Human immunodeficiency viruses: SIV infection in wild gorillas

Comparative Analysis of Tat-Dependent and Tat-Deficient Natural Lentiviruses

The emergence of human immunodeficiency virus (HIV) causing acquired immunodeficiency syndrome (AIDS) in infected humans has resulted in a global pandemic that has killed millions. HIV-1 and HIV-2 belong to the lentivirus genus of the Retroviridae family. This genus also includes viruses that infect other vertebrate animals, among them caprine arthritis-encephalitis virus (CAEV) and Maedi-Visna virus (MVV), the prototypes of a heterogeneous group of viruses known as small ruminant lentiviruses (SRLVs), affecting both goat and sheep worldwide. Despite their long host-SRLV natural history, SRLVs were never found to be responsible for immunodeficiency in contrast to primate lentiviruses. SRLVs only replicate productively in monocytes/macrophages in infected animals but not in CD4+ T cells. The focus of this review is to examine and compare the biological and pathological properties of SRLVs as prototypic Tat-independent lentiviruses with HIV-1 as prototypic Tat-dependent lentiviruses. Results from this analysis will help to improve the understanding of why and how these two prototypic lentiviruses evolved in opposite directions in term of virulence and pathogenicity. Results may also help develop new strategies based on the attenuation of SRLVs to control the highly pathogenic HIV-1 in humans.

High Rate of Simian Immunodeficiency Virus (SIV) Infections in Wild Chimpanzees in Northeastern Gabon

The emergence of HIV-1 groups M, N, O, and P is the result of four independent cross-species transmissions between chimpanzees (cpz) and gorillas (gor) from central/south Cameroon and humans respectively. Although the first two SIVcpz were identified in wild-born captive chimpanzees in Gabon in 1989, no study has been conducted so far in wild chimpanzees in Gabon. To document the SIVcpz infection rate, genetic diversity, and routes of virus transmission, we analyzed 1458 faecal samples collected in 16 different locations across the country, and we conducted follow-up missions in two of them. We found 380 SIV antibody positive samples in 6 different locations in the north and northeast. We determined the number of individuals collected by microsatellite analysis and obtained an adjusted SIV prevalence of 39.45%. We performed parental analysis to investigate viral spread between and within communities and found that SIVs were epidemiologically linked and were transmitted by both horizontal and vertical routes. We amplified pol and gp41 fragments and obtained 57 new SIVcpzPtt strains from three sites. All strains, but one, clustered together within a specific phylogeographic clade. Given that these SIV positive samples have been collected nearby villages and that humans continue to encroach in ape's territories, the emergence of a new HIV in this area needs to be considered.

HIV-1 group O infection in Cameroon from 2006 to 2013: Prevalence, genetic diversity, evolution and public health challenges

The human immunodeficiency virus, HIV, is characterized by a tremendously high genetic diversity, leading to the currently known circulating HIV types, groups, subtypes, and recombinant forms. HIV-1 group O is one of the most diverse forms of HIV-1 and has been so far related to Cameroon or individuals originating from Cameroon. In this study, we investigated in Cameroon, the evolution of this viral group from 2006 to 2013, in terms of prevalence, genetic diversity and public health implications. Our results confirmed the predominance of HIV-1 group M (98.5%), a very low prevalence (<0.02%) for HIV-1 group N and P, and HIV-2 in this country. HIV-1 group O was found at around 0.6% (95% confidence interval: 0.4-0.8%), indicating that the frequency of this virus in Cameroon has remained stable over the last decades. However, we found an extensive high genetic diversity within this HIV-1 group, that resulted from previous steady increase on the effective number of HIV-1 group O infections through time, and the current distribution of the circulating viral strains still does not allow classification as subtypes. The frequency of dual infections with HIV-1 group M and group O was 0.8% (95% confidence interval: 0.6-1.0%), but we found no recombinant forms in co-infected patients. Natural resistance to integrase inhibitors was not identified, although we found several mutations considered as natural polymorphisms. Our study shows that infections with HIV-1 group O can be adequately managed in countries where the virus circulates, but this complex virus still represents a challenge for diagnostics and monitoring strategies.

Near full-length HIV type 1M genomic sequences from Cameroon : Evidence of early diverging under-sampled lineages in the country

Background: Cameroon is the country in which HIV-1 group M (HIV-1M) likely originated and is today a major hotspot of HIV-1M genetic diversity. It remains unclear, however, whether the highly divergent HIV-1M lineages found in this country arose during the earliest phases of the global HIV-1M epidemic, or whether they arose more recently as a result of recombination events between globally circulating HIV-1M lineages.

Methodology: To differentiate between these two possibilities, we performed phylogenetic analyses of the near full genome sequences of nine newly sequenced divergent HIV-1M isolates and 15 previously identified, apparently unique recombinant forms (URFs) from Cameroon.

Results: Although two of the new genome sequences were clearly classifiable within subtype G, the remaining seven were highly divergent and phylogenetically branched either outside of, or very near the bases of clades containing the well characterised globally circulating viral lineages that they were most closely related to. Recombination analyses further revealed that these divergent viruses were likely complex URFs. We show, however that substantial portions (>1 Kb) of three of the new genome sequences and 15 of the previously characterised Cameroonian URFs have apparently been derived from divergent parental viruses that branch phylogenetically near the bases of the major HIV-1M clades.

Conclusions and implications: Our analyses indicate the presence in Cameroon of contemporary descendants of numerous early-diverging HIV-1M lineages. Further efforts to sample and sequence viruses from such lineages could be crucial both for retracing the earliest evolutionary steps during the emergence of HIV-1M in humans, and accurately reconstructing the ancestral sequences of the major globally circulating HIV-1M lineages.

Lv4 Is a Capsid-Specific Antiviral Activity in Human Blood Cells That Restricts Viruses of the SIVMAC/SIVSM/HIV-2 Lineage Prior to Integration

HIV-2 and SIV_MAC are AIDS-causing, zoonotic lentiviruses that jumped to humans and rhesus macaques, respectively, from SIV_SM-bearing sooty mangabey monkeys. Cross-species transmission events such as these sometimes necessitate virus adaptation to species-specific, host restriction factors such as TRIM5. Here, a new human restriction activity is described that blocks viruses of the SIV_SM/SIV_MAC/HIV-2 lineage. Human T, B, and myeloid cell lines, peripheral blood mononuclear cells and dendritic cells were 4 to >100-fold less transducible by VSV G-pseudotyped SIV_MAC, HIV-2, or SIV_SM than by HIV-1. In contrast, transduction of six epithelial cell lines was equivalent to that by HIV-1. Substitution of HIV-1 CA with the SIV_MAC or HIV-2 CA was sufficient to reduce HIV-1 transduction to the level of the respective vectors. Among such CA chimeras there was a general trend such that CAs from epidemic HIV-2 Group A and B isolates were the most infectious on human T cells, CA from a 1° sooty mangabey isolate was the least infectious, and non-epidemic HIV-2 Group D, E, F, and G CAs were in the middle. The CA-specific decrease in infectivity was observed with either HIV-1, HIV-2, ecotropic MLV, or ALV Env pseudotypes, indicating that it was independent of the virus entry pathway. As₂O₃, a drug that suppresses TRIM5-mediated restriction, increased human blood cell transduction by SIV_MAC but not by HIV-1. Nonetheless, elimination of TRIM5 restriction activity did not rescue SIV_MAC transduction. Also, in contrast to TRIM5-mediated restriction, the SIV_MAC CA-specific block occurred after completion of reverse transcription and the formation of 2-LTR circles, but before establishment of the provirus. Transduction efficiency in heterokaryons generated by fusing epithelial cells with T cells resembled that in the T cells, indicative of a dominant-acting SIV_MAC restriction activity in the latter. These results suggest that the nucleus of human blood cells possesses a restriction factor specific for the CA of HIV-2/SIV_MAC/SIV_SM and that cross-species transmission of SIV_SM to human T cells necessitated adaptation of HIV-2 to this putative restriction factor.

