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.