Common cold viruses circulating in children threaten wild chimpanzees through asymptomatic adult carriers

Reverse zoonotic respiratory diseases threaten great apes across Sub-Saharan Africa. Studies of wild chimpanzees have identified the causative agents of most respiratory disease outbreaks as "common cold" paediatric human pathogens, but reverse zoonotic transmission pathways have remained unclear. Between May 2019 and August 2021, we conducted a prospective cohort study of 234 children aged 3-11 years in communities bordering Kibale National Park, Uganda, and 30 adults who were forest workers and regularly entered the park. We collected 2047 respiratory symptoms surveys to quantify clinical severity and simultaneously collected 1989 nasopharyngeal swabs approximately monthly for multiplex viral diagnostics. Throughout the course of the study, we also collected 445 faecal samples from 55 wild chimpanzees living nearby in Kibale in social groups that have experienced repeated, and sometimes lethal, epidemics of human-origin respiratory viral disease. We characterized respiratory pathogens in each cohort and examined statistical associations between PCR positivity for detected pathogens and potential risk factors. Children exhibited high incidence rates of respiratory infections, whereas incidence rates in adults were far lower. COVID-19 lockdown in 2020-2021 significantly decreased respiratory disease incidence in both people and chimpanzees. Human respiratory infections peaked in June and September, corresponding to when children returned to school. Rhinovirus, which caused a 2013 outbreak that killed 10% of chimpanzees in a Kibale community, was the most prevalent human pathogen throughout the study and the only pathogen present at each monthly sampling, even during COVID-19 lockdown. Rhinovirus was also most likely to be carried asymptomatically by adults. Although we did not detect human respiratory pathogens in the chimpanzees during the cohort study, we detected human metapneumovirus in two chimpanzees from a February 2023 outbreak that were genetically similar to viruses detected in study participants in 2019. Our data suggest that respiratory pathogens circulate in children and that adults become asymptomatically infected during high-transmission times of year. These asymptomatic adults may then unknowingly carry the pathogens into forest and infect chimpanzees. This conclusion, in turn, implies that intervention strategies based on respiratory symptoms in adults are unlikely to be effective for reducing reverse zoonotic transmission of respiratory viruses to chimpanzees.

Asymptomatic Orthopoxvirus Circulation in Humans in the Wake of a Monkeypox Outbreak among Chimpanzees in Cameroon

Monkeypox virus is a zoonotic Orthopoxvirus (OPXV) that causes smallpox-like illness in humans. In Cameroon, human monkeypox cases were confirmed in 2018, and outbreaks in captive chimpanzees occurred in 2014 and 2016. We investigated the OPXV serological status among staff at a primate sanctuary (where the 2016 chimpanzee outbreak occurred) and residents from nearby villages, and describe contact with possible monkeypox reservoirs. We focused specifically on Gambian rats (Cricetomys spp.) because they are recognized possible reservoirs and because contact with Gambian rats was common enough to render sufficient statistical power. We collected one 5-mL whole blood specimen from each participant to perform a generic anti-OPXV ELISA test for IgG and IgM antibodies and administered a questionnaire about prior symptoms of monkeypox-like illness and contact with possible reservoirs. Our results showed evidence of OPXV exposures (IgG positive, 6.3%; IgM positive, 1.6%) among some of those too young to have received smallpox vaccination (born after 1980, n = 63). No participants reported prior symptoms consistent with monkeypox. After adjusting for education level, participants who frequently visited the forest were more likely to have recently eaten Gambian rats (OR: 3.36, 95% CI: 1.91-5.92, P < 0.001) and primate sanctuary staff were less likely to have touched or sold Gambian rats (OR: 0.23, 95% CI: 0.19-0.28, P < 0.001). The asymptomatic or undetected circulation of OPXVs in humans in Cameroon is likely, and contact with monkeypox reservoirs is common, raising the need for continued surveillance for human and animal disease.

Lethal Respiratory Disease Associated with Human Rhinovirus C in Wild Chimpanzees, Uganda, 2013

We describe a lethal respiratory outbreak among wild chimpanzees in Uganda in 2013 for which molecular and epidemiologic analyses implicate human rhinovirus C as the cause. Postmortem samples from an infant chimpanzee yielded near-complete genome sequences throughout the respiratory tract; other pathogens were absent. Epidemiologic modeling estimated the basic reproductive number (R₀) for the epidemic as 1.83, consistent with the common cold in humans. Genotyping of 41 chimpanzees and examination of 24 published chimpanzee genomes from subspecies across Africa showed universal homozygosity for the cadherin-related family member 3 CDHR3-Y₅₂₉ allele, which increases risk for rhinovirus C infection and asthma in human children. These results indicate that chimpanzees exhibit a species-wide genetic susceptibility to rhinovirus C and that this virus, heretofore considered a uniquely human pathogen, can cross primate species barriers and threatens wild apes. We advocate engineering interventions and prevention strategies for rhinovirus infections for both humans and wild apes.

A Radical Approach to Ebola: Saving Humans and Other Animals

As the usual regulatory framework did not fit well during the last Ebola outbreak, innovative thinking still needed. In the absence of an outbreak, randomised controlled trials of clinical efficacy in humans cannot be done, while during an outbreak such trials will continue to face significant practical, philosophical, and ethical challenges. This article argues that researchers should also test the safety and effectiveness of novel vaccines in wild apes by employing a pluralistic approach to evidence. There are three reasons to test vaccines in wild populations of apes: i) protect apes; ii) reduce Ebola transmission from wild animals to humans; and iii) accelerate vaccine development and licensing for humans. Data obtained from studies of vaccines among wild apes and chimpanzees may even be considered sufficient for licensing new vaccines for humans. This strategy will serve to benefit both wild apes and humans.

Spatiotemporal Fluctuations and Triggers of Ebola Virus Spillover

Because the natural reservoir of Ebola virus remains unclear and disease outbreaks in humans have occurred only sporadically over a large region, forecasting when and where Ebola spillovers are most likely to occur constitutes a continuing and urgent public health challenge. We developed a statistical modeling approach that associates 37 human or great ape Ebola spillovers since 1982 with spatiotemporally dynamic covariates including vegetative cover, human population size, and absolute and relative rainfall over 3 decades across sub-Saharan Africa. Our model (area under the curve 0.80 on test data) shows that spillover intensity is highest during transitions between wet and dry seasons; overall, high seasonal intensity occurs over much of tropical Africa; and spillover intensity is greatest at high (>1,000/km²) and very low (<100/km²) human population densities compared with intermediate levels. These results suggest strong seasonality in Ebola spillover from wild reservoirs and indicate particular times and regions for targeted surveillance.