HIV-1 and HIV-2, the two lentiviruses that cause AIDS in humans, are members of a family of such viruses that infect African primates. HIV-1 is a zoonosis that was transmitted to humans from chimpanzees. HIV-2 was transmitted to humans from sooty mangabey monkeys. In several documented cases of cross-species transmission of lentiviruses it has been shown that replication of the virus in the new host species necessitated that the virus adapt to species-specific antiviral factors in the host. Here we report that human blood cells possess an antiviral activity that exhibits specificity for viruses of the HIV-2/SIV_MAC/SIV_SM lineage, with restriction being greatest for SIV_SM and the least for epidemic HIV-2. Here we show that this dominant-acting, antiviral activity is specific for the capsid and blocks the virus after it enters the nucleus. The evidence suggests that, in order to jump from sooty mangabey monkeys to humans, the capsid of these viruses changed in order to adapt to this antiviral activity. In keeping with the practice concerning anti-lentiviral activities we propose to call this new antiviral activity Lv4.

Neutralization properties of simian immunodeficiency viruses infecting chimpanzees and gorillas

Broadly cross-reactive neutralizing antibodies (bNabs) represent powerful tools to combat human immunodeficiency virus type 1 (HIV-1) infection. Here, we examined whether HIV-1-specific bNabs are capable of cross-neutralizing distantly related simian immunodeficiency viruses (SIVs) infecting central (Pan troglodytes troglodytes) (SIVcpzPtt) and eastern (Pan troglodytes schweinfurthii) (SIVcpzPts) chimpanzees (n = 11) as well as western gorillas (Gorilla gorilla gorilla) (SIVgor) (n = 1). We found that bNabs directed against the CD4 binding site (n = 10), peptidoglycans at the base of variable loop 3 (V3) (n = 5), and epitopes at the interface of surface (gp120) and membrane-bound (gp41) envelope glycoproteins (n = 5) failed to neutralize SIVcpz and SIVgor strains. In addition, apex V2-directed bNabs (n = 3) as well as llama-derived (heavy chain only) antibodies (n = 6) recognizing both the CD4 binding site and gp41 epitopes were either completely inactive or neutralized only a fraction of SIVcpzPtt strains. In contrast, one antibody targeting the membrane-proximal external region (MPER) of gp41 (10E8), functional CD4 and CCR5 receptor mimetics (eCD4-Ig, eCD4-Ig(mim2), CD4-218.3-E51, and CD4-218.3-E51-mim2), as well as mono- and bispecific anti-human CD4 (iMab and LM52) and CCR5 (PRO140, PRO140-10E8) receptor antibodies neutralized >90% of SIVcpz and SIVgor strains with low-nanomolar (0.13 to 8.4 nM) potency. Importantly, the latter antibodies blocked virus entry not only in TZM-bl cells but also in Cf2Th cells expressing chimpanzee CD4 and CCR5 and neutralized SIVcpz in chimpanzee CD4(+) T cells, with 50% inhibitory concentrations (IC50s) ranging from 3.6 to 40.5 nM. These findings provide new insight into the protective capacity of anti-HIV-1 bNabs and identify candidates for further development to combat SIVcpz infection.

IMPORTANCE

SIVcpz is widespread in wild-living chimpanzees and can cause AIDS-like immunopathology and clinical disease. HIV-1 infection of humans can be controlled by antiretroviral therapy; however, treatment of wild-living African apes with current drug regimens is not feasible. Nonetheless, it may be possible to curb the spread of SIVcpz in select ape communities using vectored immunoprophylaxis and/or therapy. Here, we show that antibodies and antibody-like inhibitors developed to combat HIV-1 infection in humans are capable of neutralizing genetically diverse SIVcpz and SIVgor strains with considerable breadth and potency, including in primary chimpanzee CD4(+) T cells. These reagents provide an important first step toward translating intervention strategies currently developed to treat and prevent AIDS in humans to SIV-infected apes.

Multiple Cross-Species Transmission Events of Human Adenoviruses (HAdV) during Hominine Evolution

Human adenoviruses (HAdV; species HAdV-A to -G) are highly prevalent in the human population, and represent an important cause of morbidity and, to a lesser extent, mortality. Recent studies have identified close relatives of these viruses in African great apes, suggesting that some HAdV may be of zoonotic origin. We analyzed more than 800 fecal samples from wild African great apes and humans to further investigate the evolutionary history and zoonotic potential of hominine HAdV. HAdV-B and -E were frequently detected in wild gorillas (55%) and chimpanzees (25%), respectively. Bayesian ancestral host reconstruction under discrete diffusion models supported a gorilla and chimpanzee origin for these viral species. Host switches were relatively rare along HAdV evolution, with about ten events recorded in 4.5 My. Despite presumably rare direct contact between sympatric populations of the two species, transmission events from gorillas to chimpanzees were observed, suggesting that habitat and dietary overlap may lead to fecal-oral cross-hominine transmission of HAdV. Finally, we determined that two independent HAdV-B transmission events to humans occurred more than 100,000 years ago. We conclude that HAdV-B circulating in humans are of zoonotic origin and have probably affected global human health for most of our species lifetime.

Origin of the HIV-1 group O epidemic in western lowland gorillas

HIV-1, the cause of AIDS, is composed of four phylogenetic lineages, groups M, N, O, and P, each of which resulted from an independent cross-species transmission event of simian immunodeficiency viruses (SIVs) infecting African apes. Although groups M and N have been traced to geographically distinct chimpanzee communities in southern Cameroon, the reservoirs of groups O and P remain unknown. Here, we screened fecal samples from western lowland (n = 2,611), eastern lowland (n = 103), and mountain (n = 218) gorillas for gorilla SIV (SIVgor) antibodies and nucleic acids. Despite testing wild troops throughout southern Cameroon (n = 14), northern Gabon (n = 16), the Democratic Republic of Congo (n = 2), and Uganda (n = 1), SIVgor was identified at only four sites in southern Cameroon, with prevalences ranging from 0.8-22%. Amplification of partial and full-length SIVgor sequences revealed extensive genetic diversity, but all SIVgor strains were derived from a single lineage within the chimpanzee SIV (SIVcpz) radiation. Two fully sequenced gorilla viruses from southwestern Cameroon were very closely related to, and likely represent the source population of, HIV-1 group P. Most of the genome of a third SIVgor strain, from central Cameroon, was very closely related to HIV-1 group O, again pointing to gorillas as the immediate source. Functional analyses identified the cytidine deaminase APOBEC3G as a barrier for chimpanzee-to-gorilla, but not gorilla-to-human, virus transmission. These data indicate that HIV-1 group O, which spreads epidemically in west central Africa and is estimated to have infected around 100,000 people, originated by cross-species transmission from western lowland gorillas.

Molecular characterization of HIV-1 infection in Northwest Spain (2009-2013): Investigation of the subtype F outbreak

BACKGROUND

HIV-1 subtype B is the predominant one in European regions several, while other subtypes and recombinants are also circulating with high prevalence. A sub-epidemic of subtype F with specific characteristics and low response to treatment has been recently identified in Galicia. In this study we investigated the characteristics of the HIV-1 subtype F sub-epidemic in A Coruña and Santiago de Compostela in Northwest Spain.

