Flagellin/NLRC4 Pathway Rescues NLRP3-Inflammasome Defect in Dendritic Cells From HIV-Infected Patients: Perspective for New Adjuvant in Immunocompromised Individuals.

Introduction: NLRP3 inflammasome plays a key role in dendritic cells (DC) activation in response to vaccine adjuvants, however we previously showed that it is not properly activated in DC from HIV-infected patients (HIV-DC), explaining, at least in part, the poor response to immunization of these patients. Taking in account that several cytoplasmic receptors are able to activate inflammasome, and that bacterial components are considered as a novel and efficient adjuvant, we postulated that bacterial flagellin (FLG), a natural ligand of NAIP/NLRC4 inflammasome, could rescue the activation of the complex in HIV-DC. Objective: Demonstrate that FLG is able to activate monocyte-derived dendritic cells from HIV-infected individuals better than LPS, and to what extent the entity of inflammasome activation differs between DC from HIV-infected patients and healthy donors. Methods: Monocyte-derived dendritic cells from HIV-infected patients (HIV-DC) and healthy donors (HD-DC) were stimulated with FLG, and inflammasome as well as DC activation (phenotypic profile, cytokine production, autologous lymphocytes activation) were compared. Chemical and genetic inhibitors were used to depict the relative contribution of NLRC4 and NLRP3 in HIV/HD-DC response to FLG. Results: FLG properly activates HD-DC and HIV-DC. FLG induces higher inflammasome activation than LPS in HIV-DC. FLG acts through NLRC4 and NLRP3 in HD-DC, but at a lesser extent in HIV-DC due to intrinsic NLRP3 defect. Conclusions: FLG by-passes NLRP3 defect in HIV-DC, through the activation of NAIP/NLRC4 inflammasome, indicating possible future use of the bacterial component as an efficient adjuvant in immunocompromised individuals.

Exosomes are possibly used as a tool of immune regulation during the dendritic cell-based immune therapy against HIV-I.

Dendritic cell (DC)-based immune therapy (IT) against HIV showed variable results. It is known that different factors influence host response to DC-IT. Exosomes derived from DC are regulators of the immune system. In this context, here we hypothesize about the role of the DC-derived exosomes on the DC-IT response. Based on data from RT-PCR array genes expression (focused on the TSG101 gene, an exosome marker) and flow cytometry experiments of a DC-IT against HIV-1 clinical trial, we hypothesize that: During the DC-IT exosomes are used as an additional tool for immune system modulation. In addition, we believe that a low release of exosomes can be more beneficial for the DC-IT response than a high release of exosomes. Our data reinforce the concept that exosomes can act as an immune regulatory tool, however not in a generalized manner, but in a highly precise way. Our hypothesis is based in preliminary experimental data, thus, it should be tested using experimental and functional strategies involving a great number of patients. Once the hypothesis confirmed, the immunomodulatory role of the exosomes during DC-IT must be considered as an important factor in the (I) evaluation, (II) modulation, and (III) success of DC-IT against HIV.