Characterization of antigens on mosquito midgut stages of Plasmodium gallinaceum. II. Comparison of surface antigens of male and female gametes and zygotes.

Surface proteins of male and female gametes of Plasmodium gallinaceum were radioiodinated by the lactoperoxidase method, immunoprecipitated with stage specific antisera and separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Stage specificity of the surface antigens was further studied by competition between surface iodinated gametes and unlabeled extracts of gametes, zygotes, or asexual parasites during immunoprecipitation reactions. These studies have identified four proteins: 250 kDa (PgZ-1), 215 kDa (PgZ-3) and 56 and 54 kDa (PgZ-13a and b), which were present in indistinguishable antigenic form on both male and female gametes. Three immunogenic proteins, 48 kDa (PgZ-14) and 19 and 17 kDa (PgZ-17a and b), were present on female but not male gametes as were several weakly labeled, non-immunogenic proteins of less than 45 kDa. A 26 kDa protein (PgZ-16) was present on male but not female gametes. Two proteins of 205 and 83 kDa (PgZ-4 and PgZ-11) were labeled on female but not male gametes. Nevertheless preparations of male gametes appeared to contain epitopes cross-reacting with these two proteins since anti-male gamete serum precipitated PgZ-4 and 11. Immune competition studies indicated that each of the surface proteins labeled on sexual stages was antigenically distinct from material present in asexual parasites.