The origins of HIV and implications for the global epidemic

A Coupled Spatial-Network Model: A Mathematical Framework for Applications in Epidemiology

There is extensive evidence that network structure (e.g., air transport, rivers, or roads) may significantly enhance the spread of epidemics into the surrounding geographical area. A new compartmental modeling framework is proposed which couples well-mixed (ODE in time) population centers at the vertices, 1D travel routes on the graph's edges, and a 2D continuum containing the rest of the population to simulate how an infection spreads through a population. The edge equations are coupled to the vertex ODEs through junction conditions, while the domain equations are coupled to the edges through boundary conditions. A numerical method based on spatial finite differences for the edges and finite elements in the 2D domain is described to approximate the model, and numerical verification of the method is provided. The model is illustrated on two simple and one complex example geometries, and a parameter study example is performed. The observed solutions exhibit exponential decay after a certain time has passed, and the cumulative infected population over the vertices, edges, and domain tends to a constant in time but varying in space, i.e., a steady state solution.

The Hepatoprotective Effects of Moringa oleifera against Antiretroviral-Induced Cytotoxicity in HepG2 Cells: A Review

The untreated human immunodeficiency virus (HIV), a lentivirus species that attacks immune cells (CD4+ T cells), causes acquired immunodeficiency syndrome (AIDS). HIV-positive people manage HIV/AIDS by using antiretroviral therapy (ART). The ART treatment regimen contains two nucleoside reverse transcriptase inhibitors (NRTIs) and one non-nucleoside reverse transcriptase inhibitor/integrase strand transfer inhibitor. Tenofovir, an NRTI approved for managing HIV infection, is associated with hepatic steatosis and lactic acidosis, which are linked to mitochondrial toxicity and oxidative stress. Due to side-effects associated with ART, people living with HIV often use medicinal plants or a combination of medicinal plants with ART to promote adherence and diminish the side-effects and cytotoxicity. The Moringa oleifera (MO) tree from the family of Moringaceae is among the medicinal trees studied in managing HIV/AIDS in sub-Saharan Africa. The MO tree extracts have been reported to have inhibitory activity primarily against HIV due to their bioactive compounds. However, there is a scarcity of knowledge about the use of the MO tree amongst HIV/AIDS patients receiving ART in South Africa and its effect on patient compliance and outcomes. Thus, this review aims to outline the impact of MO aqueous leaf extract on oxidative stress and antioxidant responses in human HepG2 liver cells after exposure to antiretrovirals such as tenofovir. The review will contribute to a comprehensive understanding of the potential protective effect of MO aqueous leaf extract on tenofovir-induced cytotoxicity.

Primate hemorrhagic fever-causing arteriviruses are poised for spillover to humans

Simian arteriviruses are endemic in some African primates and can cause fatal hemorrhagic fevers when they cross into primate hosts of new species. We find that CD163 acts as an intracellular receptor for simian hemorrhagic fever virus (SHFV; a simian arterivirus), a rare mode of virus entry that is shared with other hemorrhagic fever-causing viruses (e.g., Ebola and Lassa viruses). Further, SHFV enters and replicates in human monocytes, indicating full functionality of all of the human cellular proteins required for viral replication. Thus, simian arteriviruses in nature may not require major adaptations to the human host. Given that at least three distinct simian arteriviruses have caused fatal infections in captive macaques after host-switching, and that humans are immunologically naive to this family of viruses, development of serology tests for human surveillance should be a priority.

Culture, eating behavior, and infectious disease control and prevention

Humans need to obtain nutrients from foods for survival and health. Culture and belief play important roles in food selection and intake. Throughout human history, dietary factor has been one of the important factors inducing and causing outbreaks of infectious diseases. If unhealthy eating behavior, like eating raw/undercooked food or meat and products from wild animals, are not abandoned, foodborne infectious diseases will remain an important risk factor of outbreaks and epidemics. The misconception of dietary culture is one of the important factors that triggers unhealthy eating behavior. Therefore, it is vital to change people’s conceptions and knowledge about what is healthy to eat, in order to completely eliminate unhealthy eating behavior and prevent the recurrence of foodborne infectious diseases. Meanwhile, many factors such as family, society, region, and religion should be involved in.

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.

Bushmeat and Emerging Infectious Diseases: Lessons from Africa

Zoonotic diseases are the main contributor to emerging infectious diseases (EIDs) and present a major threat to global public health. Bushmeat is an important source of protein and income for many African people, but bushmeat-related activities have been linked to numerous EID outbreaks, such as Ebola, HIV, and SARS. Importantly, increasing demand and commercialization of bushmeat is exposing more people to pathogens and facilitating the geographic spread of diseases. To date, these linkages have not been systematically assessed. Here we review the literature on bushmeat and EIDs for sub-Saharan Africa, summarizing pathogens (viruses, fungi, bacteria, helminths, protozoan, and prions) by bushmeat taxonomic group to provide for the first time a comprehensive overview of the current state of knowledge concerning zoonotic disease transmission from bushmeat into humans. We conclude by drawing lessons that we believe are applicable to other developing and developed regions and highlight areas requiring further research to mitigate disease risk.

A twin-cysteine motif in the V2 region of gp120 is associated with SIV envelope trimer stabilization

The V1 and V2 variable regions of the primate immunodeficiency viruses contribute to the trimer association domain of the gp120 exterior envelope glycoprotein. A pair of V2 cysteine residues at 183 and 191 (“twin cysteines”) is present in several simian immunodeficiency viruses, human immunodeficiency virus type 2 (HIV-2) and some SIV_cpz lineages, but not in HIV-1. To examine the role of this potentially disulfide-bonded twin-cysteine motif, the cysteine residues in the SIVmac239 envelope glycoproteins were individually and pairwise substituted by alanine residues. All of the twin-cysteine mutants exhibited decreases in gp120 association with the Env trimer, membrane-fusing activity, and ability to support virus entry. Thus, the twin-cysteine motif plays a role in Env trimer stabilization in SIV and may do so in HIV-2 and some SIV_cpz as well. This implies that HIV-1 lost the twin-cysteines, and may have relatively unstable Env trimers compared to SIV and HIV-2.

Molecular evidence for the presence of Rickettsia Felis in the feces of wild-living African apes

BACKGROUND

Rickettsia felis is a common emerging pathogen detected in mosquitoes in sub-Saharan Africa. We hypothesized that, as with malaria, great apes may be exposed to the infectious bite of infected mosquitoes and release R. felis DNA in their feces.

