Nonpathogenic SIV and Pathogenic HIV Infections Associate with Disparate Innate Cytokine Signatures in Response to Mycobacterium bovis BCG.

Infections with mycobacteria, including Mycobacterium tuberculosis (Mtb) and Mycobacterium bovis (M. bovis) BCG, are a leading cause of morbidity and mortality for HIV-infected persons. In contrast to HIV, nonpathogenic SIV infections of sooty mangabeys are characterized by a lack of clinical disease including an absence of opportunistic infections. The goal of this study was to identify innate immune responses to M. bovis BCG maintained during nonpathogenic lentiviral infections through a comparison of functional responses during pathogenic HIV or nonpathogenic SIV infections. Monocytes were evaluated for their ability to express key anti-mycobacterial cytokines TNF-α and IL-12 following a six-hour ex vivo BCG exposure. While HIV-infection was associated with a decreased percentage of IL-12-producing monocytes, nonpathogenic SIV-infection was associated with an increased percentage of monocytes producing both cytokines. Gene expression analysis of PBMC following ex vivo BCG exposure identified differential expression of NK cell-related genes and several cytokines, including IFN-γ and IL-23, between HIV-infected and control subjects. In contrast, SIV-infected and uninfected-control mangabeys exhibited no significant differences in gene expression after BCG exposure. Finally, differential gene expression patterns were identified between species, with mangabeys exhibiting lower IL-6 and higher IL-17 in response to BCG when compared to humans. Overall, this comparison of immune responses to M. bovis BCG identified unique immune signatures (involving cytokines IL-12, TNF-α, IL-23, IL-17, and IL-6) that are altered during HIV, but maintained or increased during nonpathogenic SIV infections. These unique cytokine and transcriptome signatures provide insight into the differential immune responses to Mycobacteria during pathogenic HIV-infection that may be associated with an increased incidence of mycobacterial co-infections.

High rates of infection with novel enterovirus variants in wild populations of mandrills and other old world monkey species.

UNLABELLED: Enteroviruses (EVs) are a genetically and antigenically diverse group of viruses infecting humans. A mostly distinct set of EV variants have additionally been documented to infect wild apes and several, primarily captive, Old World monkey (OWM) species. To investigate the prevalence and genetic characteristics of EVs infecting OWMs in the wild, fecal samples from mandrills (Mandrillus sphinx) and other species collected in remote regions of southern Cameroon were screened for EV RNA. Remarkably high rates of EV positivity were detected in M. sphinx (100 of 102 screened), Cercocebus torquatus (7/7), and Cercopithecus cephus (2/4), with high viral loads indicative of active infection. Genetic characterization in VP4/VP2 and VP1 regions allowed EV variants to be assigned to simian species H (EV-H) and EV-J (including one or more new types), while seven matched simian EV-B variants, SA5 and EV110 (chimpanzee). Sequences from the remaining 70 formed a new genetic group distinct in VP4/2 and VP1 region from all currently recognized human or simian EV species. Complete genome sequences were obtained from three to determine their species assignment. In common with EV-J and the EV-A A13 isolate, new group sequences were chimeric, being most closely related to EV-A in capsid genes and to EV-B in the nonstructural gene region. Further recombination events created different groupings in 5' and 3' untranslated regions. While clearly a distinct EV group, the hybrid nature of new variants prevented their unambiguous classification as either members of a new species or as divergent members of EV-A using current International Committee on Taxonomy of Viruses (ICTV) assignment criteria. IMPORTANCE: This study is the first large-scale investigation of the frequency of infection and diversity of enteroviruses (EVs) infecting monkeys (primarily mandrills) in the wild. Our findings demonstrate extremely high frequencies of active infection (95%) among mandrills and other Old World monkey species inhabiting remote regions of Cameroon without human contact. EV variants detected were distinct from those infecting human populations, comprising members of enterovirus species B, J, and H and a large novel group of viruses most closely related to species A in the P1 region. The viral sequences obtained contribute substantially to our growing understanding of the genetic diversity of EVs and the existence of interspecies chimerism that characterizes the novel variants in the current study, as well as in previously characterized species A and J viruses infecting monkeys. The latter findings will contribute to future development of consensus criteria for species assignments in enteroviruses and other picornavirus genera.

