Adjuvant capacity of S-layer glycoprotein from Lactobacillus kefiri depends on glycan recognition by Mincle

MALAMUD M; SERRADELL MA; LEPENIES B

Buenos Aires

Simposio; Tercer Simposio Argentino de Glicobiología (GlycoAR2019); 2019

Universidad Nacional de San Martín

The S-layer is a (glyco)-proteinaceous envelope constituted by subunits that self-assemble to form a two-dimensional lattice that covers the surface of different species of Bacteria and Archaea. Due to their ability to self-assemble in solution, S-layer proteins are attractive tools to be used as antigen/hapten carriers or adjuvants. Recently, we have demonstrated that the adjuvant capacity of the S-layer glycoprotein from Lactobacillus kefiri CIDCA 8348 (SLP-8348) depends on of the biological activity of the SLP-8348 glycans, but the receptors involved remained unknown. Therefore, in this study, we aim to identify lectin receptors recognizing this bacterial surface glycoprotein and to investigate their role in the immunostimulatory activity of SLP-8348. An ELISA-based method using C-type lectin receptor (CLR)?hFc fusion proteins showed that SLP-8348 interacts with different CLRs such as Mincle, SingR3 and hDC-SIGN. Using BMDCs derived from CLR-deficient mice, we show that SLP-8348 uptake is dependent of Mincle. Furthermore, we demonstrate that the Mincle/CARD9 signaling axis contributes to the SLP-8348-induced activation of BMDCs, since SLP-8348-activated BMDCs from Mincle-/- or CARD9-/- mice were not capable of enhancing OVA-specific effector functions in CD4+ T cells purified from T cell receptor-transgenic OT-II mice. These findings highlight the utility to search for glycan-based adjuvants derived from non-pathogenic microorganisms.