| Popis: |
Special problems are encountered in the attempt to develop a vaccine against malaria. The parasite stages which offer a suitable target are restricted to these which are not protected by a host cell, i.e., are free in the human blood circulation for at least a short period of time, and thus open to immunological attack by antibodies. The isolation and production of antigens from these stages is therefore a major task in the development of a vaccine for active immunization against the malaria parasite. It has already been shown that such antigens can produce partial protection in animals (Perrin et al. 1985). Merozoites are the asexual blood stage of the parasite which are released from the infected host cell at the end of the developmental cycle. They immediately recognize uninfected erythrocytes, make contact with them, orient themselves on the erythrocyte membrane and finally invade the host cell, all within about 30 sec. About 18–20 merozoites then develop in the erythrocyte. Specific triggers for invasion and development, most of them probably surface antigens, must be present in the merozoite. |
