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The discovery of the zoonotic potential of retroviruses infecting non-human primates (NHPs) aroused the interest in simian retroviruses such as simian immunodeficiency virus, simian T-cell leukemia virus or simian foamy virus (SFV).
However, investigations of retroviral circulation in wild primate communities are rare.
Of particular interest are the transmission modalities of SFV, obviously successful strategies, which have led to frequent, persistent infections of NHPs for at least 40 million years. This work is an attempt to determine these modalities in wild chimpanzees from the Taï National Park, Côte d’Ivoire, where SFVs are highly endemic.
These analyses presume a fine diagnostic tool to estimate the SFV diversity within each host and identify superinfection cases, i.e., the simultaneous infection of the same individual host with several strains of the same virus. So far, methods possibly allowing such investigations from samples collected non-invasively (such as feces) have never been properly compare. Therefore, the costs and benefits of the gold standard (end-point dilution PCR, EPD-PCR) and multiple bulk-PCR cloning methods were assessed for SFV super-infections based on a case study using fecal samples of two different chimpanzee subspecies ( Pan troglodytes verus and P. t. schweinfurthii ). It could be shown that in these conditions EPD-PCR can lead to massive consumption of biological material. This constitutes a serious drawback in a field in which rarity of biological material is a fundamental constraint. In addition, data demonstrated that EPD-PCR results (single/multiple infection; founder strains) could be well predicted from multiple bulk-PCR clone experiments, by applying simple statistical and network analyses to sequence alignments. Therefore, the implementation of the latter method can be recommended, when the focus is put on retroviral super-infection and only low retroviral loads are encountered. Using this approach, SFV diversity was then estimated for each sample of the study community in Taï National Park to investigate dynamics of SFVs.
The results indicate, that vertical transmission (being here understood as mother-offspring transmission) is a common route of SFV transmission within the community whereas previous studies so far only pointed at horizontal transmissions of SFVs.
The strong bond between mother and offspring is likely to be responsible for primary infections. With increasing age subsequent infections with SFVs could be observed (super-infections). The development of truly aggressive behavior during the onset of adulthood is hypothesized to result into frequent horizontal transmissions of SFVs between other members of the group. Finally, these data gives evidence for complex SFV dynamics in wild chimpanzees, even at a single community scale, and show that linking wild NHP social interactions and their microorganisms’ dynamics is feasible.