METHODS

420 newly HIV-1 diagnosed patients during 2009-2013 were enrolled in this study. HIV-1 subtyping was carried out using automated subtyping tools and phylogenetic analysis. Molecular epidemiology investigation of subtypes B and F was performed by means of phylogenetic analysis using fast maximum likelihood. Phylodynamic analysis was performed using Bayesian method as implemented in BEAST v1.8.

RESULTS

Subtype B found to be the predominant (61.2% and 70.4%) followed by subtype F (25.6% and 12.0%) in both areas (A Coruña and Santiago de Compostela, respectively). The latter found to mainly spread among men having sex with men (MSM). The vast majority of subtype F lineages from both areas clustered monophyletically, while subtype B sequences clustered in several tree branches. The exponential growth of subtype F sub-epidemic dated back in 2008 by means of phylodynamic analysis. Most of new infections during 2009-2013 occurred within the subtype F transmission cluster.

CONCLUSIONS

Subtype F circulates at high prevalence in A Coruña and Santiago de Compostela in Northwest Spain, suggesting that the HIV-1 epidemic in this region has distinct characteristics to the rest of Spain. Subtype F has being spreading among MSM and is currently the most actively spreading network. The single cluster spread of this local sub-epidemic might provide an explanation for the distinct characteristics and the low response to antiretroviral treatment.

Challenges in the design of a T cell vaccine in the context of HIV-1 diversity

The extraordinary variability of HIV-1 poses a major obstacle to vaccine development. The effectiveness of a vaccine is likely to vary dramatically in different populations infected with different HIV-1 subtypes, unless innovative vaccine immunogens are developed to protect against the range of HIV-1 diversity. Immunogen design for stimulating neutralizing antibody responses focuses on “breadth” – the targeting of a handful of highly conserved neutralizing determinants on the HIV-1 Envelope protein that can recognize the majority of viruses across all HIV-1 subtypes. An effective vaccine will likely require the generation of both broadly cross-neutralizing antibodies and non-neutralizing antibodies, as well as broadly cross-reactive T cells. Several approaches have been taken to design such broadly-reactive and cross-protective T cell immunogens. Artificial sequences have been designed that reduce the genetic distance between a vaccine strain and contemporary circulating viruses; “mosaic” immunogens extend this concept to contain multiple potential T cell epitope (PTE) variants; and further efforts attempt to focus T cell immunity on highly conserved regions of the HIV-1 genome. Thus far, a number of pre-clinical and early clinical studies have been performed assessing these new immunogens. In this review, the potential use of these new immunogens is explored.

Recombination pattern reanalysis of some HIV-1 circulating recombination forms suggest the necessity and difficulty of revision

BACKGROUND

Recombination is one of the major mechanisms underlying the generation of HIV-1 variability. Currently 61 circulating recombinant forms of HIV-1 have been identified. With the development of recombination detection techniques and accumulation of HIV-1 reference stains, more accurate mosaic structures of circulating recombinant forms (CRFs), like CRF04 and CRF06, have undergone repeated analysis and upgrades. Such revisions may also be necessary for other CRFs. Unlike previous studies, whose results are based primarily on a single recombination detection program, the current study was based on multiple recombination analysis, which may have produced more impartial results.

METHODS

Representative references of 3 categories of intersubtype recombinants were selected, including BC recombinants (CRF07 and CRF08), BG recombinants (CRF23 and CRF24), and BF recombinants (CRF38 and CRF44). They were reanalyzed in detail using both the jumping profile hidden Markov model and RDP3.

RESULTS

The results indicate that revisions and upgrades are very necessary and the entire re-analysis suggested 2 types of revision: (i) length of inserted fragments; and (ii) number of inserted fragments. The reanalysis also indicated that determination of small regions of about 200 bases or fewer should be performed with more caution.

CONCLUSION

Results indicated that the involvement of multiple recombination detection programs is very necessary. Additionally, results suggested two major challenges, one involving the difficulty of accurately determining the locations of breakpoints and the second involving identification of small regions of about 200 bases or fewer with greater caution. Both indicate the complexity of HIV-1 recombination. The resolution would depend critically on development of a recombination analysis algorithm, accumulation of HIV-1 stains, and a higher sequencing quality. With the changes in recombination pattern, phylogenetic relationships of some CRFs may also change. All these results may be critical to understand the role of recombination in a complex and dynamic HIV evolution.

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.

Identification and characterization of a novel HIV-1 circulating recombinant form (CRF59_01B) identified among men-who-have-sex-with-men in China

The HIV-1 epidemic among men-who-have-sex-with-men (MSM) continues to expand in China. A large-scale national survey we conducted on HIV-1 strains among MSM in 11 provinces in China from 2008 to 2013 (n = 920) identified a novel transmission cluster consisting of six strains (0.7%) that belonged to a new circulating recombinant form (designated CRF59_01B). CRF59_01B contains two subtype B segments of U.S.-European origin (in the pol and vpu-env regions) in a CRF01_AE backbone. CRF59_01B is the second CRF (after CRF55_01B) circulating primarily among MSM in China. CRF59_01B occurs at a low frequency (less than 1%), but it was detected in four different provinces/regions in China: Liaoning (northeast China) (n = 3); Hunan (central China) (n = 1); Guangdong (south China) (n = 1); Yunnan (southwest China) (n = 1). One additional recombinant strain was detected in a heterosexual individual in Liaoning province but is not the focus of this paper. Bayesian molecular clock analyses indicate that CRF59_01B emerged as a result of recombination between CRF01_AE and subtype B around the year 2001. The emergence of multiple forms of recombinants and CRFs reflects the ever-increasing contribution of homosexual transmission in China's HIV epidemic and indicates an active HIV transmission network among MSM in China.

Assessment of gastrointestinal parasites in wild chimpanzees (Pan troglodytes troglodytes) in southeast Cameroon

We tested 114 faecal samples from wild simian immunodeficiency virus (SIV)-positive (n = 43) and SIV-negative (n = 71) chimpanzees (Pan troglodytes troglodytes) in southeast Cameroon for the presence of gastrointestinal parasites by direct smear. We observed cysts from different protozoa (Entamoeba coli and Entamoeba histolytica / Entamoeba dispar, Endolimax nana, Iodamoeba butschlii, Chilomastix mesnili, Balantidium coli and Blastocystis cells) and trophozoites from Troglodytella abrassarti and Balantidium coli. Eggs from different helminths (strongylids, Ascaris lumbricoides, Abbreviata caucasica, Trichuris sp., Capillaria sp., Enterobius anthropopeci, Bertiella sp., Hymenolepis diminuta and an undetermined fluke) were also observed. Finally, we observed eggs that could not be properly identified and classified. We did not observe any differences between the SIV+ and SIV- samples except for the unidentified eggs. The studied chimpanzees were highly parasitised by strongylid (85.1% of prevalence), Troglodytella (43.8%) and Blastocystis (2.9%), and the frequency of the other parasites ranged from 0.9 to 8.8%. These high levels of parasite infections could represent an additional burden in a population where there is a high rate of the SIV virus in circulation.

