Emergence of unique primate T-lymphotropic viruses among central African bushmeat hunters.
ABSTRACT: The human T-lymphotropic viruses (HTLVs) types 1 and 2 originated independently and are related to distinct lineages of simian T-lymphotropic viruses (STLV-1 and STLV-2, respectively). These facts, along with the finding that HTLV-1 diversity appears to have resulted from multiple cross-species transmissions of STLV-1, suggest that contact between humans and infected nonhuman primates (NHPs) may result in HTLV emergence. We investigated the diversity of HTLV among central Africans reporting contact with NHP blood and body fluids through hunting, butchering, and keeping primate pets. We show that this population is infected with a wide variety of HTLVs, including two previously unknown retroviruses: HTLV-4 is a member of a phylogenetic lineage that is distinct from all known HTLVs and STLVs; HTLV-3 falls within the phylogenetic diversity of STLV-3, a group not previously seen in humans. We also document human infection with multiple STLV-1-like viruses. These results demonstrate greater HTLV diversity than previously recognized and suggest that NHP exposure contributes to HTLV emergence. Our discovery of unique and divergent HTLVs has implications for HTLV diagnosis, blood screening, and potential disease development in infected persons. The findings also indicate that cross-species transmission is not the rate-limiting step in pandemic retrovirus emergence and suggest that it may be possible to predict and prevent disease emergence by surveillance of populations exposed to animal reservoirs and interventions to decrease risk factors, such as primate hunting.
Project description:Of the seven known species of human retroviruses only one, human T-cell lymphotropic virus type 4 (HTLV-4), lacks a known animal reservoir. We report the largest screening for simian T-cell lymphotropic virus (STLV-4) to date in a wide range of captive and wild non-human primate (NHP) species from Cameroon. Among the 681 wild and 426 captive NHPs examined, we detected STLV-4 infection only among gorillas by using HTLV-4-specific quantitative polymerase chain reaction. The large number of samples analyzed, the diversity of NHP species examined, the geographic distribution of infected animals relative to the known HTLV-4 case, as well as detailed phylogenetic analyses on partial and full genomes, indicate that STLV-4 is endemic to gorillas, and that rather than being an ancient virus among humans, HTLV-4 emerged from a gorilla reservoir, likely through the hunting and butchering of wild gorillas. Our findings shed further light on the importance of gorillas as keystone reservoirs for the evolution and emergence of human infectious diseases and provide a clear course for preventing HTLV-4 emergence through management of human contact with wild gorillas, the development of improved assays for HTLV-4/STLV-4 detection and the ongoing monitoring of STLV-4 among gorillas and for HTLV-4 zoonosis among individuals exposed to gorilla populations.
Project description:Human retroviral infections such as Human Immunodeficiency Virus (HIV) or Human T-cell Lymphotropic Virus (HTLV) are the result of simian zoonotic transmissions through handling and butchering of Non-Human Primates (NHP) or by close contact with pet animals. Recent studies on retroviral infections in NHP bushmeat allowed for the identification of numerous Simian Immunodeficiency Viruses (SIV) and Simian T-cell Lymphotropic Viruses (STLV) to which humans are exposed. Nevertheless, today, data on simian retroviruses at the primate/hunter interface remain scarce. We conducted a pilot study on 63 blood and/or tissues samples derived from NHP bushmeat seized by the competent authorities in different locations across the country.SIV and STLV were detected by antibodies to HIV and HTLV antigens, and PCRs were performed on samples with an HIV or/and HTLV-like or indeterminate profile. Fourteen percent of the samples cross-reacted with HIV antigens and 44% with HTLV antigens. We reported STLV-1 infections in five of the seven species tested. STLV-3 infections, including a new STLV-3 subtype, STLV-1 and -3 co-infections, and triple SIV, STLV-1, STLV-3 infections were observed in red-capped mangabeys (C.torquatus). We confirmed SIV infections by PCR and sequence analyses in mandrills, red-capped mangabeys and showed that mustached monkeys in Gabon are infected with a new SIV strain basal to the SIVgsn/mus/mon lineage that did not fall into the previously described SIVmus lineages reported from the corresponding species in Cameroon. The same monkey (sub)species can thus be carrier of, at least, three distinct SIVs. Overall, the minimal prevalence observed for both STLV and SIV natural infections were 26.9% and 11.1% respectively.Overall, these data, obtained from a restricted sampling, highlight the need for further studies on simian retroviruses in sub-Saharan Africa to better understand their evolutionary history and to document SIV strains to which humans are exposed. We also show that within one species, a high genetic diversity may exist for SIVs and STLVs and observe a high genetic diversity in the SIVgsn/mon/mus lineage, ancestor of HIV-1/SIVcpz/SIVgor.
