Antibody-Induced Ultrastructural Changes of Malarial Sporozoites

[摘要] Immunization with irradiated sporozoites produces a considerable degree of protection against rodent, simian, and human malaria. This protection is in part antibody mediated. Antibodies neutralize sporozoites (SNA), i.e., abolish their infectivity, and cause, in vitro, the formation of a thread-like precipitate on the parasites (CSP reaction). The present study was undertaken to characterize the ultrastructural aspects of antibody-sporozoite interaction. Gradient concentrated sporozoites of Plasmodium berghei and Plasmodium cynomolgi were incubated with immune and normal sera. Transmission electron microscopy revealed the presence of a prominent, thick coat surrounding the outer membrane of the sporozoites incubated in immune serum. The inner structure of these parasites appeared to be relatively unaltered. The coat was absent or minimal on parasites incubated in normal serum. Incubation of immune serum-pretreated sporozoites with rabbit anti-mouse γ-globulin conjugated with hemocyanin demonstrated the participation of immunglobulin in the formation of this surface deposition. Coat formation occurred also on the surface of metabolically inactive, non-secreting parasites such as formalin-treated sporozoites and parasites kept on ice. Metabolically inactive sporozoites failed, however, to produce a positive CSP reaction. Scanning electron microscopy and negative staining indicated that the anterior end of the parasites was free of coat deposition and that the thread-like precipitate (CSP) was located at the posterior end of the sporozoites.

[学科分类] 生物科学（综合）