IL-7 as an adjuvant for mucosal vaccine development
Résumé
Background: 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.
Domaines
Sciences du Vivant [q-bio]
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THPEA017_IL-7 as an adjuvant for mucosal vaccine development_AIDS 2018_MRbis.pdf (8.6 Mo)
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Commentaire | poster AIDS2018 |