HTLV-3/4 and simian foamy retroviruses in humans: discovery, epidemiology, cross-species transmission and molecular virology

Decline in human T-cell lymphotropic virus seroprevalence in blood donors from Minas Gerais, Brazil over a 12-year period (2006-2017)

To investigate a 12-year historical series (2006-2017) of human T-cell lymphotropic virus (HTLV)-positive blood donations from Fundação Hemominas, Minas Gerais, Brazil, an observational retrospective study was performed to evaluate data of blood donor candidates who were screened for HTLV-1/2 by enzyme-linked immunosorbent assay or chemiluminescence assays and confirmed by Western blot. We analyzed 3 309 716 blood donations covering 2006-2017 that were extracted from the institutional database. In a total of 3 308 738 donations that have complete algorithm tests, the global frequency of HTLV-positive donations was 0.012%. The seroprevalence in first-time blood donors was 28.82/100 000 donors; 0.95/100 000 donations were HTLV-positive in repeat blood donors. The frequency of HTLV-seropositive females was significantly higher than males (odds ratio = 1.85, p < 0.001) in first-time donors. The median age of HTLV-positive first-time and repeat donors was similar (36 and 32 years, respectively). First-time donors ≥41 years had higher odds to be infected. There was a clear tendency of decline in the HTLV-positive donations in the period analyzed, going from 19.26/100 000 donations to 8.50/100 000 donations. The increase in the proportion of repeat donors over the period analyzed (from 23% in 2006 to 67% in 2017) must be the principal factor that contributed to this drop. Our results showed a continuous decline in the frequency of HTLV-positive donations from Minas Gerais, Brazil throughout 12 years and emphasize the importance of having a high rate of repeat donors in blood centers to reduce the residual risk of transfusion-transmitted infections.

Different Mutation Tolerance of Lentiviral (HIV-1) and Deltaretroviral (BLV and HTLV) Protease Precursors

The bovine leukemia virus (BLV) and the human T-lymphothropic viruses (HTLVs) are members of the deltaretrovirus genus of Retroviridae family. An essential event of the retroviral life cycle is the processing of the polyproteins by the viral protease (PR); consequently, these enzymes became important therapeutic targets of the anti-retroviral drugs. As compared to human immunodeficiency viruses (HIVs), the deltaretroviruses have a different replication strategy, as they replicate predominantly in the DNA form, by forcing the infected cell to divide, unlike HIV-1, which replicates mainly by producing a vast number of progeny virions and by reinfection. Due to bypassing the error-prone reverse transcription step of replication, the PRs of deltaretroviruses did not undergo such extensive evolution as HIV PRs and remained more highly conserved. In this work, we studied the abilities of wild-type and modified BLV, HTLV (type 1, 2 and 3), and HIV-1 PRs (fused to an N-terminal MBP tag) for self-processing. We designed a cleavage site mutant MBP-fused BLV PR precursor as well, this recombinant enzyme was unable for self-proteolysis, the MBP fusion tag decreased its catalytic efficiency but showed an unusually low K_i for the IB-268 protease inhibitor. Our results show that the HTLV and BLV deltaretrovirus PRs exhibit lower mutation tolerance as compared to HIV-1 PR, and are less likely to retain their activity upon point mutations at various positions, indicating a higher flexibility of HIV-1 PR in tolerating mutations under selective pressure.

Plasma antibodies from humans infected with zoonotic simian foamy virus do not inhibit cell-to-cell transmission of the virus despite binding to the surface of infected cells

Zoonotic simian foamy viruses (SFV) establish lifelong infection in their human hosts. Despite repeated transmission of SFV from nonhuman primates to humans, neither transmission between human hosts nor severe clinical manifestations have been reported. We aim to study the immune responses elicited by chronic infection with this retrovirus and previously reported that SFV-infected individuals generate potent neutralizing antibodies that block cell infection by viral particles. Here, we assessed whether human plasma antibodies block SFV cell-to-cell transmission and present the first description of cell-to-cell spreading of zoonotic gorilla SFV. We set-up a microtitration assay to quantify the ability of plasma samples from 20 Central African individuals infected with gorilla SFV and 9 uninfected controls to block cell-associated transmission of zoonotic gorilla SFV strains. We used flow-based cell cytometry and fluorescence microscopy to study envelope protein (Env) localization and the capacity of plasma antibodies to bind to infected cells. We visualized the cell-to-cell spread of SFV by real-time live imaging of a GFP-expressing prototype foamy virus (CI-PFV) strain. None of the samples neutralized cell-associated SFV infection, despite the inhibition of cell-free virus. We detected gorilla SFV Env in the perinuclear region, cytoplasmic vesicles and at the cell surface. We found that plasma antibodies bind to Env located at the surface of cells infected with primary gorilla SFV strains. Extracellular labeling of SFV proteins by human plasma samples showed patchy staining at the base of the cell and dense continuous staining at the cell apex, as well as staining in the intercellular connections that formed when previously connected cells separated from each other. In conclusion, SFV-specific antibodies from infected humans do not block cell-to-cell transmission, at least in vitro, despite their capacity to bind to the surface of infected cells.

Trial registration: Clinical trial registration: www.clinicaltrials.gov, https://clinicaltrials.gov/ct2/show/NCT03225794/.

Foamy viruses are the oldest known retroviruses and have been mostly described to be nonpathogenic in their natural animal hosts. Simian foamy viruses (SFVs) can be transmitted to humans, in whom they establish persistent infection, as have the simian viruses that led to the emergence of two major human pathogens, human immunodeficiency virus type 1 (HIV-1) and human T lymphotropic virus type 1 (HTLV-1). Such cross-species transmission of SFV is ongoing in many parts of the world where humans have contact with nonhuman primates. We previously showed high titers of neutralizing antibodies in the plasma of most SFV-infected individuals. These antiviral antibodies can inhibit cell-free virus entry. However, SFV efficiently spread from one cell to another. Here, we demonstrate that plasma antibodies do not block such cell-to-cell transmission, despite their capacity to bind to the surface of infected cells. In addition, we document for the first time the cell-to-cell spread of primary zoonotic gorilla SFV.

