Moreover, reticulocytes infected with R428 order Plasmodium yoelii released exosomes capable of activating a protective anti-malaria immune response in naïve mice in an adjuvant-independent

manner [39]. Our present data, demonstrating the protective efficacy of exosomes in controlling an M. tuberculosis infection, supports the potential application for this type of cell-free vaccine. Unexpectedly, we did not see much protection with the BCG 9 months after vaccination. Examination of the data suggests that the BCG-vaccinated mice showed only a slightly lower CFU compared to unvaccinated mice (i.e. PBS control versus BCG, or BCG plus exosomes from untreated macrophages). However, the 0.3 log drop in spleen CFU between BCG-vaccinated and nonvaccinated mice was statistically significant. In a number of published studies, there was

protection by the initial BCG vaccination even in the absences of a booster vaccine. In most of these studies, a shorter window between BCG vaccination and boosting was used [40, 41]. Nevertheless, in some studies where protection with the primary BCG vaccination was observed, the intervals between BCG vaccination and M. tuberculosis infection were on the same https://www.selleckchem.com/products/Fulvestrant.html timeframe as in our study [42]. Interestingly, in the study by Dietrich et al. a similar ∼0.3 log drop in spleen CFU was observed when comparing unvaccinated mice to those vaccinated with BCG 8 months prior to M. tuberculosis infection [42]. These results suggest that in some cases, the protection may be minimal Anacetrapib after a long interval between vaccination and infection. The incomplete protection we observed is likely due to limited antigen-specific memory T cells available for reactivation 9 months after the initial BCG vaccination (see Fig. 7). It is unclear

why we see this limited immune/protective response but one hypothesis is that our BCG strain failed to survive in vivo for the time necessary to induce a potent long-term memory response. Previous studies of BCG-vaccinated mice treated with antibiotics suggest that viable BCG is required for vaccine efficacy [43]. For most individuals, M. tuberculosis infection induces a protective TH1-mediated immune response characterized by the development of antigen-specific CD4+ and CD8+ lymphocytes producing IFN-γ and other TH1-type cytokines [28]. During the subunit vaccine studies, it was evident that the control of an M. tuberculosis infection required an adjuvant that induces a robust TH1 but limited TH2 immune response [44, 45]. It has been demonstrated that exosomes carrying parasitic or tumor antigens could generate a strong antigen-specific TH1 immune responses resulting in control of the parasitic infection or in limiting tumor progression [29-31]. Our previous studies indicated that exosomes released from M.