Evaluation of Alum-Naltrexone Adjuvant Activity, on Efficacy of Anti-Leishmania Immunization with Autoclaved Leishmania major (MRHO/IR/75/ER) Antigens in BALB/C Mice

BACKGROUND Naltrexone, an opioid receptor antagonist shifts the immune response toward a Th1 profile. In the current study, we evaluated the efficacy of the mixture of NTX and alum, as a new adjuvant, to enhance immune response and induce protection against Leishmania major in a mouse model. METHODS BALB/c mice were immunized three times either autoclaved L. major promastigotes' antigens alone or in combination with the adjuvant alum, naltrexone or the alum-naltrexone mixture. Both humoral and cellular immune responses were assessed two weeks after the last immunization and compared with control mice. RESULTS The administration of alum- NTX in combination with the parasite antigen, significantly increased production of IFN-γ IFN-γ /IL-5 ratio, lymphocyte proliferation and improved DTH response against L. major. There was no significant difference in survival following challenge among groups. CONCLUSION Immunization with the alum- naltrexone mixture as an adjuvant, in combination with the autoclaved L. major promastigotes antigens, can enhance cellular immunity and shift the immune responses to a Th1 pattern.