Non-M variants of human immunodeficiency virus type 1

The AIDS pandemic that started in the early 1980s is due to human immunodeficiency virus type 1 (HIV-1) group M (HIV-M), but apart from this major group, many divergent variants have been described (HIV-1 groups N, O, and P and HIV-2). The four HIV-1 groups arose from independent cross-species transmission of the simian immunodeficiency viruses (SIVs) SIVcpz, infecting chimpanzees, and SIVgor, infecting gorillas. This, together with human adaptation, accounts for their genomic, phylogenetic, and virological specificities. Nevertheless, the natural course of non-M HIV infection seems similar to that of HIV-M. The virological monitoring of infected patients is now possible with commercial kits, but their therapeutic management remains complex. All non-M variants were principally described for patients linked to Cameroon, where HIV-O accounts for 1% of all HIV infections; only 15 cases of HIV-N infection and 2 HIV-P infections have been reported. Despite improvements in our knowledge, many fascinating questions remain concerning the origin, genetic evolution, and slow spread of these variants. Other variants may already exist or may arise in the future, calling for close surveillance. This review provides a comprehensive, up-to-date summary of the current knowledge on these pathogens, including the historical background of their discovery; the latest advances in the comprehension of their origin and spread; and clinical, therapeutic, and laboratory aspects that may be useful for the management and the treatment of patients infected with these divergent viruses.

Understanding restriction factors and intrinsic immunity: insights and lessons from the primate lentiviruses

Primate lentiviruses include the HIVs, HIV-1 and HIV-2; the SIVs, which are endemic to more than 40 species of nonhuman primates in Africa; and SIVmac, an AIDS-causing pathogen that emerged in US macaque colonies in the 1970s. Because of the worldwide spread of HIV and AIDS, primate lentiviruses have been intensively investigated for more than 30 years. Research on these viruses has played a leading role in the discovery and characterization of intrinsic immunity, and in particular the identification of several antiviral effectors (also known as restriction factors) including APOBEC3G, TRIM5α, BST-2/tetherin and SAMHD1. Comparative studies of the primate lentiviruses and their hosts have proven critical for understanding both the evolutionary significance and biological relevance of intrinsic immunity, and the role intrinsic immunity plays in governing viral host range and interspecies transmission of viruses in nature.

Discovery and full genome characterization of two highly divergent simian immunodeficiency viruses infecting black-and-white colobus monkeys (Colobus guereza) in Kibale National Park, Uganda

Background

African non-human primates (NHPs) are natural hosts for simian immunodeficiency viruses (SIV), the zoonotic transmission of which led to the emergence of HIV-1 and HIV-2. However, our understanding of SIV diversity and evolution is limited by incomplete taxonomic and geographic sampling of NHPs, particularly in East Africa. In this study, we screened blood specimens from nine black-and-white colobus monkeys (Colobus guereza occidentalis) from Kibale National Park, Uganda, for novel SIVs using a combination of serology and “unbiased” deep-sequencing, a method that does not rely on genetic similarity to previously characterized viruses.

Results

We identified two novel and divergent SIVs, tentatively named SIVkcol-1 and SIVkcol-2, and assembled genomes covering the entire coding region for each virus. SIVkcol-1 and SIVkcol-2 were detected in three and four animals, respectively, but with no animals co-infected. Phylogenetic analyses showed that SIVkcol-1 and SIVkcol-2 form a lineage with SIVcol, previously discovered in black-and-white colobus from Cameroon. Although SIVkcol-1 and SIVkcol-2 were isolated from the same host population in Uganda, SIVkcol-1 is more closely related to SIVcol than to SIVkcol-2. Analysis of functional motifs in the extracellular envelope glycoprotein (gp120) revealed that SIVkcol-2 is unique among primate lentiviruses in containing only 16 conserved cysteine residues instead of the usual 18 or more.

Conclusions

Our results demonstrate that the genetic diversity of SIVs infecting black-and-white colobus across equatorial Africa is greater than previously appreciated and that divergent SIVs can co-circulate in the same colobine population. We also show that the use of “unbiased” deep sequencing for the detection of SIV has great advantages over traditional serological approaches, especially for studies of unknown or poorly characterized viruses. Finally, the detection of the first SIV containing only 16 conserved cysteines in the extracellular envelope protein gp120 further expands the range of functional motifs observed among SIVs and highlights the complex evolutionary history of simian retroviruses.

Vif proteins from diverse primate lentiviral lineages use the same binding site in APOBEC3G

APOBEC3G (A3G) is a cytidine deaminase that restricts human immunodeficiency virus type 1 (HIV-1) and other lentiviruses. Most of these viruses encode a Vif protein that directly binds A3G and leads to its proteasomal degradation. Both Vif proteins of HIV-1 and African green monkey simian immunodeficiency virus (SIVagm) bind residue 128 of A3G. However, this position does not control the A3G degradation by Vif variants derived from HIV-2 and SIVmac, which both originated from SIV of sooty mangabey monkeys (SIVsmm), suggesting that the A3G binding site for Vif proteins of the SIVsmm/HIV-2 lineage differs from that of HIV-1. To map the SIVsmm Vif binding site of A3G, we performed immunoprecipitations of individual A3G domains, Vif/A3G degradation assays and a detailed mutational analysis of human A3G. We show that A3G residue 129, but not the adjacent position 128, confers susceptibility to degradation by SIVsmm Vif. An artificial A3G mutant, the P129D mutant, was resistant to degradation by diverse Vifs from HIV-1, HIV-2, SIVagm, and chimpanzee SIV (SIVcpz), suggesting a conserved lentiviral Vif binding site. Gorilla A3G naturally contains a glutamine (Q) at position 129, which makes its A3G resistant to Vifs from diverse lineages. We speculate that gorilla A3G serves as a barrier against SIVcpz strains. In summary, we show that Vif proteins from distinct lineages bind to the same A3G loop, which includes positions 128 and 129. The multiple adaptations within this loop among diverse primates underscore the importance of counteracting A3G in lentiviral evolution.

Use of RNAlater as a preservation method for parasitic coprology studies in wild-living chimpanzees

We evaluated the use of an RNA stabilisation buffer, RNAlater (Ambion, Austin, Texas), as a preservation medium for parasitic coprology analysis of faecal samples collected from chimpanzees living in the wild (Pan troglodytes troglodytes). Thirty faecal samples collected in the forests of south-east Cameroon (Mambele area) from 2003 to 2011 were preserved in RNAlater at -80 °C and analysed for their parasite content. We identified and counted parasitic elements and assessed their shape, size and morphology in relation to the storage time of the samples. We found that parasite elements were identifiable in RNAlater preserved samples after as many as 7 years, showing that RNAlater could be an effective and reliable preservation medium for coprology. Thus, its use could be an interesting way to optimise sample collection for several types of studies (parasitology and bacteriology/virology) at once, especially considering the logistically challenging and time-consuming field campaigns needed to obtain these faecal samples.

Genome Sequences of a Novel HIV-1 Circulating Recombinant Form (CRF59_01B) Identified among Men Who Have Sex with Men in Northeastern China

We report here a novel HIV-1 circulating recombinant form (CRF) (CRF59_01B) comprised of CRF01_AE and subtype B, with two recombination breakpoints in the pol and vpu-env regions, respectively. CRF59_01B was identified from three epidemiologically unlinked men who have sex with men (MSM) in northeast China. This represents the second CRF identified in the MSM population in China.