Link between primate lentiviral coreceptor usage and Nef function.

Simian immunodeficiency virus (SIVsmm) infection of sooty mangabeys (Cercocebus atys) is characterized by stable CD4(+) T cell counts despite high plasma levels of CCR5-tropic viruses. However, in rare instances, SIVsmm acquires CXCR4 coreceptor tropism and causes severe CD4(+) T cell depletion, albeit without clinical signs of immunodeficiency. Here, we show that CXCR4-tropic SIVsmm strains lost their ability to downmodulate TCR-CD3 by evolving unusual Nef mutations that initially reduced (I132V) and subsequently disrupted (I123L and L146F) interaction with the CD3 ζ chain. This coevolution of Env and Nef function suggests that CD3 downmodulation is advantageous for viral replication in activated CCR5(+) memory T cells, but not in resting naive CXCR4(+) T cells that have not yet undergone TCR-CD3-mediated stimulation. This may explain why HIV-1, which generally lacks the CD3 downmodulation function, commonly switches to CXCR4 usage, whereas this is extremely rare for SIV strains that have retained this Nef activity.

Coagulation biomarkers predict disease progression in SIV-infected nonhuman primates.

HIV infection is associated with increased risk of cardiovascular complications, the underlying mechanism of which remains unclear. Plasma levels of the coagulation biomarker D-dimer (DD) correlate with increased mortality and cardiovascular events in HIV-infected patients. We compared the incidence of cardiovascular lesions and the levels of the coagulation markers DD and thrombin antithrombin in pathogenic SIV infections of rhesus and pigtailed macaques (PTMs) and in nonpathogenic SIV infection of African green monkeys (AGMs) and sooty mangabeys. Hypercoagulability and cardiovascular pathology were only observed in pathogenic SIV infections. In PTMs infected with SIV from AGMs (SIVagm), DD levels were highly indicative of AIDS progression and increased mortality and were associated with cardiovascular lesions, pointing to SIVagm-infected PTMs as an ideal animal model for the study of HIV-associated cardiovascular disease. In pathogenic SIV infection, DD increased early after infection, was strongly correlated with markers of immune activation/inflammation and microbial translocation (MT), and was only peripherally associated with viral loads. Endotoxin administration to SIVagm-infected AGMs (which lack chronic SIV-induced MT and immune activation) resulted in significant increases of DD. Our results demonstrate that hypercoagulation and cardiovascular pathology are at least in part a consequence of excessive immune activation and MT in SIV infection.

Full-length genome sequence of a simian immunodeficiency virus (SIV) infecting a captive agile mangabey (Cercocebus agilis) is closely related to SIVrcm infecting wild red-capped mangabeys (Cercocebus torquatus) in Cameroon.

Simian immunodeficiency viruses (SIVs) are lentiviruses that infect an extensive number of wild African primate species. Here we describe for the first time SIV infection in a captive agile mangabey (Cercocebus agilis) from Cameroon. Phylogenetic analysis of the full-length genome sequence of SIVagi-00CM312 showed that this novel virus fell into the SIVrcm lineage and was most closely related to a newly characterized SIVrcm strain (SIVrcm-02CM8081) from a wild-caught red-capped mangabey (Cercocebus torquatus) from Cameroon. In contrast to red-capped mangabeys, no 24 bp deletion in CCR5 has been observed in the agile mangabey. Further studies on wild agile mangabeys are needed to determine whether agile and red-capped mangabeys are naturally infected with the same SIV lineage, or whether this agile mangabey became infected with an SIVrcm strain in captivity. However, our study shows that agile mangabeys are susceptible to SIV infection.

A novel simian immunodeficiency virus from black mangabey (Lophocebus aterrimus) in the Democratic Republic of Congo.