Work-Related Human T-lymphotropic Virus 1 and 2 (HTLV-1/2) Infection: A Systematic Review

Human T-lymphotropic virus 1 and 2 (HTLV-1/2) belong to the delta group of retroviruses which may cause a life-long infection in humans, HTLV-1 leading to adult T-cell leukemia/lymphoma and other diseases. Different transmission modes have been described, such as breastfeeding, and, as for other blood-borne pathogens, unsafe sexual activity, intravenous drug usage, and blood transfusion and transplantation. The present systematic review was conducted to identify all peer-reviewed studies concerning the work-related infection by HTLV-1/2. A literature search was conducted from January to May 2021, according to the PRISMA methodology, selecting 29 studies: seven related to health care workers (HCWs), five to non-HCWs, and 17 to sex workers (SWs). The findings showed no clear evidence as to the possibility of HTLV-1/2 occupational transmission in HCWs, according to the limited number and quality of the papers. Moreover, non-HCWs showed a higher prevalence in jobs consistent with a lower socioeconomic status or that could represent a familial cluster, and an increased risk of zoonotic transmission from STLV-1-infected non-human primates has been observed in African hunters. Finally, a general increase of HTLV-1 infection was observed in SWs, whereas only one paper described an increased prevalence for HTLV-2, supporting the urgent need for prevention and control measures, including screening, diagnosis, and treatment of HTLV-1/2, to be offered routinely as part of a comprehensive approach to decrease the impact of sexually transmitted diseases in SWs.

Novel Genetic Constructs for Production of Recombinant HTLV-1/2 Antigens and Evaluation of Their Reactivity to Plasma Samples from HTLV-1-Infected Patients

Human T-cell leukemia virus type 1 (HTLV-1) can cause life-threatening diseases for which there are no effective treatments. Prevention of HTLV-1 infection requires massive testing of pregnant women, blood for transfusion, and organs for transplantation, as well as safe sex. In this context, serological assays are widely used for monitoring HTLV-1 infections. Despite the necessity for recombinant antigens to compose serological tests, there is little information available on procedures to produce recombinant HTLV-1/2 antigens for serological diagnostic purposes. In this work, we tested a series of genetic constructions to select those more amenable for production in bacterial systems. To overcome the constraints in expressing sections of viral envelope proteins in bacteria, we have used the p24 segment of the gag protein as a scaffold to display the immunogenic regions of gp46 and gp21. Nine recombinant antigenic proteins derived from HTLV-1 and five derived from HTLV-2 were successfully purified. The HTLV-1 antigens showed high efficiency in discriminating HTLV-positive samples from HTLV-negative samples using enzyme-linked immunosorbent assays. Interestingly, HTLV-1-positive samples showed a high level of cross-reaction with HTLV-2 antigens. This finding is explained by the high sequence conservation between the structural proteins of these two highly related viruses. In summary, the results presented in this work provide a detailed description of the methods used to produce recombinant HTLV-1 and HTLV-2 antigens, and they demonstrate that the HTLV-1 antigens show strong potential for serological diagnosis of HTLV-1 infections.

Foamy Viruses, Bet, and APOBEC3 Restriction

Non-human primates (NHP) are an important source of viruses that can spillover to humans and, after adaptation, spread through the host population. Whereas HIV-1 and HTLV-1 emerged as retroviral pathogens in humans, a unique class of retroviruses called foamy viruses (FV) with zoonotic potential are occasionally detected in bushmeat hunters or zookeepers. Various FVs are endemic in numerous mammalian natural hosts, such as primates, felines, bovines, and equines, and other animals, but not in humans. They are apathogenic, and significant differences exist between the viral life cycles of FV and other retroviruses. Importantly, FVs replicate in the presence of many well-defined retroviral restriction factors such as TRIM5α, BST2 (Tetherin), MX2, and APOBEC3 (A3). While the interaction of A3s with HIV-1 is well studied, the escape mechanisms of FVs from restriction by A3 is much less explored. Here we review the current knowledge of FV biology, host restriction factors, and FV-host interactions with an emphasis on the consequences of FV regulatory protein Bet binding to A3s and outline crucial open questions for future studies.

The origin of porcine endogenous retroviruses (PERVs)

Porcine endogenous retroviruses (PERVs) are integrated in the genome of all pigs, and they produce viral particles that are able to infect human cells and therefore pose a special risk for xenotransplantation. In contrast to other pig microorganisms that also pose a risk, such as porcine cytomegalovirus and hepatitis E virus, PERVs cannot be eliminated from pigs by vaccines, antiviral drugs, early weaning, or embryo transfer. Since PERVs are relevant for xenotransplantation, their biology and origin are of great interest. Recent studies have shown that PERVs are the result of a transspecies transmission of precursor retroviruses from different animals and further evolution in the pig genome. PERVs acquired different long terminal repeats (LTRs), and recombination took place. In parallel, it has been shown that the activity of the LTRs and recombination in the envelope are important for the transmissibility and pathogenesis of PERVs. Transspecies transmission of retroviruses is common, a well-known example being the transmission of precursor retroviruses from non-human primates to humans, resulting in human immunodeficiency virus (HIV). Here, recent findings concerning the origin of PERVs, their LTRs, and recombination events that occurred during evolution are reviewed and compared with other findings regarding transspecies transmission of retroviruses.

Biochemical Characterization, Specificity and Inhibition Studies of HTLV-1, HTLV-2, and HTLV-3 Proteases

The human T-lymphotropic viruses (HTLVs) are causative agents of severe diseases including adult T-cell leukemia. Similar to human immunodeficiency viruses (HIVs), the viral protease (PR) plays a crucial role in the viral life-cycle via the processing of the viral polyproteins. Thus, it is a potential target of anti-retroviral therapies. In this study, we performed in vitro comparative analysis of human T-cell leukemia virus type 1, 2, and 3 (HTLV-1, -2, and -3) proteases. Amino acid preferences of S4 to S1′ subsites were studied by using a series of synthetic oligopeptide substrates representing the natural and modified cleavage site sequences of the proteases. Biochemical characteristics of the different PRs were also determined, including catalytic efficiencies and dependence of activity on pH, temperature, and ionic strength. We investigated the effects of different HIV-1 PR inhibitors (atazanavir, darunavir, DMP-323, indinavir, ritonavir, and saquinavir) on enzyme activities, and inhibitory potentials of IB-268 and IB-269 inhibitors that were previously designed against HTLV-1 PR. Comparative biochemical analysis of HTLV-1, -2, and -3 PRs may help understand the characteristic similarities and differences between these enzymes in order to estimate the potential of the appearance of drug-resistance against specific HTLV-1 PR inhibitors.

Case-Control Study of the Immune Status of Humans Infected With Zoonotic Gorilla Simian Foamy Viruses

BACKGROUND

Zoonotic simian foamy viruses (SFVs) establish persistent infections in humans, for whom the long-term consequences for health are poorly described. In this study, we aimed to characterize blood-cell phenotypes and plasma biomarkers associated with gorilla SFV infection in humans.

METHODS

We used a case-control design to compare 15 Cameroonian hunters infected with gorilla SFV (cases) to 15 controls matched for age and ethnicity. A flow cytometry-based phenotypic study and quantification of plasma immune biomarkers were carried out on blood samples from all participants. Wilcoxon signed-rank tests were used to compare cases and controls.

