Molecular epidemiology of simian immunodeficiency virus SIVsm in U.S. primate centers unravels the origin of SIVmac and SIVstm

Simian immunodeficiency virus infection in free-ranging sooty mangabeys (Cercocebus atys atys) from the Taï Forest, Côte d'Ivoire: implications for the origin of epidemic human immunodeficiency virus type 2

Simian immunodeficiency virus of sooty mangabeys (SIVsmm) is recognized as the progenitor of human immunodeficiency virus type 2 (HIV-2) and has been transmitted to humans on multiple occasions, yet the epidemiology and genetic diversity of SIVsmm infection in wild-living populations remain largely unknown. Here, we report the first molecular epidemiological survey of SIVsmm in a community of approximately 120 free-ranging sooty mangabeys in the Taï Forest, Côte d'Ivoire. Fecal samples (n = 39) were collected from 35 habituated animals (27 females and 8 males) and tested for SIVsmm virion RNA (vRNA). Viral gag (800 bp) and/or env (490 bp) sequences were amplified from 11 different individuals (eight females and three males). Based on the sensitivity of fecal vRNA detection and the numbers of samples analyzed, the prevalence of SIVsmm infection was estimated to be 59% (95% confidence interval, 0.35 to 0.88). Behavioral data collected from this community indicated that SIVsmm infection occurred preferentially in high-ranking females. Phylogenetic analysis of gag and env sequences revealed an extraordinary degree of genetic diversity, including evidence for frequent recombination events in both the recent and distant past. Some sooty mangabeys harbored near-identical viruses (<2% interstrain distance), indicating epidemiologically linked infections. These transmissions were identified by microsatellite analyses to involve both related (mother/daughter) and unrelated individuals, thus providing evidence for vertical and horizontal transmission in the wild. Finally, evolutionary tree analyses revealed significant clustering of the Taï SIVsmm strains with five of the eight recognized groups of HIV-2, including the epidemic groups A and B, thus pointing to a likely geographic origin of these human infections in the eastern part of the sooty mangabey range.

Control of viral infectivity by tripartite motif proteins

It is of great interest to understand the molecular details of the pathways that constitute species barriers to viral infection. The tripartite motif protein TRIM5alpha has emerged as an important mediator of species-specific retroviral replication and innate immunity. This review considers the role of TRIM5alpha as an antiviral protein in mammals. The methods used to identify species-specific restriction to retroviral infection, and the identification of TRIM5alpha itself, are outlined. TRIM5alpha mediates an early postentry block to sensitive retroviral infection, usually before viral DNA synthesis. Results from mutational analysis of TRIM5alpha and their contribution to a mechanistic model for TRIM5alpha antiviral activity are discussed. The antiviral role of other TRIM proteins is considered, as is the role of TRIM5alpha cytoplasmic bodies.