Mountain gorilla lymphocryptovirus has Epstein-Barr virus-like epidemiology and pathology in infants

Epstein-Barr virus (EBV) infects greater than 90% of humans, is recognized as a significant comorbidity with HIV/AIDS, and is an etiologic agent for some human cancers. The critically endangered mountain gorilla population was suspected of infection with an EBV-like virus based on serology and infant histopathology similar to pulmonary reactive lymphoid hyperplasia (PRLH), a condition associated with EBV in HIV-infected children. To further examine the presence of EBV or an EBV-like virus in mountain gorillas, we conducted the first population-wide survey of oral samples for an EBV-like virus in a nonhuman great ape. We discovered that mountain gorillas are widely infected (n = 143/332) with a specific strain of lymphocryptovirus 1 (GbbLCV-1). Fifty-two percent of infant mountain gorillas were orally shedding GbbLCV-1, suggesting primary infection during this stage of life, similar to what is seen in humans in less developed countries. We then identified GbbLCV-1 in post-mortem infant lung tissues demonstrating histopathological lesions consistent with PRLH, suggesting primary infection with GbbLCV-1 is associated with PRLH in infants. Together, our findings demonstrate that mountain gorilla's infection with GbbLCV-1 could provide valuable information for human disease in a natural great ape setting and have potential conservation implications in this critically endangered species.

Genetic and phylogenetic characterization of novel bocaparvovirus infecting chimpanzee

Primate bocaparvoviruses were first described in 2005, since then further human and gorilla bocaparvoviruses have been identified. To uncover diversity of non-human primates' bocaparvoviruses, their phylogenetic relationship and potential to cross the host species barrier, we tested 153 fecal samples from 17 captive primate species. The only one captive female of central chimpanzee (coded CPZh2) has been identified as bocaparvovirus positive. Based on the full genome phylogenetic analyses, CPZh2 strain shows close relationship to HBoV3 and GBoV. Further recombination analysis confirmed expected mosaic origin of CPZh2 strain. According the phylogenetic position, following the ICTV recommendations, we propose a novel genotype within the Primate bocaparvovirus 1 species infecting chimpanzee.

Simian Immunodeficiency Virus Infection of Chimpanzees (Pan troglodytes) Shares Features of Both Pathogenic and Non-pathogenic Lentiviral Infections

The virus-host relationship in simian immunodeficiency virus (SIV) infected chimpanzees is thought to be different from that found in other SIV infected African primates. However, studies of captive SIVcpz infected chimpanzees are limited. Previously, the natural SIVcpz infection of one chimpanzee, and the experimental infection of six chimpanzees was reported, with limited follow-up. Here, we present a long-term study of these seven animals, with a retrospective re-examination of the early stages of infection. The only clinical signs consistent with AIDS or AIDS associated disease was thrombocytopenia in two cases, associated with the development of anti-platelet antibodies. However, compared to uninfected and HIV-1 infected animals, SIVcpz infected animals had significantly lower levels of peripheral blood CD4+ T-cells. Despite this, levels of T-cell activation in chronic infection were not significantly elevated. In addition, while plasma levels of β2 microglobulin, neopterin and soluble TNF-related apoptosis inducing ligand (sTRAIL) were elevated in acute infection, these markers returned to near-normal levels in chronic infection, reminiscent of immune activation patterns in ‘natural host’ species. Furthermore, plasma soluble CD14 was not elevated in chronic infection. However, examination of the secondary lymphoid environment revealed persistent changes to the lymphoid structure, including follicular hyperplasia in SIVcpz infected animals. In addition, both SIV and HIV-1 infected chimpanzees showed increased levels of deposition of collagen and increased levels of Mx1 expression in the T-cell zones of the lymph node. The outcome of SIVcpz infection of captive chimpanzees therefore shares features of both non-pathogenic and pathogenic lentivirus infections.

The HIV-1/AIDS pandemic is the result of cross-species transmission of simian immunodeficiency virus (SIVcpz) from chimpanzees to humans. Many African primates are infected with SIV, but those studied in captivity generally do not develop disease. However, wild chimpanzees infected with SIVcpz are at increased risk of death and may develop an AIDS-like disease. It has therefore been suggested that the viral features which SIVcpz and HIV-1 share, that differentiate them from other species’ SIV, may be critical in the development of disease in both humans and chimpanzees. Here, we present a long-term follow-up of 7 SIVcpz infected chimpanzees, housed in primate centres in the US and Europe, under similar conditions to other studied models. These animals did not develop an AIDS-like disease, after up to 25 years of infection, and showed features similar to other species where disease rarely develops, such as limited immune activation in the blood. However, they also had significantly reduced CD4+ T-cells and disruption to the secondary lymphoid tissues, normally associated with pathogenic primate lentiviral infections. Thus, while SIVcpz infection of chimpanzees shares features of both pathogenic and non-pathogenic infections, disease has not developed in captivity.

Human metapneumovirus infection in chimpanzees, United States

Zoonotic disease transmission and infections are of particular concern for humans and closely related great apes. In 2009, an outbreak of human metapneumovirus infection was associated with the death of a captive chimpanzee in Chicago, Illinois, USA. Biosecurity and surveillance for this virus in captive great ape populations should be considered.

Human herpes simplex virus type 1 in confiscated gorilla

In 2007, we detected human herpes simplex virus type 1, which caused stomatitis, in a juvenile confiscated eastern lowland gorilla (Gorilla beringei graueri) that had a high degree of direct contact with human caretakers. Our findings confirm that pathogens can transfer between nonhuman primate hosts and humans.

A new approach for monitoring ebolavirus in wild great apes

BACKGROUND

Central Africa is a "hotspot" for emerging infectious diseases (EIDs) of global and local importance, and a current outbreak of ebolavirus is affecting multiple countries simultaneously. Ebolavirus is suspected to have caused recent declines in resident great apes. While ebolavirus vaccines have been proposed as an intervention to protect apes, their effectiveness would be improved if we could diagnostically confirm Ebola virus disease (EVD) as the cause of die-offs, establish ebolavirus geographical distribution, identify immunologically naïve populations, and determine whether apes survive virus exposure.

METHODOLOGY/PRINCIPAL FINDINGS

Here we report the first successful noninvasive detection of antibodies against Ebola virus (EBOV) from wild ape feces. Using this method, we have been able to identify gorillas with antibodies to EBOV with an overall prevalence rate reaching 10% on average, demonstrating that EBOV exposure or infection is not uniformly lethal in this species. Furthermore, evidence of antibodies was identified in gorillas thought previously to be unexposed to EBOV (protected from exposure by rivers as topological barriers of transmission).