RESULTS

Cases had a significantly higher percentage of CD8 T lymphocytes than controls (median, 17.6% vs 13.7%; P = .03) but similar levels of B, natural killer, and CD4 T lymphocytes. Cases also had a lower proportion of recent CD4 thymic emigrants (10.9% vs 18.6%, P = .05), a higher proportion of programmed death receptor 1 (PD-1) expressing memory CD4 T lymphocytes (31.7% vs 24.7%, P = .01), and higher plasma levels of the soluble CD163 scavenger receptor (0.84 vs .59 µg/mL, P = .003) than controls.

CONCLUSIONS

We show, for the first time, that chronic infection with SFV is associated with T lymphocyte differentiation and monocyte activation.

Human T-cell lymphotropic virus type 1 transmission dynamics in rural villages in the Democratic Republic of the Congo with high nonhuman primate exposure

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.

Antisense Transcripts and Antisense Protein: A New Perspective on Human Immunodeficiency Virus Type 1

It was first predicted in 1988 that there may be an Open Reading Frame (ORF) on the negative strand of the Human Immunodeficiency Virus type 1 (HIV-1) genome that could encode a protein named AntiSense Protein (ASP). In spite of some controversy, reports began to emerge some years later describing the detection of HIV-1 antisense transcripts, the presence of ASP in transfected and infected cells, and the existence of an immune response targeting ASP. Recently, it was established that the asp gene is exclusively conserved within the pandemic group M of HIV-1. In this review, we summarize the latest findings on HIV-1 antisense transcripts and ASP, and we discuss their potential functions in HIV-1 infection together with the role played by antisense transcripts and ASPs in some other viruses. Finally, we suggest pathways raised by the study of antisense transcripts and ASPs that may warrant exploration in the future.

The Role of APOBECs in Viral Replication

Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) proteins are a diverse and evolutionarily conserved family of cytidine deaminases that provide a variety of functions from tissue-specific gene expression and immunoglobulin diversity to control of viruses and retrotransposons. APOBEC family expansion has been documented among mammalian species, suggesting a powerful selection for their activity. Enzymes with a duplicated zinc-binding domain often have catalytically active and inactive domains, yet both have antiviral function. Although APOBEC antiviral function was discovered through hypermutation of HIV-1 genomes lacking an active Vif protein, much evidence indicates that APOBECs also inhibit virus replication through mechanisms other than mutagenesis. Multiple steps of the viral replication cycle may be affected, although nucleic acid replication is a primary target. Packaging of APOBECs into virions was first noted with HIV-1, yet is not a prerequisite for viral inhibition. APOBEC antagonism may occur in viral producer and recipient cells. Signatures of APOBEC activity include G-to-A and C-to-T mutations in a particular sequence context. The importance of APOBEC activity for viral inhibition is reflected in the identification of numerous viral factors, including HIV-1 Vif, which are dedicated to antagonism of these deaminases. Such viral antagonists often are only partially successful, leading to APOBEC selection for viral variants that enhance replication or avoid immune elimination.

Systematic Review of Important Viral Diseases in Africa in Light of the 'One Health' Concept

Emerging and re-emerging viral diseases are of great public health concern. The recent emergence of Severe Acute Respiratory Syndrome (SARS) related coronavirus (SARS-CoV-2) in December 2019 in China, which causes COVID-19 disease in humans, and its current spread to several countries, leading to the first pandemic in history to be caused by a coronavirus, highlights the significance of zoonotic viral diseases. Rift Valley fever, rabies, West Nile, chikungunya, dengue, yellow fever, Crimean-Congo hemorrhagic fever, Ebola, and influenza viruses among many other viruses have been reported from different African countries. The paucity of information, lack of knowledge, limited resources, and climate change, coupled with cultural traditions make the African continent a hotspot for vector-borne and zoonotic viral diseases, which may spread globally. Currently, there is no information available on the status of virus diseases in Africa. This systematic review highlights the available information about viral diseases, including zoonotic and vector-borne diseases, reported in Africa. The findings will help us understand the trend of emerging and re-emerging virus diseases within the African continent. The findings recommend active surveillance of viral diseases and strict implementation of One Health measures in Africa to improve human public health and reduce the possibility of potential pandemics due to zoonotic viruses.

Monkeypox Rash Severity and Animal Exposures in the Democratic Republic of the Congo

Experimental studies have suggested a larger inoculum of monkeypox virus may be associated with increased rash severity; however, little data are available on the relationship between specific animal exposures and rash severity in endemic regions. Using cross-sectional data from an active surveillance program conducted between 2005 and 2007 in the Sankuru Province of the Democratic Republic of the Congo, we explored the possible relationship between rash severity and exposures to rodents and non-human primates among confirmed MPX cases. Among the 223 PCR-confirmed MPX cases identified during active surveillance, the majority of cases (n = 149) presented with mild rash (5-100 lesions) and 33% had a more serious presentation (> 100 lesions). No association between exposure to rodents and rash severity was found in the multivariable analysis. Those that self-reported hunting NHP 3 weeks prior to onset of MPX symptoms had 2.78 times the odds of severe rash than those that did not report such exposure (95% CI: 1.18, 6.58). This study provides a preliminary step in understanding the association between animal exposure and rash severity and demonstrates correlation with exposure to NHPs and human MPX presentation. Additional research exploring the relationship between rash severity and NHPs is warranted.

Emerging sexually transmitted viral infections: Review of human T-lymphotropic virus-1 disease

Human T-lymphotropic virus-1 is a preventable sexually transmitted infection. In the majority of people it is asymptomatic, remaining undiagnosed and thereby contributing to its silent transmission. When it does manifest it causes significant morbidity and mortality. This review summarises the existing evidence for its role in sexual transmission and offers suggestions for those working in the area of sexual health. This is the third part of a series looking at novel sexually transmitted infections.

NF-κB and MicroRNA Deregulation Mediated by HTLV-1 Tax and HBZ

The risk of developing adult T-cell leukemia/lymphoma (ATLL) in individuals infected with human T-cell lymphotropic virus 1 (HTLV-1) is about 3–5%. The mechanisms by which the virus triggers this aggressive cancer are still an area of intensive investigation. The viral protein Tax-1, together with additional regulatory proteins, in particular HTLV-1 basic leucine zipper factor (HBZ), are recognized as relevant viral factors required for both viral replication and transformation of infected cells. Tax-1 deregulates several cellular pathways affecting the cell cycle, survival, and proliferation. The effects of Tax-1 on the NF-κB pathway have been thoroughly studied. Recent studies also revealed the impact of Tax-1 and HBZ on microRNA expression. In this review, we summarize the recent progress in understanding the contribution of HTLV-1 Tax- and HBZ-mediated deregulation of NF-κB and the microRNA regulatory network to HTLV-1 pathogenesis.

