Coagglutination and indirect hemagglutination in the detection of an excreted immunologically active substance from Leishmania

The methods of coagglutination and indirect hemagglutination were used to detect the production of the immunologically active excreted factor (EF) of Leishmania. Staphylococci, rich in protein A and sensitized with specific anti-Leishmania antibodies, coagglutinated with supernatant fractions of cultures, thus enabling continuous monitoring of the excretion of EF by multiplying parasites. Papain-treated human red blood cells, sensitized with crude or purified EF, also agglutinated with the coagglutination reagent. The sensitized papain-treated red blood cells may be employed in indirect hemagglutination to detect specific antibodies to Leishmania in rabbit and human sera. As the EF is specific for each Leishmania serotype group, coagglutination and indirect hemagglutination offer the possibility of rapid, easy, sensitive and specific diagnostic tools in the determinations of both antigen and antibody in specimens from suspected cases of leishmaniasis.