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

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.