Lutzomyia longipalpis: pH in the gut, digestive glycosidases, and some speculations upon Leishmania development.

Screening for digestive glycosidases in different parts of the gut and associated organs of Lutzomyia longipalpis is reported. Searches for the enzymes were made in blood-fed and non-blood-fed females and the enzymes were characterized as soluble or membrane-bound molecules. A total of four different activities were detected, corresponding to the following specificities: an alpha-glucosidase, an N-acetyl-beta-d-glucosaminidase, an N-acetyl-beta-d-galactosaminidase, and an alpha-l-fucosidase. Their possible role and importance for Leishmania development are discussed and the alpha-glucosidase enzyme was partially characterized. The pH inside the gut of non-blood-fed phlebotomines was measured with pH indicator dyes. The pH ranges obtained for crop, midgut, and hindgut were, respectively, higher than pH 6, pH 6, and lower than pH 6. A hypothesis concerning these data and Leishmania development is proposed.

Randomised trial of efficacy of benznidazole in treatment of early Trypanosoma cruzi infection.

BACKGROUND: Benznidazole, a nitroimidazole derivative, has been recommended for the treatment of acute and congenital Trypanosoma cruzi infection (Chagas' disease). We have examined the safety and efficacy of this drug in the treatment of the early chronic phase of T cruzi infection. METHODS: Between 1991 and 1995, we carried out a randomised, double-blind, placebo-controlled trial in a rural area of Brazil with endemic Chagas' disease. 82% of 2434 schoolchildren (aged 7-12 years) identified in a census were screened for antibodies to T cruzi by indirect immunofluorescence, indirect haemagglutination, and ELISA. 130 were positive in all tests and were randomly assigned benznidazole (7.5 mg/kg daily for 60 days by mouth) or placebo. The primary endpoint for efficacy was the disappearance of specific antibodies (negative seroconversion) by the end of 3-year follow-up. The secondary endpoint was the reduction of antibody titres on repeated serological tests. One child moved away from the area just after randomisation and was excluded from the analyses. Insecticidal measures were taken throughout the trial to reduce the risk of reinfection. FINDINGS: Minor side-effects requiring no specific medication were recorded in a small proportion of individuals. On a chemiluminescent ELISA with purified trypomastigote glycoconjugate, serum from all participants was positive at the beginning of the trial. At the end of follow-up, 37 (58%) of the 64 benznidazole-treated participants and 3 (5%) of those who received placebo were negative for T cruzi antibodies. The efficacy of benznidazole treatment estimated by intention to treat was 55.8% (95% CI 40.8-67.0). At the end of follow-up, children who received benznidazole had five-fold lower geometric mean titres by indirect immunofluorescence than placebo-treated children (196[147-256] vs 1068[809-1408], p < 0.00001). INTERPRETATION: The trial showed that a 60-day course of benznidazole treatment of early chronic T cruzi infection was safe and 55.8% effective in producing negative seroconversion of specific antibodies. The results are very encouraging and justify the recommendation of treatment for seropositive children as public health policy.

Glycosidases in Leishmania and their importance for Leishmania in phlebotomine sandflies with special reference to purification and characterization of a sucrase.

Culture forms of Leishmania (Leishmania) amazonensis (IFLA/BR/67/PH8) produce an extracellular enzyme that hydrolyzes sucrose molecules into their component monosaccharides. This is important because phlebotomine sand flies, the invertebrate hosts of Leishmania, ingest plant sap or aphid and coccid honeydew rich in sucrose between blood meals and Leishmania promastigotes cannot uptake sucrose. The sucrase was purified and characterized; its molecular weight, estimated by gel filtration chromatography and SDS-PAGE electrophoresis, was about 73 kDa. K(m) and V(max) measured with sucrose as substrate were respectively 4.4 mM and 6.9 mumole glucose.min-1 (mg sucrase)-1, with maximum pH activity at pH 5.5. A series of natural and p-nitrophenyl-derived substrates were assayed, characterizing the enzyme as a highly specific beta-D-fructofuranoside fructohydrolase. When 11 species of Leishmania and 7 genera of trypanosomatids were screened, only the species of the genus Trypanosoma did not produce an enzyme with saccharolytic activity. These data are in agreement with the fact that the latter vectors do not acquire sucrose or raffinose in their meals. Searching for glycolytic enzymes other than sucrase, we found an N-acetyl-beta-D-galactosaminolytic activity. This N-acetyl-galactosaminidase, here described for the first time, might have a role in peritrophic membrane disruption. The importance of sucrase and N-acetyl-beta-D-galactosaminidase in the Leishmania life cycle is discussed.