Mixture of Alum--Naloxone and Alum--Naltrexone as a novel adjuvant elicits immune responses for Toxoplasma gondii lysate antigen in BALB /c mice.

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite. Treatment of the infection induced by this parasite is not straightforward due to the toxic side effects of the available drugs. Vaccine development could be a solution to this problem. In the present study, T.gondii Lysate Antigen (TLA), as a model vaccine, in combination with the Alum-NLT (Aluminum phosphate-Naltrexone) and Alum-NLX (Aluminum phosphate-Naloxone) were evaluated for immunization BALB/c. 147 female BALB/c mice which were divided into seven groups of 21, were allocated to immunization experiments. The first group was selected as the negative control group, followed by the second, third, fourth, fifth, sixth and seventh groups which were immunized with Vac, Vac-Alum, Vac-NLX, Vac-NLT, Vac-Alum-NLX, Vac-Alum-NLT, respectively. Ten days after the final immunization, mice in all groups were divided into three groups for evaluating cellular immune responses, measuring the delayed-type hypersensitivity responses (DTHs) and evaluating survival. The DTH and cellular immune responses showed that in mice immunized with the TLA vaccine combined with the Alum-NLT mixture, the efficacy improved by increasing the production of Interleukin-5(IL-5) and Interferon gamma. This consequently shifted the immune responses toward a Th1 profile by increasing the IFN-γ/IL-5 ratios. In challenge experiments, immunized mice with the Alum-NLT-Vac mixture survived for a longer period of time which indicated an improvement in protective immunity against T. gondii. Administration of the Alum-NLT mixture adjuvant in combination with TLA vaccine enhanced the cellular immunity by shifting the immune response to a Th1 pattern. This shift to the Th1 pattern plays an important role in the induction of cellular.