Effects of physico-chemical treatments on haemagglutination activity of Anopheles gambiae haemolymph and midgut extract.

Anopheles gambiae midgut extracts and haemolymph possessed agglutinins, titre 1:16 to 1:256, against human red blood cells (RBCs). Subjection of both tissues to protein precipitation reagents, organic chemical and selected protease, neuraminidase and other glycosidic hydrolase treatments revealed the haemagglutinins to be protein, most likely glycoprotein, in nature--not lipoprotein, lipid, glycolipid or nucleic acid. An.gambiae agglutinins were thermo-labile > 40 degrees C, affected by freezing and thawing treatments, and contained disulphide and hydrogen bonds on the basis of sensitivity following exposure to dithiothreitol and urea respectively. Optimum haemagglutination depended generally on slightly acid to neutral pH conditions and agglutinin activity was Ca2+ ion, albeit to a lesser extent Mg2+ ion, dependent. The midgut extract agglutinin subunit molecule had a relative molecular weight (M(r)) of 65 kDa whilst that of haemolymph was 40 kDa. This study presents the first report on selected physico-chemical properties, the glycoproteinaceous nature and tentative subunit M(r) of mosquito midgut extract and haemolymph anti-RBC agglutinin(s).