CONCLUSIONS/SIGNIFICANCE

Our new approach will contribute to a strategy to protect apes from future EBOV infections by early detection of increased incidence of exposure, by identifying immunologically naïve at-risk populations as potential targets for vaccination, and by providing a means to track vaccine efficacy if such intervention is deemed appropriate. Finally, since human EVD is linked to contact with infected wildlife carcasses, efforts aimed at identifying great ape outbreaks could have a profound impact on public health in local communities, where EBOV causes case-fatality rates of up to 88%.

Characterization of Enteroviruses from non-human primates in cameroon revealed virus types widespread in humans along with candidate new types and species

Enteroviruses (EVs) infecting African Non-Human Primates (NHP) are still poorly documented. This study was designed to characterize the genetic diversity of EVs among captive and wild NHP in Cameroon and to compare this diversity with that found in humans. Stool specimens were collected in April 2008 in NHP housed in sanctuaries in Yaounde and neighborhoods. Moreover, stool specimens collected from wild NHP from June 2006 to October 2008 in the southern rain forest of Cameroon were considered. RNAs purified directly from stool samples were screened for EVs using a sensitive RT-nested PCR targeting the VP1 capsid coding gene whose nucleotide sequence was used for molecular typing. Captive chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla) were primarily infected by EV types already reported in humans in Cameroon and elsewhere: Coxsackievirus A13 and A24, Echovirus 15 and 29, and EV-B82. Moreover EV-A119, a novel virus type recently described in humans in central and west Africa, was also found in a captive Chimpanzee. EV-A76, which is a widespread virus in humans, was identified in wild chimpanzees, thus suggesting its adaptation and parallel circulation in human and NHP populations in Cameroon. Interestingly, some EVs harbored by wild NHP were genetically distinct from all existing types and were thus assigned as new types. One chimpanzee-derived virus was tentatively assigned as EV-J121 in the EV-J species. In addition, two EVs from wild monkeys provisionally registered as EV-122 and EV-123 were found to belong to a candidate new species. Overall, this study indicates that the genetic diversity of EVs among NHP is more important than previously known and could be the source of future new emerging human viral diseases.

Serological evidence of Ebola virus infection in Indonesian orangutans

Ebola virus (EBOV) and Marburg virus (MARV) belong to the family Filoviridae and cause severe hemorrhagic fever in humans and nonhuman primates. Despite the discovery of EBOV (Reston virus) in nonhuman primates and domestic pigs in the Philippines and the serological evidence for its infection of humans and fruit bats, information on the reservoirs and potential amplifying hosts for filoviruses in Asia is lacking. In this study, serum samples collected from 353 healthy Bornean orangutans (Pongo pygmaeus) in Kalimantan Island, Indonesia, during the period from December 2005 to December 2006 were screened for filovirus-specific IgG antibodies using a highly sensitive enzyme-linked immunosorbent assay (ELISA) with recombinant viral surface glycoprotein (GP) antigens derived from multiple species of filoviruses (5 EBOV and 1 MARV species). Here we show that 18.4% (65/353) and 1.7% (6/353) of the samples were seropositive for EBOV and MARV, respectively, with little cross-reactivity among EBOV and MARV antigens. In these positive samples, IgG antibodies to viral internal proteins were also detected by immunoblotting. Interestingly, while the specificity for Reston virus, which has been recognized as an Asian filovirus, was the highest in only 1.4% (5/353) of the serum samples, the majority of EBOV-positive sera showed specificity to Zaire, Sudan, Cote d'Ivoire, or Bundibugyo viruses, all of which have been found so far only in Africa. These results suggest the existence of multiple species of filoviruses or unknown filovirus-related viruses in Indonesia, some of which are serologically similar to African EBOVs, and transmission of the viruses from yet unidentified reservoir hosts into the orangutan populations. Our findings point to the need for risk assessment and continued surveillance of filovirus infection of human and nonhuman primates, as well as wild and domestic animals, in Asia.

Recovery potential of a western lowland gorilla population following a major Ebola outbreak: results from a ten year study

Investigating the recovery capacity of wildlife populations following demographic crashes is of great interest to ecologists and conservationists. Opportunities to study these aspects are rare due to the difficulty of monitoring populations both before and after a demographic crash. Ebola outbreaks in central Africa have killed up to 95% of the individuals in affected western lowland gorilla (Gorilla gorilla gorilla) populations. Assessing whether and how fast affected populations recover is essential for the conservation of this critically endangered taxon. The gorilla population visiting Lokoué forest clearing, Odzala-Kokoua National Park, Republic of the Congo, has been monitored before, two years after and six years after Ebola affected it in 2004. This allowed us to describe Ebola's short-term and long-term impacts on the structure of the population. The size of the population, which included around 380 gorillas before the Ebola outbreak, dropped to less than 40 individuals after the outbreak. It then remained stable for six years after the outbreak. However, the demographic structure of this small population has significantly changed. Although several solitary males have disappeared, the immigration of adult females, the formation of new breeding groups, and several birth events suggest that the population is showing potential to recover. During the outbreak, surviving adult and subadult females joined old solitary silverbacks. Those females were subsequently observed joining young silverbacks, forming new breeding groups where they later gave birth. Interestingly, some females were observed joining silverbacks that were unlikely to have sired their infant, but no infanticide was observed. The consequences of the Ebola outbreak on the population structure were different two years and six years after the outbreak. Therefore, our results could be used as demographic indicators to detect and date outbreaks that have happened in other, non-monitored gorilla populations.

Detection of retroviral super-infection from non-invasive samples

While much attention has been focused on the molecular epidemiology of retroviruses in wild primate populations, the correlated question of the frequency and nature of super-infection events, i.e., the simultaneous infection of the same individual host with several strains of the same virus, has remained largely neglected. In particular, methods possibly allowing the investigation of super-infection from samples collected non-invasively (such as faeces) have never been properly compared. Here, we fill in this gap by assessing the costs and benefits of end-point dilution PCR (EPD-PCR) and multiple bulk-PCR cloning, as applied to a case study focusing on simian foamy virus super-infection in wild chimpanzees (Pan troglodytes). We show that, although considered to be the gold standard, EPD-PCR can lead to massive consumption of biological material when only low copy numbers of the target are expected. This constitutes a serious drawback in a field in which rarity of biological material is a fundamental constraint. In addition, we demonstrate that EPD-PCR results (single/multiple infection; founder strains) can be well predicted from multiple bulk-PCR clone experiments, by applying simple statistical and network analyses to sequence alignments. We therefore recommend the implementation of the latter method when the focus is put on retroviral super-infection and only low retroviral loads are encountered.

