S-Layer Glycoprotein From Lactobacillus kefiri Exerts Its Immunostimulatory Activity Through Glycan Recognition by Mincle

ASSANDRI, MATÍAS H.; SERRADELL, MARÍA DE LOS ÁNGELES; ASSANDRI, MATÍAS H.; SERRADELL, MARÍA DE LOS ÁNGELES; CARASI, PAULA; LEPENIES, BERND; CARASI, PAULA; LEPENIES, BERND; MALAMUD, MARIANO; FREIRE, TERESA; MALAMUD, MARIANO; FREIRE, TERESA

Frontiers in immunology

Frontiers Media

Año: 2019 vol. 10

1664-3224

The development of new subunit vaccines has promoted the rational design of adjuvantsable to induce a strong T-cell activation by targeting specific immune receptors. TheS-layer is a (glyco)-proteinaceous envelope constituted by subunits that self-assembleto form a two-dimensional lattice that covers the surface of different species of Bacteriaand Archaea. Due to their ability to self-assemble in solution, they are attractive toolsto be used as antigen/hapten carriers or adjuvants. Recently, we have demonstratedthat S-layer glycoprotein from Lactobacillus kefiri CIDCA 8348 (SLP-8348) enhancedthe LPS-induced response on macrophages in a Ca2+-dependent manner, but thereceptors involved in these immunomodulatory properties remain unknown. Therefore,we aim to determine the C-type lectin receptors (CLRs) recognizing this bacterial surfaceglycoprotein as well as to investigate the role of glycans in both the immunogenicityand adjuvant capacity of SLP-8348. Here, using a mild periodate oxidation protocol,we showed that loss of SLP-8348 glycan integrity impairs the cell-mediated immuneresponse against the protein. Moreover, our data indicate that the adjuvant capacity ofSLP-8348 is also dependent of the biological activity of the SLP-8348 glycans. In orderto evaluate the CLRs involved in the interaction with SLP-8348 an ELISA-based methodusing CLR?hFc fusion proteins showed that SLP-8348 interacts with different CLRs suchas Mincle, SingR3, and hDC-SIGN. Using BMDCs derived from CLR-deficient mice,we show that SLP-8348 uptake is dependent of Mincle. Furthermore, we demonstratethat the SLP-8348-induced activation of BMDCs as well as its adjuvant capacityrelies on the presence of Mincle and its signaling adaptor CARD9 on BMDCs, sinceSLP-8348-activated BMDCs from Mincle−/− or CARD9−/− mice were not capableto enhance OVA-specific response in CD4+ T cells purified from OT-II mice. Thesefindings significantly contribute to the understanding of the role of glycans in theimmunomodulation elicited by bacterial SLPs and generate a great opportunity in thesearch for new adjuvants derived from non-pathogenic microorganisms.