Inhibitors of the interferon response increase the replication of gorilla simian foamy viruses

Simian foamy viruses (SFVs) are complex retroviruses that are widespread throughout nonhuman primates. SFVs can also be transmitted to humans, mostly through bites. We previously observed that primary zoonotic gorilla SFV strains grow much more slowly than laboratory-adapted chimpanzee strains. Here, we tested the hypothesis that the growth of SFV is limited by interferon (IFN) using inhibitors of cellular pathways involved in the induction or action of type I IFN. Inhibitors of JAK1/2 (Ruxolitinib) and TBK-1 (BX795) led to a 2- to 4-fold higher percentage of cells infected with zoonotic gorilla SFVs but did not affect the replication of laboratory-adapted chimpanzee SFVs. IKK2 inhibitors (TPCA-1 and BMS345541) had no effect on any of the SFV strains. In conclusion, the addition of molecules that inhibit the type I IFN response to the culture medium can be used as a simple and efficient method to enhance the replication of zoonotic gorilla SFVs.

Restriction factors in human retrovirus infections and the unprecedented case of CIITA as link of intrinsic and adaptive immunity against HTLV-1

Background

Immunity against pathogens evolved through complex mechanisms that only for sake of simplicity are defined as innate immunity and adaptive immunity. Indeed innate and adaptive immunity are strongly intertwined each other during evolution. The complexity is further increased by intrinsic mechanisms of immunity that rely on the action of intracellular molecules defined as restriction factors (RFs) that, particularly in virus infections, counteract the action of pathogen gene products acting at different steps of virus life cycle.

Main body and conclusion

Here we provide an overview on the nature and the mode of action of restriction factors involved in retrovirus infection, particularly Human T Leukemia/Lymphoma Virus 1 (HTLV-1) infection. As it has been extensively studied by our group, special emphasis is given to the involvement of the MHC class II transactivator CIITA discovered in our laboratory as regulator of adaptive immunity and subsequently as restriction factor against HIV-1 and HTLV-1, a unique example of dual function linking adaptive and intrinsic immunity during evolution. We describe the multiple molecular mechanisms through which CIITA exerts its restriction on retroviruses. Of relevance, we review the unprecedented findings pointing to a concerted action of several restriction factors such as CIITA, TRIM22 and TRIM19/PML in synergizing against retroviral replication. Finally, as CIITA profoundly affects HTLV-1 replication by interacting and inhibiting the function of HTLV-1 Tax-1 molecule, the major viral product associated to the virus oncogenicity, we also put forward the hypothesis of CIITA as counteractor of HTLV-1-mediated cancer initiation.

Clinical Signs and Blood Test Results Among Humans Infected With Zoonotic Simian Foamy Virus: A Case-Control Study

Background

A spillover of simian foamy virus (SFV) to humans, following bites from infected nonhuman primates (NHPs), is ongoing in exposed populations. These retroviruses establish persistent infections of unknown physiological consequences to the human host.

Methods

We performed a case-control study to compare 24 Cameroonian hunters infected with gorilla SFV and 24 controls matched for age and ethnicity. A complete physical examination and blood test were performed for all participants. Logistic regression and Wilcoxon signed rank tests were used to compare cases and controls.

Results

The cases had significantly lower levels of hemoglobin than the controls (median, 12.7 vs 14.4 g/dL; P = .01). Basophil levels were also significantly lower in cases than controls, with no differences for other leukocyte subsets. Cases had significantly higher urea, creatinine, protein, creatinine phosphokinase, and lactate dehydrogenase levels and lower bilirubin levels than controls. Cases and controls had similar frequencies of general, cutaneous, gastrointestinal, neurological, and cardiorespiratory signs.

Conclusions

The first case-control study of apparently healthy SFV-infected Cameroonian hunters showed the presence of hematological abnormalities. A thorough clinical and laboratory workup is now needed to establish the medical relevance of these observations because more than half of cases had mild or moderate anemia.

Clinical Trials Registration

NCT03225794.

Molecular Analysis of the Complete Genome of a Simian Foamy Virus Infecting Hylobates pileatus (pileated gibbon) Reveals Ancient Co-Evolution with Lesser Apes

Foamy viruses (FVs) are complex retroviruses present in many mammals, including nonhuman primates, where they are called simian foamy viruses (SFVs). SFVs can zoonotically infect humans, but very few complete SFV genomes are available, hampering the design of diagnostic assays. Gibbons are lesser apes widespread across Southeast Asia that can be infected with SFV, but only two partial SFV sequences are currently available. We used a metagenomics approach with next-generation sequencing of nucleic acid extracted from the cell culture of a blood specimen from a lesser ape, the pileated gibbon (Hylobates pileatus), to obtain the complete SFVhpi_SAM106 genome. We used Bayesian analysis to co-infer phylogenetic relationships and divergence dates. SFVhpi_SAM106 is ancestral to other ape SFVs with a divergence date of ~20.6 million years ago, reflecting ancient co-evolution of the host and SFVhpi_SAM106. Analysis of the complete SFVhpi_SAM106 genome shows that it has the same genetic architecture as other SFVs but has the longest recorded genome (13,885-nt) due to a longer long terminal repeat region (2,071 bp). The complete sequence of the SFVhpi_SAM106 genome fills an important knowledge gap in SFV genetics and will facilitate future studies of FV infection, transmission, and evolutionary history.

An Immunodominant and Conserved B-Cell Epitope in the Envelope of Simian Foamy Virus Recognized by Humans Infected with Zoonotic Strains from Apes