HIV-1 Genetic Variability and Clinical Implications

Despite advances in antiretroviral therapy that have revolutionized HIV disease management, effective control of the HIV infection pandemic remains elusive. Beyond the classic non-B endemic areas, HIV-1 non-B subtype infections are sharply increasing in previous subtype B homogeneous areas such as Europe and North America. As already known, several studies have shown that, among non-B subtypes, subtypes C and D were found to be more aggressive in terms of disease progression. Luckily, the response to antiretrovirals against HIV-1 seems to be similar among different subtypes, but these results are mainly based on small or poorly designed studies. On the other hand, differences in rates of acquisition of resistance among non-B subtypes are already being observed. This different propensity, beyond the type of treatment regimens used, as well as access to viral load testing in non-B endemic areas seems to be due to HIV-1 clade specific peculiarities. Indeed, some non-B subtypes are proved to be more prone to develop resistance compared to B subtype. This phenomenon can be related to the presence of subtype-specific polymorphisms, different codon usage, and/or subtype-specific RNA templates. This review aims to provide a complete picture of HIV-1 genetic diversity and its implications for HIV-1 disease spread, effectiveness of therapies, and drug resistance development.

The HIV-1 pandemic: does the selective sweep in chimpanzees mirror humankind's future?

An HIV-1 infection progresses in most human individuals sooner or later into AIDS, a devastating disease that kills more than a million people worldwide on an annual basis. Nonetheless, certain HIV-1-infected persons appear to act as long-term non-progressors, and elite control is associated with the presence of particular MHC class I allotypes such as HLA-B*27 or -B*57. The HIV-1 pandemic in humans arose from the cross-species transmission of SIV_cpz originating from chimpanzees. Chimpanzees, however, appear to be relatively resistant to developing AIDS after HIV-1/SIV_cpz infection. Mounting evidence illustrates that, in the distant past, chimpanzees experienced a selective sweep resulting in a severe reduction of their MHC class I repertoire. This was most likely caused by an HIV-1/SIV-like retrovirus, suggesting that chimpanzees may have experienced long-lasting host-virus relationships with SIV-like viruses. Hence, if natural selection is allowed to follow its course, prospects for the human population may look grim, thus underscoring the desperate need for an effective vaccine.

Cross-group neutralization of HIV-1 and evidence for conservation of the PG9/PG16 epitopes within divergent groups

OBJECTIVE

HIV-1 has been classified into four groups: M, N, O and P. The aim of this study was to revisit the cross-group neutralization using a highly diverse panel of primary isolates.

DESIGN

The panel of viruses included nine HIV-1 group O primary isolates, one recombinant M/O primary isolate, one group N primary isolates, one group P primary isolate, two group M (subtype B) primary isolates and the HIV-1 group M adapted strain MN.

METHODS

All the viruses were tested for neutralization in TZM-bl cells, using sera issued from patients infected by viruses of group M (n = 11), O (n = 12) and P (n = 1), and a panel of nine human monoclonal broadly neutralizing antibodies (HuMo bNAbs).

RESULTS

Although the primary isolates displayed a wide spectrum of sensitivity to neutralization by the human sera, cross-group neutralization was clearly observed. In contrast, the bNAbs did not show any cross-group neutralization, except PG9 and PG16. Interestingly, the group N prototype strain YBF30 was highly sensitive to neutralization by PG9 (IC50: 0.28 μg/ml) and PG16 (IC50: < 0.12 μg/ml). The interaction between PG9 and key residues of YBF30 was confirmed by molecular modeling.

CONCLUSION

The conservation of the PG9 and PG16 epitopes within groups M and N provides an argument for their relevance as components of a potentially efficient HIV vaccine immunogen.

Lentivirus restriction by diverse primate APOBEC3A proteins

Rhesus macaque APOBEC3A (rhA3A) is capable of restricting both simian-human immunodeficiency virus (SHIVΔvif) and human immunodeficiency virus (HIV-1Δvif) to a greater extent than hA3A. We constructed chimeric A3A proteins to define the domains required for differential lentivirus restriction. Substitution of amino acids 25-33 from rhA3A into hA3A was sufficient to restrict HIVΔvif to levels similar to rhA3A restriction of SHIVΔvif. We tested if differential lentivirus restriction is conserved between A3A from Old World monkey and hominid lineages. A3A from African green monkey restricted SHIVΔvif but not HIV-1Δvif and colobus monkey A3A restricted both wild type and SHIVΔvif and HIV-1Δvif. In contrast, the gibbon ape A3A restricted neither SHIVΔvif nor HIV-1Δvif. Restriction of SHIVΔvif and HIV-1Δvif by New World monkey A3A proteins was not conserved as the A3A from the squirrel monkey but not the northern owl monkey restricted SHIVΔvif. Finally, the colobus A3A protein appears to restrict by a novel post-entry mechanism.

Origins of HIV and the AIDS pandemic

Acquired immunodeficiency syndrome (AIDS) of humans is caused by two lentiviruses, human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2). Here, we describe the origins and evolution of these viruses, and the circumstances that led to the AIDS pandemic. Both HIVs are the result of multiple cross-species transmissions of simian immunodeficiency viruses (SIVs) naturally infecting African primates. Most of these transfers resulted in viruses that spread in humans to only a limited extent. However, one transmission event, involving SIVcpz from chimpanzees in southeastern Cameroon, gave rise to HIV-1 group M-the principal cause of the AIDS pandemic. We discuss how host restriction factors have shaped the emergence of new SIV zoonoses by imposing adaptive hurdles to cross-species transmission and/or secondary spread. We also show that AIDS has likely afflicted chimpanzees long before the emergence of HIV. Tracing the genetic changes that occurred as SIVs crossed from monkeys to apes and from apes to humans provides a new framework to examine the requirements of successful host switches and to gauge future zoonotic risk.

The transmembrane domain of HIV-1 Vpu is sufficient to confer anti-tetherin activity to SIVcpz and SIVgor Vpu proteins: cytoplasmic determinants of Vpu function

BACKGROUND

The acquisition of effective Vpu-mediated anti-tetherin activity to promote virion release following transmission of SIVcpzPtt from central chimpanzees (Pan troglodytes troglodytes) to humans distinguishes pandemic HIV-1 group M strains from non-pandemic group N, O and P viruses and may have been a prerequisite for their global spread. Some functional motifs in the cytoplasmic region of HIV-1 M Vpus proposed to be important for anti-tetherin activity are more frequently found in the Vpu proteins of SIVcpzPtt than in those of SIVcpzPts infecting eastern chimpanzees (P. t. schweinfurthii), that have not been detected in humans, and SIVgor from gorillas, which is closely related to HIV-1 O and P. Thus, SIVcpzPtt strains may require fewer adaptive changes in Vpu than SIVcpzPts or SIVgor strains to counteract human tetherin.

RESULTS

To examine whether SIVcpzPtt may only need changes in the transmembrane domain (TMD) of Vpu to acquire anti-tetherin activity, whereas SIVcpzPts and SIVgor may also require changes in the cytoplasmic region, we analyzed chimeras between the TMD of an HIV-1 M Vpu and the cytoplasmic domains of SIVcpzPtt (n = 2), SIVcpzPts (n = 2) and SIVgor (n = 2) Vpu proteins. Unexpectedly, all of these chimeras were capable of counteracting human tetherin to enhance virion release, irrespective of the presence or absence of the putative adaptor protein binding sites and the DSGxxS β-TrCP binding motif reported to be critical for effective anti-tetherin activity of M Vpus. It was also surprising that in three of the six chimeras the gain of anti-tetherin function was associated with a loss of the CD4 degradation activity since this function was conserved among all parental HIV-1, SIVcpz and SIVgor Vpu proteins.

CONCLUSIONS

Our results show that changes in the TMD of SIVcpzPtt, SIVcpzPts and SIVgor Vpus are sufficient to render them active against human tetherin. Thus, several previously described domains in the extracellular region of Vpu are not absolutely essential for tetherin antagonism but may be required for other Vpu functions.

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.

