At present, studies are being carried out in the nasopharynx to analyse the immune mechanisms induced at this level by the recombinant vaccine and by the probiotic strain. On the other hand, analysis of the IgG1/IgG2a ratio revealed PF-02341066 concentration that there exist differences

in the specific IgG subtype induced for each immunization protocol. Thus, although the two anti-PppA IgG subtypes were induced with all the treatments assayed, when the probiotic was used as an oral and nasal adjuvant associated with the inactivated vaccine the cellular response became polarized towards the predominance of Th1 cells, as shown by an IgG1/IgG2a ratio < 1. The effectiveness of anti-PppA antibodies induced by vaccination was demonstrated by passive immunization in a previous study [16]. Our results demonstrated that only vaccination with the live and dead recombinant strains associated

with oral administration of the probiotic was able to prevent lung colonization and the dissemination into blood of the two serotypes assessed (3 and 14). Recently it was shown that IgG2a has a great ability to mediate complement deposition on the pneumococcal surface [38], which would account partly for the protection afforded by vaccination with D-LL + Lc (O), but not the results obtained for administration of D-LL + Lc (N), which enabled the lung colonization of serotype 3. In the LL and D-LL check details groups high IgG1 production would interfere with the complement-fixing activity of the IgG2a anti-PppA and would partly explain the lung colonization (serotypes 3 and 14) and the passage into RAS p21 protein activator 1 blood (serotype 14) of the pathogen. This was not found in the LL + Lc (O) group, in which IgG1 production was favoured, and there was full protection. In this sense, IgG1 contributes to protection against pneumococcal infection through Fc receptor binding or by preventing attachment and colonization of the

pathogen on mucosal surfaces. The participation of specific humoral immunity in protection against S. pneumoniae is undeniable, although recent reports have indicated that T CD4+ cells would also play a relevant role in the host’s defences against pneumococcal infections [39]. In order to increase our knowledge concerning the possible mechanisms involved in vaccine-induced protective immunity, we assessed the cytokines that characterize different CD4+ T cell populations. Th1, IL-2 and IFN-γ cytokines were increased in all the assessed groups, although the profiles induced for each immunization showed important differences. Thus, LL + Lc (O) induced high levels of both interleukins (IL-2 and IFN-γ), while D-LL + Lc (O) induced mainly an increase in IL-2 and D-LL + Lc (N) in IFN-γ.