Cross-species transmission of simian foamy viruses (SFVs) from nonhuman primates (NHPs) to humans is currently ongoing. These zoonotic retroviruses establish lifelong persistent infection in their human hosts. SFV are apparently nonpathogenic in vivo, with ubiquitous in vitro tropism. Here, we aimed to identify envelope B-cell epitopes that are recognized following a zoonotic SFV infection. We screened a library of 169 peptides covering the external portion of the envelope from the prototype foamy virus (SFVpsc_huHSRV.13) for recognition by samples from 52 Central African hunters (16 uninfected and 36 infected with chimpanzee, gorilla, or Cercopithecus SFV). We demonstrate the specific recognition of peptide N₉₆-V₁₁₀ located in the leader peptide, gp18^LP Forty-three variant peptides with truncations, alanine substitutions, or amino acid changes found in other SFV species were tested. We mapped the epitope between positions 98 and 108 and defined six amino acids essential for recognition. Most plasma samples from SFV-infected humans cross-reacted with sequences from apes and Old World monkey SFV species. The magnitude of binding to peptide N₉₆-V₁₁₀ was significantly higher for samples of individuals infected with a chimpanzee or gorilla SFV than those infected with a Cercopithecus SFV. In conclusion, we have been the first to define an immunodominant B-cell epitope recognized by humans following zoonotic SFV infection.IMPORTANCE Foamy viruses are the oldest known retroviruses and have been mostly described to be nonpathogenic in their natural animal hosts. SFVs can be transmitted to humans, in whom they establish persistent infection, like the simian lenti- and deltaviruses that led to the emergence of two major human pathogens, human immunodeficiency virus type 1 and human T-lymphotropic virus type 1. This is the first identification of an SFV-specific B-cell epitope recognized by human plasma samples. The immunodominant epitope lies in gp18^LP, probably at the base of the envelope trimers. The NHP species the most genetically related to humans transmitted SFV strains that induced the strongest antibody responses. Importantly, this epitope is well conserved across SFV species that infect African and Asian NHPs.

Molecular biology of human T cell leukemia virus

Human T cell leukemia virus type 1 (HTLV-1) is a horizontally transmitted virus infection of CD4+ lymphocytes which causes adult T cell leukemia-lymphoma (ATLL) and HTLV-associated myelopathy (HAM). The viral genome encodes two oncoproteins, transactivator protein (Tax) and helix basic zipper protein (HBZ), which are considered tumor initiator and maintenance factors, respectively. Tax is the primary inducer of clonal infected T cell expansion, and genetic instability. The immune response to Tax results in the selection of cells with little or no Tax expression, which have undergone genetic and epigenetic alterations that promote T cell activation, proliferation, and resistance to apoptosis. This selection of malignant cells occurs over several decades in 5% of infected individuals. Novel insights into the molecular details of each of these events has led to targeted therapies for ATLL.

Using physical contact heterogeneity and frequency to characterize dynamics of human exposure to nonhuman primate bodily fluids in central Africa

Emerging infectious diseases of zoonotic origin constitute a recurrent threat to global health. Nonhuman primates (NHPs) occupy an important place in zoonotic spillovers (pathogenic transmissions from animals to humans), serving as reservoirs or amplifiers of multiple neglected tropical diseases, including viral hemorrhagic fevers and arboviruses, parasites and bacteria, as well as retroviruses (simian foamy virus, PTLV) that are pathogenic in human beings. Hunting and butchering studies in Africa characterize at-risk human social groups, but overlook critical factors of contact heterogeneity and frequency, NHP species differences, and meat processing practices. In southeastern Cameroon, a region with a history of zoonotic emergence and high risk of future spillovers, we conducted a novel mixed-method field study of human physical exposure to multiple NHP species, incorporating participant-based and ecological methodologies, and qualitative interviews (n = 25). We find frequent physical contact across adult human populations, greater physical contact with monkeys than apes, especially for meat handling practices, and positive correlation of human exposure with NHP species abundance and proximity to human settlement. These fine-grained results encourage reconsideration of the likely dynamics of human-NHP contact in past and future NTD emergence events. Multidisciplinary social science and ecological approaches should be mobilized to generate more effective human and animal surveillance and risk communications around neglected tropical diseases. At a moment when the WHO has included "Disease X", a presumably zoonotic pathogen with pandemic potential, on its list of blueprint priority diseases as, new field-based tools for investigating zoonotic disease emergence, both known and unknown, are of critical importance.

Potent neutralizing antibodies in humans infected with zoonotic simian foamy viruses target conserved epitopes located in the dimorphic domain of the surface envelope protein

Human diseases of zoonotic origin are a major public health problem. Simian foamy viruses (SFVs) are complex retroviruses which are currently spilling over to humans. Replication-competent SFVs persist over the lifetime of their human hosts, without spreading to secondary hosts, suggesting the presence of efficient immune control. Accordingly, we aimed to perform an in-depth characterization of neutralizing antibodies raised by humans infected with a zoonotic SFV. We quantified the neutralizing capacity of plasma samples from 58 SFV-infected hunters against primary zoonotic gorilla and chimpanzee SFV strains, and laboratory-adapted chimpanzee SFV. The genotype of the strain infecting each hunter was identified by direct sequencing of the env gene amplified from the buffy coat with genotype-specific primers. Foamy virus vector particles (FVV) enveloped by wild-type and chimeric gorilla SFV were used to map the envelope region targeted by antibodies. Here, we showed high titers of neutralizing antibodies in the plasma of most SFV-infected individuals. Neutralizing antibodies target the dimorphic portion of the envelope protein surface domain. Epitopes recognized by neutralizing antibodies have been conserved during the cospeciation of SFV with their nonhuman primate host. Greater neutralization breadth in plasma samples of SFV-infected humans was statistically associated with smaller SFV-related hematological changes. The neutralization patterns provide evidence for persistent expression of viral proteins and a high prevalence of coinfection. In conclusion, neutralizing antibodies raised against zoonotic SFV target immunodominant and conserved epitopes located in the receptor binding domain. These properties support their potential role in restricting the spread of SFV in the human population.

STLV-1 co-infection is correlated with an increased SFV proviral load in the peripheral blood of SFV/STLV-1 naturally infected non-human primates

Simian T-Leukemia Virus type 1 and Simian Foamy Virus infect non-human primates. While STLV-1, as HTLV-1, causes Adult T-cell Leukemia/lymphoma, SFV infection is asymptomatic. Both retroviruses can be transmitted from NHPs to humans through bites that allow contact between infected saliva and recipient blood. Because both viruses infect CD4+ T-cells, they might interfere with each other replication, and this might impact viral transmission. Impact of STLV-1 co-infection on SFV replication was analyzed in 18 SFV-positive/STLV-1-negative and 18 naturally SFV/STLV-1 co-infected Papio anubis. Even if 9 animals were found STLV-1-positive in saliva, STLV-1 PVL was much higher in the blood. SFV proviruses were detected in the saliva of all animals. Interestingly, SFV proviral load was much higher in the blood of STLV-1/SFV co-infected animals, compared to STLV-1-negative animals. Given that soluble Tax protein can enter uninfected cells, we tested its effect on foamy virus promoter and we show that Tax protein can transactivate the foamy LTR. This demonstrates that true STLV-1 co-infection or Tax only has an impact on SFV replication and may influence the ability of the virus to be zoonotically transmitted as well as its ability to promote hematological abnormalities.

