Multiply spliced env and nef transcripts of simian immunodeficiency virus from West African green monkey (SIVagm-sab).

We have characterized the spliced transcripts of nef and envelope genes of SIVagm from African green monkey of the sabaeus subspecies. Most of the transcripts we have studied, representing the most abundant mRNA species in our assay, have undergone a specific splicing event that removes a part of the trans-activation response (TAR) element. This region is predicted to form a stable secondary structure (four stem-loop elements in SIVagm-sab) that affects the trans-activation of viral gene expression by Tat and the translation of the viral transcripts. Contrary to what is observed in other viruses, in which this R-region splicing has also been described (e.g., HIV-2), the LTR splicing in SIVagm-sab removes part of the first stem-loop and the following ones, nearly completely disrupting the TAR element secondary structure. Because LTR splicing seems to be a conserved feature among the strains we have characterized, these results suggest that this phenomenon could have important consequences for virus replication, pathogenicity, and latency.

[Virus transmission in the tropical environment, the socio-ecology of primates and the balance of ecosystems]. / Circulation des virus en milieu tropical, socio-écologie des primates et équilibre des écosystèmes.

We studied the contribution of non human primates to the transmission of yellow fever and HIV in the wild. We demonstrate the consequences of the modification of ecosystems on the emergence of new viral diseases and the reappearance of diseases believed to be eradicated. In the primary forest, the natural yellow fever cycle is limited to monkeys and mosquitoes living high in the canopy. Transmission to man is an anomaly, requiring the circumstances found in the forest and savanna contact zones, where man has changed the forest to a mosaic and decimated the simian population, favoring contact between mosquitoes and man. In these contact zones, the amaril virus circulates in episodic cycles. During each episode, most of the local monkeys are infected, and thereby acquire immunity. Yellow fever can only reappear subsequently when a sufficiently large new generation of non-immune young monkeys is available. Monkeys do not become ill when infected, presumably as a result of typical host-parasite cross selection having led to the development of a balance between the parasite and its host. AIDS is a transmissible viral disease which appeared recently. Various African non-human primates are hosts to SIV, a retrovirus closely related to HIV which causes AIDS in man. SIV-infected African monkeys do not develop AIDS. However, when used to infect species from other continents (for example Asian macaco monkeys) SIV can cause AIDS. Does pathogenicity appear during transmission of the virus from one primate host to another, and is this the case for human AIDS? Experimental inoculations, the demonstration of SIVagm in other species, the mosaic structure of the genome (implying cross species recombinations), and the high probability of cross-species transmission of the viruses in the wild all favor this idea. Possibly counterbalancing the pessimism about the development of an HIV1 vaccine in the near future, the non-human SIV models holds out some hope. The emergence of new diseases, such as Ebola, or diseases from other niches, and the reappearance of diseases believed to be eradicated, are frequent when man modifies the ecosystem, the structure and balance of which he does not control, and when he puts into contact species which have never met before.

Genetic diversity of simian immunodeficiency viruses from West African green monkeys: evidence of multiple genotypes within populations from the same geographical locale.

High simian immunodeficiency virus (SIV) seroprevalence rates have been reported in the different African green monkey (AGM) subspecies. Genetic diversity of these viruses far exceeds the diversity observed in the other lentivirus-infected human and nonhuman primates and is thought to reflect ancient introduction of SIV in the AGM population. We investigate here genetic diversity of SIVagm in wild-living AGM populations from the same geographical locale (i.e., sympatric population) in Senegal. For 11 new strains, we PCR amplified and sequenced two regions of the genome spanning the first tat exon and part of the transmembrane glycoprotein. Phylogenetic analysis of these sequences shows that viruses found in sympatric populations cluster into distinct lineages, with at least two distinct genotypes in each troop. These data strongly suggest an ancient introduction of these divergent viruses in the AGM population.

Simian immunodeficiency virus infection in a patas monkey (Erythrocebus patas): evidence for cross-species transmission from African green monkeys (Cercopithecus aethiops sabaeus) in the wild.

Socio-ethological studies on troops of African green monkeys (AGMs) (Cercopithecus aethiops sabaeus) and patas monkeys (Erythrocebus patas) in Senegal have documented physical contacts between these two species. Elevated simian immunodeficiency virus (SIV) seroprevalence rates have been reported for the different AGM subspecies. We report here the extent to which patas monkeys are infected and compare the relatedness of the viruses isolated from theses two different species. Among the 85 AGMs and 54 patas monkeys studied, 47% of 7.5%, respectively, had antibodies that cross-reacted with HIV-2 envelope proteins. From two AGMs a virus was isolated. From the patas monkeys, virus isolation was generally not possible, but from one animal that was ill a virus designated pamG31 was amplified by PCR. In addition, for the two SIVagm isolates, an 830 bp region spanning the env and nef genes was amplified and sequenced. Comparisons of sequences from the env/nef region revealed 80% identity between pam G31 and SIVagm isolates from AGMs of the sabaeus subspecies, and 94% identity between the two SIVagm isolates. Phylogenetic analysis showed that pamG31 belongs to the SIVagm sabaeus subgroup. This is the first report of a lentiviral infection in a patas monkey. The close genetic relatedness between pamG31 and SIVagm sabaeus viruses is a strong argument in favour of cross-species transmission of SIV between AGMs and patas monkeys in the wild. For these reasons, we propose to refer to this patas virus as SIVagm-pamG31.

Regulatory genes of simian immunodeficiency viruses from west African green monkeys (Cercopithecus aethiops sabaeus).

The high seroprevalence of simian immunodeficiency viruses (SIVs) in African green monkeys (AGMs) without immunological defects in their natural hosts has prompted consideration of SIV-infected AGMs as a model of apathogenic SIV infection. Study of the molecular mechanisms of SIVagm asymptomatic infection could thus provide clues for understanding the pathogenesis of human immunodeficiency viruses. Regulatory genes could be candidates for genetic control of SIVagm apathogenicity. We have characterized Vpr, Tat, Rev, and Nef genes of two SIVagm strains isolated from naturally infected sabaeus monkeys captured in Senegal. The results provide further evidence that SIVagm from West African green monkeys is the most divergent class of AGM viruses, with structural features in long terminal repeat sequences and Vpr and Tat genes that distinguish them from viruses isolated from other AGM species (vervet, grivet, and tantalus monkeys).

[Electrophoretic polymorphism in different subspecies of Cercopithecus aethiops]. / Polymorphisme électrophorétique des différentes sous-espèces de Cercopithecus aethiops.

Variations were observed in prealbumin, transferrin, ceruloplasmin, haptoglobin, PGM-II and AK systems in various subspecies of Cercopithecus aethiops. The electrophoretic distance between three forms seems to indicate an intermediary status between populations and subspecies. The reasons for this moderate differentiation are discussed with regard to divergence of ethological characters, as recently studied.