In order to understand primate lentivirus evolution, characterization of additional simian immunodeficiency virus (SIV) strains is essential. Here, an SIV from a black mangabey (Lophocebus aterrimus) originating from the Democratic Republic of Congo was analysed phylogenetically. The monkey had cross-reactive antibodies against human immunodeficiency virus type 1 (HIV-1) and HIV-2. The viral pol region sequence was amplified by nested PCR and sequence analysis confirmed that it was related to known SIV sequences. This is the first report to characterize genetically an SIV from the monkey genus Lophocebus. Phylogenetic analysis of the pol region revealed that this novel SIV, designated SIVbkm, fell into the SIVsyk and SIVgsn virus group, containing viruses isolated from the genus Cercopithecus, and suggests that cross-species transmission has occurred between species of the genera Lophocebus and Cercopithecus.

Molecular epidemiology of simian T-cell lymphotropic virus type 1 in wild and captive sooty mangabeys.

A study was conducted to evaluate the prevalence and diversity of simian T-cell lymphotropic virus (STLV) isolates within the long-established Tulane National Primate Research Center (TNPRC) colony of sooty mangabeys (SMs; Cercocebus atys). Serological analysis determined that 22 of 39 animals (56%) were positive for STLV type 1 (STLV-1). A second group of thirteen SM bush meat samples from Sierra Leone in Africa was also included and tested only by PCR. Twenty-two of 39 captive animals (56%) and 3 of 13 bush meat samples (23%) were positive for STLV-1, as shown by testing with PCR. Nucleotide sequencing and phylogenetic analysis of viral strains obtained demonstrated that STLV-1 strains from SMs (STLV-1sm strains) from the TNPRC colony and Sierra Leone formed a single cluster together with the previously reported STLV-1sm strain from the Yerkes National Primate Research Center. These data confirm that Africa is the origin for TNPRC STLV-1sm and suggest that Sierra Leone is the origin for the SM colonies in the United States. The TNPRC STLV-1sm strains further divided into two subclusters, suggesting STLV-1sm infection of two original founder SMs at the time of their importation into the United States. STLV-1sm diversity in the TNPRC colony matches the high diversity of SIVsm in the already reported colony. The lack of correlation between the lineage of the simian immunodeficiency virus from SMs (SIVsm) and the STLV-1sm subcluster distribution of the TNPRC strains suggests that intracolony transmissions of both viruses were independent events.

Direct inoculation of simian immunodeficiency virus from sooty mangabeys in black mangabeys (Lophocebus aterrimus): first evidence of AIDS in a heterologous African species and different pathologic outcomes of experimental infection.

A unique opportunity for the study of the role of serial passage and cross-species transmission was offered by a series of experiments carried out at the Tulane National Primate Research Center in 1990. To develop an animal model for leprosy, three black mangabeys (BkMs) (Lophocebus aterrimus) were inoculated with lepromatous tissue that had been serially passaged in four sooty mangabeys (SMs) (Cercocebus atys). All three BkMs became infected with simian immunodeficiency virus from SMs (SIVsm) by day 30 postinoculation (p.i.) with lepromatous tissue. One (BkMG140) died 2 years p.i. from causes unrelated to SIV, one (BkMG139) survived for 10 years, whereas the third (BkMG138) was euthanized with AIDS after 5 years. Histopathology revealed a high number of giant cells in tissues from BkMG138, but no SIV-related lesions were found in the remaining two BkMs. Four-color immunofluorescence revealed high levels of SIVsm associated with both giant cells and T lymphocytes in BkMG138 and no detectable SIV in the remaining two. Serum viral load (VL) showed a significant increase (>1 log) during the late stage of the disease in BkMG138, as opposed to a continuous decline in VL in the remaining two BkMs. With the progression to AIDS, neopterin levels increased in BkMG138. This study took on new significance when phylogenetic analysis unexpectedly showed that all four serially inoculated SMs were infected with different SIVsm lineages prior to the beginning of the experiment. Furthermore, the strain infecting the BkMs originated from the last SM in the series. Therefore, the virus infecting BkMs has not been serially passaged. In conclusion, we present the first compelling evidence that direct cross-species transmission of SIV may induce AIDS in heterologous African nonhuman primate (NHP) species. The results showed that cross-species-transmitted SIVsm was well controlled in two of three BkMs for 2 and 10 years, respectively. Finally, this case of AIDS in an African monkey suggests that the dogma of SIV nonpathogenicity in African NHP hosts should be reconsidered.