Foamy viruses infect a lot of mammalian hosts including non-human primates (NHP) and humans. Foamy infection is not associated with disease, although a recent report described hematological abnormalities in infected humans. Some NHP species are also naturally infected with another retrovirus i.e. Simian T lymphotropic virus type 1, while humans are infected with the Human T lymphotropic virus type 1 counterpart. Both viruses cause leukemia. Here we report that natural foamy/STLV-1 co-infection is associated with a higher foamy virus proviral load in blood. Co-infected animals might therefore present a higher risk of developing hematological disease.

HTLV-1: A real pathogen or a runaway guest of a diseased cell?

The human T-cell lymphotropic virus type 1 (HTLV-1) is a deltaretrovirus claimed to be aetiologically linked to the adult T-cell leukaemia/lymphoma (ATLL) and associated myelopathy/tropical spastic paraparesis (HAM/TSP) besides other minor pathologies. HTLV-1 infection is worldwide distributed, despite its heterogeneous prevalence. Environmental factors and host-genetic background are very likely to determine the epidemiological profile of HTLV-1 prevalence and related disease confinement in distinct human ethnic populations and geographical coordinates, which raises the question if the virus is a real pathogen or a runaway well-organized packed genome of a burden host cell near death process. New methodological approaches need to be proposed and applied in order to prove or discard the hypotheses emerged in the present review.

The invariant arginine within the chromatin-binding motif regulates both nucleolar localization and chromatin binding of Foamy virus Gag

BACKGROUND

Nuclear localization of Gag is a property shared by many retroviruses and retrotransposons. The importance of this stage for retroviral replication is still unknown, but studies on the Rous Sarcoma virus indicate that Gag might select the viral RNA genome for packaging in the nucleus. In the case of Foamy viruses, genome encapsidation is mediated by Gag C-terminal domain (CTD), which harbors three clusters of glycine and arginine residues named GR boxes (GRI-III). In this study we investigated how PFV Gag subnuclear distribution might be regulated.

RESULTS

We show that the isolated GRI and GRIII boxes act as nucleolar localization signals. In contrast, both the entire Gag CTD and the isolated GRII box, which contains the chromatin-binding motif, target the nucleolus exclusively upon mutation of the evolutionary conserved arginine residue at position 540 (R540), which is a key determinant of FV Gag chromatin tethering. We also provide evidence that Gag localizes in the nucleolus during FV replication and uncovered that the viral protein interacts with and is methylated by Protein Arginine Methyltransferase 1 (PRMT1) in a manner that depends on the R540 residue. Finally, we show that PRMT1 depletion by RNA interference induces the concentration of Gag C-terminus in nucleoli.

CONCLUSION

Altogether, our findings suggest that methylation by PRMT1 might finely tune the subnuclear distribution of Gag depending on the stage of the FV replication cycle. The role of this step for viral replication remains an open question.

2017 international meeting of the Global Virus Network

The Global Virus Network (GVN) was established in 2011 to strengthen research and responses to emerging viral causes of human disease and to prepare against new viral pandemics. There are now 40 GVN Centers of Excellence and 6 Affiliate laboratories in 24 countries. The 2017 meeting was held from September 25–27 in Melbourne, Australia, and was hosted by the Peter Doherty Institute for Infection and Immunity and the Institut Pasteur. This report highlights the recent accomplishments of GVN researchers in several important areas of medical virology, including the recent Zika epidemic, infections by human papillomavirus, influenza, HIV, hepatitis C, HTLV-1, and chikungunya viruses, and new and emerging viruses in the Australasia region. Plans for the 2018 meeting also are noted.

•

The GVN is an international research network comprised of 40 Centers of Excellence and 6 Affiliates in 24 countries.

•

The 2017 Global Virus Network (GVN) Meeting was held in Melbourne, Australia from September 25–27.

•

New data were presented on various aspects of medical virology, therapies, and emerging viruses in the Australasia region.

•

International collaboration is critical to developing new and effective viral vaccines and therapeutics.

•

The 2018 international GVN meeting will be held on November 28–30 in Annecy, France.

Complete Genome Sequence of the African Green Monkey Simian Foamy Virus Serotype 3 Strain FV2014 (SFVcae_FV2014)

The full-length sequence of simian foamy virus serotype 3 (SFV-3) strain FV2014, an African green monkey (Chlorocebus aethiops) isolate, was obtained using high-throughput sequencing. SFVcae_FV2014 consisted of 13,127 bp and had a genomic organization similar to those of other SFVs but was distinct from SFV strain LK3, isolated from the same monkey species.

Highlights from the HTLV-1 symposium at the 2017 Australasian HIV and AIDS Conference held jointly with the 2017 Australasian Sexual Health Conference, November 2017, Canberra, Australia

We are pleased to report on the inaugural HTLV-1 symposium at the 2017 Australasian HIV and AIDS Conference joint with 2017 Australasian Sexual Health Conference in Canberra, Australia. Our understanding of HTLV-1 epidemiology, pathogenesis, laboratory diagnostics and treatment options for HTLV-1 diseases has advanced tremendously over the last 40 years. However, the awareness of healthcare providers and the general population about HTLV-1, and the effective promotion and implementation of HTLV-1 transmission-prevention strategies, lag behind current knowledge. Here we present a summary of the symposium, plenary and poster presentations on HTLV-1.

Rethinking Human-Nonhuman Primate Contact and Pathogenic Disease Spillover

Zoonotic transmissions are a major global health risk, and human-animal contact is frequently raised as an important driver of transmission. A literature examining zooanthroponosis largely agrees that more human-animal contact leads to more risk. Yet the basis of this proposition, the term contact, has not been rigorously analyzed. To understand how contact is used to explain cross-species spillovers, we conducted a multi-disciplinary review of studies addressing human-nonhuman primate (NHP) engagements and pathogenic transmissions and employing the term contact. We find that although contact is frequently invoked, it is employed inconsistently and imprecisely across these studies, overlooking the range of pathogens and their transmission routes and directions. We also examine a related but more expansive approach focusing on human and NHP habitats and their spatial overlap, which can potentially facilitate pathogenic transmission. Contact and spatial overlap investigations cannot, however, explain the processes that bring together people, animals and pathogens. We therefore examine another approach that enhances our understanding of zoonotic spillovers: anthropological studies identifying such historical, social, environmental processes. Comparable to a One Health approach, our ongoing research in Cameroon draws contact, spatial overlap and anthropological-historical approaches into dialog to suggest where, when and how pathogenic transmissions between people and NHPs may occur. In conclusion, we call for zoonotic disease researchers to specify more precisely the human-animal contacts they investigate and to attend to how broader ecologies, societies and histories shape pathogen-human-animal interactions.