Project description:Human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 encode auxiliary proteins that play important roles in viral replication, viral latency, and immune escape. The presence of auxiliary protein-encoding open reading frames (ORFs) in HTLV-3, the latest HTLV to be discovered, is unknown. Simian T-cell lymphotropic virus type 3 (STLV-3) is almost identical to HTLV-3. Given the lack of HTLV-3-infected cell lines, we took advantage of STLV-3-infected cells and of an STLV-3 molecular clone to search for the presence of auxiliary transcripts. Using reverse transcriptase PCR (RT-PCR), we first uncovered the presence of three unknown viral mRNAs encoding putative proteins of 5, 8, and 9 kDa and confirmed the presence of the previously reported RorfII transcript. The existence of these viral mRNAs was confirmed by using splice site-specific RT-PCR with ex vivo samples. We showed that p5 is distributed throughout the cell and does not colocalize with a specific organelle. The p9 localization is similar to that of HTLV-1 p12 and induced a strong decrease in the calreticulin signal, similarly to HTLV-1 p12. Although p8, RorfII, and Rex-3 share an N-terminal sequence that is predicted to contain a nucleolar localization signal (NoLS), only p8 is found in the nucleolus. The p8 location in the nucleolus is linked to a bipartite NoLS. p8 and, to a lesser extent, p9 repressed viral expression but did not alter Rex-3-dependent mRNA export. Using a transformation assay, we finally showed that none of the STLV-3 auxiliary proteins had the ability to induce colony formation, while both Tax-3 and antisense protein of HTLV-3 (APH-3) promoted cellular transformation. Altogether, these results complete the characterization of the newly described primate T-lymphotropic virus type 3 (PTLV-3).Together with their simian counterparts, HTLVs form the primate T-lymphotropic viruses. HTLVs arose from interspecies transmission between nonhuman primates and humans. HTLV-1 and HTLV-2 encode auxiliary proteins that play important roles in viral replication, viral latency, and immune escape. The presence of ORFs encoding auxiliary proteins in HTLV-3 or STLV-3 genomes was unknown. Using in silico analyses, ex vivo samples, or in vitro experiments, we have uncovered the presence of 3 previously unknown viral mRNAs encoding putative proteins and confirmed the presence of a previously reported viral transcript. We characterized the intracellular localization of the four proteins. We showed that two of these proteins repress viral expression but that none of them have the ability to induce colony formation. However, both Tax and the antisense protein APH-3 promote cell transformation. Our results allowed us to characterize 4 new retroviral proteins for the first time.
Project description:Zoonotic transmission of simian retroviruses in West-Central Africa occurring in primate hunters has resulted in pandemic spread of human immunodeficiency viruses (HIVs) and human T-lymphotropic viruses (HTLVs). While simian foamy virus (SFV) and simian T- lymphotropic virus (STLV)-like infection were reported in healthy persons exposed to nonhuman primates (NHPs) in West-Central Africa, less is known about the distribution of these viruses in Western Africa and in hospitalized populations. We serologically screened for SFV and STLV infection using 1,529 specimens collected between 1985 and 1997 from Côte d'Ivoire patients with high HIV prevalence. PCR amplification and analysis of SFV, STLV, and HIV/SIV sequences from PBMCs was used to investigate possible simian origin of infection. We confirmed SFV antibodies in three persons (0.2%), two of whom were HIV-1-infected. SFV polymerase (pol) and LTR sequences were detected in PBMC DNA available for one HIV-infected person. Phylogenetic comparisons with new SFV sequences from African guenons showed infection likely originated from a Chlorocebus sabaeus monkey endemic to Côte d'Ivoire. 4.6% of persons were HTLV seropositive and PCR testing of PBMCs from 15 HTLV seroreactive persons identified nine with HTLV-1 and one with HTLV-2 LTR sequences. Phylogenetic analysis showed that two persons had STLV-1-like infections, seven were HTLV-1, and one was an HTLV-2 infection. 310/858 (53%), 8/858 (0.93%), and 18/858 (2.1%) were HIV-1, HIV-2, and HIV-positive but undifferentiated by serology, respectively. No SIV sequences were found in persons with HIV-2 antibodies (n = 1) or with undifferentiated HIV results (n = 7). We document SFV, STLV-1-like, and dual SFV/HIV infection in Côte d'Ivoire expanding the geographic range for zoonotic simian retrovirus transmission to West Africa. These findings highlight the need to define the public health consequences of these infections. Studying dual HIV-1/SFV infections in immunocompromised populations may provide a new opportunity to better understand SFV pathogenicity and transmissibility in humans.
