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Formes recombinantes inter-groupes M et O du VIH-1 : Etude de leur potentiel réplicatif et de leur émergence in vitro/in vivo

Abstract : HIV-1 are characterized by a high genetic diversity and genetic recombination has an strong impact on their evolution. Despite their great genetic divergence, HIV-1 group M, pandemic, and group O, endemic in Cameroon, can generate HIV-1/MO intergroup recombinants. The current description of 19 HIV-1/MO recombinant forms (URF_MO), including 10 in the last ten years, raises the question of a possible benefit of the recombination and the modalities of their emergence. Therefore, the objectives of this study were to study the replicative potential and the in vitro and in vivo emergence of HIV-1/MO recombinant forms. The replicative potential was analyzed, based on a simple recombination pattern, [Ogag/pol-Menv], harbouring a breakpoint in Vpr, due to a recombination hotspot in this region. After many attemptsto generate Chimeric Infectious Molecular Clone (CIMC) from HIV-1/M subtype B and HIV-1/O subgroup T parental infectious molecular clones, a CIMC pVIH-1/OM was synthesized and provided recombinant viruses by transfection and co-culture. A stock was generated to compare the replicative potential of recombinant viruses with HIV-1/M and HIV-1/O parental strains. Two markers were monitored in culture supernatants: Reverse Transcriptase (RT) activity and P24 antigen quantity. The results showed a superiority of the group M parental strain compared to group O for both markers. In contrast, for the HIV-1/OM recombinant strain, RT activity data did not overlap with the amount of P24 antigen, suggesting an hybrid behaviour of the recombinant, in terms of enzyme activity and P24 production. In vitro, the emergence modalities were apprehended by the study of the generation of breakpoints within the LTRs, initially discordant, of the generated HIV-1/OM recombinants and in which a recombination event had to occure to become identical. Emergence kinetics and recombination profiles were analysed, using a Single Genome Amplification strategy, in order to characterize RNA and DNA quasi-species. Our results showed a preferential localization of recombination in the R region of LTRs, with three major recombination patterns (506-513bp, 513-522bp and 523-547bp), the second one predominating at the end of culture. Our experimental model was validated by comparing these results with the in vivo data from URF_MOs. Other recombination patterns were observed in vivo, suggesting that patterns and mechanisms of recombination are not unique. In vivo, we had the opportunity to describe a unique case of HIV-1/MO recombination which revealed an undiagnosed HIV-1/M+O dual infection, based on discordant results in a routine drug-resistance test in an individual initially diagnosed as HIV-1/M. This work allowed us to characterize the replication dynamics of the HIV-1/M and HIV-1/O viral populations before recombination, and that of the HIV-1/MO recombinant. The immunovirological follow-up of this patient has allowed to date the emergence of this recombinant form, probably favored by therapeutic dysobservances and the succession of virological failures. This case highlights the complexity of following such situations and the need, in particular, for antiretroviral therapy active on the three viral populations. In conclusion, our findings provide new insights into the phenomenon of HIV recombination and offer many opportunities to work.
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Alice Moisan. Formes recombinantes inter-groupes M et O du VIH-1 : Etude de leur potentiel réplicatif et de leur émergence in vitro/in vivo. Virologie. Normandie Université, 2019. Français. ⟨NNT : 2019NORMR126⟩. ⟨tel-02509644⟩

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