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pubmed:otherAbstract |
PIP: A great deal of activity is being focused on the possibility of developing an effective vaccine for malaria. Drug resistance is the main problem. Of the new drugs under examination, only meflaquine, a quinine analogue, is at the stage of a clinical trial and even here it appears that resistance may be a problem. This review summarizes the current state of research on malaria immunization and adds some Zimbabwean perspectives. Natural immunity to malaria is directed against the blood stages of the parasites and is mediated by both humoral and cellular mechanisms. Resistance to malaria in both humans and animals can be transferred by passive immunization using immunoglobin infusions. Evidence indicates that the spleen has a central role in resistance to malaria. Malarial infection is known to be associated with immunosuppression. Of considerable practical importance is the observation that antibody responses to irradiated sporozoites in rodents were suppressed by acute Plasmodium berghei infection. Immunity is species specific, develops slowly and is short lived. There are 3 stages in the malaria life cycle at which immunization might be expected to be effective: the sporozoite, merozoite and gametocyte stages. 95% of malaria in Zimbabwe is caused by Plasmodium falciparum. A major requirement for effective immunization is an antigen preparation, which, while causing no harmful effects in itself will stimulate an immune response capable of inactivating the infective agent in question. A significant breakthrough has been achieved by Ruth Nussensweig and her colleagues using the techniques of molecular biology. There is a wide variation in the body's response to injected malarial antigens. Repeated injection with irradiated sporozoites (which are incapable of multiplying in the body) are able to induce shortlived immunity in man. Funding problems also exist in developing a useful vaccine; much of the research is funded by the WHO.
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