Simian retrovirus

Simian retrovirus (SRV) is a species of retroviruses that usually infect and cause a fatal immune deficiency in Asian macaques.^[1] This virus appears sporadically in captive macaques at breeding facilities which expected as the natural host, but prevalence of this virus in feral macaques remain unknown.^[2] SRV was transmitted naturally by virus-containing body fluids (saliva, urine, blood, etc.), via biting or scratching. Contaminated instrument or equipment (fomite) can also spread this virus among animals.

Some clinical and pathological symptoms of SRV-infected macaques are diarrhea, weight loss, splenomegaly, lymphadenopahty, anemia, neutropenia, neoplastic diseases (retroperitonial fibromatosis or rare B-cell lymphomas). To prevent the infection of this virus, two vaccinations have been developed. Those two effective vaccinations are formalin-inactivated whole SRV-1 vaccine and recombinant vaccine expressing SRV envelope glycoprotein gp70 and gp 22.^[1]

History

Until 2006, six types of SRVs have been identified. The original prototype of SRV is Mason-Pfizer monkey virus (MPMV), which derived from breast tumor tissue of a rhesus macaque (Macaca mulatta) in 1970. This prototype virus now belongs to SRV serotype-3 group. SRV-1 serotype was identified in early 1980s in rhesus macaque, M. cyclopis, and M. fascicularis at National Primate Research Center (NPRC), California and New England. The SRV serotype-2 was found in endemic infections of pig-tailed monkey (M. nemestrina), cynomolgus macaques, Japanese macaque (M. fuscata), at Washington NPRC, and in rhesus and Celebes black macaques (M. nigra) at Oregon NPRC.^[3] SRV-3 is present at Wisconsin Primate Center, while SRV-4 and SRV-5 have been identified at University of California and Beijing Primate Center. In 2010, a Japanese research group reported two SRV isolates from seropositive cynomolgus macaques and tentatively designated them as SRV/D-Tsukuba (SRV/D-T).^[1]

In 2011, players of Foldit helped to decipher the crystal structure of the Mason-Pfizer monkey virus (M-PMV) retroviral protease, an AIDS-causing monkey virus. While the puzzle was available to play for a period of three weeks, players produced an accurate 3D model of the enzyme in just ten days. The problem of how to configure the structure of the enzyme had stumped scientists for 15 years.

Morphology and genetic structure

SRV is an enveloped RNA retrovirus with icosahedral capsid. The extracellular mature particles are about 125 nm in diameter, while the nucleoid and core shell are central cylindrical structures separated by a space of about 8-10 nm. This virus utilize a glycoprotein-lipid bilayer from host cell membrane to perform budding process in the end of its replication cycles.

The SRV genome contains four genes: 5'-gag-prt-pol-env-3'. Gag encodes group-specific antigen, Prt for protease, Pol responsible for RNA-dependent DNA polimerase (reverse-transcriptase) region, and Env encodes the envelope glycoprotein. Same with all restroviruses, SRV is able to transcribe its own RNA genome into double-stranded DNA by using reverse transcriptase enzyme(Mg+2 dependent for betaretroviruses).

References

External Links

• "Simian retrovirus 1". NCBI Taxonomy Browser. 11942.