METHODS

We conducted a study of 17 forest sites in Central Africa, testing 1,028 fecal samples from 313 chimpanzees, 430 gorillas and 285 bonobos. The presence of rickettsial DNA was investigated by specific quantitative real-time PCR. Positive results were confirmed by a second PCR using primers and a probe targeting a specific gene for R. felis. All positive samples were sequenced.

RESULTS

Overall, 113 samples (11%) were positive for the Rickettsia-specific gltA gene, including 25 (22%) that were positive for R. felis. The citrate synthase (gltA) sequence and outer membrane protein A (ompA) sequence analysis indicated 99% identity at the nucleotide level to R. felis. The 88 other samples (78%) were negative using R. felis-specific qPCR and were compatible with R. felis-like organisms.

CONCLUSION

For the first time, we detected R. felis in wild-living ape feces. This non invasive detection of human pathogens in endangered species opens up new possibilities in the molecular epidemiology and evolutionary analysis of infectious diseases, beside HIV and malaria.

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

Non-human primates are considered to be likely sources of viruses that can infect humans and thus pose a significant threat to human population. This is well illustrated by some retroviruses, as the simian immunodeficiency viruses and the simian T lymphotropic viruses, which have the ability to cross-species, adapt to a new host and sometimes spread. This leads to a pandemic situation for HIV-1 or an endemic one for HTLV-1. Here, we present the available data on the discovery, epidemiology, cross-species transmission and molecular virology of the recently discovered HTLV-3 and HTLV-4 deltaretroviruses, as well as the simian foamy retroviruses present in different human populations at risk, especially in central African hunters. We discuss also the natural history in humans of these retroviruses of zoonotic origin (magnitude and geographical distribution, possible inter-human transmission). In Central Africa, the increase of the bushmeat trade during the last decades has opened new possibilities for retroviral emergence in humans, especially in immuno-compromised persons.

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.

Cross-species transmission of simian retroviruses: how and why they could lead to the emergence of new diseases in the human population

The HIV-1 group M epidemic illustrates the extraordinary impact and consequences resulting from a single zoonotic transmission. Exposure to blood or other secretions of infected animals, through hunting and butchering of bushmeat, or through bites and scratches inflicted by pet nonhuman primates (NHPs), represent the most plausible source for human infection with simian immunodeficiency virus (SIV), simian T-cell lymphotropic virus (STLV) and simian foamy virus. The chance for cross-species transmissions could increase when frequency of exposure and retrovirus prevalence is high. According to the most recent data, human exposure to SIV or STLV appears heterogeneous across the African countries surveyed. Exposure is not sufficient to trigger disease: viral and host molecular characteristics and compatibility are fundamental factors to establish infection. A successful species jump is achieved when the pathogen becomes transmissible between individuals within the new host population. To spread efficiently, HIV likely required changes in human behavior. Given the increasing exposure to NHP pathogens through hunting and butchering, it is likely that SIV and other simian viruses are still transmitted to the human population. The behavioral and socio-economic context of the twenty-first century provides favorable conditions for the emergence and spread of new epidemics. Therefore, it is important to evaluate which retroviruses the human population is exposed to and to better understand how these viruses enter, infect, adapt and spread to its new host.

The evolution of HIV: inferences using phylogenetics

Molecular phylogenetics has revolutionized the study of not only evolution but also disparate fields such as genomics, bioinformatics, epidemiology, ecology, microbiology, molecular biology and biochemistry. Particularly significant are its achievements in population genetics as a result of the development of coalescent theory, which have contributed to more accurate model-based parameter estimation and explicit hypothesis testing. The study of the evolution of many microorganisms, and HIV in particular, have benefited from these new methodologies. HIV is well suited for such sophisticated population analyses because of its large population sizes, short generation times, high substitution rates and relatively small genomes. All these factors make HIV an ideal and fascinating model to study molecular evolution in real time. Here we review the significant advances made in HIV evolution through the application of phylogenetic approaches. We first examine the relative roles of mutation and recombination on the molecular evolution of HIV and its adaptive response to drug therapy and tissue allocation. We then review some of the fundamental questions in HIV evolution in relation to its origin and diversification and describe some of the insights gained using phylogenies. Finally, we show how phylogenetic analysis has advanced our knowledge of HIV dynamics (i.e., phylodynamics).

Characterization of a monoclonal anti-capsid antibody that cross-reacts with three major primate lentivirus lineages

Mouse monoclonal antibodies with varying specificities against the Gag capsid of simian and human immunodeficiency virus (SIV/HIV) were generated by immunizing mice with whole inactivated SIVagmTYO-1. Monoclonal antibody AG3.0 showed the broadest reactivity recognizing the Gag capsid protein (p24-27) and Gag precursors p38, p55, and p150 of HIV-1, HIV-2, SIVmac, and SIVagm. Using overlapping peptides, the AG3.0 epitope was mapped in capsid to a sequence (SPRTLNA) conserved among HIV-1, HIV-2, SIVrcm, SIVsm/mac, and SIVagm related viruses. Because of its broad cross-reactivity, AG3.0 was used to develop an antigen capture assay with a lower detection limit of 100 pg/ml HIV-1 Gag p24. Interestingly, AG3.0 was found to have a faster binding on/off rate for SIVagmVer and SIVmac Gag than for SIVagmSab Gag, possibly due to differences outside the SPRTLNA motif. In addition, the ribonucleic acid (RNA) coding for AG3.0 was sequenced to facilitate the development of humanized monoclonal antibodies.

Novel multiplexed HIV/simian immunodeficiency virus antibody detection assay

Like most emerging infectious disease viruses, HIV is also of zoonotic origin. To assess the risk for cross-species transmission of simian immunodeficiency viruses (SIVs) from nonhuman primates to humans in the Democratic Republic of Congo, we collected 330 samples derived from nonhuman primate bushmeat at 3 remote forest sites. SIV prevalences were estimated by using a novel high-throughput assay that included 34 HIV and SIV antigens in a single well. Overall, 19% of nonhuman primate bushmeat was infected with SIVs, and new SIV lineages were identified. Highest SIV prevalences were seen in red-tailed guenons (25%) and Tshuapa red colobus monkeys (24%), representing the most common hunted primate species, thus increasing the likelihood for cross-species transmission. Additional studies are needed to determine whether other SIVs crossed the species barrier. With the newly developed assay, large-scale screening against many antigens is now easier and faster.

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.

