Submitted to: Coccidiosis International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: July 8, 1997
Publication Date: N/A
Technical Abstract: The past ten years of research aimed at developing subunit vaccines against a number of apicomplexans, including Eimeria, Plasmodium, and...... Toxoplasma, has, if anything, revealed the complex nature of parasite-host interactions. The knowledge gained from this research has shown why developing a subunit vaccine based on a single recombinant antigen from one edevelopmental stage of the parasite was an overly optimistic approach. Fo instance, many apicomplexan parasites have evolved a variety of strategies to evade protective immune responses by the host. The development of a recombinant vaccine against these parasites will depend on identifying which antigens and intracellular processes are vital to the parasite life cycle and which exist merely as a way of evading immunity. The recent success in transfection of apicomplexans with plasmids containing reporter and parasite DNA sequences will allow the study of specific protozoan genes and the possible role the encoded products play in intracellular survival and development. Studies of natural immunity against non-attenuated, irradiated, and drug-arrested Eimeria spp. have shown that metabolizing intracellular sporozoites both elicit and are targeted by the protective immune response. Although early trophozoites are an important component stimulating the immunity that developes, antigens associated with later developing stages (e.g. merozoites and gametocytes) induce cellular and humoral immune responses that are effective in natural and passive immunity. The critical role of helper and cytotoxic T lymphocytes and natural killer cells and associated lymphokines in immunity to coccidia indicate that immunization must mimick antigen-processing.