Increased thiol levels in antimony-resistant Leishmania infantum isolated from treatment-refractory visceral leishmaniasis in Brazil

BACKGROUND Treatment-refractory visceral leishmaniasis (VL) has become an important problem in many countries. OBJECTIVES We evaluated the antimony-resistance mechanisms of Leishmania infantum isolated from VL patients refractory or responsive to treatment with pentavalent antimony. METHODS Strains isolated from antimony-refractory patients (in vitro antimony-resistant isolates) and antimony-responsive patients (in vitro antimony-sensitive isolates) were examined. Morphological changes were evaluated by transmission electron microscopy after trivalent antimony exposure. P-glycoprotein (P-gp) efflux pump activity was evaluated using the pump-specific inhibitor verapamil hydrochloride, and the role of thiol in trivalent antimony resistance was investigated using the enzymatic inhibitor L-buthionine sulfoximine. FINDINGS Antimony treatment induced fewer alterations in the cellular structure of L. infantum resistant isolates than in that of sensitive isolates. P-gp efflux activity was not involved in antimony resistance in these isolates. Importantly, the resistant isolates contained higher levels of thiol compared to the sensitive isolates, and inhibition of thiol synthesis in the resistant isolates recovered their sensitivity to trivalent antimony treatment, and enhanced the production of reactive oxygen species in promastigotes exposed to the drug. MAIN CONCLUSIONS Our results demonstrate that isolates from patients with antimony-refractory VL exhibited higher thiol levels than antimony-sensitive isolates. This indicates that redox metabolism plays an important role in the antimony-resistance of New World VL isolates.

Increased thiol levels in antimony-resistant Leishmania infantum isolated from treatment-refractory visceral leishmaniasis in Brazil.

BACKGROUND Treatment-refractory visceral leishmaniasis (VL) has become an important problem in many countries. OBJECTIVES We evaluated the antimony-resistance mechanisms of Leishmania infantum isolated from VL patients refractory or responsive to treatment with pentavalent antimony. METHODS Strains isolated from antimony-refractory patients (in vitro antimony-resistant isolates) and antimony-responsive patients (in vitro antimony-sensitive isolates) were examined. Morphological changes were evaluated by transmission electron microscopy after trivalent antimony exposure. P-glycoprotein (P-gp) efflux pump activity was evaluated using the pump-specific inhibitor verapamil hydrochloride, and the role of thiol in trivalent antimony resistance was investigated using the enzymatic inhibitor L-buthionine sulfoximine. FINDINGS Antimony treatment induced fewer alterations in the cellular structure of L. infantum resistant isolates than in that of sensitive isolates. P-gp efflux activity was not involved in antimony resistance in these isolates. Importantly, the resistant isolates contained higher levels of thiol compared to the sensitive isolates, and inhibition of thiol synthesis in the resistant isolates recovered their sensitivity to trivalent antimony treatment, and enhanced the production of reactive oxygen species in promastigotes exposed to the drug. MAIN CONCLUSIONS Our results demonstrate that isolates from patients with antimony-refractory VL exhibited higher thiol levels than antimony-sensitive isolates. This indicates that redox metabolism plays an important role in the antimony-resistance of New World VL isolates.

Association of cytokines, neurological disability, and disease duration in HAM/TSP patients

OBEJETIVO: Identificar marcadores clínicos e imunológicos associados com a mielopatia associada ao HTLV-I/paraparesia espástica tropical (MAH/PET). MÉTODO: 237 indivíduos infectados pelo HTLV-I foram clinicamente avaliados. Eles foram classificados de acordo com a escala expandida do estado de incapacidade de Kurtzke (EDSS) e escala de incapacidade motora de Osame (OMDS). Níveis de citocinas foram determinados nos indivíduos. RESULTADOS: 37 pacientes tinham MAH/PET. Houve correlação entre os graus de incapacidade pelas escalas. Houve também correlação entre a duração da MAH/PET e o grau da incapacidade pelas escalas. Níveis elevados de IFN-g foram detectados em células mononucleares de sangue periférico (CMSP) não estimuladas de pacientes com MAH/PET quando comparados com indivíduos HTLV-I positivos assintomáticos. CONCLUSÃO: Os dados demonstram a validade das escalas neurológicas para classificar o grau de incapacidade neurológica em portadores do HTLV-I e sugerem o comportamento progressivo da MAH/PET. Este estudo também demonstra que os níveis de IFN-g em sobrenadante de CMSP são marcadores da MAH/PET.

Avaliaçäo da resposta imune celular em pacientes com candidíase recorrente / Evaluation of cellular immune response in patients with recurrent candidiasis

A candidíase recorrente cutânea ou mucosa é caracterizada pela ocorrência de, no mínimo, 4 episódios de candidíase no período de um ano. Näo säo conhecidos os fatores que levam à recorrência desta infecçäo. O presente estudo avaliou a resposta linfoproliferativa e a produçäo de IFN-g de pacientes com candidíase recorrente. Os índices de estimulaçäo da resposta linfoproliferativa em culturas de células de pacientes com candidíase recorrente estimuladas com antígeno de Candida albicans, PPD e TT foram respectivamente de 6±8, 17±20 e 65±30. A adiçäo de anticorpo monoclonal anti-IL-10 às culturas de células de 6 pacientes aumentou a resposta linfoproliferativa de 735±415 para 4143±1746 cpm. A produçäo de IFN-g em culturas de células estimuladas com antígeno de Candida, foi 162±345pg/ml. Pacientes com candidíase recorrente apresentam uma deficiência na resposta linfoproliferativa e na produçäo de IFN-g, podendo a resposta imune celular ao antígeno de Candida ser restaurada parcialmente através da neutralizaçäo da IL-10 in vitro