Project description:Simian T-lymphotropic virus 1 (STLV-1) enters human populations through contact with nonhuman primate (NHP) bushmeat. We tested whether differences in the extent of contact with STLV-1-infected NHP bushmeat foster regional differences in prevalence of human T-lymphotropic virus 1 (HTLV-1). Using serological and PCR assays, we screened humans and NHPs at two Sub-Saharan African sites where subsistence hunting was expected to be less (Taï region, Côte d'Ivoire [CIV]) or more (Bandundu region, Democratic Republic of the Congo [DRC]) developed. Only 0.7% of human participants were infected with HTLV-1 in CIV (n = 574), and 1.3% of humans were infected in DRC (n = 302). Two of the Ivorian human virus sequences were closely related to simian counterparts, indicating ongoing zoonotic transmission. Multivariate analysis of human demographic parameters and behavior confirmed that participants from CIV were less often exposed to NHPs than participants from DRC through direct contact, e.g., butchering. At the same time, numbers of STLV-1-infected NHPs were higher in CIV (39%; n = 111) than in DRC (23%; n = 39). We conclude that similar ultimate risks of zoonotic STLV-1 transmission-defined as the product of prevalence in local NHP and human rates of contact to fresh NHP carcasses-contribute to the observed comparable rates of HTLV-1 infection in humans in CIV and DRC. We found that young adult men and mature women are most likely exposed to NHPs at both sites. In view of the continued difficulties in controlling zoonotic disease outbreaks, the identification of such groups at high risk of NHP exposure may guide future prevention efforts.IMPORTANCE Multiple studies report a high risk for zoonotic transmission of blood-borne pathogens like retroviruses through contact with NHPs, and this risk seems to be particularly high in tropical Africa. Here, we reveal high levels of exposure to NHP bushmeat in two regions of Western and Central tropical Africa. We provide evidence for continued zoonotic origin of HTLV-1 in humans at CIV, and we found that young men and mature women represent risk groups for zoonotic transmission of pathogens from NHPs. Identifying such risk groups can contribute to mitigation of not only zoonotic STLV-1 transmission but also transmission of any blood-borne pathogen onto humans in Sub-Saharan Africa.
Project description:Four types of human T cell lymphotropic viruses (HTLV) have been described (HTLV-1 to HTLV-4) with three of them having closely related simian virus analogues named STLV-1, -2, and -3. To assess the risk of cross-species transmissions of STLVs from nonhuman primates to humans in the Democratic Republic of Congo, a total of 330 samples, derived from primate bushmeat, were collected at remote forest sites where people rely on bushmeat for subsistence. STLV prevalences and genetic diversity were estimated by PCR and sequence analysis of tax-rex and LTR fragments. Overall, 7.9% of nonhuman primate bushmeat is infected with STLVs. We documented new STLV-1 and STLV-3 variants in six out of the seven species tested and showed for the first time STLV infection in C. mona wolfi, C. ascanius whitesidei, L. aterrimus aterrimus, C. angolensis, and P. tholloni. Our results provide increasing evidence that the diversity and geographic distribution of PTLVs are much greater than previously thought.
Project description: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.
