CD4+ T lymphocytes play a critical role in the host immune responses during bacterial infection [40, 41]. CD4+ T
cells have been shown to differentiate into Th1, Th2 and lately Th17 (important to intracellular bacteria) cells. Th1 cells are characterized by their production of IFN-γ and are involved in cellular immunity [42, 43], and Th2 cells produce IL-4 and are required for humoral immunity . In this experiment, the secretion of IFN-γ was more distinct than that of IL-4 when the splenocytes P505-15 manufacturer were stimulated with the epitopes. We did not detect any significant secretion of IL-4 in epitope-stimulated NVP-BSK805 splenocyte cultures. It is possible that the levels of IL-4 were below detection limit. The results implied that the selected epitopes were BALB/c-specific Th1-type epitope. Immune protection against leptospires in mice is primarily correlated with Th1-mediated immunity and IFN-γ secretion . This result is consistent with our previous findings on Leptospira antigens
LipL32 and LipL21 this website proteins, suggesting that epitopes of outer membrane proteins (eg, OmpL1, LipL21, LipL32 and LipL41) can induce strong cell-mediated immune response as well humoral immune responses. These epitopes may help us to investigate the role of Th1 or Th2 responses in the pathogenesis and immunity during Leptospira interrogans infection. Conclusions The Western blot data present here indicated that the combined T and B cells epitopes in
outer membrane proteins of L. interrogans can be recognized by antibodies in the sera from leptospire-infected patients or rabbits immunized with recombinant proteins of outer membrane proteins. The data from T cell proliferation assay and cytokines secretion analysis showed that the selected epitopes can induce a Th1- orientated response. The present study revealed that peptides OmpL1173-191 of OmpL1 and LipL41233-256 of LipL41 are both T cell and B cell epitopes Pyruvate dehydrogenase which collaborate in the production of antibodies against leptospire and induction of lymphocyte differentiation. The identification of these immune dominant epitopes may greatly facilitate the development of novel leptospiral vaccines which may provide protections across different serogroups or serovars. Acknowledgements We thank Prof. Iain C. Bruce for reading our manuscript. We are thankful to Dr. Jing Qian for the assistance with the study. This work was supported by grants from “”AIDS and viral hepatitis and other major infectious diseases prevention and control”" special project (2008ZX10004-015) and State Key Laboratory for Diagnosis and Treatment of Infectious Diseases. Electronic supplementary material Additional file 1: PCR amplification of epitopes. Predicted epitope fragments of OmpL1 and LipL41 were amplified from genomic DNA of Lai strain. M is the DNA ladder. 1-4 are the epitope fragments 59-78, 87-98, 173-191 and 297-320 of OmpL1.