Frequent and recent human acquisition of simian foamy viruses through apes' bites in central Africa

Human infection by simian foamy viruses (SFV) can be acquired by persons occupationally exposed to non-human primates (NHP) or in natural settings. This study aimed at getting better knowledge on SFV transmission dynamics, risk factors for such a zoonotic infection and, searching for intra-familial dissemination and the level of peripheral blood (pro)viral loads in infected individuals. We studied 1,321 people from the general adult population (mean age 49 yrs, 640 women and 681 men) and 198 individuals, mostly men, all of whom had encountered a NHP with a resulting bite or scratch. All of these, either Pygmies (436) or Bantus (1085) live in villages in South Cameroon. A specific SFV Western blot was used and two nested PCRs (polymerase, and LTR) were done on all the positive/borderline samples by serology. In the general population, 2/1,321 (0.2%) persons were found to be infected. In the second group, 37/198 (18.6%) persons were SFV positive. They were mostly infected by apes (37/39) FV (mainly gorilla). Infection by monkey FV was less frequent (2/39). The viral origin of the amplified sequences matched with the history reported by the hunters, most of which (83%) are aged 20 to 40 years and acquired the infection during the last twenty years. The (pro)viral load in 33 individuals infected by a gorilla FV was quite low (<1 to 145 copies per 10⁵ cells) in the peripheral blood leucocytes. Of the 30 wives and 12 children from families of FV infected persons, only one woman was seropositive in WB without subsequent viral DNA amplification. We demonstrate a high level of recent transmission of SFVs to humans in natural settings specifically following severe gorilla bites during hunting activities. The virus was found to persist over several years, with low SFV loads in infected persons. Secondary transmission remains an open question.

Most of the viral pathogens that have emerged in humans during the last decades have a zoonotic origin. After the initial interspecies transmission, these viruses have followed different evolutionary routes and have spread among humans through distinct mechanisms. The understanding of the initial steps of the emergence of several viruses and associated diseases often remains quite poor. Human infection by simian foamy viruses (SFV) can be acquired by persons occupationally exposed to non-human primates (NHP) or in natural settings. Epidemiological and microbiological studies in specific high-risk populations are necessary to gain new insights into the early events of the emergence process, and the potential to spread or cause disease among humans. The present study found that hunting is still a very common and risky activity for SFV infection in forest areas of South Cameroon. Indeed, recent interspecies transmission of SFVs to young adults is still very frequent, as 1 person out of 5 among the hunters who have reported a bite or scratch by a non-human primate and 2 persons out of a thousand in the general population are persistently infected by a SFV, mostly from an ape. Secondary transmission to other family members and presence of a disease in infected persons are still open questions that are being investigated.

Noninvasive monitoring of respiratory viruses in wild chimpanzees

To diagnose respiratory disease among wild great apes, there is a need for noninvasive diagnostic methods. Therefore, we analyzed fecal samples from habituated chimpanzees from Taï National Park, Côte d'Ivoire. Samples had been collected during four distinct outbreaks: two with known aetiology (March 2004 and February 2006) and two with unknown aetiology (October 2004 and August 2005). Fecal samples were screened by polymerase chain reaction (PCR) for the presence of human metapneumovirus (HMPV) and human respiratory syncytial virus (HRSV), two paramyxoviruses previously found in lung tissue of chimpanzees that died due to respiratory disease. In the March 2004 outbreak, 72% of the tested individuals were positive for HMPV, and during the 2006 epidemic, 25% tested HRSV-positive. In the outbreaks where no causative pathogen was previously known, fecal samples tested positive for either HRSV or HMPV, showing that reinfection occurred. Virus sequences were generated and compared with sequences previously found in tissue; nearly identical virus sequences in both tissue and fecal samples were found. These results demonstrate that fecal samples collected during outbreak times can be used for the diagnostic and phylogenetic analysis of HMPV and HRSV. Using such diagnostic tools, systematic noninvasive disease investigation of respiratory outbreaks in wild great apes becomes possible. The methods presented here may also be applied for the investigation of further acute diseases in great apes and other species.

[The origin and evolution of HIV]

Understanding HIV-1 evolution is crucial for tracing its ape origin as well as considering genetic variation within and among hosts. Here, we review the current evidence documenting cross-species transmission from chimpanzees and gorillas to human. First, each HIV-1 groups M, N, O and P arose through 4 different cross-species transmissions of SIVcpz and SIVgor. Second, in vitro studies demonstrate that SIVcpz and SIVgor have many of the biological properties necessary for establishing a persistent infection in humans.

Molecular ecology and natural history of simian foamy virus infection in wild-living chimpanzees

Identifying microbial pathogens with zoonotic potential in wild-living primates can be important to human health, as evidenced by human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2) and Ebola virus. Simian foamy viruses (SFVs) are ancient retroviruses that infect Old and New World monkeys and apes. Although not known to cause disease, these viruses are of public health interest because they have the potential to infect humans and thus provide a more general indication of zoonotic exposure risks. Surprisingly, no information exists concerning the prevalence, geographic distribution, and genetic diversity of SFVs in wild-living monkeys and apes. Here, we report the first comprehensive survey of SFVcpz infection in free-ranging chimpanzees (Pan troglodytes) using newly developed, fecal-based assays. Chimpanzee fecal samples (n = 724) were collected at 25 field sites throughout equatorial Africa and tested for SFVcpz-specific antibodies (n = 706) or viral nucleic acids (n = 392). SFVcpz infection was documented at all field sites, with prevalence rates ranging from 44% to 100%. In two habituated communities, adult chimpanzees had significantly higher SFVcpz infection rates than infants and juveniles, indicating predominantly horizontal rather than vertical transmission routes. Some chimpanzees were co-infected with simian immunodeficiency virus (SIVcpz); however, there was no evidence that SFVcpz and SIVcpz were epidemiologically linked. SFVcpz nucleic acids were recovered from 177 fecal samples, all of which contained SFVcpz RNA and not DNA. Phylogenetic analysis of partial gag (616 bp), pol-RT (717 bp), and pol-IN (425 bp) sequences identified a diverse group of viruses, which could be subdivided into four distinct SFVcpz lineages according to their chimpanzee subspecies of origin. Within these lineages, there was evidence of frequent superinfection and viral recombination. One chimpanzee was infected by a foamy virus from a Cercopithecus monkey species, indicating cross-species transmission of SFVs in the wild. These data indicate that SFVcpz (i) is widely distributed among all chimpanzee subspecies; (ii) is shed in fecal samples as viral RNA; (iii) is transmitted predominantly by horizontal routes; (iv) is prone to superinfection and recombination; (v) has co-evolved with its natural host; and (vi) represents a sensitive marker of population structure that may be useful for chimpanzee taxonomy and conservation strategies.

