Evaluation of Cellular Immune Responses in Dogs Immunized with Alum-Precipitated Autoclaved Leishmania major along with BCG and Imiquimod

Abstract

Background: We aimed to investigate the potential effects of BCG and imiquimod on improvement of current experimental L. major vaccine against dogs in an endemic area of Zoonotic visceral leishmaniasis (ZVL) in Iran. Methods: During 2012 till 2014, seven mixedbreed shepherd dogs with no anti-Leishmania antibodies and no response to Leishmanin reagent were immunized with 2 doses of alum-precipitated autoclaved L. major (Alum-AML) while BCG and imiquimod (for skin pre-treatment) were used as adjuvants. The productions of a few characteristic cytokines of T-helper immune responses and the development of delayed-type hypersensitivity (DTH) of the immunized animals were then evaluated, up to 300 days. Blood samples were collected at 0, 30, 80 and 300 d post-vaccination and the concentrations of IFN-γ, IL10, IL-12 and TGF-β cytokines secreted from PBMCs at these time-points were quantified by ELISA. DTH was evaluated by Leishmanin skin test (LST). Results: Although a similar LST conversion was observed at all time-points, the cytokine measurement results indicated significantly higher levels of IFN-γ at day 80 and elevated levels of IL-10 at days 80 and 300, post-vaccination. Moreover, a significantly higher IFN-γ/IL-10 ratio was observed at day 30 post-vaccination compared to the other time-points. Conclusion: Although a Th1-like response could be observed at day 30 post-vaccination, the development of cytokine profiles was inclined toward mixed Th1 and Th2 responses at days 80 and 300 post-vaccination. This situation may indicate the requirement of an additional boosting by this Alum-AML formula, in order to induce long-lasting protection against ZVL.

Keywords

• Zoonotic visceral leishmani-asis (ZVL);
• Alum-ALM vaccine
• BCG and imiquimod adju-vant
• Cytokines
• Leishmanin skin test (LST)