Differential Inhibition of HIV Replication by the 12 Interferon Alpha Subtypes.

Type I interferons (IFNs) are a family of cytokines that represent a first line of defense against virus infections. The 12 different IFN-α subtypes share a receptor on target cells and trigger similar signaling cascades. Several studies have collectively shown that this apparent redundancy conceals qualitatively different responses induced by individual subtypes, which display different efficacies of inhibition of HIV replication. Some studies, however, provided evidence that the disparities are quantitative rather than qualitative. Since RNA expression analyses show a large but incomplete overlap of the genes induced, they may support both models. To explore if the IFN-α subtypes induce functionally relevant different anti-HIV activities, we have compared the efficacies of inhibition of all 12 subtypes on HIV spread and on specific steps of the viral replication cycle, including viral entry, reverse transcription, protein synthesis, and virus release. Finding different hierarchies of inhibition would validate the induction of qualitatively different responses. We found that while most subtypes similarly inhibit virus entry, they display distinctive potencies on other early steps of HIV replication. In addition, only some subtypes were able to target effectively the late steps. The extent of induction of known anti-HIV factors helps to explain some, but not all differences observed, confirming the participation of additional IFN-induced anti-HIV effectors. Our findings support the notion that different IFN-α subtypes can induce the expression of qualitatively different antiviral activities. IMPORTANCE The initial response against viruses relies in large part on type I interferons, which include 12 subtypes of IFN-α. These cytokines bind to a common receptor on the cell surface and trigger the expression of incompletely overlapping sets of genes. Whether the anti-HIV responses induced by IFN-α subtypes differ in the extent of expression or in the nature of the genes involved remains debated. Also, RNA expression profiles led to opposite conclusions, depending on the importance attributed to the induction of common or distinctive genes. To explore if relevant anti-HIV activities can be differently induced by the IFN-α subtypes, we compared their relative efficacies on specific steps of the replication cycle. We show that the hierarchy of IFN potencies depends on the step analyzed, supporting qualitatively different responses. This work will also prompt the search for novel IFN-induced anti-HIV factors acting on specific steps of the replication cycle.

Mécanismes immunologiques impliqués dans la persistance des réservoirs du VIH.

Résumé Les thérapies antirétrovirales (TAR) permettent de contrôler la réplication virale et ont considérablement amélioré la qualité et l'espérance de vie des personnes vivant avec le VIH (PVVIH). Toutefois, près de 40 ans après la découverte du virus, il n'existe toujours pas de traitement curatif permettant d'éliminer le VIH de l'organisme : Même après des années de TAR efficace, le virus persiste dans des cellules, principalement des lymphocytes T CD4 mémoires, qui constituent une source pérenne de virus infectieux et qui nécessitent de poursuivre les traitements à vie. Les recherches sur les réservoirs du VIH menées au cours des 25 dernières années ont permis de mieux comprendre comment certaines cellules infectées persistent pendant des décennies sans être éliminées, ni par les TAR, ni par les réponses immunitaires. Le VIH « se cache ¼ dans des cellules à durée de vie très longue, qui ont la capacité de proliférer par différents mécanismes et qui expriment préférentiellement certains récepteurs leur permettant de demeurer invisibles au système immunitaire. Une meilleure compréhension de ces mécanismes de persistance est un prérequis nécessaire à la mise au point de stratégies thérapeutiques visant à éradiquer le VIH.

Immunological mechanisms involved in the persistence of HIV reservoirs.

Antiretroviral therapy (ART) controls viral replication and has dramatically improved the quality and life expectancy of people living with HIV (PLHIV). However, almost 40 years after the discovery of HIV, there is still no cure; even after years of effective ART, the virus persists in cells, primarily memory CD4 T cells. These cells are a perennial source of infectious viruses, which necessitate that people living with HIV continue ART for life. Research on HIV reservoirs over the past 25 years has provided insight into how some infected cells persist for decades without being cleared by ART nor by immune responses. HIV "hides" in cells with extended lifespans, which have the capacity to proliferate through diverse mechanisms and which preferentially express several receptors that allow them to remain invisible to the immune system. A better understanding of these mechanisms of persistence is a necessary prerequisite for the development of therapeutic strategies aimed at eradicating HIV.