HEMOGLOBIN INHIBITS THE DEVELOPMENT OF INFECTIVE PROMASTIGOTES AND CHITINASE SECRETION IN LEISHMANIA-MAJOR CULTURES

Haemoglobin or blood in the growth medium of Leishmania major inhibite d the formation of infective promastigotes and the secretion of chitin ases. Inoculation of mice with stationary-phase parasites from control medium caused infections in 20/29 mice, compared to 3/20 mice injecte d with parasites grown with 10% rabbit blood, or 1/30 mice that receiv ed parasites grown with rabbit haemoglobin. The concentration of peanu t lectin (PNA) required to agglutinate promastigotes was used as an in dex of their infectivity, ranging from a high concentration for infect ive populations to a low concentration for relatively non-infective po pulations. Agglutination of 50% of the parasites from control medium o r from medium containing rabbit haemoglobin required 4.1 mu g PNA/ml a nd 0.1 mu g PNA/ml, respectively. Chitinase activities/10(7) parasites decreased from 4.8 units chitinase and 12.5 units N-acetylglucosamini dase (NAGase) in the control to 2.0 units chitinase and 8.5 units NAGa se in cultures containing rabbit haemoglobin. Rabbit, human, bovine an d pigeon haemoglobins had various inhibitory effects on the activity o f chitinases and not on the virulence, as expressed by PNA agglutinati on. The relevance of the results to the cycle of Leishmania is discuss ed.