New Strain of Simian Immunodeficiency Virus Identified in Wild-Born Chimpanzees from Central Africa

Sandrine Souquière,Mirdad Kazanji,Maria Makuwa,Bettina Sallé

doi:10.1371/journal.pone.0044298

Sandrine Souquière, Mirdad Kazanji + Show 2 more

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https://doi.org/10.1371/journal.pone.0044298

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Abstract

Studies of primate lentiviruses continue to provide information about the evolution of simian immunodeficiency viruses (SIVs) and the origin and emergence of HIV since chimpanzees in west–central Africa (Pan troglodytes troglodytes) were recognized as the reservoir of SIVcpzPtt viruses, which have been related phylogenetically to HIV-1. Using in-house peptide ELISAs to study SIV prevalence, we tested 104 wild-born captive chimpanzees from Gabon and Congo. We identified two new cases of SIVcpz infection in Gabon and characterized a new SIVcpz strain, SIVcpzPtt-Gab4. The complete sequence (9093 bp) was obtained by a PCR-based ‘genome walking’ approach to generate 17 overlapping fragments. Phylogenetic analyses of separated genes (gag, pol-vif and env-nef) showed that SIVcpzPtt-Gab4 is closely related to SIVcpzPtt-Gab1 and SIVcpzPtt-Gab2. No significant variation in viral load was observed during 3 years of follow-up, but a significantly lower CD4+ T cells count was found in infected than in uninfected chimpanzees (p<0.05). No clinical symptoms of SIV infection were observed in the SIV-positive chimpanzees. Further field studies with non-invasive methods are needed to determine the prevalence, geographic distribution, species association, and natural history of SIVcpz strains in the chimpanzee habitat in Gabon.

Highlights

Simian immunodeficiency virus (SIV), a member of the Lentivirus genus (Retroviridae), has been isolated from various African nonhuman primates, including Cercopithecidae species and great apes (Pan troglodytes and Gorilla spp.) [1,2]
In 1998, identification of the HIV-1 group N strain which does not belong to HIV-1 group M or O, in Cameroon, provided evidence of a close phylogenetic relation with SIVcpzPtt circulating in the same geographic area [11,12,15]
We examined the phylogenetic relation between the SIVcpzPttGab4 strain and other primate lentiviruses and the relation with SIVcpzPtt-Gab1 and SIVcpzPtt-Gab2 strains, by diversity plot analyses of concatenated nucleotide sequences

Summary

Introduction

Simian immunodeficiency virus (SIV), a member of the Lentivirus genus (Retroviridae), has been isolated from various African nonhuman primates, including Cercopithecidae species and great apes (Pan troglodytes and Gorilla spp.) [1,2]. SIV from chimpanzees (SIVcpz) has been found to be genetically related to human immunodeficiency virus (HIV-1), with the same genomic organization [4], and the strong homology suggested that HIV-1 originated from chimpanzees [5] This hypothesis was strengthened by the identification and characterization of two SIVcpz strains (SIVcpzPtt-Gab and SIVcpzPtt-Gab2) from captive wild-born chimpanzees in Gabon [6,7,8,9] and of one strain (SIVcpzPtt-US) in chimpanzees from an unknown central African country but kept in captivity in the USA [4]. Studies of hundreds of captive wild-born P. troglodytes troglodytes (P.t.t), revealed four SIVcpzPtt strains (SIVcpzPtt-Cam, Cam, Cam and Cam 155) in Cameroon [11,12,13,14] These SIVcpz sequences clustered with SIVcpzPtt-US and SIVcpzPtt-Gab. In 1998, identification of the HIV-1 group N strain which does not belong to HIV-1 group M or O, in Cameroon, provided evidence of a close phylogenetic relation with SIVcpzPtt circulating in the same geographic area [11,12,15]

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