Use of purified and whole parasite antgens as candidate transmission blocking vaccines against leishmania major in BALB/c mice
Tonui, Willy Kiprotich
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The ability of antibodies in bloodmeals of mice immunized with leishmania major-derived recombinant 63 kilodalton glycoprotein (rgp63) lipophospoglycan (LPG) or their cocktail and crude whole parasite antigens to inhibit development of L. major in its vector phlebotomus dubsoscqi was examined. Antibodies from mice immunized with either crude whole parasite antigen or a cocktail composed of rgp63 and LPG antigens significantly inhibited parasite development in the sandfly as compared to that of rgp63 or LPG alone and controls (p<0.05). Parasite development in the vector was significantly inhibited at the nectomonad stage by antibodies from both rgp63 and LPG-immununized animals as compared to the controls. Sandflies which had fed on LPG-immunized mice also showed a very significant number of procyclic promastigotes. Parasite development in control sandflies which had fed on naive mice displayed normal growth upto the metacyclic stage. Studies showed that two mechanisms through which antibodies from mice immunized with L. major-derived antigens can cause inhibition of parasite development were by inhibiting the flagella emergence and degeneration of the sandfly midgut epithelium as revealed by light and electron microscopy studies respectively. Sandflies which had previously fed on both immunized and infected bloodmeals were able to infect naive BALB/c mice. Mice which were infected using sandflies previously fed on crude parasite antigen-immunized mice showed foodpad lesion sizes which were significantly lower in the beginning but which increased as the disease progressed. However, footpad lesion sizes of mice which had been infected using sandflies previously fed on LPG-immunized mice were significantly lower as compared to that of control mice throughout the experiment (P<0.05). Control mice infected using sandflies which had fed on naive mice showed significantly bigger footpad lesion sizes throughout the experiment. This study had demonstrated that it is possible to use major surface molecules gp63 and LPG-based transmission-blocking vaccines to limit transmission of cutaneous leishmaniasis. Further, results from this experiment indicate that LPG is promising both as a transmission blocking vaccine and as a candidate vaccine molecule.
- MST-Zoological Sciences