Malaria vaccines

Abstract

Malaria remains one of the most important vector-borne human diseases. Control of malaria caused by Plasmodium falciparum is a major goal, particularly for populations in sub-Saharan Africa. An effective vaccine against malaria that would protect nonimmune individuals from the disease has long been a dream. But will it be a reality? The concept that vaccination may be a useful tool to control the disease is based on a number of observations. Individuals continually exposed to infection by the parasitic protozoan responsible do eventually develop immunity to the disease, and passive immunization with antibody from immune donors can have a dramatic effect on blood stage parasitemia (1). Furthermore, inoculation of live attenuated parasites can protect naive volunteers against infection (2), and immunization with whole killed organisms can protect in animal models (3). Intensive studies of the immune response to the malaria parasite in humans and in models, particularly rodent malaria parasites in laboratory mice, have provided a wealth of information on potential protective mechanisms. Twenty years of antigen identification and gene cloning and expression, have produced many candidates for subunit vaccines (for a comprehensive recent review see ref. 4). Single proteins or peptides have been shown to be at least partially protective when used in vaccination studies in humans or in animal models (see, for example ref. 5). Within these antigens important epitopes have been identified, such as those recognized by neutralizing antibodies (6). All of these findings may suggest that an effective vaccine is “just around the corner,” but what is reality, and what are the scientific obstacles? By its very nature malaria vaccine research is a mix of empirical and rational approaches. It is hampered by the complexity of the parasite life cycle, imperfect tools to assess the efficacy of immune responses, and limited knowledge and understanding of the …