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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.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.

SUBMITTER: Ma D

PROVIDER: S-EPMC4019088 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Factors associated with siman immunodeficiency virus transmission in a natural African nonhuman primate host in the wild.

Ma Dongzhu D Jasinska Anna J AJ Feyertag Felix F Wijewardana Viskam V Kristoff Jan J He Tianyu T Raehtz Kevin K Schmitt Christopher A CA Jung Yoon Y Cramer Jennifer Danzy JD Dione Michel M Antonio Martin M Tracy Russell R Turner Trudy T Robertson David L DL Pandrea Ivona I Freimer Nelson N Apetrei Cristian C

Journal of virology 20140312 10

<h4>Unlabelled</h4>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 ...[more]

PMID: 24623416

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Project description:Comprehensive assessments of immune correlates of protection in human immunodeficiency virus (HIV) vaccine trials are essential to vaccine design. Neutralization sieve analysis compares the neutralization sensitivity of the breakthrough transmitted/founder (TF) viruses from vaccinated and control animals to infer the molecular mechanisms of vaccine protection. Here, we report a robust neutralization sieve effect in a nonhuman primate simian immunodeficiency virus (SIV) vaccine trial (DNA prime/recombinant adenovirus type 5 [rAd5] boost) (VRC-10-332) that demonstrated substantial protective efficacy and revealed a genetic signature of neutralization resistance in the C1 region of env. We found significant enrichment for neutralization resistance in the vaccine compared to control breakthrough TF viruses when tested with plasma from vaccinated study animals, plasma from chronically SIV-infected animals, and a panel of SIV-specific monoclonal antibodies targeting six discrete Env epitopes (P < 0.008 for all comparisons). Neutralization resistance was significantly associated with the previously identified genetic signature of resistance (P < 0.0001), and together, the results identify virus neutralization as a correlate of protection. These findings further demonstrate the in vivo relevance of our previous in vitro analyses of the SIVsmE660 challenge stock, which revealed a broad range of neutralization sensitivities of its component viruses. In sum, this report demonstrates proof-of-concept that phenotypic sieve analyses can elucidate mechanistic correlates of immune protection following vaccination and raises a cautionary note for SIV and SHIV (simian-human immunodeficiency virus) vaccine studies that employ challenge strains with envelope glycoproteins that fail to exhibit neutralization resistance profiles typical of TF viruses.With more than 2 million new infections annually, the development of an effective vaccine against HIV-1 is a global health priority. Understanding immunologic correlates of protection generated in vaccine trials is critical to advance vaccine development. Here, we assessed the role of vaccine-elicited neutralizing antibodies in a recent nonhuman primate study of a vaccine that showed significant protection against simian immunodeficiency virus (SIV) challenge and suggested a genetic signature of neutralization sensitivity. We found that breakthrough viruses able to establish infection in vaccinated animals were substantially more resistant to antibody-mediated neutralization than were viruses from controls. These findings suggest that vaccine-elicited neutralizing antibodies selectively blocked the transmission of more sensitive challenge viruses. Sieve analysis also corroborated a genetic signature of neutralization sensitivity and highlighted the impact of challenge swarm diversity. Our findings suggest an important role for neutralization sieve analyses as an informative component of comprehensive immune-correlates analyses.

Dataset Information

Factors associated with siman immunodeficiency virus transmission in a natural African nonhuman primate host in the wild.

Publications

Factors associated with siman immunodeficiency virus transmission in a natural African nonhuman primate host in the wild.

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