title: Factors associated with siman immunodeficiency virus transmission in a natural African nonhuman primate host in the wild.
abstract: African green monkeys (AGMs) are naturally infected with simian immunodeficiency virus (SIV) at high prevalence levels and do not progress to AIDS. Sexual transmission is the main transmission route in AGM, while mother-to-infant transmission (MTIT) is negligible. We investigated SIV transmission in wild AGMs to assess whether or not high SIV prevalence is due to differences in mucosal permissivity to SIV (i.e., whether the genetic bottleneck of viral transmission reported in humans and macaques is also observed in AGMs in the wild). We tested 121 sabaeus AGMs (Chlorocebus sabaeus) from the Gambia and found that 53 were SIV infected (44%). By combining serology and viral load quantitation, we identified 4 acutely infected AGMs, in which we assessed the diversity of the quasispecies by single-genome amplification (SGA) and documented that a single virus variant established the infections. We thus show that natural SIV transmission in the wild is associated with a genetic bottleneck similar to that described for mucosal human immunodeficiency virus (HIV) transmission in humans. Flow cytometry assessment of the immune cell populations did not identify major differences between infected and uninfected AGM. The expression of the SIV coreceptor CCR5 on CD4+ T cells dramatically increased in adults, being higher in infected than in uninfected infant and juvenile AGMs. Thus, the limited SIV MTIT in natural hosts appears to be due to low target cell availability in newborns and infants, which supports HIV MTIT prevention strategies aimed at limiting the target cells at mucosal sites. Combined, (i) the extremely high prevalence in sexually active AGMs, (ii) the very efficient SIV transmission in the wild, and (iii) the existence of a fraction of multiparous females that remain uninfected in spite of massive exposure to SIV identify wild AGMs as an acceptable model of exposed, uninfected individuals.
  
  
  OBJECTIVE
  We report an extensive analysis of the natural history of SIVagm infection in its sabaeus monkey host, the African green monkey species endemic to West Africa. Virtually no study has investigated the natural history of SIV infection in the wild. The novelty of our approach is that we report for the first time that SIV infection has no discernible impact on the major immune cell populations in natural hosts, thus confirming the nonpathogenic nature of SIV infection in the wild. We also focused on the correlates of SIV transmission, and we report, also for the first time, that SIV transmission in the wild is characterized by a major genetic bottleneck, similar to that described for HIV-1 transmission in humans. Finally, we report here that the restriction of target cell availability is a major correlate of the lack of SIV transmission to the offspring in natural hosts of SIVs.
authors.affiliation: Center for Vaccine Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Dongzhu
authors.initials: D
authors.lastname: Ma
authors.forename: Anna J
authors.initials: AJ
authors.lastname: Jasinska
authors.forename: Felix
authors.initials: F
authors.lastname: Feyertag
authors.forename: Viskam
authors.initials: V
authors.lastname: Wijewardana
authors.forename: Jan
authors.initials: J
authors.lastname: Kristoff
authors.forename: Tianyu
authors.initials: T
authors.lastname: He
authors.forename: Kevin
authors.initials: K
authors.lastname: Raehtz
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Schmitt
authors.forename: Yoon
authors.initials: Y
authors.lastname: Jung
authors.forename: Jennifer Danzy
authors.initials: JD
authors.lastname: Cramer
authors.forename: Michel
authors.initials: M
authors.lastname: Dione
authors.forename: Martin
authors.initials: M
authors.lastname: Antonio
authors.forename: Russell
authors.initials: R
authors.lastname: Tracy
authors.forename: Trudy
authors.initials: T
authors.lastname: Turner
authors.forename: David L
authors.initials: DL
authors.lastname: Robertson
authors.forename: Ivona
authors.initials: I
authors.lastname: Pandrea
authors.forename: Nelson
authors.initials: N
authors.lastname: Freimer
authors.forename: Cristian
authors.initials: C
authors.lastname: Apetrei
mesh_terms: D000818:Animals; D002522:Chlorocebus aethiops; D016000:Cluster Analysis; D005260:Female; D005434:Flow Cytometry; D005714:Gambia; D005838:Genotype; D016180:Lentivirus Infections / Q000276:immunology / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D016131:Lymphocyte Subsets / Q000276:immunology; D008297:Male; D008969:Molecular Sequence Data; D008992:Monkey Diseases / Q000635:transmission* / Q000821:virology*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D015302:Simian Immunodeficiency Virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*