HIV-1 subtype distribution and its demographic determinants in newly diagnosed patients in Europe suggest highly compartmentalized epidemics

Background

Understanding HIV-1 subtype distribution and epidemiology can assist preventive measures and clinical decisions. Sequence variation may affect antiviral drug resistance development, disease progression, evolutionary rates and transmission routes.

Results

We investigated the subtype distribution of HIV-1 in Europe and Israel in a representative sample of patients diagnosed between 2002 and 2005 and related it to the demographic data available. 2793 PRO-RT sequences were subtyped either with the REGA Subtyping tool or by a manual procedure that included phylogenetic tree and recombination analysis. The most prevalent subtypes/CRFs in our dataset were subtype B (66.1%), followed by sub-subtype A1 (6.9%), subtype C (6.8%) and CRF02_AG (4.7%). Substantial differences in the proportion of new diagnoses with distinct subtypes were found between European countries: the lowest proportion of subtype B was found in Israel (27.9%) and Portugal (39.2%), while the highest was observed in Poland (96.2%) and Slovenia (93.6%). Other subtypes were significantly more diagnosed in immigrant populations. Subtype B was significantly more diagnosed in men than in women and in MSM > IDUs > heterosexuals. Furthermore, the subtype distribution according to continent of origin of the patients suggests they acquired their infection there or in Europe from compatriots.

Conclusions

The association of subtype with demographic parameters suggests highly compartmentalized epidemics, determined by social and behavioural characteristics of the patients.

Primates, Pathogens, and Evolution: A Context for Understanding Emerging Disease

The world is rife with potential pathogens. Of those that infect humans, it is estimated that roughly 20 % are of nonhuman primate origin. The same ease characterizes pathogen transmission in the other direction, from humans to nonhuman primates. This latter problem has increasingly serious ramifications for conservation efforts, as growing numbers of ecotourists and researchers serve as potential vectors of disease. Here, we present an analysis of major cross-species transmission events between human and nonhuman primates. In particular, we consider HIV and malaria as case studies in which nonhuman primate pathogens emerged and became permanent fixtures in human populations. The human practices that facilitate such events are considered, as well as the evolutionary consequences of these events. In addition, we describe human-to-nonhuman primate transmission events and discuss the potential of human pathogens to adapt to nonhuman primate hosts. The topic of emerging infections is addressed, in both human and nonhuman species, in light of changing patterns of contact and novel adaptations on the part of pathogens and hosts.

Human-Wildlife Contact and Emerging Infectious Diseases

The majority of all emerging pathogens in humans are zoonotic (nonhuman animal) in origin. Population, ecological, and behavioral changes that increase contact with wildlife exacerbate emergence of these pathogens. Anthropogenic modification of the physical environment has altered not only our risk of zoonotic infection from wildlife but also the likelihood of pathogen transmission from human to nonhuman animal populations. This is particularly the case for primates that share a number of common infections with humans. In this chapter, I use a series of case studies involving SARS, HIV, Nipah virus, Lyme disease, malaria, and Ebola to exemplify how various anthropogenic factors have facilitated pathogen transmission between human and nonhuman animal populations. The costs and benefits of primate-based ecotourism are also reviewed to better illustrate how human-wildlife contact can affect both populations. Responsible health monitoring of human-wildlife interactions is a necessary prerequisite for prevention of the transmission of future emerging infectious diseases.

Cellular entry of retroviruses

The retrovirus family contains several important human and animal pathogens, including the human immunodeficiency virus (HIV), the causative agent of acquired immunodeficiency syndrome (AIDS). Studies with retroviruses were instrumental to our present understanding of the cellular entry of enveloped viruses in general. For instance, studies with alpharetroviruses defined receptor engagement, as opposed to low pH, as a trigger for the envelope protein-driven membrane fusion. The insights into the retroviral entry process allowed the generation of a new class of antivirals, entry inhibitors, and these therapeutics are at present used for treatment of HIV/AIDS. In this chapter, we will summarize key concepts established for entry of avian sarcoma and leukosis virus (ASLV), a widely used model system for retroviral entry. We will then review how foamy virus and HIV, primate- and human retroviruses, enter target cells, and how the interaction of the viral and cellular factors involved in the cellular entry of these viruses impacts viral tropism, pathogenesis and approaches to therapy and vaccine development.

SIVagm infection in wild African green monkeys from South Africa: epidemiology, natural history, and evolutionary considerations

Pathogenesis studies of SIV infection have not been performed to date in wild monkeys due to difficulty in collecting and storing samples on site and the lack of analytical reagents covering the extensive SIV diversity. We performed a large scale study of molecular epidemiology and natural history of SIVagm infection in 225 free-ranging AGMs from multiple locations in South Africa. SIV prevalence (established by sequencing pol, env, and gag) varied dramatically between infant/juvenile (7%) and adult animals (68%) (p<0.0001), and between adult females (78%) and males (57%). Phylogenetic analyses revealed an extensive genetic diversity, including frequent recombination events. Some AGMs harbored epidemiologically linked viruses. Viruses infecting AGMs in the Free State, which are separated from those on the coastal side by the Drakensberg Mountains, formed a separate cluster in the phylogenetic trees; this observation supports a long standing presence of SIV in AGMs, at least from the time of their speciation to their Plio-Pleistocene migration. Specific primers/probes were synthesized based on the pol sequence data and viral loads (VLs) were quantified. VLs were of 10(4)-10(6) RNA copies/ml, in the range of those observed in experimentally-infected monkeys, validating the experimental approaches in natural hosts. VLs were significantly higher (10(7)-10(8) RNA copies/ml) in 10 AGMs diagnosed as acutely infected based on SIV seronegativity (Fiebig II), which suggests a very active transmission of SIVagm in the wild. Neither cytokine levels (as biomarkers of immune activation) nor sCD14 levels (a biomarker of microbial translocation) were different between SIV-infected and SIV-uninfected monkeys. This complex algorithm combining sequencing and phylogeny, VL quantification, serology, and testing of surrogate markers of microbial translocation and immune activation permits a systematic investigation of the epidemiology, viral diversity and natural history of SIV infection in wild African natural hosts.

Single real-time reverse transcription-PCR assay for detection and quantification of genetically diverse HIV-1, SIVcpz, and SIVgor strains

Although antiretroviral treatment availability has improved, the virological monitoring of patients remains largely uneven across regions. In addition, viral quantification tests are suffering from human immunodeficiency virus type 1 (HIV-1) genetic diversity, fueled by the emergence of new recombinants and of lentiviruses from nonhuman primates. We developed a real-time reverse transcription-PCR (RT-PCR) assay that is relatively inexpensive and able to detect and quantify all circulating forms of HIV-1 and its simian immunodeficiency virus (SIV) precursors, SIVcpz and SIVgor. Primers and a probe were designed to detect all variants of the HIV-1/SIVcpz/SIVgor lineage. HIV-1 M plasma (n = 190; 1.68 to 7.78 log(10) copies/ml) representing eight subtypes, nine circulating recombinant forms, and 21 unique recombinant forms were tested. The mean PCR efficiency was 99%, with low coefficients of intra- and interassay variation (<5%) and a limit of quantification of <2.50 log(10) copies/ml, with a 200-μl plasma volume. On the studied range, the specificity and the analytical sensitivity were 100 and 97.4%, respectively. The viral loads were highly correlated (r = 0.95, P < 0.0001) with the reference method (generic HIV assay; Biocentric) and had no systematic difference, irrespective of genotype. Furthermore, 22 HIV-1 O plasmas were screened and were better quantified compared to the gold-standard RealTime HIV-1 assay (Abbott), including four samples that were only quantified by our assay. Finally, we could quantify SIVcpzPtt and SIVcpzPts from chimpanzee plasma (n = 5) and amplify SIVcpz and SIVgor from feces. Thus, the newly developed real-time RT-PCR assay detects and quantifies strains from the HIV-1/SIVcpz/SIVgor lineage, including a wide diversity of group M strains and HIV-1 O. It can therefore be useful in geographical areas of high HIV diversity and at risk for the emergence of new HIV variants.