Molecular evolution of Azagny virus, a newfound hantavirus harbored by the West African pygmy shrew (Crocidura obscurior) in Côte d'Ivoire

Background

Tanganya virus (TGNV), the only shrew-associated hantavirus reported to date from sub-Saharan Africa, is harbored by the Therese's shrew (Crocidura theresae), and is phylogenetically distinct from Thottapalayam virus (TPMV) in the Asian house shrew (Suncus murinus) and Imjin virus (MJNV) in the Ussuri white-toothed shrew (Crocidura lasiura). The existence of myriad soricid-borne hantaviruses in Eurasia and North America would predict the presence of additional hantaviruses in sub-Saharan Africa, where multiple shrew lineages have evolved and diversified.

Methods

Lung tissues, collected in RNAlater^®, from 39 Buettikofer's shrews (Crocidura buettikoferi), 5 Jouvenet's shrews (Crocidura jouvenetae), 9 West African pygmy shrews (Crocidura obscurior) and 21 African giant shrews (Crocidura olivieri) captured in Côte d'Ivoire during 2009, were systematically examined for hantavirus RNA by RT-PCR.

Results

A genetically distinct hantavirus, designated Azagny virus (AZGV), was detected in the West African pygmy shrew. Phylogenetic analysis of the S, M and L segments, using maximum-likelihood and Bayesian methods, under the GTR+I+Γ model of evolution, showed that AZGV shared a common ancestry with TGNV and was more closely related to hantaviruses harbored by soricine shrews than to TPMV and MJNV. That is, AZGV in the West African pygmy shrew, like TGNV in the Therese's shrew, did not form a monophyletic group with TPMV and MJNV, which were deeply divergent and basal to other rodent- and soricomorph-borne hantaviruses. Ancestral distributions of each hantavirus lineage, reconstructed using Mesquite 2.74, suggested that the common ancestor of all hantaviruses was most likely of Eurasian, not African, origin.

Conclusions

Genome-wide analysis of many more hantaviruses from sub-Saharan Africa are required to better understand how the biogeographic origin and radiation of African shrews might have contributed to, or have resulted from, the evolution of hantaviruses.

Preparation and evaluation of the 1st international standard for the quantitation of HIV-2 RNA in plasma

An international standard for the quantitation of HIV-2 RNA in plasma samples was developed. A collaborative study involving 29 laboratories from 15 countries was carried out in order to evaluate HIV-2 RNA candidate materials for use with nucleic acid-based tests (NATs). Candidate reference standards consisted of duplicate copies of two HIV-2 genotype A viruses, HIV-2 CAM2 and HIV-2 ROD and were coded S1-S4. Each laboratory assayed all four candidates on at least three separate occasions and data were collated and analysed at NIBSC. Of the data sets returned the majority were from qualitative assays. All assays detected both candidate standards with the exception of one commercial assay, the Nuclisens Easy Q, which was designed primarily for HIV-1 detection which did not detect HIV-2 CAM2 but showed good detection of HIV-2 ROD. This highlighted possible cross reactivity with HIV-2 ROD with some NAT primer/probe combinations; as a result the HIV-2 CAM2 material was established as the 1st international standard for HIV-2 RNA with an assigned unitage of 1000 International Units (IU) per ampoule and is available upon request from the National Institute for Biological Standardisation and Control (NIBSC) (www.nibsc.ac.uk).

Distinctive TLR7 signaling, type I IFN production, and attenuated innate and adaptive immune responses to yellow fever virus in a primate reservoir host

Why cross-species transmissions of zoonotic viral infections to humans are frequently associated with severe disease when viruses responsible for many zoonotic diseases appear to cause only benign infections in their reservoir hosts is unclear. Sooty mangabeys (SMs), a reservoir host for SIV, do not develop disease following SIV infection, unlike nonnatural HIV-infected human or SIV-infected rhesus macaque (RM) hosts. SIV infections of SMs are characterized by an absence of chronic immune activation, in association with significantly reduced IFN-α production by plasmacytoid dendritic cells (pDCs) following exposure to SIV or other defined TLR7 or TLR9 ligands. In this study, we demonstrate that SM pDCs produce significantly less IFN-α following ex vivo exposure to the live attenuated yellow fever virus 17D strain vaccine, a virus that we show is also recognized by TLR7, than do RM or human pDCs. Furthermore, in contrast to RMs, SMs mount limited activation of innate immune responses and adaptive T cell proliferative responses, along with only transient antiviral Ab responses, following infection with yellow fever vaccine 17D strain. However, SMs do raise significant and durable cellular and humoral immune responses comparable to those seen in RMs when infected with modified vaccinia Ankara, a virus whose immunogenicity does not require TLR7/9 recognition. Hence, differences in the pattern of TLR7 signaling and type I IFN production by pDCs between primate species play an important role in determining their ability to mount and maintain innate and adaptive immune responses to specific viruses, and they may also contribute to determining whether disease follows infection.

Multiple barriers to recombination between divergent HIV-1 variants revealed by a dual-marker recombination assay

Recombination is a major force for generating human immunodeficiency virus type 1 (HIV-1) diversity and produces numerous recombinants circulating in the human population. We previously established a cell-based system using green fluorescent protein gene (gfp) as a reporter to study the mechanisms of HIV-1 recombination. We now report an improved system capable of detecting recombination using authentic viral sequences. Frameshift mutations were introduced into the gag gene so that parental viruses do not express full-length Gag; however, recombination can generate a progeny virus that expresses a functional Gag. We demonstrate that this Gag reconstitution assay can be used to detect recombination between two group M HIV-1 variants of the same or of different subtypes. Using both gfp and gag assays, we found that, similar to group M viruses, group O viruses also recombine frequently. When recombination between a group M virus and a group O virus was examined, we found three distinct barriers for intergroup recombination. First, similar to recombination within group M viruses, intergroup recombination is affected by the identity of the dimerization initiation signal (DIS); variants with the same DIS recombined at a higher rate than those with different DIS. Second, using the gfp recombination assay, we showed that intergroup recombination occurs much less frequently than intragroup recombination, even though the gfp target sequence is identical in all viruses. Finally, Gag reconstitution between variants from different groups is further reduced compared with green fluorescent protein, indicating that sequence divergence interferes with recombination efficiency in the gag gene. Compared with identical sequences, we estimate that recombination rates are reduced by 3-fold and by 10- to 13-fold when the target regions in gag contain 91% and 72-73% sequence identities, respectively. These results show that there are at least three distinct mechanisms preventing exchange of genetic information between divergent HIV-1 variants from different groups.