Hepatitis C virus p7 protein is crucial for assembly and release of infectious virions

Hepatitis C virus (HCV) infection is associated with chronic liver disease and currently affects about 3% of the world population. Although much has been learned about the function of individual viral proteins, the role of the HCV p7 protein in virus replication is not known. Recent data, however, suggest that it forms ion channels that may be targeted by antiviral compounds. Moreover, this protein was shown to be essential for infectivity in chimpanzee. Employing the novel HCV infection system and using a genetic approach to investigate the function of p7 in the viral replication cycle, we find that this protein is essential for efficient assembly and release of infectious virions across divergent virus strains. We show that p7 promotes virus particle production in a genotype-specific manner most likely due to interactions with other viral factors. Virus entry, on the other hand, is largely independent of p7, as the specific infectivity of released virions with a defect in p7 was not affected. Together, these observations indicate that p7 is primarily involved in the late phase of the HCV replication cycle. Finally, we note that p7 variants from different isolates deviate substantially in their capacity to promote virus production, suggesting that p7 is an important virulence factor that may modulate fitness and in turn virus persistence and pathogenesis.

The hepatitis C virus (HCV), a major human pathogen associated with severe liver disease, encodes a small membrane protein designated p7. Although recent reports indicated that p7 forms channels conducting ions across membranes and is essential for HCV infection, its exact role in the viral life cycle remained elusive. In this study, we illustrate that HCV relies on p7 function for efficient assembly and release of infectious progeny virions from liver cells. Conversely, entry of HCV particles into new host cells is independent of p7. This new evidence supports the recent proposal to include p7 into the family of viroporins that comprises proteins from diverse viruses, for instance, HIV-1 and influenza A virus. Members of this group of functionally related proteins form membrane pores that promote virus release and in some cases also virus entry. Moreover, we identify several conserved p7 residues crucial for functioning of this protein. These amino acids possibly stabilize the structure of p7 or directly participate in channelling of ions. Interestingly, p7 variants from divergent patient isolates differ with regard to their ability to promote virus production, suggesting that p7 modulates viral fitness. Together these observations shed new light on fundamental aspects of the HCV replication strategy.

Isolates of Zaire ebolavirus from wild apes reveal genetic lineage and recombinants

Over the last 30 years, Zaire ebolavirus (ZEBOV), a virus highly pathogenic for humans and wild apes, has emerged repeatedly in Central Africa. Thus far, only a few virus isolates have been characterized genetically, all belonging to a single genetic lineage and originating exclusively from infected human patients. Here, we describe the first ZEBOV sequences isolated from great ape carcasses in the Gabon/Congo region that belong to a previously unrecognized genetic lineage. According to our estimates, this lineage, which we also encountered in the two most recent human outbreaks in the Republic of the Congo in 2003 and 2005, diverged from the previously known viruses around the time of the first documented human outbreak in 1976. These results suggest that virus spillover from the reservoir has occurred more than once, as predicted by the multiple emergence hypothesis. However, the young age of both ZEBOV lineages and the spatial and temporal sequence of outbreaks remain at odds with the idea that the virus simply emerged from a long-established and widespread reservoir population. Based on data from two ZEBOV genes, we also demonstrate, within the family Filoviridae, recombination between the two lineages. According to our estimates, this event took place between 1996 and 2001 and gave rise to a group of recombinant viruses that were responsible for a series of outbreaks in 2001-2003. The potential for recombination adds an additional level of complexity to unraveling and potentially controlling the emergence of ZEBOV in humans and wildlife species.

Monitoring of hepatitis C virus quasispecies in chronic infection by matrix-assisted laser desorption ionization-time of flight mass spectrometry mutation detection

Using both a mass spectrometry-based method and the classical method of cloning and sequencing, we demonstrated weekly changes in the hypervariable region 1 quasispecies of a chimpanzee infected with an infectious clone, coinciding with neutralizing antibody emergence. We also used the mass spectrometry method in the clinical follow-up of a chronically infected patient over a 5-year period.

All three variable regions of the TRIM5alpha B30.2 domain can contribute to the specificity of retrovirus restriction

Recent studies have revealed the contribution of TRIM5alpha to retrovirus restriction in cells from a variety of primate species. TRIM5alpha consists of a tripartite motif (the RBCC domain) followed by a B30.2 domain. The B30.2 domain is thought to be involved in determination of restriction specificity and contains three variable regions. To investigate the relationship between the phylogeny of primate TRIM5alpha and retrovirus restriction specificity, a series of chimeric TRIM5alpha consisting of the human RBCC domain followed by the B30.2 domain from various primates was constructed. These constructs showed restriction profiles largely consistent with the origin of the B30.2 domain. Restriction specificity was further investigated with a variety of TRIM5alphas containing mixed or mutated B30.2 domains. This study revealed the importance of all three variable regions for determining restriction specificity. Based on the molecular structures of other PRYSPRY domains solved recently, a model for the molecular structure of the B30.2 domain of TRIM5alpha was developed. The model revealed that the variable regions of the B30.2 domain are present as loops located on one side of the B30.2 core structure. It is hypothesized that these three loops form a binding surface for virus and that evolutionary changes in any one of the loops can alter restriction specificity.

Transmission of simian immunodeficiency virus SIVcpz and the evolution of infection in the presence and absence of concurrent human immunodeficiency virus type 1 infection in chimpanzees

Current data suggest that the human immunodeficiency virus type 1 (HIV-1) epidemic arose by transmission of simian immunodeficiency virus (SIV) SIVcpz from a subspecies of common chimpanzees (Pan troglodytes troglodytes) to humans. SIVcpz of chimpanzees is itself a molecular chimera of SIVs from two or more different monkey species, suggesting that recombination was made possible by coinfection of one individual animal with different lentiviruses. However, very little is known about SIVcpz transmission and the susceptibility to lentivirus coinfection of its natural host, the chimpanzee. Here, it is revealed that either infected plasma or peripheral blood mononuclear cells readily confer infection when exposure occurs by the intravenous or mucosal route. Importantly, the presence of preexisting HIV-1 infection did not modify the kinetics of SIVcpz infection once it was established by different routes. Although humoral responses appeared as early as 4 weeks postinfection, neutralization to SIVcpz-ANT varied markedly between animals. Analysis of the SIVcpz env sequence over time revealed the emergence of genetic viral variants and persistent SIVcpz RNA levels of between 10(4) and 10(5) copies/ml plasma regardless of the presence or absence of concurrent HIV-1 infection. These unique data provide important insight into possible routes of transmission, the kinetics of acute SIVcpz infection, and how readily coinfection with SIVcpz and other lentiviruses may be established as necessary preconditions for potential recombination.

