Quantitation of malaria sporozoites transmitted in vitro during salivation by wild Afrotropical Anopheles

Abstract. The malaria transmission potential of wild, infective Anopheles from western Kenya was evaluated by determining the number of sporozoites transmitted in vitro by salivation when their mouthparts were inserted into capillary tubes containing either sucrose or blood. With sucrose, 86.6% of 102 infective Anopheles transmitted a geometric mean (GM) of 3.84 sporozoites (range 1–34). With blood, 23.1% of 104 infective Anopheles , tested on the day of collection, transmitted a GM of 2.30 sporozoites (range 1–117). For Anopheles held 5 days postcapture before testing with blood, 53.6% of 56 transmitted a GM of 6.04 sporozoites (range 1–420). Transmitting Anopheles contained significantly more salivary gland sporozoites than non-transmitters. No significant differences were detected between Anopheles gambiae Giles sensu lato and Anopheles funestus Giles in sporozoite transmission by individuals with sporozoites in their salivary glands.
Sporozoites were detected microscopically in the salivary duct from heads in 80.3% of 117 infective Anopheles (GM=11.2, range 1–71). Sporozoite detection in mosquito heads by ELISA was 25% less efficient than microscopic detection.
Over 98% of the infective Anopheles transmitted less than twenty-five sporozoites. Transmitted sporozoites represented only about 3% of the total sporozoites in the salivary glands suggesting that sporozoite transmission may be restricted to sporozoites in the salivary duct at the time of feeding. Results are discussed in relation to anti-sporozoite vaccine development.     

Genetic Control of Variable and Constant Regions of Immunoglobulin Heavy Chains

IMMUNOGLOBULIN polypeptide chains consist of two well defined regions designated the “variable region” and the “constant region”. Whereas great diversity exists in amino-acid sequences of variable regions, the constant regions of a given subclass of heavy chains (C_H)^* are essentially invariant in sequence^{1, 2}. Exceptions are the allelic forms, such as the rabbit allotypes A14 and A15^{3, 4}, where a threonine-alanine interchange occurs in the constant region of γ chains (Appella, Chersi, R. G. M. and Dubiski, in preparation). The markers unique to a chains (for example, A14-A15) are closely linked to allotypic markers at the a locus (a1, a2, a3)^{3, 4} which seem to be present on four different Ig heavy chain classes (α, γ, ε, µ)^5–7. These puzzling observations can be explained if the a locus determinants are variable region markers which reflect genetically controlled differences in some relatively constant residues within the V_H region sequences⁷.     

Antigens of the Ii System on Lymphocytes

USUALLY Ii specificity is assigned to cold agglutinins on the basis of their reactions with the red cells of human adults (adult red cells) and newborn infants (cord red cells). Those which react more strongly with adult red cells are said to detect I antigen and are designated anti-I; those which react more strongly with cord red cells are said to detect i antigen and are designated anti-i^1,2. We have now found that I and i antigens can be easily detected on lymphocytes.