No evidence for transmission of SIVwrc from western red colobus monkeys (Piliocolobus badius badius) to wild West African chimpanzees (Pan troglodytes verus) despite high exposure through hunting

BACKGROUND

Simian Immunodeficiency Viruses (SIVs) are the precursors of Human Immunodeficiency Viruses (HIVs) which have led to the worldwide HIV/AIDS pandemic. By studying SIVs in wild primates we can better understand the circulation of these viruses in their natural hosts and habitat, and perhaps identify factors that influence susceptibility and transmission within and between various host species. We investigated the SIV status of wild West African chimpanzees (Pan troglodytes verus) which frequently hunt and consume the western red colobus monkey (Piliocolobus badius badius), a species known to be infected to a high percentage with its specific SIV strain (SIVwrc).

RESULTS

Blood and plasma samples from 32 wild chimpanzees were tested with INNO-LIA HIV I/II Score kit to detect cross-reactive antibodies to HIV antigens. Twenty-three of the samples were also tested for antibodies to 43 specific SIV and HIV lineages, including SIVwrc. Tissue samples from all but two chimpanzees were tested for SIV by PCRs using generic SIV primers that detect all known primate lentiviruses as well as primers designed to specifically detect SIVwrc. Seventeen of the chimpanzees showed varying degrees of cross-reactivity to the HIV specific antigens in the INNO-LIA test; however no sample had antibodies to SIV or HIV strain- and lineage-specific antigens in the Luminex test. No SIV DNA was found in any of the samples.

CONCLUSIONS

We could not detect any conclusive trace of SIV infection from the red colobus monkeys in the chimpanzees, despite high exposure to this virus through frequent hunting. The results of our study raise interesting questions regarding the host-parasite relationship of SIVwrc and wild chimpanzees in their natural habitat.

Adaptation of HIV-1 to cells expressing rhesus monkey TRIM5α

The cross-species transmission of retroviruses is limited by host restriction factors that exhibit inter-species diversity. For example, the TRIM5α proteins of Old World monkeys block the early, post-entry steps in human immunodeficiency virus (HIV-1) infection. We adapted an HIV-1 isolate to replicate in cells expressing TRIM5α(rh) from rhesus monkeys, an Old World species. A single amino acid change in the cyclophilin-binding loop of the HIV-1 capsid protein allowed virus replication in cells expressing TRIM5α(rh). The capsid of the escape virus exhibited a reduced affinity for TRIM5α(rh), but retained the ability to bind cyclophilin A efficiently. Thus, a preferred HIV-1 escape pathway involves decreased binding to TRIM5α, a capsid-destabilizing factor, and retention of binding to cyclophilin A, a capsid-stabilizing factor.

Trans-biopolitics: Complexity in interspecies relations

This article introduces the concept of trans-biopolitics to account for complexity in the intermingling of animal and human bodies, with particular attention to diseases capable of crossing the species divide from animals to humans. While zoonotic diseases never disappeared, they had re-emerged as pressing concerns by the 21st century. The concept of trans-biopolitics takes into account the power relations inherent in human and nonhuman lives in contemporary global, industrial, and technological formations. More specifically, trans-biopolitics revolves around practices determining whose lives are possible or legitimate to prolong, whose bodies are sacrificed in order to preserve the vitality of other bodies, and whose bodies are sustained yet ultimately rendered insignificant. To illustrate, we examine connections between bovine spongiform encephalopathy and feline spongiform encephalopathy, to show how certain bodies (humans, livestock) are taken into consideration in terms of health and food regulations, whereas other bodies (pets) remain at the periphery. Acknowledging human—animal relations in contemporary technological and global contexts challenges us to rethink ways in which the politics of health continues to evolve.

Lack of Evidence of Simian Immunodeficiency Virus Infection Among Nonhuman Primates in Taï National Park, Côte d'Ivoire: Limitations of Noninvasive Methods and SIV Diagnostic Tools for Studies of Primate Retroviruses

It is now well established that the human immunodeficiency viruses, HIV-1 and HIV-2, are the results of cross-species transmissions of simian immunodeficiency viruses (SIV) naturally infecting nonhuman primates in sub-Saharan Africa. SIVs are found in many African primates, and humans continue to be exposed to these viruses by hunting and handling primate bushmeat. Sooty mangabeys (Cercocebus atys) and western red colobus (Piliocolobus badius badius) are infected with SIV at a high rate in the Taï Forest, Côte d'Ivoire. We investigated the SIV infection and prevalence in 6 other monkey species living in the Taï Forest using noninvasive methods. We collected 127 fecal samples from 2 colobus species (Colobus polykomos and Procolobus verus) and 4 guenon species (C. diana, C. campbelli, C. petaurista, and C. nictitans). We tested these samples for HIV cross-reactive antibodies and performed reverse transcriptase-polymerase chain reactions (RT-PCR) targeting the gag, pol, and env regions of the SIV genome. We screened 16 human microsatellites for use in individual discrimination and identified 4-6 informative markers per species. Serological analysis of 112 samples yielded negative (n=86) or uninterpretable (n=26) results. PCR analysis on 74 samples confirmed the negative results. These results may reflect either the limited number of individuals sampled or a low prevalence of infection. Further research is needed to improve the sensitivity of noninvasive methods for SIV detection.

The presence of a vpu gene and the lack of Nef-mediated downmodulation of T cell receptor-CD3 are not always linked in primate lentiviruses

Nef is an accessory protein critical for the ability of human and simian immunodeficiency viruses (HIV and SIV) to replicate efficiently in their respective hosts. Previous analyses of members of 15 different primate lentivirus lineages revealed a link between Nef function and the presence of a vpu gene. In particular, Nef proteins of all vpu-containing viruses had lost their ability to downmodulate the T cell (TCR-CD3) receptor. Here we examined Nef proteins from eight additional SIV lineages, including SIVgor, SIVwrc, SIVolc, SIVgri, SIVdrl, SIVlho, SIVden, and SIVasc, from western lowland gorillas, western red colobus monkeys, olive colobus monkeys, grivet monkeys, drills, L'Hoest's monkeys, Dent's mona monkeys, and red-tailed monkeys, respectively. We found that except for the nef gene of SIVdrl, all of them were efficiently expressed and modulated CD4, major histocompatibility complex class I (MHC-I), CD28, CXCR4, and Ii cell surface expression and/or enhanced viral infectivity and replication. Furthermore, the Nef proteins of SIVgri, SIVlho, SIVwrc, SIVolc, and SIVgor antagonized tetherin. As expected, the Nef protein of SIVgor, which carries vpu, failed to downmodulate CD3, whereas those of SIVwrc, SIVgri, SIVlho, and SIVasc, which lack vpu, were capable of performing this function. Surprisingly, however, the Nef protein of the vpu-containing SIVden strain retained the ability to downmodulate TCR-CD3, whereas that of SIVolc, which does not contain vpu, was unable to perform this function. Although the SIVden Vpu is about 20 amino acids shorter than other Vpu proteins, it degrades CD4 and antagonizes tetherin. Our data show that there are exceptions to the link between the presence of a vpu gene and nef alleles deficient in CD3 modulation, indicating that host properties also affect the selective pressure for Nef-mediated disruption of TCR-CD3 signaling. Our results are also further evidence that tetherin antagonism is a common function of primate lentivirus Nef proteins and that the resistance of human tetherin to Nef represents a relevant barrier to cross-species transmission of SIVs to humans.