Simian T-cell leukemia virus (STLV) infection in wild primate populations in Cameroon: evidence for dual STLV type 1 and type 3 infection in agile mangabeys (Cercocebus agilis).

Three types of human T-cell leukemia virus (HTLV)-simian T-cell leukemia virus (STLV) (collectively called primate T-cell leukemia viruses [PTLVs]) have been characterized, with evidence for zoonotic origin from primates for HTLV type 1 (HTLV-1) and HTLV-2 in Africa. To assess human exposure to STLVs in western Central Africa, we screened for STLV infection in primates hunted in the rain forests of Cameroon. Blood was obtained from 524 animals representing 18 different species. All the animals were wild caught between 1999 and 2002; 328 animals were sampled as bush meat and 196 were pets. Overall, 59 (11.2%) of the primates had antibodies cross-reacting with HTLV-1 and/or HTLV-2 antigens; HTLV-1 infection was confirmed in 37 animals, HTLV-2 infection was confirmed in 9, dual HTLV-1 and HTLV-2 infection was confirmed in 10, and results for 3 animals were indeterminate. Prevalences of infection were significantly lower in pets than in bush meat, 1.5 versus 17.0%, respectively. Discriminatory PCRs identified STLV-1, STLV-3, and STLV-1 and STLV-3 in HTLV-1-, HTLV-2-, and HTLV-1- and HTLV-2-cross-reactive samples, respectively. We identified for the first time STLV-1 sequences in mustached monkeys (Cercopithecus cephus), talapoins (Miopithecus ogouensis), and gorillas (Gorilla gorilla) and confirmed STLV-1 infection in mandrills, African green monkeys, agile mangabeys, and crested mona and greater spot-nosed monkeys. STLV-1 long terminal repeat (LTR) and env sequences revealed that the strains belonged to different PTLV-1 subtypes. A high prevalence of PTLV infection was observed among agile mangabeys (Cercocebus agilis); 89% of bush meat was infected with STLV. Cocirculation of STLV-1 and STLV-3 and STLV-1-STLV-3 coinfections were identified among the agile mangabeys. Phylogenetic analyses of partial LTR sequences indicated that the agile mangabey STLV-3 strains were more related to the STLV-3 CTO604 strain isolated from a red-capped mangabey (Cercocebus torquatus) from Cameroon than to the STLV-3 PH969 strain from an Eritrean baboon or the PPA-F3 strain from a baboon in Senegal. Our study documents for the first time that (i) a substantial proportion of wild-living monkeys in Cameroon is STLV infected, (ii) STLV-1 and STLV-3 cocirculate in the same primate species, (iii) coinfection with STLV-1 and STLV-3 occurs in agile mangabeys, and (iv) humans are exposed to different STLV-1 and STLV-3 subtypes through handling primates as bush meat.

A novel, divergent simian T-cell lymphotropic virus type 3 in a wild-caught red-capped mangabey (Cercocebus torquatus torquatus) from Nigeria.

We present here a novel, distinct simian T-cell lymphotropic virus (STLV) found in a red-capped mangabey (Cercocebus torquatus) (CTO-NG409), wild-caught in Nigeria, that showed an HTLV-2-like Western blot (WB) seroreactivity. The complete genome (8920 bp) of CTO-NG409 STLV was related to but different from STLV-3/PHA-PH969 (13.5 %) and STLV-3/PPA-F3 (7.6 %), and STLV-3/CTO604 (11.3 %), found in Eritrean and Senegalese baboons, and red-capped mangabeys from Cameroon, respectively. Phylogenetic analysis of a conserved tax (180 bp) sequence and the env gene (1482 bp) confirmed the relatedness of STLV-3/CTO-NG409 to the STLV-3 subgroup. Molecular clock analysis of env estimated that STLV-3/CTO-NG409 diverged from East and West/Central African STLV-3s about 140,900+/-12,400 years ago, suggesting an ancient African origin of STLV-3. Since phylogenetic evidence suggests multiple interspecies transmissions of STLV-1 to humans, and given the antiquity and wide distribution of STLV-3 in Africa, a search for STLV-3 in human African populations with HTLV-2-like WB patterns is warranted.