Detection of Emerging Zoonotic Pathogens: An Integrated One Health Approach

The emergence of novel zoonotic pathogens is one of the greatest challenges to global health security. The advent of increasingly sophisticated diagnostics tools has revolutionized our capacity to detect and respond to these health threats more rapidly than ever before. Yet, no matter how sophisticated these tools become, the initial identification of emerging infectious diseases begins at the local community level. It is here that the initial human or animal case resides, and it is here that early pathogen detection would have maximum benefit. Unfortunately, many areas at highest risk of zoonotic disease emergence lack sufficient infrastructure capacity to support robust laboratory diagnostic systems. Multiple factors are essential for pathogen detection networks, including an understanding of the complex sociological and ecological factors influencing disease transmission risk, community engagement, surveillance along high-risk human-animal interfaces, and a skilled laboratory workforce. Here we discuss factors relevant to the emerging disease paradigm, recent technical advances in diagnostic methods, and strategies for comprehensive and sustainable approaches to rapid zoonotic disease detection.

Zoonotic infection of Brazilian primate workers with New World simian foamy virus

Simian foamy viruses (SFVs) are retroviruses present in nearly all nonhuman primates (NHPs), including Old World primates (OWP) and New World primates (NWP). While all confirmed human infections with SFV are from zoonotic transmissions originating from OWP, little is known about the zoonotic transmission potential of NWP SFV. We conducted a longitudinal, prospective study of 56 workers occupationally exposed to NWP in Brazil. Plasma from these workers was tested using Western blot (WB) assays containing NWP SFV antigens. Genomic DNA from blood and buccal swabs was analyzed for the presence of proviral SFV sequences by three nested PCR tests and a new quantitative PCR assay. Exposure histories were obtained and analyzed for associations with possible SFV infection. Ten persons (18%) tested seropositive and two persons were seroindeterminate (3.6%) for NWP SFV. Six persons had seroreactivity over 2–3 years suggestive of persistent infection. All SFV NWP WB-positive workers reported at least one incident involving NWP, including six reporting NWP bites. NWP SFV viral DNA was not detected in the blood or buccal swabs from all 12 NWP SFV seroreactive workers. We also found evidence of SFV seroreversion in three workers suggestive of possible clearance of infection. Our findings suggest that NWP SFV can be transmitted to occupationally-exposed humans and can elicit specific humoral immune responses but infection remains well-controlled resulting in latent infection and may occasionally clear.

Human Exposure to Wild Animals in the Sankuru Province of the Democratic Republic of the Congo

Due to the high level of biological diversity in the Congo Basin and human population dependence on bushmeat, the DRC represents an ideal location for expanding knowledge on wild animal exposures and thus the potential for transmission of zoonotic pathogens. However, limited information exists on patterns and extent of contact with wildlife in such communities. Using a cross-sectional study, 14 villages in the Sankuru Province of the DRC were surveyed between August and September 2007. Villagers ≥ 1 year of age and at home of the time of the survey were eligible and enrolled to describe and assess factors associated with animal exposures (both activity and type of animal). Among respondents, 91% reported exposure to rodents, 89% to duikers, 78% to non-human primates (NHPs), and 32% reported contact with bats in the month prior to the survey. The most frequently reported activities included eating (95%), cooking (70%), and butchering or skinning of animals (55%). The activities and animals to which subjects had contact varied by sex and age. Moreover, we observed a high correlation of the same activities across animal types. In this and other populations that rely on bushmeat, there is a high frequency of exposure to multiple animal species through various modalities. In the event of future zoonotic disease outbreaks, effective public health interventions and campaigns that mitigate the risk of animal contact during outbreaks need to be broad to include various modes of contact and should be directed to both men and women across all age groups. As available information is limited, further studies are necessary to better understand the complex relationships and exposures individuals have with animals.

No significant HTLV seroprevalence in German people who inject drugs

Background

Although human T-lymphotropic virus (HTLV) is transmitted via the same routes as human immunodeficiency virus (HIV), its worldwide seroprevalence differs drastically because HTLV is transmitted mainly via infected cells rather than free virus. The sharing of needles and other equipment places people who inject drugs (PWID) at particularly high-risk for such blood-borne diseases.

Methods

To validate the methodology used to process and analyze the dried blood spots (DBS) utilized in the study, dried serum spots (DSS) with dilutions of sera from known HTLV infected individuals were analyzed by ELISA and Western blot. DBS collected between 2011 and 2015 from 2,077 PWID in eight German cities recruited by respondent-driven sampling were tested for HTLV-specific antibodies.

Results

The validation demonstrated that the use of DSS allowed identification of samples with even low titers of HTLV-specific antibodies, although a confirmatory Western blot with an additional venous blood sample would often be required. Despite numerous HIV and HCV positive individuals being identified within the study population, none tested positive for HTLV.

Conclusion

While the HIV and HCV prevalences in German PWID are comparable to those in other European countries, the very low prevalence of HTLV reflects the situation in the general population.

Complete Genome Sequence of a Naturally Occurring Simian Foamy Virus Isolate from Rhesus Macaque (SFVmmu_K3T)

The full-length genome sequence of a simian foamy virus (SFVmmu_K3T), isolated from a rhesus macaque (Macaca mulatta), was obtained using high-throughput sequencing. SFVmmu_K3T consisted of 12,983 bp and had a genomic organization similar to that of other SFVs, with long terminal repeats (LTRs) and open reading frames for Gag, Pol, Env, Tas, and Bet.

A Review of Zoonotic Infection Risks Associated with the Wild Meat Trade in Malaysia

The overhunting of wildlife for food and commercial gain presents a major threat to biodiversity in tropical forests and poses health risks to humans from contact with wild animals. Using a recent survey of wildlife offered at wild meat markets in Malaysia as a basis, we review the literature to determine the potential zoonotic infection risks from hunting, butchering and consuming the species offered. We also determine which taxa potentially host the highest number of pathogens and discuss the significant disease risks from traded wildlife, considering how cultural practices influence zoonotic transmission. We identify 51 zoonotic pathogens (16 viruses, 19 bacteria and 16 parasites) potentially hosted by wildlife and describe the human health risks. The Suidae and the Cervidae families potentially host the highest number of pathogens. We conclude that there are substantial gaps in our knowledge of zoonotic pathogens and recommend performing microbial food safety risk assessments to assess the hazards of wild meat consumption. Overall, there may be considerable zoonotic risks to people involved in the hunting, butchering or consumption of wild meat in Southeast Asia, and these should be considered in public health strategies.

Bushmeat Hunting and Zoonotic Transmission of Simian T-Lymphotropic Virus 1 in Tropical West and Central Africa

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.