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

Simian immunodeficiency viruses (SIVs) are lentiviruses that infect an extensive number of wild African primate species. Here we describe for the first time SIV infection in a captive agile mangabey (Cercocebus agilis) from Cameroon. Phylogenetic analysis of the full-length genome sequence of SIVagi-00CM312 showed that this novel virus fell into the SIVrcm lineage and was most closely related to a newly characterized SIVrcm strain (SIVrcm-02CM8081) from a wild-caught red-capped mangabey (Cercocebus torquatus) from Cameroon. In contrast to red-capped mangabeys, no 24&emsp14;bp deletion in CCR5 has been observed in the agile mangabey. Further studies on wild agile mangabeys are needed to determine whether agile and red-capped mangabeys are naturally infected with the same SIV lineage, or whether this agile mangabey became infected with an SIVrcm strain in captivity. However, our study shows that agile mangabeys are susceptible to SIV infection.

Patterns of Human Immunodeficiency Virus type 1 recombination ex vivo provide evidence for coadaptation of distant sites, resulting in purifying selection for intersubtype recombinants during replication

High-frequency recombination is a hallmark of HIV-1 replication. Recombination can occur between two members of the same subtype or between viruses from two different subtypes, generating intra- or intersubtype recombinants, respectively. Many intersubtype recombinants have been shown to circulate in human populations. We hypothesize that sequence diversity affects the emergence of viable recombinants by decreasing recombination events and reducing the ability of the recombinants to replicate. To test our hypothesis, we compared recombination between two viruses containing subtype B pol genes (B/B) and between viruses with pol genes from subtype B or F (B/F). Recombination events generated during a single cycle of infection without selection pressure on pol gene function were analyzed by single-genome sequencing. We found that recombination occurred slightly ( approximately 30%) less frequently in B/F than in B/B viruses, and the overall distribution of crossover junctions in pol was similar for the two classes of recombinants. We then examined the emergence of recombinants in a multiple cycle assay, so that functional pol gene products were selected. We found that the emerging B/B recombinants had complex patterns, and the crossover junctions were distributed throughout the pol gene. In contrast, selected B/F recombinants had limited recombination patterns and restricted crossover junction distribution. These results provide evidence for the evolved coadapted sites in variants from different subtypes; these sites may be segregated by recombination events, causing the newly generated intersubtype recombinants to undergo purifying selection. Therefore, the ability of the recombinants to replicate is the major barrier for many of these viruses.

Tetherin-driven adaptation of Vpu and Nef function and the evolution of pandemic and nonpandemic HIV-1 strains

Vpu proteins of pandemic HIV-1 M strains degrade the viral receptor CD4 and antagonize human tetherin to promote viral release and replication. We show that Vpus from SIVgsn, SIVmus, and SIVmon infecting Cercopithecus primate species also degrade CD4 and antagonize tetherin. In contrast, SIVcpz, the immediate precursor of HIV-1, whose Vpu shares a common ancestry with SIVgsn/mus/mon Vpu, uses Nef rather than Vpu to counteract chimpanzee tetherin. Human tetherin, however, is resistant to Nef and thus poses a significant barrier to zoonotic transmission of SIVcpz to humans. Remarkably, Vpus from nonpandemic HIV-1 O strains are poor tetherin antagonists, whereas those from the rare group N viruses do not degrade CD4. Thus, only HIV-1 M evolved a fully functional Vpu following the three independent cross-species transmissions that resulted in HIV-1 groups M, N, and O. This may explain why group M viruses are almost entirely responsible for the global HIV/AIDS pandemic.

Tetherin: holding on and letting go

Mammalian cells are equipped with so-called "restriction factors" that suppress virus replication and help to prevent virus transmission from one species to another. This Essay discusses the host restriction factor tetherin, which blocks the release of enveloped viruses like HIV-1, and the factors evolved by primate lentiviruses, such as Vpu and Nef, that antagonize tetherin's action.

International multicenter study to assess a panel of reference materials for quantification of simian immunodeficiency virus RNA in plasma

An international multicenter study was conducted to assess the performance of a panel of simian immunodeficiency virus (SIV) RNA reference materials for plasma viral load determinations. Reliable quantification was demonstrated across an approximately 6 log(10) dynamic range. Availability of external reference materials will enable independent calibration of SIV plasma viral load assays.

Extensive survey on the prevalence and genetic diversity of SIVs in primate bushmeat provides insights into risks for potential new cross-species transmissions

To evaluate the risk of cross-species transmissions of SIVs from non-human primates to humans at the primate/hunter interface, a total of 2586 samples, derived from primate bushmeat representing 11 different primate species, were collected at 6 distinct remote forest sites in southeastern Cameroon and in Yaoundé, the capital city. SIV prevalences were estimated with an updated SIV lineage specific gp41 peptide ELISA covering the major part of the SIV diversity. SIV positive samples were confirmed by PCR and sequence analysis of partial pol fragments. The updated SIV ELISA showed good performance with overall sensitivity and specificity of 96% and 97.5% respectively. The overall SIV seroprevalence was low, 2.93% (76/2586) and ranged between 0.0% and 5.7% at forest sites, and reached up to 10.3% in Yaoundé. SIV infection was documented in 8 of the 11 species with significantly different prevalence rates per species: 9/859 (1.0%) in Cercopithecus nictitans, 9/864 (1.0%) Cercopithecus cephus, 10/60 (16.7%) Miopithecus ogouensis, 14/78 (17.9%) Colobus guereza, 15/37 (40.5%) Cercopithecus neglectus, 10/27 (33.3%) Mandrillus sphinx, 6/12 (50%) Cercocebus torquatus, and 3/6 (50%) Chlorocebus tantalus. No SIV infection was identified in Cercopithecus pogonias (n=293), Lophocebus albigena (n=168) and Cercocebus agilis (n=182). The SIV prevalences also seem to vary within species according to the sampling site, but most importantly, the highest SIV prevalences are observed in the primate species which represent only 8.5% of the overall primate bushmeat. The phylogenetic tree of partial pol sequences illustrates the high genetic diversity of SIVs between and within different primate species. The tree also showed some interesting features within the SIVdeb lineage suggesting phylogeographic clusters. Overall, the risk for additional cross-species transmissions is not equal throughout southern Cameroon and depends on the hunted species and SIV prevalences in each species. However, humans are still exposed to a high diversity of SIVs as illustrated by the high inter and intra SIV lineage genetic diversity.