Attempted therapeutic immunization in a chimpanzee chronic HBV carrier with a high viral load

BACKGROUND

We previously reported successful therapeutic immunization in a chimpanzee having a relatively low viral load, which was immunized with recombinant plasmid hepatitis B surface antigen (HBsAg) DNA and boosted with recombinant HBsAg encoding canarypox virus. In the present study, we attempted to confirm these findings in an animal with a high virus load.

METHODS AND RESULTS

We tested three immunization strategies successively over a 3-year period. In the first of these, we administered four monthly injections of DNA encoding HBsAg + PreS2 + hepatitis B core antigen (HBcAg) + DNA encoding interleukin (IL)-12, (given 3 days later), and boosted with canarypox expressing all of the above HBV genes 6 months after initial immunization. No reduction in viral load was observed. In the second trial, we administered lamivudine for 8 weeks, and then began monthly DNA-based immunization with plasmids expressing the above viral genes; however, viral loads rebounded 1 week after termination of lamivudine therapy. In a third trial, we continued lamivudine therapy for 30 weeks and immunized with vaccinia virus expressing the above viral genes 18 and 23 weeks after the start of lamivudine therapy. Again viral loads rebounded shortly after cessation of lamivudine treatment. Analysis of cell-mediated immune responses, and their avidity, revealed that DNA-based immunization produced the strongest enhancement of high avidity T-cell responses, while recombinant vaccinia immunization during lamivudine therapy enhanced low avidity responses only. The strongest low and high avidity responses were directed to the middle surface antigen.

CONCLUSIONS

Three strategies for therapeutic immunization failed to control HBV viremia in a chronically infected chimpanzee with a high viral load.

Chimpanzee reservoirs of pandemic and nonpandemic HIV-1

Human immunodeficiency virus type 1 (HIV-1), the cause of human acquired immunodeficiency syndrome (AIDS), is a zoonotic infection of staggering proportions and social impact. Yet uncertainty persists regarding its natural reservoir. The virus most closely related to HIV-1 is a simian immunodeficiency virus (SIV) thus far identified only in captive members of the chimpanzee subspecies Pan troglodytes troglodytes. Here we report the detection of SIVcpz antibodies and nucleic acids in fecal samples from wild-living P. t. troglodytes apes in southern Cameroon, where prevalence rates in some communities reached 29 to 35%. By sequence analysis of endemic SIVcpz strains, we could trace the origins of pandemic (group M) and nonpandemic (group N) HIV-1 to distinct, geographically isolated chimpanzee communities. These findings establish P. t. troglodytes as a natural reservoir of HIV-1.

Detection and molecular characterization of foamy viruses in Central African chimpanzees of the Pan troglodytes troglodytes and Pan troglodytes vellerosus subspecies

BACKGROUND

Foamy viruses are exogenous retroviruses that are highly endemic in non-human primates (NHPs). Recent studies, mainly performed in North America, indicated frequent simian foamy virus (SFV) infection in persons occupationally exposed to NHPs. This zoonotic infection was demonstrated mainly after bites by chimpanzees [Pan troglodytes (P. t.)] of the West African P. t. verus subspecies in primatology centers or zoos in the USA.

METHODS

We studied 32 chimpanzees from the Central African subspecies P. t. troglodytes and P. t. vellerosus, originating from Cameroon (29 cases) or Gabon (3 cases). We screened first plasma or sera of the animals with a Western blot detecting the SFVs Gag doublet proteins. Then, we performed two nested polymerase chain reactions (PCRs) amplifying a fragment of the integrase and LTR regions and, finally, we made phylogenetical analyses on the sequences obtained from the integrase PCR products.

RESULTS

By serological and/or molecular assays, we detected foamy viruses (FVs) infection in 14 chimpanzees. Sequence comparison and phylogenetic analyses of a 425 bp fragment of the integrase gene obtained for 10 of the 14 positive apes, demonstrated a wide diversity of new FVs strains that belong phylogenetically either to the P. t. troglodytes or P. t. vellerosus foamy viral clade.

CONCLUSIONS

This study shows that chimpanzees living in these areas of Central Africa are infected by several specific foamy viruses. This raises, in such regions, the potential risk of a human retroviral infection of zoonotic origin linked to chimpanzees contacts, as already exemplified for STLV-1 and SIV infections.

Fruit bats as reservoirs of Ebola virus

The first recorded human outbreak of Ebola virus was in 1976, but the wild reservoir of this virus is still unknown. Here we test for Ebola in more than a thousand small vertebrates that were collected during Ebola outbreaks in humans and great apes between 2001 and 2003 in Gabon and the Republic of the Congo. We find evidence of asymptomatic infection by Ebola virus in three species of fruit bat, indicating that these animals may be acting as a reservoir for this deadly virus.

Medical anthropology and Ebola in Congo: cultural models and humanistic care

Seldom have medical anthropologists been involved in efforts to control high mortality diseases such as Ebola hemorrhagic fever (EHF) This paper describes the results of two distinct but complementary interventions during the first phases of an outbreak in the Republic of Congo in 2003. The first approach emphasized understanding local peoples cultural models and political-economic explanations for the disease while the second approach focused on providing more humanitarian care of patients by identifying and incorporating local beliefs and practices into patient care and response efforts.

The epidemiology of simian immunodeficiency virus infection in a large number of wild- and captive-born chimpanzees: evidence for a recent introduction following chimpanzee divergence

Simian immunodeficiency virus (SIVcpz) from the chimpanzee subspecies Pan troglodytes troglodytes has been linked phylogenetically to the origin of HIV-1. Related but distinct SIVcpz strains have also been found in P. t. schweinfurthii , suggesting that SIVcpz may have coevolved among the four chimpanzee subspecies. However, SIVcpz strains from P. t. verus and P. t. vellerosus have not yet been identified. To better understand the epidemiology and natural history of SIVcpz among chimpanzees, we tested serum samples from 1415 chimpanzees housed at eight U.S. research centers and six zoos. Records indicated that 264 (18.6%) of the chimpanzees were African-born. Subspecies identities for 161 chimpanzees, based on analysis of mitochondrial DNA sequences, were found to be P. t. troglodytes (n = 14), P. t. schweinfurthii (n = 3), P. t. verus (n = 143), and P. t. vellerosus (n = 1). All samples were screened for HIV/SIV antibodies by using an HIV-1/2 peptide- based enzyme immunoassay (EIA). Reactive samples were tested further by Western blot (WB). Eight sera (0.57%) were EIA reactive, but none was HIV-1/2 WB positive. Two samples were HIV-1 WB indeterminate. Both samples tested negative for SIVcpz and HIV-1 sequences by reverse transcriptase PCR, suggesting an absence of infection. We also tested sera available from 8 male sexual partners, 6 offspring, and 12 cage mates of a known SIVcpz-infected chimpanzee. All samples were negative, suggesting that SIVcpz may not be easily transmitted to close contacts. Our data show that this large population of chimpanzees is not infected with SIVcpz. The absence of SIVcpz infection in P. t. verus suggests that SIVcpz may not be endemic to this subspecies and implies that SIVcpz may have been introduced more recently into the chimpanzee subspecies following divergence.