Divergent simian T-cell lymphotropic virus type 3 (STLV-3) in wild-caught Papio hamadryas papio from Senegal: widespread distribution of STLV-3 in Africa.

Among eight samples obtained from a French primatology research center, six adult guinea baboons (Papio hamadryas papio), caught in the wild in Senegal, had a peculiar human T-cell leukemia virus type 2 (HTLV-2)-like Western blot seroreactivity (p24(+), GD21(+), K55(+/-)). Partial sequence analyses of the tax genes (433 bp) indicated that these baboons were infected by a novel divergent simian T-cell lymphotropic virus (STLV). Analyses of the complete proviral sequence (8,892 bp) for one of these strains (STLV-3/PPA-F3) indicate that this STLV was highly divergent from the HTLV-1 (61.6% of nucleotide similarity), HTLV-2 (61.2%), or STLV-2 (60.6%) prototype. It was, however, much more closely related to the few other known STLV-3 strains, exhibiting 87 and 89% of nucleotide similarity with STLV-3/PHA-PH969 (formerly PTLV-L/PH969) and STLV-3/CTO-604, respectively. The STLV-3/PPA-F3 sequence possesses the major HTLV or STLV open reading frames corresponding to the structural, enzymatic, and regulatory proteins. However, its long terminal repeat comprises only two 21-bp repeats. In all phylogenetic analyses, STLV-3/PPA-F3 clustered together in a highly supported single clade with the other known strains of STLV-3, indicating an independent evolution from primate T-cell lymphotropic virus type 1 (PTLV-1) and PTLV-2. The finding of a new strain of STLV-3 in a West African monkey (Guinea baboon) greatly enlarges the geographical distribution and the host range of species infected by this PTLV type in the African continent. The recent discovery of several different STLV-3 strains in many different African monkey species, often in contact with humans, strongly suggests potential interspecies transmission events, as it was described for STLV-1, between nonhuman primates but also to humans.

Complete sequence of a novel highly divergent simian T-cell lymphotropic virus from wild-caught red-capped mangabeys (Cercocebus torquatus) from Cameroon: a new primate T-lymphotropic virus type 3 subtype.

Among 65 samples obtained from a primate rescue center located in Cameroon, two female adult red-capped mangabeys (Cercocebus torquatus) (CTO-602 and CTO-604), of wild-caught origin, had a peculiar human T-cell lymphotropic virus type 2 (HTLV-2)-like Western blot seroreactivity (p24, RGD21, +/-K55). Analyses of the simian T-cell lymphotropic virus type 3 (STLV-3)/CTO-604 complete proviral sequence (8,919 bp) indicated that this novel strain was highly divergent from HTLV-1 (60% nucleotide similarity), HTLV-2 (62%), or STLV-2 (62%) prototypes. It was, however, related to STLV-3/PH-969 (87%), a divergent STLV strain previously isolated from an Eritrean baboon. The STLV-3/CTO-604 sequence possesses the major open reading frames corresponding to the structural, enzymatic, and regulatory proteins. However, its long terminal repeat is shorter, with only two 21-bp repeats. Furthermore, as demonstrated by reverse transcriptase PCR, this new STLV exhibits significant differences from STLV-3/PH-969 at the mRNA splice junction position level. In all phylogenetic analyses, STLV-3/CTO-604 and STLV-3/PH-969 clustered in a highly supported single clade, indicating an evolutionary lineage independent from primate T-lymphotropic virus type 1 (PTLV-1) and PTLV-2. Nevertheless, the nucleotide divergence between STLV-3/PH-969 and STLV-3/CTO-604 is equivalent to or higher than the divergence observed between the different HTLV-1 or HTLV-2 subtypes. Thus, the STLV-3/CTO-604 strain can be considered the prototype of a second subtype in the PTLV-3 type. The presence of two related viruses in evolutionarily distantly related African monkeys species, living in two opposite ecosystems (rain forest versus desert), reinforces the possible African origin of PTLV and opens new avenues regarding the search for a possible human counterpart of these viruses in individuals exhibiting such HTLV-2-like seroreactivities.

Molecular epidemiology of simian T-lymphotropic virus (STLV) in wild-caught monkeys and apes from Cameroon: a new STLV-1, related to human T-lymphotropic virus subtype F, in a Cercocebus agilis.