Project description:Homologous env sequences from 17 human T-leukemia/lymphotropic virus type I (HTLV-I) strains from throughout the world and from 25 simian T-leukemia/lymphotropic virus type I (STLV-I) strains from 12 simian species in Asia and Africa were analyzed in a phylogenetic context as an approach to resolving the natural history of these related retroviruses. STLV-I exhibited greater overall sequence variation between strains (1 to 18% compared with 0 to 9% for HTLV-I), supporting the simian origin of the modern viruses in all species. Three HTLV-I phylogenetic clusters or clades (cosmopolitan, Zaire, and Melanesia) were resolved with phenetic, parsimony, and likelihood analytical procedures. Seven phylogenetic clusters of STLV-I were resolved with the most primitive (deeply rooted) divergence involving several STLV-I strains from Asian primate species. Combined analysis of HTLV-I and STLV-I revealed that neither STLV-I clusters nor HTLV-I clusters recapitulated host species specificity; rather, multiple clades from the same species were closer to clades from other species than to each other. We interpret these evolutionary associations as support for the occurrence of multiple discrete interspecies transmissions of ancestral viruses between primate species (including human) that led to recognizable phylogenetic clades that persist in modern species. Geographic concordance of divergent host species that harbor closely related viruses reinforces that physical feasibility for hypothesized interspecies virus transmission in the past and in the present.
Project description:The Democratic Republic of the Congo (DRC) has a history of nonhuman primate (NHP) consumption and exposure to simian retroviruses yet little is known about the extent of zoonotic simian retroviral infections in DRC. We examined the prevalence of human T-lymphotropic viruses (HTLV), a retrovirus group of simian origin, in a large population of persons with frequent NHP exposures and a history of simian foamy virus infection. We screened plasma from 3,051 persons living in rural villages in central DRC using HTLV EIA and western blot (WB). PCR amplification of HTLV tax and LTR sequences from buffy coat DNA was used to confirm infection and to measure proviral loads (pVLs). We used phylogenetic analyses of LTR sequences to infer evolutionary histories and potential transmission clusters. Questionnaire data was analyzed in conjunction with serological and molecular data. A relatively high proportion of the study population (5.4%, n = 165) were WB seropositive: 128 HTLV-1-like, 3 HTLV-2-like, and 34 HTLV-positive but untypeable profiles. 85 persons had HTLV indeterminate WB profiles. HTLV seroreactivity was higher in females, wives, heads of households, and increased with age. HTLV-1 LTR sequences from 109 persons clustered strongly with HTLV-1 and STLV-1 subtype B from humans and simians from DRC, with most sequences more closely related to STLV-1 from Allenopithecus nigroviridis (Allen's swamp monkey). While 18 potential transmission clusters were identified, most were in different households, villages, and health zones. Three HTLV-1-infected persons were co-infected with simian foamy virus. The mean and median percentage of HTLV-1 pVLs were 5.72% and 1.53%, respectively, but were not associated with age, NHP exposure, village, or gender. We document high HTLV prevalence in DRC likely originating from STLV-1. We demonstrate regional spread of HTLV-1 in DRC with pVLs reported to be associated with HTLV disease, supporting local and national public health measures to prevent spread and morbidity.
Project description:An unusual serological profile against human T-cell leukemia/lymphotropic virus type I and II (HTLV-I and -II) proteins was reported in several human Pygmy tribes in Zaire and Cameroon with serum antibodies reactive with gp21 and p24. Here we describe a similar pattern of serum antibodies in a colony of captive pygmy chimpanzees and the isolation of a novel retrovirus, simian T-cell lymphotropic virus from Pan paniscus (STLVpan-p), from the peripheral blood mononuclear cells of several seropositive animals. Cocultures of peripheral blood mononuclear cells from three seropositive pygmy chimpanzees with human cord blood mononuclear cells led to the expression of an HTLV-I- and HTLV-II-related virus initially demonstrated by electron microscopy. Furthermore, several of these cocultures became immortalized T-cell lines expressing the CD4+ CD8+ DR+ phenotype of mature activated T cells. Southern blotting and DNA sequencing of a PCR fragment of viral DNA from these cell cultures demonstrated a distant evolutionary relationship of these viruses to HTLV-I and -II and distinct from the known STLV isolates. We designated this virus STLVpan-p. A genealogical analysis of the captive pygmy chimpanzees colony, originated from wild-caught animals, revealed a prevalence of seropositive offspring from infected mothers, as also observed with HTLVs. The presence in this old African Great Ape species of a virus which is genetically quite distinct from HTLV-I and -II could provide new insights in the phylogenesis of STLVs and HTLVs and be instrumental in the discovery of related human viruses.