RESUMEN
Leishmania infantum, the causative agent of visceral leishmaniasis (VL) in Brazil, is spread mostly by the bite of the sand fly Lutzomyia longipalpis (Lutz & Neiva). We trapped sand flies in endemic neighborhoods near Natal, Brazil, where cases of human and dog VL were documented. Amplification of species-specific cytochrome b (Cyt b) genes by polymerase chain reaction revealed that sand flies from rural and periurban areas harbored blood from different sources. The most common source ofbloodmeal was human, but blood from dog, chicken, and armadillo was also present. We tested the preference for a source of bloodmeal experimentally by feeding L. longipalpis F1 with blood from different animals. There were significant differences between the proportion of flies engorged and number of eggs laid among flies fed on different sources, varying from 8.4 to 19 (P < 0.0001). Blood from guinea pig or horse was best to support sand fly oviposition, but human blood also supported sand fly oviposition well. No sand flies fed on cats, and sand flies feeding on the opossum Monodelphis domestica Wagner produced no eggs. These data support the hypothesis that L. longipalpis is an eclectic feeder, and humans are an important source of blood for this sand fly species in periurban areas of Brazil.
Asunto(s)
Preferencias Alimentarias , Especificidad del Huésped , Insectos Vectores/fisiología , Psychodidae/fisiología , Animales , Biodiversidad , Brasil , Citocromos b/genética , Perros , Femenino , Humanos , Leishmania infantum , Leishmaniasis Visceral/transmisión , Oviposición , Reacción en Cadena de la Polimerasa , TemperaturaRESUMEN
Control of human visceral leishmaniasis in regions where it is endemic is hampered in part by limited accessibility to medical care and emerging drug resistance. There is no available protective vaccine. Leishmania spp. protozoa express multiple antigens recognized by the vertebrate immune system. Since there is not one immunodominant epitope recognized by most hosts, strategies must be developed to optimize selection of antigens for prevention and immunodiagnosis. For this reason, we generated a cDNA library from the intracellular amastigote form of Leishmania chagasi, the cause of South American visceral leishmaniasis. We employed a two-step expression screen of the library to systematically identify T-cell antigens and T-dependent B-cell antigens. The first step was aimed at identifying the largest possible number of clones producing an epitope-containing polypeptide by screening with a pool of sera from Brazilians with documented visceral leishmaniasis. After removal of clones encoding heat shock proteins, positive clones underwent a second-step screen for their ability to cause proliferation and gamma interferon responses in T cells from immune mice. Six unique clones were selected from the second screen for further analysis. The corresponding antigens were derived from glutamine synthetase, a transitional endoplasmic reticulum ATPase, elongation factor 1gamma, kinesin K39, repetitive protein A2, and a hypothetical conserved protein. Humans naturally infected with L. chagasi mounted both cellular and antibody responses to these proteins. Preparations containing multiple antigens may be optimal for immunodiagnosis and protective vaccines.
Asunto(s)
Antígenos de Protozoos/aislamiento & purificación , Epítopos de Linfocito T/aislamiento & purificación , Biblioteca de Genes , Leishmania/genética , Leishmania/inmunología , Secuencia de Aminoácidos , Animales , Anticuerpos Antiprotozoarios/inmunología , Antígenos de Protozoos/genética , Antígenos de Protozoos/inmunología , Northern Blotting , ADN Complementario/genética , Epítopos de Linfocito T/biosíntesis , Epítopos de Linfocito T/genética , Humanos , Sueros Inmunes/análisis , Sueros Inmunes/inmunología , Ratones , Datos de Secuencia Molecular , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/genética , Proteínas Recombinantes/inmunologíaRESUMEN
Peri-urban visceral leishmaniasis (VL) caused by Leishmania chagasi is emerging in a new epidemiologic pattern in Brazilian cities. We studied peri-urban VL in endemic neighborhoods surrounding Natal, Brazil, identified through hospitalized individuals with VL. Clinical and environmental information obtained for 1106 members of 216 families living in endemic neighborhoods enabled us to identify 4 groups: VL: individuals with current or prior symptomatic visceral leishmaniasis (n = 135); DTH+: individuals with positive delayed-type hypersensitivity response with no history of VL (n = 390); Ab +: individuals with negative DTH response and seropositive (n = 21); DTH -: individuals with negative DTH and seronegative (n = 560). The mean +/-SD age of VL was 9.3+/-12.3 y. The gender distribution was nearly equal below age 5, but skewed toward males at higher ages. Acutely infected VL subjects had significantly lower hematocrits, neutrophils, and eosinophils than other categories. AB+ subjects also had lower eosinophil counts than others, a possible immune marker of early infection. VL was not associated with ownership of dogs or other animals, raising the question whether the reservoir differs in peri-urban settings. This new pattern of L. chagasi infection enables us to identify epidemiological and host factors underlying this emerging infectious disease.
Asunto(s)
Anticuerpos Antiprotozoarios/sangre , Enfermedades Transmisibles Emergentes/epidemiología , Leishmania/inmunología , Leishmaniasis Visceral/epidemiología , Población Urbana , Adolescente , Adulto , Distribución por Edad , Anciano , Anciano de 80 o más Años , Animales , Brasil/epidemiología , Niño , Preescolar , Enfermedades Transmisibles Emergentes/parasitología , Enfermedades Transmisibles Emergentes/fisiopatología , Femenino , Humanos , Hipersensibilidad Tardía , Lactante , Recién Nacido , Leishmaniasis Visceral/parasitología , Leishmaniasis Visceral/fisiopatología , Masculino , Persona de Mediana Edad , Distribución por SexoRESUMEN
The sensitivity and specificity of a Leishmania chagasi recombinant K39 (rK39)-based enzyme-linked immunosorbent assay (ELISA) for visceral leishmaniasis (VL) was assessed in Natal, Brazil. Anti-rK39 antibodies were detected in 93.3% of patients with parasitologically confirmed VL (n = 120) and in 33 others with clinically diagnosed disease. Anti-rK39 antibodies decreased significantly following treatment. The presence of antibodies was inversely correlated with development of a positive leishmanin skin test result. Anti-rK39 antibodies were detected in only 2.9% of asymptomatic subjects with a positive skin test result (n = 168). They were not detected in healthy controls (n = 30) or in persons with Chagas' disease (n = 13) or active tuberculosis (n = 31). Antibodies were found in only one of 13 patients with cutaneous leishmaniasis. In contrast, an ELISA using total L. chagasi promastigote antigen was sensitive, but not specific. The results indicate that the rK39-based ELISA is a sensitive and specific diagnostic test for symptomatic VL and can differentiate progressive from self-resolving infection.