Genetic variability of the envelope gene of Type D simian retrovirus-2 (SRV-2) subtypes associated with SAIDS-related retroperitoneal fibromatosis in different macaque species

Virol J. 2006 Mar 6;3:11. doi: 10.1186/1743-422X-3-11.


Background: D-type simian retrovirus-2 (SRV-2) causes an AIDS-like immune deficiency syndrome (SAIDS) in various macaque species. SAIDS is often accompanied by retroperitoneal fibromatosis (RF), an aggressive fibroproliferative disorder reminiscent of Kaposi's sarcoma in patients with HIV-induced AIDS. In order to determine the association of SRV-2 subtypes with SAIDS-RF, and study the evolution and transmission of SRV-2 in captive macaque populations, we have molecularly characterized the env gene of a number of SRV-2 isolates from different macaque species with and without RF.

Results: We sequenced the env gene from eighteen SRV-2 isolates and performed sequence comparisons and phylogenetic analyses. Our studies revealed the presence of six distinct subtypes of SRV-2, three of which were associated with SAIDS-RF cases. We found no association between SRV-2 subtypes and a particular macaque species. Little sequence variation was detected in SRV-2 isolates from the same individual, even after many years of infection, or from macaques housed together or related by descent from a common infected parent. Seventy-two amino acid changes were identified, most occurring in the larger gp70 surface protein subunit. In contrast to the lentiviruses, none of the amino acid variations involved potential N-linked glycosylation sites. Structural analysis of a domain within the gp22/gp20 transmembrane subunit that was 100% conserved between SRV-2 subtypes, revealed strong similarities to a disulfide-bonded loop that is crucial for virus-cell fusion and is found in retroviruses and filoviruses.

Conclusion: Our study suggests that separate introductions of at least six parental SRV-2 subtypes into the captive macaque populations in the U.S. have occurred with subsequent horizontal transfer between macaque species and primate centers. No specific association of a single SRV-2 subtype with SAIDS-RF was seen. The minimal genetic variability of the env gene within a subtype over time suggests that a strong degree of adaptation to its primate host has occurred during evolution of the virus.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Gene Expression Regulation, Viral
  • Genetic Variation*
  • Macaca / virology*
  • Mason-Pfizer monkey virus / genetics*
  • Mason-Pfizer monkey virus / physiology
  • Molecular Sequence Data
  • Phylogeny
  • Retroperitoneal Fibrosis / complications*
  • Retroperitoneal Fibrosis / virology*
  • Simian Acquired Immunodeficiency Syndrome / complications*
  • Species Specificity
  • Viral Envelope Proteins / chemistry
  • Viral Envelope Proteins / genetics*


  • Viral Envelope Proteins