The development of antiretroviral therapy and its impact on the HIV-1/AIDS pandemic

In the last 25 years, HIV-1, the retrovirus responsible for the acquired immunodeficiency syndrome (AIDS), has gone from being an "inherently untreatable" infectious agent to one eminently susceptible to a range of approved therapies. During a five-year period, starting in the mid-1980s, my group at the National Cancer Institute played a role in the discovery and development of the first generation of antiretroviral agents, starting in 1985 with Retrovir (zidovudine, AZT) in a collaboration with scientists at the Burroughs-Wellcome Company (now GlaxoSmithKline). We focused on AZT and related congeners in the dideoxynucleoside family of nucleoside reverse transcriptase inhibitors (NRTIs), taking them from the laboratory to the clinic in response to the pandemic of AIDS, then a terrifying and lethal disease. These drugs proved, above all else, that HIV-1 infection is treatable, and such proof provided momentum for new therapies from many sources, directed at a range of viral targets, at a pace that has rarely if ever been matched in modern drug development. Antiretroviral therapy has brought about a substantial decrease in the death rate due to HIV-1 infection, changing it from a rapidly lethal disease into a chronic manageable condition, compatible with very long survival. This has special implications within the classic boundaries of public health around the world, but at the same time in certain regions may also affect a cycle of economic and civil instability in which HIV-1/AIDS is both cause and consequence. Many challenges remain, including (1) the life-long duration of therapy; (2) the ultimate role of pre-exposure prophylaxis (PrEP); (3) the cardiometabolic side-effects or other toxicities of long-term therapy; (4) the emergence of drug-resistance and viral genetic diversity (non-B subtypes); (5) the specter of new cross-species transmissions from established retroviral reservoirs in apes and Old World monkeys; and (6) the continued pace of new HIV-1 infections in many parts of the world. All of these factors make refining current therapies and developing new therapeutic paradigms essential priorities, topics covered in articles within this special issue of Antiviral Research. Fortunately, there are exciting new insights into the biology of HIV-1, its interaction with cellular resistance factors, and novel points of attack for future therapies. Moreover, it is a short journey from basic research to public health benefit around the world. The current science will lead to new therapeutic strategies with far-reaching implications in the HIV-1/AIDS pandemic. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, Vol. 85, issue 1, 2010.

Molecular epidemiology of simian immunodeficiency virus infection in wild-living gorillas

Chimpanzees and gorillas are the only nonhuman primates known to harbor viruses closely related to HIV-1. Phylogenetic analyses showed that gorillas acquired the simian immunodeficiency virus SIVgor from chimpanzees, and viruses from the SIVcpz/SIVgor lineage have been transmitted to humans on at least four occasions, leading to HIV-1 groups M, N, O, and P. To determine the geographic distribution, prevalence, and species association of SIVgor, we conducted a comprehensive molecular epidemiological survey of wild gorillas in Central Africa. Gorilla fecal samples were collected in the range of western lowland gorillas (n = 2,367) and eastern Grauer gorillas (n = 183) and tested for SIVgor antibodies and nucleic acids. SIVgor antibody-positive samples were identified at 2 sites in Cameroon, with no evidence of infection at 19 other sites, including 3 in the range of the Eastern gorillas. In Cameroon, based on DNA and microsatellite analyses of a subset of samples, we estimated the prevalence of SIVgor to be 1.6% (range, 0% to 4.6%), which is significantly lower than the prevalence of SIVcpzPtt in chimpanzees (5.9%; range, 0% to 32%). All newly identified SIVgor strains formed a monophyletic lineage within the SIVcpz radiation, closely related to HIV-1 groups O and P, and clustered according to their field site of origin. At one site, there was evidence for intergroup transmission and a high intragroup prevalence. These isolated hot spots of SIVgor-infected gorilla communities could serve as a source for human infection. The overall low prevalence and sporadic distribution of SIVgor could suggest a decline of SIVgor in wild populations, but it cannot be excluded that SIVgor is still more prevalent in other parts of the geographical range of gorillas.

A rare null allele potentially encoding a dominant-negative TRIM5alpha protein in Baka pygmies

The global acquired immunodeficiency syndrome (AIDS) pandemic is thought to have arisen by the transmission of human immunodeficiency virus (HIV-1)-like viruses from chimpanzees in southeastern Cameroon to humans. TRIM5alpha is a restriction factor that can decrease the susceptibility of cells of particular mammalian species to retrovirus infection. A survey of TRIM5 genes in 127 indigenous individuals from southeastern Cameroon revealed that approximately 4% of the Baka pygmies studied were heterozygous for a rare variant with a stop codon in exon 8. The predicted product of this allele, TRIM5 R332X, is truncated in the functionally important B30.2(SPRY) domain, does not restrict retrovirus infection, and acts as a dominant-negative inhibitor of wild-type human TRIM5alpha. Thus, some indigenous African forest dwellers potentially exhibit diminished TRIM5alpha function; such genetic factors, along with the high frequency of exposure to chimpanzee body fluids, may have predisposed to the initial cross-species transmission of HIV-1-like viruses.

Simian foamy virus infection in humans: prevalence and management

Simian foamy viruses (SFVs) are highly prevalent in all nonhuman primate species and can infect humans following occupational and non-occupational exposure to infected animals and their tissues, blood or body fluids. Virus transmission results in a stable, persistent infection that seems to be latent. SFV infections are thus far nonpathogenic, with no evidence of adverse clinical outcome in their natural nonhuman primate hosts or by experimental injection in animals and upon cross-species transmission in humans. Since the emergence of pathogenic viruses from nonpathogenic viruses upon cross-species infection is well-documented for several retroviruses, it is prudent to take necessary precautions to deter SFV infections in humans. These steps will help prevent the emergence of a novel pathogen and reduce the risk of transmission of another potential pathogenic human retrovirus.

