Current antiretroviral drugs available for the treatment of HIV infection enable the control of viral replication but, despite an early initiation, do not eliminate the viral reservoir. Understanding the mechanisms controlling viral replication is a major challenge for the development of new therapeutic strategies.

We were interested in the control of HIV replication in vivo in two different contexts: on one hand the control of viral replication by the cellular restriction factor HUSH in infected subjects and on the other hand the kinetics of viral replication and of the number of infected cells in the genital compartment in men receiving either integrase inhibitor or protease inhibitor based triple therapy from the time of primary infection.

The HUSH complex was recently identified as a cellular restriction factor involved in the transcription’s epigenetic repression of cellular genes and genome of retroviruses in viral latency models in vitro. In this context, we developed a study supported by the ANRS to determine the role of HUSH in the control of HIV replication in vivo in 44 untreated subjects, HIV-1 or HIV-2 infected, in primary infection or chronic stage. The activity of HUSH was assessed by quantifying the transcription of seven potential cellular HUSH targets described in the literature in HeLa, KBM7 or HEK293T cellular models. No study has so far investigated the impact of HUSH in primary CD4 T cells. This activity was compared to different viral markers reflecting viral transcription and replication in these patients. Our study suggests a correlation between the level of transcription of ZNF225 and ZNF350 genes, potential cellular HUSH targets, and the level of HIV transcription. To understand the variability of the results observed in vivo for the seven cellular genes studied, we investigated whether these genes were targeted by HUSH in primary CD4 T lymphocytes first by a candidate gene approach and then by a deeper approach with the performance of an RNA-Seq in collaboration with the group of F. Margottin-Goguet. The diverse results from the literature and analyses on primary CD4 cells indicate that HUSH impacts different cellular targets depending on the cell type considered.

The second part of my work concerns the study of the decrease of viral replication and of the number of infected cells in semen, estimated by HIV RNA and HIV DNA loads, upon initiation of two tritherapies from the primary infection. Primary infection is a critical period at the individual level with a peak of viral replication, a drop of CD4 T lymphocytes, an early constitution of the viral reservoir; and at the collective level because of the high risk of transmission linked to the high levels of virions and infected cells in the semen. Dolutegravir (DTG), a second-generation integrase inhibitor has recently been recommended in this indication. We conducted a genital compartment ancillary study in the ANRS OPTIPRIM2 multicenter randomized trial comparing the impact of DTG-based versus darunavir-based (DRV: protease inhibitor) triple therapy on blood HIV DNA levels. Our results indicate that both viral particules and infected cells are no longer detected in semen after 48 weeks of treatment in 80% of cases of early DTG-based therapy initiated 20 days (median) after the first clinical signs of primary infection which is not different from DRV-based therapy (Mariaggi et al. JAC 2022). Because viral loads in semen are high in the first weeks after infection, a reduction in treatment should not be considered too early.

We have assessed the impact of the HUSH complex in vivo on viral replication. Further studies are needed to understand the diversity of results obtained with different cellular targets of HUSH. Furthermore, the high viral loads in semen during primary infection highlight the importance to evaluate new therapeutic strategies in the genital compartment to limit the transmission of the infection.

Key words : Viral replication control, Restriction factors, HUSH complex; Genital compartment; HIV reservoirs, Primary HIV infection; Dolutegravir