A serological survey for human T-lymphotropic virus (HTLV)/simian T-lymphotropic virus (STLV) antibodies was performed in 102 wild-caught monkeys and apes from 15 (sub)species originating from Cameroon. Two animals (a Mandrillus sphinx and a Cercocebus agilis) exhibited a complete HTLV-1 seroreactivity pattern while two others lacked either the p24 (a Mandrillus sphinx) or the MTA-1/gp46 bands (a Pan troglodytes). Sequence comparison and phylogenetic analyses, using a 522 bp env gene fragment and the complete LTR, indicated that the two mandrill STLV strains belonged to the HTLV/STLV subtype D clade while the chimpanzee strain clustered in the HTLV/STLV subtype B clade. The Cercocebus agilis STLV strain, the first one found in this species, was closely related to the two HTLV/STLV subtype F strains. Such data indicate that the African biodiversity of STLV-1 in the wild is far from being known and reinforces the hypothesis of interspecies transmission of STLV-1 from monkeys and apes to humans leading to the present day distribution of HTLV-1 in African inhabitants.

Characterization of novel simian immunodeficiency viruses from red-capped mangabeys from Nigeria (SIVrcmNG409 and -NG411).

Two novel simian immunodeficiency virus (SIV) strains from wild-caught red-capped mangabeys (Cercocebus torquatus torquatus) from Nigeria were characterized. Sequence analysis of the fully sequenced SIV strain rcmNG411 (SIVrcmNG411) and gag and pol sequence of SIVrcmNG409 revealed that they were genetically most closely related to the recently characterized SIVrcm from Gabon (SIVrcmGB1). Thus, red-capped mangabeys from distant geographic locations harbor a common lineage of SIV. SIVrcmNG411 carried a vpx gene in addition to vpr, suggesting a common evolutionary ancestor with SIVsm (from sooty mangabeys). However, SIVrcm was only marginally closer to SIVsm in that region than to any of the other lentiviruses. SIVrcm showed the highest similarity in pol with SIVdrl, isolated from a drill, a primate that is phylogenetically distinct from mangabey monkeys, and clustered with other primate lentiviruses (primarily SIVcpz [from chimpanzees] and SIVagmSab [from African green monkeys]) discordantly in different regions of the genome, suggesting a history of recombination. Despite the genetic relationship to SIVcpz in the pol gene, SIVrcmNG411 did not replicate in chimpanzee peripheral blood mononuclear cells (PBMC), although two other viruses unrelated to SIVcpz, SIVmndGB1 (from mandrills) and SIVlhoest (from L'Hoest monkeys), were able to grow in chimpanzee PBMC. The CCR5 24-bp deletion previously described in red-capped mangabeys from Gabon was also observed in Nigerian red-capped mangabeys, and SIVrcmNG411, like SIVrcmGB1, used CCR2B and STRL33 as coreceptors for virus entry. SIVrcm, SIVsm, SIVmndGB1, and all four SIVlhoest isolates but not SIVsun (from sun-tailed monkeys) replicated efficiently in human PBMC, suggesting that the ability to infect the human host can vary within one lineage.

A novel simian immunodeficiency virus (SIVdrl) pol sequence from the drill monkey, Mandrillus leucophaeus.

The drill monkey has been shown by serology and PCR to harbor a unique simian immunodeficiency virus (SIVdrl). A pol sequence, amplified from uncultured peripheral blood cells, is most closely related to the equivalent SIV sequences from the red-capped mangabey (SIVrcm), the sabaeus African green monkey (SIVagmSAB), and the chimpanzee (SIVcpz) and to the human immunodeficiency virus type 1 (HIV-1) sequence of humans. It is as yet unclear whether SIVdrl has a mosaic genome like SIVrcm and SIVagmSAB, is a member of the SIVcpz/HIV-1 lineage, or represents a novel primate lentivirus lineage.

SIVrcm infection of macaques.

