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

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. 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. 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. 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.