barr virus as well as viruses that infect both Old World monkeys and New World monkeys...
of rhesus monkeys and Herpesvirus papio of baboon
Baboon
Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. There are five species, which are some of the largest non-hominoid members of the primate order; only the mandrill and the drill are larger...
s, whereas the rhadinoviruses (gamma-2) include Herpesvirus saimiri (HVS), Kaposi's sarcoma-associated herpesvirus
Kaposi's sarcoma-associated herpesvirus
Kaposi's sarcoma-associated herpesvirus is one of seven currently known human cancer viruses, or oncoviruses. It is also the eighth human herpesvirus; its formal name according to the International Committee on Taxonomy of Viruses is HHV-8. Like other herpesviruses, its informal name is used...
(KSHV) or Human herpesvirus 8, Rhesus monkey rhadinovirus (RRV), Equine herpesvirus 2
Equine herpesvirus 2
Equine herpesvirus 2 is a virus of the family Herpesviridae, originally known as equine cytomegalovirus due to its slow replication in tissue culture. However, complete sequencing of the EHV-2 genome has demonstrated that it is a member of the subfamily Gammaherpesvirinae, in the genus...
and Mouse herpesvirus 68. The gammaherpesviruses, including HVS, EBV, KSHV, and RRV, are capable of establishing latent infection in lymphocytes.
Within this genus there are a number of unclassified viruses including cynomys herpesvirus 1 (CynGHV-1)
Virus Life cycle
The main stages in the lifecycle of Gamma herpes virus are namely• Virus attachment and entry
• Viral DNA injection through nuclear
Nuclear
Nuclear may refer to:* Nuclear DNAIn physics:* Nuclear engineering* Nuclear physics* Nuclear power* Nuclear reactor technology* Nuclear weaponIn mathematics:* Nuclear space* Nuclear operator* Nuclear C*-algebra-See also:...
pore complex (NPC) into nucleus
• Assembly of nucleocapsids and encapsidation of viral genome
• Primary envelopment, invagination
Invagination
Invagination means to fold inward or to sheath. In biology, this can refer to a number of processes.* Invagination is the morphogenetic processes by which an embryo takes form, and is the initial step of gastrulation, the massive reorganization of the embryo from a simple spherical ball of cells,...
s of nuclear membrane(s) and nuclear egress
• Tegumentation and secondary envelopment in the cytoplasm
• Egress
Egress
Egress may refer to:* the act of exiting, and the antonym of ingress* Egress , the right of a person to leave a property* Egress , the passage of electromagnetic fields through the shield of a coaxial cable-See also:...
and extracellularvirions release
Lytic Cycle
The lytic cycle of the gammaherpesviruses is initiated only on rare occasions (Oehmig et al., 2004). Therefore, the least contribution to pathogenicity has to be expected from this stage. The ORFs expressed during that stage are further divided into immediate-early, early, and late.Promoter activation mediated by these proteins has also a strong effect on DNA synthesis from the origins of lytic DNA replication. As a result, virions are generated and released from the productively infected cells.Growth De-regulating genes of Gammaherpesvirus
Herpesviruses have large genomes containing a wide array of genes. Although the first ORFORF
ORF may refer to:* ORF , the Austrian public service broadcaster.* Open reading frame, a portion of the genome.* The IATA airport code for Norfolk International Airport in Norfolk, Virginia.* ORF format , Olympus raw image file format....
in these gammaherpesviruses have oncogenic potential, other viral genes may also play a role in viral transformation
Transformation
-Mathematics:* Transformation * Transformation * Integral transform* Data transformation * Transformation matrix-Natural science:* Phase transformation, a physical transition from one medium to another...
. A striking feature of the four gammaherpesviruses is that they contain distinct ORFs involved in lymphocyte signaling events. At the left end of each viral genome are located ORFs encoding distinct transforming proteins.The Gammaherpes viral genes are capable of modulating cellular signals such that cell proliferation and viral replication occur at the appropriate times in the viral life cycle.
Immune evasion strategies
Viruses that establish lifelong latent infections must ensure that the viral genome is maintained within the latently infected cell throughout the life of the host, yet at the same time must also be capable of avoiding elimination by the immune surveillanceSurveillance
Surveillance is the monitoring of the behavior, activities, or other changing information, usually of people. It is sometimes done in a surreptitious manner...
system especially must avoid being detected by host CD8+ cytotoxic T lymphocytes (CTLs). The gamma-herpesviruses are characteristically latent in lymphocytes and drive the proliferation that requires the expression of latent viral antigens. .The majority of gammaherpesviruses encode a specific protein that is critical for maintenance of the viral genome within latently infected cells termed the genome maintenance protein (GMP). GMPs are DNA-binding proteins that ensures that, as the host cell progresses through itosis, the viral episomes are partitioned to daughter cells. This provides continuous existence of the viral genome within the host cells.