casei showed a similar pattern of these Th1 cytokines and would have an influence on the results when associated with the vaccine. IL-2 would exert a strong influence

on the proliferative capacity and maintenance of memory T cells [40], which would be a desirable characteristic in the selection of an efficacious long-term vaccine. Some lactobacilli used as adjuvants in vaccination protocols increased systemic protection through an increase in the Th1 response [19]. In addition, an immune response based on the Th1 population participates actively in the resolution of S. pneumoniae infection in humans [41]. Considering our results, the probiotic strain would exert an immunostimulatory effect on the Th1 cells and on the release of their cytokines in the lung. On the other hand, regulation of the inflammatory response is most important in infectious diseases. In this sense, the probiotic administered by the oral and nasal routes was able to increase Epacadostat in vivo the regulatory Th2 Z-VAD-FMK clinical trial IL-10 cytokine. This would be of great importance to ensure a balanced immune response that would enable resolution of the infectious process, limiting a possible exacerbated inflammatory response and avoiding damage to the host’s tissues. The greatest IL-10 production was obtained on day 42 in the

groups that received the live and inactivated vaccine associated with orally administered L. casei. In contrast, the nasal administration of Lc and D-LL + Lc induced an IFN-γ/IL-10 ratio > 1, which could have negative implications for the host after infection if the Th1 response was exacerbated. However, other factors must be considered. Thus, recent works have associated IL-17 with stimulation in the production of chemokines capable of recruiting IFN-γ-producing CD4+ T cells [42,43]. In addition, IL-17 and IL-22 produced by Th17 induce the attraction of neutrophils and macrophages into the parenchymal tissue, favouring pathogen clearance [44]. It was also demonstrated that this cytokine, being a key factor in the adaptive

immunity against the above pathogen, would mediate the death of pneumococci in the presence or absence of specific antibodies [45]. Moreover, using knock-out Thiamine-diphosphate kinase mice, IL-17 was shown to be of fundamental importance to reduce nasal colonization by S. pneumoniae. Oral and nasal administration of L. casei in association with LL vaccination induced the highest IL-17 levels. It also increased IL-2 and IFN-γ cytokine levels and afforded full protection against pneumoccocal challenge. In contrast, the dead vaccine failed to prevent pneumococcal colonization by both serotypes 3 and 14 of the pathogen, although it induced high IL-17 and Th1 cytokine levels, indicating the complexity of the protective response. On the other hand, it should be pointed out that too-high levels of IL-17 could be associated with autoimmunity [44], so that a balanced response is desirable after vaccination.