The protozoan Leishmania chagasi can cause disseminated, fatal visceral leishmaniasis (VL) or asymptomatic infection in humans. We hypothesized that host genetic factors contribute to this variable response to infection. A family study was performed in neighborhoods of endemicity for L. chagasi near Natal in northeastern Brazil. Study subjects were assessed for the presence of VL or asymptomatic infection, which was defined by a positive delayed-type hypersensitivity (DTH) skin test response to Leishmania antigen without disease symptoms. A genomewide panel of 385 autosomal microsatellite markers in 1254 subjects from 191 families was analyzed to identify regions of linkage. Regions with potential linkage to the DTH response on chromosomes 15 and 19, as well as a novel region on chromosome 9 with potential linkage to VL, were identified. Understanding the genetic factors that determine whether an individual will develop symptomatic or asymptomatic infection with L. chagasi may identify proteins essential for immune protection against this parasitic disease and reveal strategies for immunotherapy or prevention.

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A proteinaceous inhibitor with high activity against trypsin-like serine proteinases was purified from seeds of the tamarind tree (Tamarindus indica) by gel filtration on Shephacryl S-200 followed by a reverse-phase HPLC Vidac C18 TP. The inhibitor, called the tamarind trypsin inhibitor (TTI), showed a Mr of 21.42 kDa by mass spectrometry analysis. TTI was a noncompetitive inhibitor with a Ki value of 1.7 x 10(-9) M. In vitro bioinsecticidal activity against insect digestive enzymes from different orders showed that TTI had remarkable activity against enzymes from coleopteran, Anthonomus grandis (29.6%), Zabrotes subfasciatus (51.6%), Callosobruchus maculatus (86.7%), Rhyzopertha dominica(88.2%), and lepidopteron, Plodia interpuncptella (26.7%), Alabama argillacea (53.8%), and Spodoptera frugiperda (75.5%). Also, digestive enzymes from Diptera, Ceratitis capitata (fruit fly), were inhibited (52.9%). In vivo bioinsecticidal assays toward C. capitata and C. maculatus larvae were developed. The concentration of TTI (w/w) in the artificial seed necessary to cause 50% mortality (LD50) of larvae was 3.6%, and that to reduce mass larvae by 50.0% (ED50) was 3.2%. Furthermore, the mass C. capitata larvae were affected at 53.2% and produced approximately 34% mortality at a level of 4.0% (w/w) of TTI incorporated in artificial diets.