Chemiluminescence activity in whole blood phagocytes of dogs naturally infected with Leishmania infantum

Dogs are the domestic reservoir of Leishmania infantum, a vector-borne intr acellular protozoan agent of human visceral leishmaniasis. The role of poly morphonuclear leukocytes (PMNs) in the immune defence against this parasite has been poorly studied. We have investigated the function of peripheral b lood PMNs in naive beagle dogs that have been naturally exposed to phleboto mine vectors in an area highly endemic for canine leishmaniasis, and found infected by Leishmania at the end of the transmission season. Whole blood p hagocyte oxidative metabolism was assessed by a rapid method that determine s a luminol-amplified chemiluminescence (CL) emission. This was evaluated u sing either a soluble stimulant, phorbol mirystate acetate (PMA), or phagoc ytic stimuli, such as zymosan unopsonized (ZYM) or opsonized with autologou s serum (OPZ). In blood samples taken 2 months after exposure to Leishmania transmission, data on CL emission revealed a significant decrease of react ive oxygen intermediates (ROI) production in the presence of both PMA and Z YM, compared with blood samples obtained from dogs before exposure. On the contrary, no variations in CL emission were detected in presence of OPZ. Ou r data indicate that immunological changes occur early in canine leishmania sis and confirm that the role of PMNs and their products need to be clarifi ed. Copyright (C) 2000 John Wiley & Sons, Ltd.