Bayesian inference reveals ancient origin of simian foamy virus in orangutans

Simian foamy viruses (SFVs) infect most nonhuman primate species and appears to co-evolve with its hosts. This co-evolutionary signal is particularly strong among great apes, including orangutans (genus Pongo). Previous studies have identified three distinct orangutan SFV clades. The first of these three clades is composed of SFV from P. abelii from Sumatra, the second consists of SFV from P. pygmaeus from Borneo, while the third clade is mixed, comprising an SFV strain found in both species of orangutan. The existence of the mixed clade has been attributed to an expansion of P. pygmaeus into Sumatra following the Mount Toba super-volcanic eruption about 73,000years ago. Divergence dating, however, has yet to be performed to establish a temporal association with the Toba eruption. Here, we use a Bayesian framework and a relaxed molecular clock model with fossil calibrations to test the Toba hypothesis and to gain a more complete understanding of the evolutionary history of orangutan SFV. As with previous studies, our results show a similar three-clade orangutan SFV phylogeny, along with strong statistical support for SFV-host co-evolution in orangutans. Using Bayesian inference, we date the origin of orangutan SFV to >4.7 million years ago (mya), while the mixed species clade dates to approximately 1.7mya, >1.6 million years older than the Toba super-eruption. These results, combined with fossil and paleogeographic evidence, suggest that the origin of SFV in Sumatran and Bornean orangutans, including the mixed species clade, likely occurred on the mainland of Indo-China during the Late Pliocene and Calabrian stage of the Pleistocene, respectively.

High Prevalences and a Wide Genetic Diversity of Simian Retroviruses in Non-human Primate Bushmeat in Rural Areas of the Democratic Republic of Congo

Like the majority of emerging infectious diseases, HIV and HTLV are of zoonotic origin. Here we assess the risk of cross-species transmissions of their simian counterparts, SIV and STLV, from non-human primates (NHP) to humans in the Democratic Republic of Congo (DRC). A total of 331 samples, derived from NHP bushmeat, were collected as dried blood spots (DBS, n = 283) or as tissue samples (n = 36) at remote forest sites mainly in northern and eastern DRC. SIV antibody prevalences in DBS were estimated with a novel high throughput immunoassay with antigens representing the actual known diversity of HIV/SIV lineages. Antibody-positive samples were confirmed by PCR and sequence analysis. Screening for STLV infection was done with universal primers in tax, and new strains were further characterized in LTR. SIV and STLV infection in tissue samples was done by PCR only. Overall, 5 and 15.4% of NHP bushmeat was infected with SIV and STLV, respectively. A new SIV lineage was identified in Allen's swamp monkeys (Allenopithecus nigroviridis). Three new STLV-1 subtypes were identified in Allen's swamp monkeys (Allenopithecus nigroviridis), blue monkeys (Cercopithecus mitis), red-tailed guenons (Cercopithecus ascanius schmidti) and agile mangabeys (Cercocebus agilis). SIV and STLV prevalences varied according to species and geographic region. Our study illustrates clearly, even on a small sample size from a limited number of geographic areas, that our knowledge on the genetic diversity and geographic distribution of simian retroviruses is still limited and that humans continue to be exposed to relative high proportions on infected NHP bushmeat.

Identification of rare HIV-1 Group N, HBV AE, and HTLV-3 strains in rural South Cameroon

Surveillance of emerging viral variants is critical to ensuring that blood screening and diagnostic tests detect all infections regardless of strain or geographic location. In this study, we conducted serological and molecular surveillance to monitor the prevalence and diversity of HIV, HBV, and HTLV in South Cameroon. The prevalence of HIV was 8.53%, HBV was 10.45%, and HTLV was 1.04% amongst study participants. Molecular characterization of 555 HIV-1 specimens identified incredible diversity, including 7 subtypes, 12 CRFs, 6 unclassified, 24 Group O and 2 Group N infections. Amongst 401 HBV sequences were found a rare HBV AE recombinant and two emerging sub-genotype A strains. In addition to HTLV-1 and HTLV-2 strains, sequencing confirmed the fifth known HTLV-3 infection to date. Continued HIV/HBV/HTLV surveillance and vigilance for newly emerging strains in South Cameroon will be essential to ensure diagnostic tests and research stay a step ahead of these rapidly evolving viruses.

Simian Immunodeficiency Virus seroreactivity in inhabitants from rural Cameroon frequently in contact with non-human primates

Central African tropical forests are home to several species of non-human primates (NHPs), infected by Simian Immunodeficiency Virus (SIV). It is well-known that HIV-1 epidemic is due to cross-transmission and adaptation of SIV to humans. The main goal of this work was to investigate if a NHP bite is a risk factor for SIV acquisition. A cross-sectional study was performed in rural Cameroon on 246 bitten individuals (mostly by adult NHPs), matched, according to sex, age, and ethnicity (Bantus and Pygmies), with an equal number of not-bitten subjects. Following a serological assay for a wide range of SIVs, we observed a high level of indeterminate seroreactivity (25.8%) in the total population, whereas 68.9% were sero-negative and 5.3% HIV-1 positive. Bites do not appear to be a risk factor for SIV seroreactivity, in contrast to Simian Foamy Virus and Simian T-Lymphotropic Virus type 1 in the same studied population.

Human T-Cell Leukemia Virus Type 1 Infection and Adult T-Cell Leukemia

Human T-cell leukemia virus type 1 (HTLV-1) is the first retrovirus discovered to cause adult T-cell leukemia (ATL), a highly aggressive blood cancer. HTLV-1 research in the past 35 years has been most revealing in the mechanisms of viral oncogenesis. HTLV-1 establishes a lifelong persistent infection in CD4⁺ T lymphocytes. The infection outcome is governed by host immunity. ATL develops in 2-5% of infected individuals 30-50 years after initial exposure. HTLV-1 encodes two oncoproteins Tax and HBZ, which are required for initiation of cellular transformation and maintenance of cell proliferation, respectively. HTLV-1 oncogenesis is driven by a clonal selection and expansion process during which both host and viral factors cooperate to impair genome stability, immune surveillance, and other mechanisms of tumor suppression. A better understanding of HTLV-1 biology and leukemogenesis will reveal new strategies and modalities for ATL prevention and treatment.

Eleventh International Foamy Virus Conference-Meeting Report

The Eleventh International Foamy Virus Conference took place on 9–10 June 2016 at the Institut Pasteur, Paris, France. The meeting reviewed progress on foamy virus (FV) research, as well as related current topics in retrovirology. FVs are complex retroviruses that are widespread in several animal species. Several research topics on these viruses are relevant to human health: cross-species transmission and viral emergence, vectors for gene therapy, development of antiretroviral drugs, retroviral evolution and its influence on the human genome. In this article, we review the conference presentations on these viruses and highlight the major questions to be answered.