Recombinant kinesin protein of Leishmania donovani and Bacille Calmette-Guerin as an immunomodulatory agent: Insights into their role against visceral leishmaniasis.

INTRODUCTION: Visceral Leishmaniasis (VL), caused by Leishmania donovani, is a fatal disease, necessitating an effective vaccine. This study aims to develop a vaccine by evaluating the combination of recombinant kinesin protein (rKIN) with Bacille Calmette-Guerin (BCG) as an adjuvant against experimental VL.

MATERIALS AND METHODS: The immune response was analyzed against the purified rKIN of L. donovani with and without BCG adjuvant by using BALB/C mice. Mice were divided into 6 groups comprising of 6 animals in each group for the vaccine intramuscularly. All 6 Groups were immunized either with BCG, rKIN, or combination of the two, with different doses. Saline was used as negative control. Each group was further divided into 2 subgroups. One subgroup of animals from each group was challenged with L. donovani promastigotes 1 × 106 cells/100 μl per animal. The extent of protection was evaluated by estimating the reduction in the number of parasites in the spleen, quantity of nitric oxide (NO), reactive oxygen species (ROS) in the peritoneal cells, and production of cytokines in blood serum.

RESULTS: Significant parasite reduction (70%-90%) was observed in the spleens of groups receiving rKIN (50µg or 100µg) with BCG. NO and ROS production increased by 60%-95% and 70%-90%, respectively. The 100µg rKIN with BCG group demonstrated substantial protection (P < 0.001) with upregulated interferon-gamma (IFN-γ), tumor necrosis factor, interleukin-2 (IL-2), and downregulated IL-4, IL-10, and IL-17. Statistical analysis confirmed significant differences (P < 0.001) between vaccinated and control groups.

CONCLUSIONS: The combination of 100µg rKIN with BCG shows potential as a vaccine candidate against VL.