Mucosal Vaccination with <i>Lactococcus lactis</i>-Secreting Surface Immunological Protein Induces Humoral and Cellular Immune Protection against Group B <i>Streptococcus</i> in a Murine Model

• Main Authors: Diego A. Diaz-Dinamarca, Carlos Hernandez, Daniel F. Escobar, Daniel A. Soto, Guillermo A. Muñoz, Jesús F. Badilla, Ricardo A. Manzo, Flavio Carrión, Alexis M. Kalergis, Abel E. Vasquez
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Vaccines
• Subjects: group b streptococcus; mucosal vaccine; surface immunogenic protein; cellular immune response; humoral immune response
• Online Access: https://www.mdpi.com/2076-393X/8/2/146

Group B <i>Streptococcus</i> (GBS) is the primary etiological agent of sepsis and meningitis in newborns and is associated with premature birth and stillbirth. The development of a licensed vaccine is one of the pending challenges for the World Health Organization. Previously, we showed that oral immunization with surface immune protein (SIP) decreases vaginal colonization of GBS and generates functional opsonizing antibodies, which was determined by opsonophagocytic assays (OPA) in vitro. We also showed that the protein has an adjuvant vaccine profile. Therefore, an oral vaccine based on SIP may be an attractive alternative to employ in the development of new vaccines against GBS. <i>Lactococcus lactis</i> is a highlighted oral vaccine probiotic inducer of the mucosal immune response. This bacterium could serve as an antigen-delivering vehicle for the development of an edible vaccine and has been used in clinical trials. In this study, we showed that an oral vaccine with a recombinant <i>L. lactis</i> strain secreting SIP from GBS (<i>rL. lactis</i>-SIP) can induce protective humoral and cellular immunity in an experimental model of GBS vaginal colonization in C57BL/6 mice. Mice immunized with <i>rL. lactis-</i>SIP were protected against clinical symptoms and bacterial colonization after GBS vaginal colonization. Our <i>rL. lactis-</i>SIP vaccine also induces an increase of immunoglobulin G (IgG) and immunoglobulin A (IgA) specifically against SIP. The adoptive transfer of serum from vaccinated mice to na&#239;ve mice generated protection against GBS vaginal colonization. Moreover, the <i>rL.</i> <i>lactis</i>-SIP strain induces the activation of SIP-specific T cells, which could decrease GBS vaginal colonization and generate protective antibodies when transferred to other mice. Our experimental observations strongly support the notion that <i>rL. lactis</i>-SIP induces protective humoral and cellular immunity and could be considered as a novel alternative in the development of vaccines for GBS.