[Analysis of genetic recombination between human immunodeficiency virus type 1 (HIV-1) and HIV-2]

It is estimated that one million people are dually infected with Human Immunodeficiency Virus type-I (HIV-1) and type-II (HIV-2) in West Africa and parts of India. HIV-1 and HIV-2 use the same receptor and coreceptors for entry into cells, and thus target the same cell populations in the host. Additionally, we first examined whether RNAs from HIV-1 and HIV-2 can be copackaged into the same virion. Therefore these properties suggest that in the dually infected population, it is likely that some cells can be infected by both HIV-1 and HIV-2, thereby providing opportunities for these two viruses to interact with each other. We constructed recombination assay system for measurement recombination frequencies and analyzed recombination rate between HIV-1 and HIV-2. We used modified near-full-length viruses that each contained a green fluorescent protein gene (gfp) with a different inactivating mutation. Thus, a functional gfp could be reconstituted via recombination, which was used to detect copackaging of HIV-1 and HIV-2 RNAs. In this study, approximately 0.2% of infection events generated the GFP phenotype. Therefore, the appearance of the GFP+ phenotype in the current system is approximately 35-fold lower than that between two homologous HIV-1 or HIV-2 viruses. We then mapped the general structures of the recombinant viruses and characterized the recombination junctions by DNA sequencing. We observed several different recombination patterns including those only had crossovers in gfp. The most common hybrid genomes had heterologous LTRs. Although infrequent, crossovers were also identified in the viral sequences. Such chimeric HIV-1 and HIV-2 viruses have yet to be observed in the infected population. It is unclear whether the lack of observed chimeras is due to the divergence between HIV-1 and HIV-2 being too great for such an event to occur, or whether such events could occur but have not yet been observed. Given the number of coinfected people, the potential for interactions between HIV-1 and HIV-2 should not be ignored.

Origin and biology of simian immunodeficiency virus in wild-living western gorillas

Western lowland gorillas (Gorilla gorilla gorilla) are infected with a simian immunodeficiency virus (SIVgor) that is closely related to chimpanzee and human immunodeficiency viruses (SIVcpz and HIV-1, respectively) in west central Africa. Although existing data suggest a chimpanzee origin for SIVgor, a paucity of available sequences has precluded definitive conclusions. Here, we report the molecular characterization of one partial (BQ664) and three full-length (CP684, CP2135, and CP2139) SIVgor genomes amplified from fecal RNAs of wild-living gorillas at two field sites in Cameroon. Phylogenetic analyses showed that all SIVgor strains clustered together, forming a monophyletic lineage throughout their genomes. Interestingly, the closest relatives of SIVgor were not SIVcpzPtt strains from west central African chimpanzees (Pan troglodytes troglodytes) but human viruses belonging to HIV-1 group O. In trees derived from most genomic regions, SIVgor and HIV-1 group O formed a sister clade to the SIVcpzPtt lineage. However, in a tree derived from 5' pol sequences ( approximately 900 bp), SIVgor and HIV-1 group O fell within the SIVcpzPtt radiation. The latter was due to two SIVcpzPtt strains that contained mosaic pol sequences, pointing to the existence of a divergent SIVcpzPtt lineage that gave rise to SIVgor and HIV-1 group O. Gorillas appear to have acquired this lineage at least 100 to 200 years ago. To examine the biological properties of SIVgor, we synthesized a full-length provirus from fecal consensus sequences. Transfection of the resulting clone (CP2139.287) into 293T cells yielded infectious virus that replicated efficiently in both human and chimpanzee CD4(+) T cells and used CCR5 as the coreceptor for viral entry. Together, these results provide strong evidence that P. t. troglodytes apes were the source of SIVgor. These same apes may also have spawned the group O epidemic; however, the possibility that gorillas served as an intermediary host cannot be excluded.

Animal-human connections, "one health," and the syndemic approach to prevention

A syndemic involves two or more afflictions that, by interacting synergistically, contribute to excess burdens of disease. A syndemic approach to prevention, meanwhile, focuses on connections among health-related problems, considers those connections when developing health policies, and aligns with forces for social change. In this short report, we expand the syndemic concept to acknowledge the extent to which animal health connects with human health and, with reference to existing publications, we demonstrate the pertinence of this expanded definition for a syndemic approach to prevention. Our demonstration assumes practical importance in relation to the concept of 'one health', which many prominent veterinary and human health scientists have recently endorsed as a sound basis for redressing human diseases, animal diseases, and environmental degradation worldwide. While social scientists have mostly ignored animal health, few 'one health' proponents have emphasized social conditions or involved social scientists. By explicitly accommodating animal-human connections in our expanded conceptualization of a syndemic, we hope to help create a space in which human health, veterinary, and social scientists may learn from one another, collaborate in research, and cooperate to clear the way for innovations in prevention.

Role of CCL3L1-CCR5 genotypes in the epidemic spread of HIV-1 and evaluation of vaccine efficacy

BACKGROUND

Polymorphisms in CCR5, the major coreceptor for HIV, and CCL3L1, a potent CCR5 ligand and HIV-suppressive chemokine, are determinants of HIV-AIDS susceptibility. Here, we mathematically modeled the potential impact of these genetic factors on the epidemic spread of HIV, as well as on its prevention.

METHODS AND RESULTS

Ro, the basic reproductive number, is a fundamental concept in explaining the emergence and persistence of epidemics. By modeling sexual transmission among HIV+/HIV- partner pairs, we find that Ro estimates, and concordantly, the temporal and spatial patterns of HIV outgrowth are highly dependent on the infecting partners' CCL3L1-CCR5 genotype. Ro was least and highest when the infected partner possessed protective and detrimental CCL3L1-CCR5 genotypes, respectively. The modeling data indicate that in populations such as Pygmies with a high CCL3L1 gene dose and protective CCR5 genotypes, the spread of HIV might be minimal. Additionally, Pc, the critical vaccination proportion, an estimate of the fraction of the population that must be vaccinated successfully to eradicate an epidemic was <1 only when the infected partner had a protective CCL3L1-CCR5 genotype. Since in practice Pc cannot be >1, to prevent epidemic spread, population groups defined by specific CCL3L1-CCR5 genotypes might require repeated vaccination, or as our models suggest, a vaccine with an efficacy of >70%. Further, failure to account for CCL3L1-CCR5-based genetic risk might confound estimates of vaccine efficacy. For example, in a modeled trial of 500 subjects, misallocation of CCL3L1-CCR5 genotype of only 25 (5%) subjects between placebo and vaccine arms results in a relative error of approximately 12% from the true vaccine efficacy.

CONCLUSIONS

CCL3L1-CCR5 genotypes may impact on the dynamics of the HIV epidemic and, consequently, the observed heterogeneous global distribution of HIV infection. As Ro is lowest when the infecting partner has beneficial CCL3L1-CCR5 genotypes, we infer that therapeutic vaccines directed towards reducing the infectivity of the host may play a role in halting epidemic spread. Further, CCL3L1-CCR5 genotype may provide critical guidance for optimizing the design and evaluation of HIV-1 vaccine trials and prevention programs.

