Protective effect of L. donovani antigens using glucan as an adjuvant

Golden hamsters were immunized with various antigen fractions of Leishmania donovani promastigotes. Beta 1,3-glucan was used as an adjuvant in these vaccination experiments. The results indicate that immunization of animals with the microsomal fraction (subcellular fraction III) in combination with glucan confers considerable immune protection against L. donovani infection. The immune protection was confirmed by correspondingly lower parasite burden in the livers and spleens of test animals compared to controls. Additionally, the vaccinated animals showed positive skin test responsiveness after challenge, along with increased antibody titres. Immunization of animals with whole and particulate antigen fractions was also found to afford a high degree of resistance. The other subcellular and soluble antigen fractions conferred very little protection. In these experiments, glucan was found to be a potent adjuvant when injected, intraperitoneally, with Leishmania antigens. Similar doses of parasite extracts given without an adjuvant were able to confer only very little or no protection.