Voronoff to virion: 1920s testis transplantation and AIDS

BACKGROUND

We address accusations linking AIDS with testis transplantation performed by a French surgeon, Serge Voronoff (1866-1951), and their implications in the future of animal-to-human organ transplantation.

METHODS

Biographical literature on Voronoff and scientific literature on xenotransplantation and the origin of HIV were reviewed.

RESULTS

IN the 1920s, Serge Voronoff transplanted testes from primates into humans to revitalize them sexually and physically, making him one of the first surgeons to perform xenotransplantation-transplanting live tissues between species. In recent years, some have postulated that Voronoff's transplants may have caused or contributed to the AIDS epidemic. However, consensus among virologists holds that HIV most likely originated from a chimpanzee virus known as simian immunodeficiency viruses (SIV) which many agree was transmitted to humans during the hunting of primates in the early 1900s. As these accusations have never been addressed, evidence is reviewed which refutes the claims. HIV isolate studies are summarized, which show that SIV was most likely transferred to humans from a chimpanzee species different from those used by Voronoff. Furthermore, literature suggests that Voronoff's experiments were performed in Europe and the United States, not central Africa.

CONCLUSIONS

Over 100,000 people await organ transplants, making the prospect of using animal organs to meet demand increasingly favorable. The accusations against Voronoff and others have led to increased concern over cross-species disease transfer. The evidence presented refutes those claims and is used to explain the need for further research into xenotransplantation.

Implications of HIV diversity for the HIV-1 pandemic

HIV-1 genetic variability within individuals and populations plays a central role in the HIV pandemic. Multiple zoonotic transmissions of SIV to humans have resulted in distinct HIV lineages in humans which have further diversified within the population over time. High rates of mutation and recombination during HIV reverse transcription create a genetic diversity in the host which is subject to selection pressures by the immune response and antiretroviral treatment. The global distribution of HIV genetic variants and the impact of HIV diversity on pathogenesis, transmission and clinical management are reviewed. Finally, the key role of escape mutations in the immune response to HIV is discussed as well as the major challenge which HIV-1 diversity poses to HIV vaccine development.

The importance of understanding the human-animal interface : from early hominins to global citizens

The complex relationships between the human and animal species have never ceased to evolve since the emergence of the human species and have resulted in a human-animal interface that has promoted the cross-species transmission, emergence and eventual evolution of a plethora of infectious pathogens. Remarkably, most of the characteristics of the human-animal interface-as we know it today-have been established long before the end of our species pre-historical development took place, to be relentlessly shaped throughout the history of our species. More recently, changes affecting the modern human population worldwide as well as their dramatic impact on the global environment have taken domestication, agriculture, urbanization, industrialization, and colonization to unprecedented levels. This has created a unique global multi-faceted human-animal interface, associated with a major epidemiological transition that is accompanied by an unexpected rise of new and emerging infectious diseases. Importantly, these developments are largely paralleled by medical, technological, and scientific progress, continuously spurred by our never-ending combat against pathogens. The human-animal interface has most likely contributed significantly to the evolutionary shaping and historical development of our species. Investment in a better understanding of this human-animal interface will offer humankind a future head-start in the never-ending battle against infectious diseases.

Enhanced heterosexual transmission hypothesis for the origin of pandemic HIV-1

HIV-1 M originated from SIVcpz endemic in chimpanzees from southeast Cameroon or neighboring areas, and it started to spread in the early 20th century. Here we examine the factors that may have contributed to simian-to-human transmission, local transmission between humans, and export to a city. The region had intense ape hunting, social disruption, commercial sex work, STDs, and traffic to/from Kinshasa in the period 1899-1923. Injection treatments increased sharply around 1930; however, their frequency among local patients was far lower than among modern groups experiencing parenteral HIV-1 outbreaks. Recent molecular datings of HIV-1 M fit better the period of maximal resource exploitation and trade links than the period of high injection intensity. We conclude that although local parenteral outbreaks might have occurred, these are unlikely to have caused massive transmission. World War I led to additional, and hitherto unrecognized, risks of HIV-1 emergence. We propose an Enhanced Heterosexual Transmission Hypothesis for the origin of HIV-1 M, featuring at the time and place of its origin a coincidence of favorable co-factors (ape hunting, social disruption, STDs, and mobility) for both cross-species transmission and heterosexual spread. Our hypothesis does not exclude a role for parenteral transmission in the initial viral adaptation.

New strain of simian immunodeficiency virus identified in wild-born chimpanzees from central Africa

Studies of primate lentiviruses continue to provide information about the evolution of simian immunodeficiency viruses (SIVs) and the origin and emergence of HIV since chimpanzees in west–central Africa (Pan troglodytes troglodytes) were recognized as the reservoir of SIVcpzPtt viruses, which have been related phylogenetically to HIV-1. Using in-house peptide ELISAs to study SIV prevalence, we tested 104 wild-born captive chimpanzees from Gabon and Congo. We identified two new cases of SIVcpz infection in Gabon and characterized a new SIVcpz strain, SIVcpzPtt-Gab4. The complete sequence (9093 bp) was obtained by a PCR-based ‘genome walking’ approach to generate 17 overlapping fragments. Phylogenetic analyses of separated genes (gag, pol-vif and env-nef) showed that SIVcpzPtt-Gab4 is closely related to SIVcpzPtt-Gab1 and SIVcpzPtt-Gab2. No significant variation in viral load was observed during 3 years of follow-up, but a significantly lower CD4+ T cells count was found in infected than in uninfected chimpanzees (p<0.05). No clinical symptoms of SIV infection were observed in the SIV-positive chimpanzees. Further field studies with non-invasive methods are needed to determine the prevalence, geographic distribution, species association, and natural history of SIVcpz strains in the chimpanzee habitat in Gabon.

Eastern chimpanzees, but not bonobos, represent a simian immunodeficiency virus reservoir

Chimpanzees in west central Africa (Pan troglodytes troglodytes) are endemically infected with simian immunodeficiency viruses (SIVcpzPtt) that have crossed the species barrier to humans and gorillas on at least five occasions, generating pandemic and nonpandemic forms of human immunodeficiency virus type 1 (HIV-1) as well as gorilla SIV (SIVgor). Chimpanzees in east Africa (Pan troglodytes schweinfurthii) are also infected with SIVcpz; however, their viruses (SIVcpzPts) have never been found in humans. To examine whether this is due to a paucity of natural infections, we used noninvasive methods to screen wild-living eastern chimpanzees in the Democratic Republic of the Congo (DRC), Uganda, and Rwanda. We also screened bonobos (Pan paniscus) in the DRC, a species not previously tested for SIV in the wild. Fecal samples (n = 3,108) were collected at 50 field sites, tested for species and subspecies origin, and screened for SIVcpz antibodies and nucleic acids. Of 2,565 samples from eastern chimpanzees, 323 were antibody positive and 92 contained viral RNA. The antibody-positive samples represented 76 individuals from 19 field sites, all sampled north of the Congo River in an area spanning 250,000 km(2). In this region, SIVcpzPts was common and widespread, with seven field sites exhibiting infection rates of 30% or greater. The overall prevalence of SIVcpzPts infection was 13.4% (95% confidence interval, 10.7% to 16.5%). In contrast, none of the 543 bonobo samples from six sites was antibody positive. All newly identified SIVcpzPts strains clustered in strict accordance to their subspecies origin; however, they exhibited considerable genetic diversity, especially in protein domains known to be under strong host selection pressure. Thus, the absence of SIVcpzPts zoonoses cannot be explained by an insufficient primate reservoir. Instead, greater adaptive hurdles may have prevented the successful colonization of humans by P. t. schweinfurthii viruses.