Could FIV zoonosis responsible of the breakdown of the pathocenosis which has reduced the European CCR5-Delta32 allele frequencies?

Background

In Europe, the north-south downhill cline frequency of the chemokine receptor CCR5 allele with a 32-bp deletion (CCR5-Δ32) raises interesting questions for evolutionary biologists. We had suggested first that, in the past, the European colonizers, principally Romans, might have been instrumental of a progressively decrease of the frequencies southwards. Indeed, statistical analyses suggested strong negative correlations between the allele frequency and historical parameters including the colonization dates by Mediterranean civilisations. The gene flows from colonizers to native populations were extremely low but colonizers are responsible of the spread of several diseases suggesting that the dissemination of parasites in naive populations could have induced a breakdown rupture of the fragile pathocenosis changing the balance among diseases. The new equilibrium state has been reached through a negative selection of the null allele.

Results

Most of the human diseases are zoonoses and cat might have been instrumental in the decrease of the allele frequency, because its diffusion through Europe was a gradual process, due principally to Romans; and that several cat zoonoses could be transmitted to man. The possible implication of a feline lentivirus (FIV) which does not use CCR5 as co-receptor is discussed. This virus can infect primate cells in vitro and induces clinical signs in macaque. Moreover, most of the historical regions with null or low frequency of CCR5-Δ32 allele coincide with historical range of the wild felid species which harbor species-specific FIVs.

Conclusion

We proposed the hypothesis that the actual European CCR5 allelic frequencies are the result of a negative selection due to a disease spreading. A cat zoonosis, could be the most plausible hypothesis. Future studies could provide if CCR5 can play an antimicrobial role in FIV pathogenesis. Moreover, studies of ancient DNA could provide more evidences regarding the implications of zoonoses in the actual CCR5-Δ32 distribution.

25 years of HIV research on virology, virus restriction, immunopathogenesis, genes and vaccines

From 19 to 21 May 2008 an important meeting was held at the Pasteur Institute in Paris to mark the 25th Anniversary of the discovery of HIV as the aetiological agent of AIDS. This review summarizes the historical findings, recent work and future directions presented at this meeting.

Macaque models of human infectious disease

Macaques have served as models for more than 70 human infectious diseases of diverse etiologies, including a multitude of agents—bacteria, viruses, fungi, parasites, prions. The remarkable diversity of human infectious diseases that have been modeled in the macaque includes global, childhood, and tropical diseases as well as newly emergent, sexually transmitted, oncogenic, degenerative neurologic, potential bioterrorism, and miscellaneous other diseases. Historically, macaques played a major role in establishing the etiology of yellow fever, polio, and prion diseases. With rare exceptions (Chagas disease, bartonellosis), all of the infectious diseases in this review are of Old World origin. Perhaps most surprising is the large number of tropical (16), newly emergent (7), and bioterrorism diseases (9) that have been modeled in macaques. Many of these human diseases (e.g., AIDS, hepatitis E, bartonellosis) are a consequence of zoonotic infection. However, infectious agents of certain diseases, including measles and tuberculosis, can sometimes go both ways, and thus several human pathogens are threats to nonhuman primates including macaques. Through experimental studies in macaques, researchers have gained insight into pathogenic mechanisms and novel treatment and vaccine approaches for many human infectious diseases, most notably acquired immunodeficiency syndrome (AIDS), which is caused by infection with human immunodeficiency virus (HIV). Other infectious agents for which macaques have been a uniquely valuable resource for biomedical research, and particularly vaccinology, include influenza virus, paramyxoviruses, flaviviruses, arenaviruses, hepatitis E virus, papillomavirus, smallpox virus, Mycobacteria, Bacillus anthracis, Helicobacter pylori, Yersinia pestis, and Plasmodium species. This review summarizes the extensive past and present research on macaque models of human infectious disease.

Emergence of simian foamy viruses in humans: facts and unanswered questions

A large proportion of viral pathogens that have emerged in humans are considered to have originated in animals. Simian viral infections of humans represent an increasing public health concern. This is well illustrated by retroviruses such as HIV-1/2 and human T-cell lymphotropic virus (HTLV)-1, which have a unique ability to cross species, adapt to a new host and spread. In this short review, we will present the currently available data on the transmission of the simian foamy retroviruses (SFVs) to humans. Indeed, recent data indicate the presence of these exogenous retroviruses, of the Spumaretrovirinae subfamily and of the Spumavirus genus, in individuals occupationally exposed to nonhuman primates (animal caretaker, veterinarian, zoo worker) and in individuals having contact with apes and monkeys, such as hunters in Central Africa. The main unanswered questions concerning the natural history of such SFVs in humans, for instance, their magnitude and geographical distribution, their interhuman transmissibility and their disease association and pathogenicity are discussed in this review.

Genetic recombination between human immunodeficiency virus type 1 (HIV-1) and HIV-2, two distinct human lentiviruses

Human immunodeficiency virus type 1 (HIV-1) and HIV-2 are genetically distinct viruses that each can cause AIDS. Approximately 1 million people are infected with both HIV-1 and HIV-2. Additionally, these two viruses use the same receptor and coreceptors and can therefore infect the same target cell populations. To explore potential genetic interactions, we first examined whether RNAs from HIV-1 and HIV-2 can be copackaged into the same virion. We used modified near-full-length viruses that each contained a green fluorescent protein gene (gfp) with a different inactivating mutation. Thus, a functional gfp could be reconstituted via recombination, which was used to detect the copackaging of HIV-1 and HIV-2 RNAs. The GFP-positive (GFP(+)) phenotype was detected in approximately 0.2% of the infection events, which was 35-fold lower than the intrasubtype HIV-1 rates. We isolated and characterized 54 GFP(+) single-cell clones and determined that all of them contained proviruses with reconstituted gfp. We then mapped the general structures of the recombinant viruses and characterized the recombination junctions by DNA sequencing. We observed several different recombination patterns, including those that had crossovers only in gfp. The most common hybrid genomes had heterologous long terminal repeats. Although infrequent, crossovers in the viral sequences were also identified. Taken together, our study demonstrates that HIV-1 and HIV-2 can recombine, albeit at low frequencies. These observations indicate that multiple factors are likely to restrict the generation of viable hybrid HIV-1 and HIV-2 viruses. However, considering the large coinfected human population and the high viral load in patients, these rare events could provide the basis for the generation of novel human immunodeficiency viruses.