In a prior report, we described the isolation and characterization of SIVrcm, a distinct primate lentivirus found in a household pet Red-Capped Mangabey (RCM) in Gabon. SIVrcm is divergent from HIV-1 and HIV-2/SIV families of primate lentiviruses. In this report, additional in vitro replication studies and the results of SIVrcm infection in macaques are presented. SIVrcm causes little cytopathic effedct in Molt 4 Clone 8 cells and in rhesus and human PBMCs. In vivo, SIVrcm is non-pathogenic after 200 days in rhesus macaques and after one year in cynomolgous macaques, but does cause a chronic infection in both macaques.

Natural infection of a household pet red-capped mangabey (Cercocebus torquatus torquatus) with a new simian immunodeficiency virus.

A seroprevalence survey was conducted for simian immunodeficiency virus (SIV) antibody in household pet monkeys in Gabon. Twenty-nine monkeys representing seven species were analyzed. By using human immunodeficiency virus type 2 (HIV-2)/SIVsm, SIVmnd, and SIVagm antigens, one red-capped mangabey (RCM) (Cercocebus torquatus torquatus) was identified as harboring SIV-cross-reactive antibodies. A virus isolate, termed SIVrcm, was subsequently established from this seropositive RCM by cocultivation of its peripheral blood mononuclear cells (PBMC) with PBMC from seronegative humans or RCMs. SIVrcm was also isolated by cocultivation of CD8-depleted RCM PBMC with Molt 4 clone 8 cells but not with CEMx174 cells. The lack of growth in CEMx174 cells distinguished this new SIV from all previously reported sooty mangabey-derived viruses (SIVsm), which grow well in this cell line. SIVrcm was also successfully transmitted (cell free) to human and rhesus PBMC as well as to Molt 4 clone 8 cells. To determine the evolutionary origins of this newly identified virus, subgenomic pol (475 bp) and gag (954 bp) gene fragments were amplified from infected cell culture DNA and sequenced. The position of SIVrcm relative to those of members of the other primate lentivirus lineages was then examined in evolutionary trees constructed from deduced protein sequences. This analysis revealed significantly discordant phylogenetic positions of SIVrcm in the two genomic regions. In trees derived from partial gag sequences, SIVrcm clustered independently from all other HIV and SIV strains, consistent with a new primate lentivirus lineage. However, in trees derived from pol sequences, SIVrcm grouped with the HIV-1/SIVcpz lineage. These findings suggest that the SIVrcm genome is mosaic and possibly is the result of a recombination event involving divergent lentiviruses in the distant past. Further analysis of this and other SIVrcm isolates may shed new light on the origin of HIV-1.

Prevalence of antibodies against simian immunodeficiency virus (SIV) and simian T-lymphotropic virus (STLV) in a colony of non-human primates in Kenya, East Africa.

Sera (165 samples in 1988 and 66, follow-up samples in 1989) were collected from olive baboons, African green monkeys, Syke's monkeys and grey mangabeys kept in a semi-free, breeding colony at the Institute of Primate Research (IPR) in Nairobi, Kenya. The levels of antibodies to simian T-lymphotropic virus (STLV) or simian immunodeficiency virus (SIV), and the reactivity patterns of positive sera to various lentivirus subgroup antigens, were then determined. The results of tests using enzyme-immunoassay kits were confirmed by western blots. The prevalence of antibodies which reacted with the Kenyan SIVagm(KEN) isolate was 28% in the African green monkeys tested and 34% in the Syke's monkeys. STLV seroprevalence was 25% in the African greens and 20% in the Syke's. No antibodies to either SIV or STLV were detected in the olive baboons or grey mangabeys. More SIV-positive samples were detected in western blots when SIVagm(KEN) was used as antigen than when SIVagm(CAR014), a geographically distinct isolate from the Central African Republic, was used. However, SIVagm(KEN)-positive sera were more reactive against SIVagm(CAR014) than SIVsmm and SIVmac subgroup antigens, indicating that the two isolates from the African green monkey, CAR014 and KEN, remain antigenetically close even though they were recovered in two geographically distinct regions. To date, no clinical disease has been linked with SIV and STLV infection in the African green or Syke's monkeys in the colony. However, the relatively high prevalence of anti-SIV and anti-STLV antibodies in these monkeys offers an opportunity for prospective studies on the transmission and natural history of both viruses in a single colony.