Noninvasive follow-up of simian immunodeficiency virus infection in wild-living nonhabituated western lowland gorillas in Cameroon

Simian immunodeficiency viruses infecting western lowland gorillas (SIVgor) are closely related to HIV-1 and are most likely the ancestors of HIV-1 groups O and P. At present, limited data are available on genetic diversity, transmission, viral evolution, and pathogenicity of SIVgor in its natural host. Between 2004 and 2011, 961 putative gorilla fecal samples were collected at the Campo Ma'an National Park, Cameroon. Among them, 16% cross-reacted with HIV-1 antibodies, corresponding to at least 34 infected gorillas. Combining host genotyping and field data, we identified four social groups composed of 7 to 15 individuals each, with SIV rates ranging from 13% to 29%. Eleven SIVgor-infected gorillas were sampled multiple times; two most likely seroconverted during the study period, showing that SIVgor continues to spread. Phylogenetic analysis of partial env and pol sequences revealed cocirculation of closely related and divergent strains among gorillas from the same social group, indicating SIVgor transmissions within and between groups. Parental links could be inferred for some gorillas infected with closely related strains, suggesting vertical transmission, but horizontal transmission by sexual or aggressive behavior was also suspected. Intrahost molecular evolution in one gorilla over a 5-year period showed viral adaptations characteristic of escape mutants, i.e., V1V2 loop elongation and an increased number of glycosylation sites. Here we show for the first time the feasibility of noninvasive monitoring of nonhabituated gorillas to study SIVgor infection over time at both the individual and population levels. This approach can also be applied more generally to study other pathogens in wildlife.

Co-evolution of primate SAMHD1 and lentivirus Vpx leads to the loss of the vpx gene in HIV-1 ancestor

Cross-species transmission and adaptation of simian immunodeficiency viruses (SIVs) to humans have given rise to human immunodeficiency viruses (HIVs). HIV type 1 (HIV-1) and type 2 (HIV-2) were derived from SIVs that infected chimpanzee (SIVcpz) and sooty mangabey (SIVsm), respectively. The HIV-1 restriction factor SAMHD1 inhibits HIV-1 infection in human myeloid cells and can be counteracted by the Vpx protein of HIV-2 and the SIVsm lineage. However, HIV-1 and its ancestor SIVcpz do not encode a Vpx protein and HIV-1 has not evolved a mechanism to overcome SAMHD1-mediated restriction. Here we show that the co-evolution of primate SAMHD1 and lentivirus Vpx leads to the loss of the vpx gene in SIVcpz and HIV-1. We found evidence for positive selection of SAMHD1 in orangutan, gibbon, rhesus macaque, and marmoset, but not in human, chimpanzee and gorilla that are natural hosts of Vpx-negative HIV-1, SIVcpz and SIVgor, respectively, indicating that vpx drives the evolution of primate SAMHD1. Ancestral host state reconstruction and temporal dynamic analyses suggest that the most recent common ancestor of SIVrcm, SIVmnd, SIVcpz, SIVgor and HIV-1 was a SIV that had a vpx gene; however, the vpx gene of SIVcpz was lost approximately 3643 to 2969 years ago during the infection of chimpanzees. Thus, HIV-1 could not inherit the lost vpx gene from its ancestor SIVcpz. The lack of Vpx in HIV-1 results in restricted infection in myeloid cells that are important for antiviral immunity, which could contribute to the AIDS pandemic by escaping the immune responses.

Bats host major mammalian paramyxoviruses

The large virus family Paramyxoviridae includes some of the most significant human and livestock viruses, such as measles-, distemper-, mumps-, parainfluenza-, Newcastle disease-, respiratory syncytial virus and metapneumoviruses. Here we identify an estimated 66 new paramyxoviruses in a worldwide sample of 119 bat and rodent species (9,278 individuals). Major discoveries include evidence of an origin of Hendra- and Nipah virus in Africa, identification of a bat virus conspecific with the human mumps virus, detection of close relatives of respiratory syncytial virus, mouse pneumonia- and canine distemper virus in bats, as well as direct evidence of Sendai virus in rodents. Phylogenetic reconstruction of host associations suggests a predominance of host switches from bats to other mammals and birds. Hypothesis tests in a maximum likelihood framework permit the phylogenetic placement of bats as tentative hosts at ancestral nodes to both the major Paramyxoviridae subfamilies (Paramyxovirinae and Pneumovirinae). Future attempts to predict the emergence of novel paramyxoviruses in humans and livestock will have to rely fundamentally on these data.

Simian retroviruses in African apes

It is now well established that simian immunodeficiency viruses (SIVs) from chimpanzees (SIVcpz) and gorillas (SIVgor) from west Central Africa are at the origin of HIV-1/AIDS. Apes are also infected with other retroviruses, notably simian T-cell lymphotropic viruses (STLVs) and simian foamy viruses (SFVs), that can be transmitted to humans. We discuss the actual knowledge on SIV, STLV and SFV infections in chimpanzees, gorillas, and bonobos. We especially elaborate on how the recent development of non-invasive methods has allowed us to identify the reservoirs of the HIV-1 ancestors in chimpanzees and gorillas, and increased our knowledge of the natural history of SIV infections in chimpanzees. Multiple cross-species events with retroviruses from apes to humans have occurred, but only one transmission of SIVcpz from chimpanzees in south-eastern Cameroon spread worldwide, and is responsible for the actual HIV pandemic. Frequent SFV transmissions have been recently reported, but no human-to-human transmission has been documented yet. Because humans are still in contact with apes, identification of pathogens in wild ape populations can signal which pathogens may be cause risk for humans, and allow the development of serological and molecular assays with which to detect transmissions to humans. Finally, non-invasive sampling also allows the study of the impact of retroviruses and other pathogens on the health and survival of endangered species such as chimpanzees, gorillas, and bonobos.

Efficient SIVcpz replication in human lymphoid tissue requires viral matrix protein adaptation

SIVs infecting wild-living apes in west central Africa have crossed the species barrier to humans on at least four different occasions, one of which spawned the AIDS pandemic. Although the chimpanzee precursor of pandemic HIV-1 strains must have been able to infect humans, the capacity of SIVcpz strains to replicate in human lymphoid tissues (HLTs) is not known. Here, we show that SIVcpz strains from two chimpanzee subspecies are capable of replicating in human tonsillary explant cultures, albeit only at low titers. However, SIVcpz replication in HLT was significantly improved after introduction of a previously identified human-specific adaptation at position 30 in the viral Gag matrix protein. An Arg or Lys at this position significantly increased SIVcpz replication in HLT, while the same mutation reduced viral replication in chimpanzee-derived CD4(+) T cells. Thus, naturally occurring SIVcpz strains are capable of infecting HLTs, the major site of HIV-1 replication in vivo. However, efficient replication requires the acquisition of a host-specific adaptation in the viral matrix protein. These results identify Gag matrix as a major determinant of SIVcpz replication fitness in humans and suggest a critical role in the emergence of HIV/AIDS.