Simian immunodeficiency virus (SIV) from sun-tailed monkeys (Cercopithecus solatus): evidence for host-dependent evolution of SIV within the C. lhoesti superspecies

Abstract

Recently we reported the characterization of simian immunodeficiency virus (SIVlhoest) from a central African l'hoest monkey (Cercopithecus lhoesti lhoesti) that revealed a distant relationship to SIV isolated from a mandrill (SIVmnd). The present report describes a novel SIV (SIVsun) isolated from a healthy, wild-caught sun-tailed monkey (Cercopithecus lhoesti solatus), another member of the l'hoest superspecies. SIVsun replicated in a variety of human T-cell lines and in peripheral blood mononuclear cells of macaques (Macaca spp.) and patas monkeys (Erythrocebus patas). A full-length infectious clone of SIVsun was derived, and genetic analysis revealed that SIVsun was most closely related to SIVlhoest, with an amino acid identity of 71% in Gag, 73% in Pol, and 67% in Env. This degree of similarity is reminiscent of that observed between SIVagm isolates from vervet, grivet, and tantalus species of African green monkeys. The close relationship between SIVsun and SIVlhoest, despite their geographically distinct habitats, is consistent with evolution from a common ancestor, providing further evidence for the ancient nature of the primate lentivirus family. In addition, this observation leads us to suggest that the SIVmnd lineage should be designated the SIVlhoest lineage.

FIG. 1

Infection of PHA-stimulated PBMC from rhesus (Rh), pigtailed (PT), and patas (PatM.) monkeys with uncloned SIVsun (MOI, 0.01). The virus stock was produced on CEMss cells. PBMC were infected for 4 h, washed three times with HBSS, and then resuspended in 3 ml of RPMI complete medium. Cell-free supernatants were taken at regular intervals for the measurement of RT activity combined with a complete exchange of medium.

FIG. 2

RIPA of viral proteins. CEMss cells infected with SIVsun (A) or CEM174 cells infected with SIVsmH4 (B) were labeled overnight with l-[³⁵S]methionine and l-[35³⁵S]cysteine (Amersham), lysed, and precipitated with plasma from different monkeys. α-SIVsun plasma was derived from two separate bleedings of the naturally infected sun-tailed monkey [α-SIVsun(1) and α-SIVsun(2)]; α-SIVlhoest, α-SIVagm, α-SIVsm, and α-SIVmac plasma were collected from experimentally SIV-infected macaques; and α-HIV-1 and α-HIV-2 plasma originated from infected humans.

FIG. 3

Diversity plots. (A) Plots comparing SIVsun with representatives of the five major lineages of primate lentiviruses, i.e., SIVlhoest, SIVmnd, SIVsyk, SIVagm(Ver), SIVsm(PBj), and SIVcpz(Gab). (B) Plots comparing SIVsun with SIVlhoest, SIVsun with SIVmnd, SIVlhoest with SIVmnd, and SIVagm(Gri) with SIVagm(Ver). The protein sequence difference is plotted for windows of 200 amino acids moved in steps of 10.

FIG. 4

Phylogenetic relationship of SIVsun (boxed) to other primate lentiviruses. The tree was derived by the maximum-likelihood analysis of a concatenated Gag-Pol-Vif-Env-Nef protein alignment (see the text for details). A tree derived by neighbor-joining analysis differed in no significant way. Stars indicate that the clade to the right was found in 100% of bootstrap replicates of the neighbor-joining analysis. Horizontal branch lengths are drawn to scale, with the bar indicating 0.1 amino acid replacement per site.

FIG. 5

Comparison of the predicted protein sequence of the surface subunit of the envelope of SIVsun, SIVlhoest, and SIVmnd reveals remarkable conservation of cysteine residues and regions such as the V3 loop homolog and the CD4 binding. Conserved cysteines are boxed. Potential N-linked glycosylation sites are underlined. The predicted sequence of gp120 of SIVsunλ20L14/S2 molecular clone is shown at the top. Substitutions relative to this sequence in the predicted sequence of gp120 of SIVlhoest and SIVmnd are aligned below. Dots indicate amino acid identity at a residue, and dashes indicate gaps introduced to optimize alignment. Variable regions analogous to those observed in HIV-1 and other SIVs are indicated, and the cleavage site for the transmembrane glycoprotein (TM) is shown.

FIG. 6

Schematic views of Africa showing the ranges occupied by l’hoest monkeys (C. lhoest lhoesti) and their close relatives, Preuss’s monkeys (C. lhoest preussi), and sun-tailed monkeys (C. lhoesti solatus) (the distribution of mandrills [Mandrillus sphinx] is indicated by cross-hatching) (A) and the geographic distribution of the four African green monkey species, i.e., the grivet (C. aethiops), tantalus (C. tantalus), vervet (C. pygerythrus), and sabaeus monkeys (C. sabaeus) (B) (44).