CONICET | Buscador de Institutos y Recursos Humanos

The nasal priming with Lactobacillus rhamnosus CRL1505 modulates the respiratory antiviral innate immuneresponse and improves protection against influenza virus (IFV) challenge in mice. However, the potentialbeneficial effect of the CRL1505 strain on the adaptive immune response triggered by IFV infection or vaccinationwas not evaluated before. In this work, we demonstrated that nasally administered L. rhamnosus CRL1505is able to improve both the humoral and cellular adaptive immune responses induced by IFV infection or vaccination.Higher levels of IFV-specific IgA and IgG as well as IFN-γ were found in the serum and the respiratorytract of CRL1505-treated mice after IFV challenge. Lactobacilli treated mice also showed reduced concentrationsof IL-17 and improved levels of IL-10 during IFV infection. The differential balance of inflammatory and regulatorycytokines induced by L. rhamnosus CRL1505 contributed to the protection against IFV by favoring aneffective effector immune response without inducing inflammatory-mediated lung damage. The optimal immunomodulatoryeffect of the CRL1505 strain was achieved with viable bacteria. However, non-viable L.rhamnosus CRL1505 was also efficient in improving the adaptive immune responses generated by IFV challengesand therefore, emerged as an interesting alternative for vaccination of immunocompromised hosts. Similar toother immunomodulatory properties of lactobacilli, it was shown here that the adjuvant effect in the context ofIFV vaccination was a strain dependent ability, since differences were found when L. rhamnosus CRL1505 and theimmunomodulatory strain L. rhamnosus IBL027 were compared. This investigation represents a thorough explorationof the role of immunobiotic lactobacilli in improving humoral and cellular adaptive immune responsesagainst IFV in the context of both infection and vaccination.

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