Evaluation of the alum–naloxone adjuvant activity against experimental murine leishmaniasis due to L. major

Leishmaniasis is caused by intracellular parasites of Leishmania species, which are transmitted by the
bite of the sandfly. Recovery and protection against the
infection depends on the induction of a strong Th1 type of
immune response. Vaccination of mice with the opioid
antagonist naloxone can promote the activation of the Th1
responses. We studied the efficacy of the mixture of
naloxone and alum, as an adjuvant, to enhance immune
responses and induce protection against Leishmania major
infection in BALB/c as a susceptible mouse model. BALB/
c mice were immunized with Ag–naloxone–alum, Ag–
alum, Ag–naloxone or PBS subcutaneously three times at
2-week intervals. The humoral and cellular specific
immune responses were assessed 2 weeks after the last
immunization and compared with the control mice. Our
results indicated that the administration of alum–naloxone
as an adjuvant increased the capability of L. major promastigote antigens to enhance lymphocyte proliferation,
the levels of IFN-c, and the IFN-c/IL-5 ratio. The results of
DTH showed that there were no significant differences in
footpad swelling between the groups of immunized mice as
compared with the non-vaccinated control group; however,
no significant differences were observed in the survival rate
among groups. It can be concluded that although immunization with the alum–naloxone mixture in combination
with the autoclaved L. major promastigote antigens could
enhance cellular immunity and shift the immune response
to a Th1 pattern, it could not protect the mice against
Leishmania major infection.
Keywords Leishmania major Alum Naloxone
Adjuvant
Introduction
Leishmaniasis is caused by intracellular parasites of
Leishmania species, which are transmitted by the bite of
the sandfly. This disease has a wide range of clinical
symptoms from chronic cutaneous lesions to visceral
leishmaniasis, which is fatal if left untreated (Singh and
Sundar 2012). Currently, 350 million people in 88 countries are at risk of infection and 14 million people are
infected (Nagill and Kaur 2011). Recovery and protection
against the infection depends on the induction of a strong
& Arezoo Bozorgomid