Front Immunol

HIV-2 infection is characterized by low viremia and slow disease progression as compared to HIV-1 infection. Circulating CD14++CD16+ monocytes were found to accumulate and CD11c+ conventional dendritic cells (cDC) to be depleted in a Portuguese cohort of people living with HIV-2 (PLWHIV-2), compared to blood bank healthy donors (HD). We studied more precisely classical monocytes; CD16+ inflammatory (intermediate, non-classical and slan+ monocytes, known to accumulate during viremic HIV-1 infection); cDC1, important for cross-presentation, and cDC2, both depleted during HIV-1 infection. We analyzed by flow cytometry these PBMC subsets from Paris area residents: 29 asymptomatic, untreated PLWHIV-2 from the IMMUNOVIR-2 study, part of the ANRS-CO5 HIV-2 cohort: 19 long-term non-progressors (LTNP; infection ≥8 years, undetectable viral load, stable CD4 counts≥500/μL; 17 of West-African origin -WA), and 10 non-LTNP (P; progressive infection; 9 WA); and 30 age-and sex-matched controls: 16 blood bank HD with unknown geographical origin, and 10 HD of WA origin (GeoHD). We measured plasma bacterial translocation markers by ELISA. Non-classical monocyte counts were higher in GeoHD than in HD (54 vs. 32 cells/μL, p = 0.0002). Slan+ monocyte counts were twice as high in GeoHD than in HD (WA: 28 vs. 13 cells/μL, p = 0.0002). Thus cell counts were compared only between participants of WA origin. They were similar in LTNP, P and GeoHD, indicating that there were no HIV-2 related differences. cDC counts did not show major differences between the groups. Interestingly, inflammatory monocyte counts correlated with plasma sCD14 and LBP only in PLWHIV-2, especially LTNP, and not in GeoHD. In conclusion, in LTNP PLWHIV-2, inflammatory monocyte counts correlated with LBP or sCD14 plasma levels, indicating a potential innate immune response to subclinical bacterial translocation. As GeoHD had higher inflammatory monocyte counts than HD, our data also show that specific controls are important to refine innate immunity studies

IL-7 as an adjuvant for mucosal vaccine development

International audienceBackground: Despite considerable research efforts, mucosal immunity remains particularly difficult to stimulate through vaccines. Systemic injection of IL-7 stimulates chemokines-induced recruitment of circulating T-cells into mucosae.Methods: The optimal dose of IL-7 to be sprayed on mucosal surface was defined on 14 rhesus macaques. On mucosal biopsies collected after IL-7 administration, we quantified local transcription of 19 chemokines by qRT-PCR and cell infiltration by immunochemistry plus image analysis. Six macaques were immunized with antigens (DT and the HIV-1 gp41-P1 peptide) applied directly on the vaginal mucosa, two days after either IL-7 or PBS administration. The immunizations were repeated thrice, four months apart, and the macaques were euthanized 2 weeks after the last immunization. Antigen-specific IgA and IgG productions were quantified in vaginal secretions by ELISA. Antigen-specific plasma cells were detected by reverse immunohistochemistry in tissue, and by B-cell ELISPOT in PBMCs.Results: A significant overexpression of twelve chemokines was observed 48 hours after mucosal administration of 10µg of IL-7. Subsequently, mDC, macrophage, NK, B- and T-cell numbers significantly raised in the IL-7-treated mucosae, suggesting massive chemokine-driven infiltration. Administration of antigens led to a stronger mucosal immune response in the IL-7-treated macaques as compared to animals immunized with antigens alone. Robust production of antigen-specific IgAs and IgGs was detected in vaginal secretions. The immunizations repeated thrice sustained mucosal specific immune responses. Antigen-specific-antibody secreting cells were recovered from PBMC and more DT-specific plasma cells were found in the vaginal mucosae (IgA isotype) and the draining lymph nodes (IgG isotype) of IL-7-treated macaques. Tertiary lymphoid organs were observed in vaginal mucosae from IL-7-treated macaques only.Conclusions: Pre-treatment by non-traumatic vaginal administration of IL-7 (10µg by spray), allows for the development of a strong mucosal immune response in macaques following subsequent mucosal vaccination, through local chemokine expression and the recruitment of immune cells in the vaginal mucosa. The mucosal localization of IgA-specific plasma cells argues for their main contribution in the high levels of specific-IgAs evidenced in the vaginal secretions. These data suggest that IL-7 could be used as a mucosal adjuvant to elicit vaginal antibody response, the most promising way to confer protection to numerous STD

IL-7 as a mucosal adjuvant in pulmonary immunization protocols

International audienceObjective: Mucosae are the gateway for many pathogens. However, few vaccines have been developed to specifically target mucosal immunity. Recent studies in the laboratory evidenced local expression of IL-7 in the acutely SIV-infected intestinal mucosa and IAV-infected lung in macaques or mice, respectively. This overexpression led to chemokine production and infiltration of immune cells into these mucosae. In addition, systemic injection of IL-7 to macaques rapidly stimulates both the production of chemokines and immune cells homing into the mucosa. These results prompted us to study if IL-7 could be used as a mucosal vaccine adjuvant.Methods: Mice were intratracheally treated with IL-7 or PBS, then immunized by the same route against diphtheria toxoid (DT) or inactivated influenza virus (IAVi) two days later. DT immunized-mice were sacrificed at day 14 while those immunized with IAVi were infected with virulent IAV at day 14 and sacrificed at day 29. We measured antigen-specific antibody responses (anti-DT & anti-IAV) in both bronchoalveolar lavages (BAL) and sera, as well as chemokine expressions in lung tissue, by ELISA. The immune cell infiltration into the pulmonary mucosa was evaluated by immunochemistry on lung sections. The effectiveness of IL-7-adjuvanted vaccine in providing protection against IAV pathology was assessed by daily monitoring of animal body weight.Results: Intratracheal administration of IL-7 stimulated the production of pro-inflammatory chemokines in the lung parenchyma, leading to massive infiltration of immune cells found to be mainly organized in lymphoid aggregates. Moreover, intratracheal administration of IL-7 before primo-immunization allowed antigens-specific IgAs and IgGs production in the pulmonary mucosa. These effects were not observed in control mice vaccinated without IL-7 administration. In addition, only IL-7-treated immunized mice were protected against influenza pathology. This protection seems to be related to a high level of IAV-specific antibodies in BAL and lymphoid aggregate appearance in the pulmonary mucosa.Conclusion: By attracting immune cells into mucosae, local IL-7 administration prepares the mucosal immune system, gathering conditions that result in enhanced antigen-specific pulmonary immune responses upon antigenic stimulation. Hence, IL-7 appears as a mucosal adjuvant able to increase mucosal antibody responses, an important immune arm implicated in the protection against most mucosal infections