A Novel Adjuvant, Mixture of Alum And Naltrexone, Elicits Humoral Immune Responses for excreted/secreted Antigens of Toxoplasma gondii Tachyzoites Vaccine In Balb/c Murine Model

OBJECTIVE: The excreted-secreted antigens (ESA) from the tachyzoites seem to play a key role in immunity against Toxoplasma gondii. The aim of this study is to investigate whether Alum-NLT mixture, as a new adjuvant, can induce humoral immunity in response to excreted secreted antigens (ESA) of Toxoplasma gondii as a model vaccine or not. METHODS: Six- to eight-week-old female Balb/c mice were divided into five groups. Mice in the experimental groups received either ESA vaccine alone or in combination with the adjuvant Alum, NLT or Alum-NLT mixture; Mice in the negative control group received phosphate buffered saline (PBS). All mice were immunised, three times subcutaneously (s.c.) with a total volume of 150μl each with a 10-day interval. Ten days after the final immunisation, immune response to Toxoplasma gondii was assessed. RESULTS: Our results revealed that Alum-NLT mixture as an adjuvant during vaccination boosts the efficacy of the ESA vaccine by means of increasing Toxoplasma gondii-specific IgG, IgG2a production and the ratio of IgG2a/IgG1 (P-value < 0.05). The use of this adjuvant mixture improved the protective immunity against Toxoplasma gondii. CONCLUSION: Administration of the Alum-NLT mixture as an adjuvant in ESA vaccine enhances humoral immunity.