Recombinant Surface Immunogenic Protein from <i>S. agalactiae</i> and hemocyanin from <i>Fisurella latimarginata</i> promote cross-presentation dependence on the TLR-4 signaling

Abstract

Abstract Improved vaccine adjuvants are needed to address infectious diseases, cancer, and future pandemics. Toll-like receptors (TLRs) have been researched as targets of vaccine adjuvants because they modulate the innate immune system and activate adaptive immunity. TLR-based adjuvants induce cross-presentation of exogenous antigens to CD8 T lymphocytes. TLR4 signaling recruits the adapters myeloid differentiation marker 88 (MyD88), which mediates the recycling of endoplasmic reticulum fusion to the phagosome as well as the TIR-domain-containing adapter-inducing interferon-β (TRIF), which is essential for translocation from the endosome to the cytosol. Given the role of TLR4 agonists, most studies have used ligands based on lipopolysaccharides, but these have side effects (especially fever). Here we propose using TLR4 protein-based agonists (TLR-4-PBA), which have multiple advantages as adjuvants: They are naturally biocompatible and biodegradable substances that induce minimal reactogenicity and toxicity. We studied mollusk hemocyanin from Fissurella latimarginata (FLH) and the recombinant surface immunogenic protein from Streptococcus agalactiae (rSIP). These two proteins differ significantly in their structure, and we show Th1 immunomodulatory properties. Using mouse bone marrow-derived dendritic cells pulsed with ovoalbumin (OVA), we then showed that rSIP and FLH promote cross-presentation in OT-I CD8+ T lymphocytes. This effect depends on TLR4 and the recruitment of MyD88 and TRIF. Studies are in progress to evaluate IRF3 and NF-κ B activation. Our results illustrate how these TLR-4-PBAs could act as a clinically useful vaccine adjuvant for innate immunity and Th1 adaptive immune response. FONDECYT 1201600 (MIB); FONDEF ID21I10370 (AEV), Instituto de Salud Pública de Chile Funding (AEV, DD-D); ANID/PhD Nacional program 21210946 (MLS) and 21200880 (DD-D); FONDAP 15130011 (MT, SL).