Novel polyomavirus detected in the feces of a chimpanzee by nested broad-spectrum PCR

In order to screen for new polyomaviruses in samples derived from various animal species, degenerated PCR primer pairs were constructed. By using a nested PCR protocol, the sensitive detection of nine different polyomavirus genomes was demonstrated. The screening of field samples revealed the presence of a new polyomavirus, tentatively designated chimpanzee polyomavirus (ChPyV), in the feces of a juvenile chimpanzee (Pan troglodytes). Analysis of the region encoding the major capsid protein VP1 revealed a unique insertion in the EF loop of the protein and showed that ChPyV is a distinct virus related to the monkey polyomavirus B-lymphotropic polyomavirus and the human polyomavirus JC polyomavirus.

Fatal inflammatory heart disease in a bonobo (Pan paniscus)

We report the first probable identification of encephalomyocarditis virus (EMCV) in a bonobo (Pan paniscus) that had been part of a forest re-introduction programme. Clinical presentation was of episodic acute on chronic heart failure and cerebral infarction with end-stage renal failure rather than sudden death which is more commonly associated with EMCV infection. A postmortem diagnosis of probable EMCV was made using gross pathological and histopathological examination. Findings included acute on chronic heart failure combined with the unusual but characteristic histopathological features of non-suppurative necrotizing myocarditis with mononuclear, inflammatory infiltration of the brain.

Wild animal mortality monitoring and human Ebola outbreaks, Gabon and Republic of Congo, 2001-2003

All human Ebola virus outbreaks during 2001-2003 in the forest zone between Gabon and Republic of Congo resulted from handling infected wild animal carcasses. After the first outbreak, we created an Animal Mortality Monitoring Network in collaboration with the Gabonese and Congolese Ministries of Forestry and Environment and wildlife organizations (Wildlife Conservation Society and Programme de Conservation et Utilisation Rationnelle des Ecosystemes Forestiers en Afrique Centrale) to predict and possibly prevent human Ebola outbreaks. Since August 2001, 98 wild animal carcasses have been recovered by the network, including 65 great apes. Analysis of 21 carcasses found that 10 gorillas, 3 chimpanzees, and 1 duiker tested positive for Ebola virus. Wild animal outbreaks began before each of the 5 human Ebola outbreaks. Twice we alerted the health authorities to an imminent risk for human outbreaks, weeks before they occurred.

Natural simian foamy virus infection in wild-caught gorillas, mandrills and drills from Cameroon and Gabon

A survey for the presence of simian foamy retroviruses (SFVs) was performed in 44 wild-caught apes and monkeys, including 27 gorillas, 11 mandrills and six drills, originating from south Cameroon or Gabon. Combined serological and/or nested-PCR assays indicated SFV infection among five Gorilla gorilla gorilla, seven Mandrillus sphinx and two Mandrillus leucophaeus. Sequences of a 425 bp fragment of the integrase gene were obtained for 11 animals. Phylogenetic studies indicated that strains from gorillas, mandrills and drills each formed a highly supported phylogenetic clade with, moreover, the existence of two different gorilla SFVs. This study demonstrates for the first time that these animals are naturally infected with specific SFVs. In the context of simian-to-human interspecies transmission, the results confirm that such viruses can also infect humans, as the SFVs identified in wild-caught animals were the same as those recently reported as infecting hunters living in the same geographical areas.

Long-term persistence of infection in chimpanzees inoculated with an infectious hepatitis C virus clone is associated with a decrease in the viral amino acid substitution rate and low levels of heterogeneity

Two chimpanzees, 1535 and 1536, became persistently infected following inoculation with RNA transcripts from cDNA clones of hepatitis C virus (HCV). Analysis of the HCV genomes from both animals showed an accumulation of amino acid substitutions over time. The appearance of substitutions in the envelope genes was associated with increased antienvelope antibody titers. However, extensive mutations were not incorporated into hypervariable region 1 (HVR1). A comparison of the nonsynonymous substitution rate/synonymous substitution rate was made at various time points to analyze selective pressure. The highest level of selective pressure occurred during the acute phase and decreased as the infection continued. The nonsynonymous substitution rate was initially higher than the synonymous substitution rate but decreased over time from 3.3 x 10(-3) (chimpanzee 1535) and 3.2 x 10(-3) (chimpanzee 1536) substitutions/site/year at week 26 to 1.4 x 10(-3) (chimpanzee 1535) and 1.7 x 10(-3) (chimpanzee 1536) at week 216, while the synonymous substitution rate remained steady at approximately 1 x 10(-3) substitutions/site/year. Analysis of PCR products using single-stranded conformational polymorphism indicated a low level of heterogeneity in the viral genome. The results of these studies confirm that the persistence of infection is not solely due to changes in HVR1 or heterogeneity and that the majority of variants observed in natural infections could not arise simply through mutation during the time period most humans and chimpanzees are observed. These data also indicate that immune pressure and selection continue throughout the chronic phase.

