CYTOSTATIC EFFECT OF LUTZOMYIA-LONGIPALPIS SALIVARY-GLAND HOMOGENATESON LEISHMANIA PARASITES

Salivary gland homogenates (SGH) of female Lutzomyia longipalpis, in c oncentrations as small as 0.05 pairs of glands/ml, inhibit the in vitr o multiplication of promastigotes of Leishmania mexicana amazonensis. The effect seems to be cytostatic since promastigote viability 24 hr a fter exposure ranged from 55% to 100% in different experiments. The ce lls cultivated in the presence of SGH were characterized by a very sle nder shape, with cell bodies that were almost two times as long as con trols. The promastigote growth inhibitory activity was not present in Anopheles albimanus SGH or in the gut extracts of Lu. longipalpis sand flies. Additionally, the salivary gland homogenates of Lu. longipalpi s did not inhibit the growth of other cell types such as Escherichia c oli or a monkey kidney cell fine (LLCMK2), suggesting that the activit y had a specific range of action. The SGH activity was sensitive to bo th trypsinization and boiling, partially resistant to heating at 56-de grees-C for 30 min, and had a molecular weight of approximately 20 kD as determined by size exclusion high-performance liquid chromatography . The results suggest that vector saliva could influence the developme nt of Leishmania parasites within the vector by inhibiting their growt h and triggering them to a differentiation pathway.