CENTRO DE REFERENCIA PARA LACTOBACILOS
Unidad Ejecutora - UE
Host immunity in the protective response to nasal immunization with a pneumococcal antigen associated to live and heat-killed Lactobacillus casei
VINTIÑI ELISA; MEDINA MARCELA
BIOMED CENTRAL LTD
Lugar: Londres; Año: 2011 vol. 12 p. 1 - 1
AbstractBackgroundAt present, available pneumococcal vaccines have failed to eradicate infections caused byS. pneumoniae. Search for effective vaccine continues and some serotype independentpneumococcal proteins are considered as candidates for the design of new vaccines,especially a mucosal vaccine, since pneumococci enter the body through mucosal surfaces.Selection of the appropriate adjuvant is important for mucosal vaccines, and lactic acidbacteria (LAB) with immunostimulant properties are promissory candidates. In this work,we assessed the adjuvant effect of a probiotic strain, Lactobacillus casei (L. casei), whennasally administered with a pneumococcal antigen (pneumococcal protective protein A:PppA) for the prevention of pneumococcal infection. Adjuvanticity of both live (LcV) andheat-killed (LcM) was evaluated and humoral and cellular antigen-specific immuneresponse was assessed in mucosal and systemic compartments. The potential mechanismsinduced by nasal immunization were discussed.ResultsNasal immunization of young mice with PppA+LcV and PppA+LcM induced anti-PppAIgA and IgG antibodies in mucosal and systemic compartments and levels of these specificantibodies remained high even at day 45 after the 3rd Immunization (3rd I). These resultswere correlated with IL-4 induction by the mixture of antigen plus LcV and LcM. Also,PppA+Lc (V and M) induced stimulation of Th1 and Th17 cells involved in the defenceagainst pneumococci. The protection against pneumococcal respiratory challenge at day 30after the 3rd I showed that PppA+LcV and PppA+LcM immunizations significantlyreduced pathogen counts in nasal lavages while prventing their passage into lung andblood. Survival of mice immunized with the co-application of PppA plus LcV and LcMwas significantly higher than in mice immunized with PppA alone and control mice whenintraperitoneal challenge was performed. No significant differences between the treatmentsinvolving LcV and LcM were found.ConclusionsLive and heat-killed L. casei enhanced the antigen-specific immune response whenadministered nasally with a pneumococcal antigen. Considering the potential riskassociated with live bacteria, the design of a nasal vaccine based on pneumococcalantigens and heat-killed L. casei emerges as a safe and effective strategy for the preventionof pneumococcal infections and opens new possibilities of application of dead LAB asadjuvants in vaccine formulations against other pathogens.