Hepatitis C virus kinetics and host responses associated with disease and outcome of infection in chimpanzees

To study determinants of clinical outcome following HCV infection, viral kinetics, immune events, and intrahepatic cytokine markers were compared in 10 naive chimpanzees. Four of the animals cleared HCV; 6 developed persistent infections. All animals developed similar acute infections with increasing viremia from 1 to 2 weeks, followed by alanine aminotransferase (ALT) elevations and seroconversion. This viremia pattern consisted of a biphasic increase, a rapid slope (mean doubling time [t(2)] = 0.5 days) followed by a slower slope after the second week (t(2) = 7.5 days). This slowing of virus replication correlated in all animals with increased intrahepatic 2'5' oligoadenylate synthetase 1 (2OAS-1) messenger RNA (mRNA) levels and was independent of disease outcome. An effective control of virus replication was observed following increases in intrahepatic interferon gamma (IFN-gamma) mRNA and ALT levels. Although this control was associated in all animals with a 2-log decrease in virus titer, the timing occurred approximately 2 weeks later in the chronic group (P <.05). Additionally, while cleared infections were characterized by a continual decrease in virus titer, the titers in the persistent infections reached a steady state level of 10(4) to 10(5) RNA copies/mL. This inability of the immune response to sustain viral clearance in the persistent infections was associated with a reduced intrahepatic CD3e and monocyte-induced protein 1alpha (MIP-1alpha) mRNA induction. In conclusion, these data indicate that, regardless of outcome, chimpanzees generate responses that control HCV replication during the early and late acute phase. However, the pathogenesis of HCV may be determined by a more rapid onset of the induced response and the cell population that migrates to the liver.

Orangutan herpesvirus

A male orangutan suffered from ulcers at the buccal mucosa. We obtained swab fluid from the base of both vesicles and ulcers and collected blood for further separation into serum, plasma and peripheral blood mononuclear cells (PBMC) for detection of antibody to herpesvirus by serology and herpesvirus DNA by polymerase chain reaction (PCR) using consensus degenerate primers. Serology was positive for human EBV IgG but negative for Epstein-Barr virus (EBV) immunoglobulin (IgM), as well as for both human cytomegalovirus and herpes simplex virus IgG and IgM. Upon PCR, we obtained a 232-bp product of virus DNA from PBMC, but not from lesions, serum or plasma. We confirmed the positive result by direct sequencing and compared the nucleotide sequence with other nucleotide sequences applying the BLAST program from GenBank. The sequence was similar to lymphocryptovirus of macaque (93%), marmoset (93%), gorilla (90%) and human EBV (90%). We aligned this sequence with other sequences in GenBank and performed phylogenetic analysis, showing that it probably belongs to the gammaherpesvirus group.

High variety of different simian T-cell leukemia virus type 1 strains in chimpanzees (Pan troglodytes verus) of the Taï National Park, Côte d'Ivoire

We found human T-cell leukemia virus type 1- and simian T-cell leukemia virus type 1 (STLV-1)-related infections in 5 of 10 chimpanzees originating from three groups of wild chimpanzees. The new virus isolates showed a surprising heterogeneity not only in comparison to STLV-1 described previously in other primate species but also between the different chimpanzee groups, within a group, or even between strains isolated from an individual animal. The interdisciplinary combination of virology, molecular epidemiology, and long-term behavioral studies suggests that the primary route of infection might be interspecies transmission from other primates, such as red colobus monkeys, that are hunted and consumed by chimpanzees.

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.

Hepatitis C virus replication kinetics in chimpanzees with self-limited and chronic infections

The availability of molecular beacon-based, real time polymerase chain reaction (PCR) and a semi-automated sample extraction procedure have made it possible for us to retrospectively examine HCV replication kinetics in HCV naive chimpanzees infected during the past 20 years. We compared these in 17 animals that developed chronic infection, and in 21 that developed self-limited infection. No differences were found in infecting dose, or replication kinetics in the acute phase between these two types of infection. An unanticipated finding was the fact that 10 of 17 animals developing chronic infection partially controlled virus replication for 48 +/- 48 weeks after typical acute phase viraemia, and prior to development of chronic infection. Twenty-nine out of 30 (29/30) sera, which were negative by quantitative PCR during the downregulated period, were, however, positive by the more sensitive Genprobe isothermal transcription-mediated amplification (TMA) assay. Thus, downregulation was not complete. Ten animals showing self-limited infection showed complete resolution of viraemia by TMA assay. Quasispecies analysis revealed that in all, except one case, the virus reappearing after downregulation was essentially identical to that of the originally infecting virus.

Frequent simian foamy virus infection in persons occupationally exposed to nonhuman primates

The recognition that AIDS originated as a zoonosis heightens public health concerns associated with human infection by simian retroviruses endemic in nonhuman primates (NHPs). These retroviruses include simian immunodeficiency virus (SIV), simian T-cell lymphotropic virus (STLV), simian type D retrovirus (SRV), and simian foamy virus (SFV). Although occasional infection with SIV, SRV, or SFV in persons occupationally exposed to NHPs has been reported, the characteristics and significance of these zoonotic infections are not fully defined. Surveillance for simian retroviruses at three research centers and two zoos identified no SIV, SRV, or STLV infection in 187 participants. However, 10 of 187 persons (5.3%) tested positive for SFV antibodies by Western blot (WB) analysis. Eight of the 10 were males, and 3 of the 10 worked at zoos. SFV integrase gene (int) and gag sequences were PCR amplified from the peripheral blood lymphocytes available from 9 of the 10 persons. Phylogenetic analysis showed SFV infection originating from chimpanzees (n = 8) and baboons (n = 1). SFV seropositivity for periods of 8 to 26 years (median, 22 years) was documented for six workers for whom archived serum samples were available, demonstrating long-standing SFV infection. All 10 persons reported general good health, and secondary transmission of SFV was not observed in three wives available for WB and PCR testing. Additional phylogenetic analysis of int and gag sequences provided the first direct evidence identifying the source chimpanzees of the SFV infection in two workers. This study documents more frequent infection with SFV than with other simian retroviruses in persons working with NHPs and provides important information on the natural history and species origin of these infections. Our data highlight the importance of studies to better define the public health implications of zoonotic SFV infections.

Simian T cell leukaemia virus type I subtype B in a wild-caught gorilla (Gorilla gorilla gorilla) and chimpanzee (Pan troglodytes vellerosus) from Cameroon

A serological survey for human T cell leukaemia virus (HTLV)/simian T cell leukaemia virus (STLV) antibodies was performed in 61 wild-caught African apes, including five gorillas and 56 chimpanzees originating from south Cameroon. Two young animals, a gorilla (Gorilla gorilla gorilla) and a chimpanzee (Pan troglodytes vellerosus), exhibited a pattern of complete HTLV-I seroreactivity. Sequence comparison and phylogenetic analyses using the complete LTR (750 bp) and a 522 bp fragment of the env gene indicated the existence of two novel STLV-I strains, both of which belonged to HTLV-I/STLV-I molecular clade subtype B, specific to central Africa. These first STLV-I strains to be characterized in gorilla and chimpanzee were closely related to each other as well as to several HTLV-I strains originating from inhabitants of south Cameroon, including pygmies. Such findings reinforce the hypothesis of interspecies transmission of STLV-I to humans, leading to the present day distribution of HTLV-I in central African inhabitants.