T-cell responses associated with resistance to Leishmania infection in individuals from endemic areas for Leishmania (Viannia) braziliensis

Subclinical or asymptomatic infection is documented in individuals living in endemic areas for leishmaniasis suggesting that the development of an appropriate immune response can control parasite replication and maintain tissue integrity. A low morbidity indicates that intrinsic factors could favor resistance to Leishmania infection. Herein, leishmanial T-cell responses induced in subjects with low susceptibility to leishmaniasis as asymptomatic subjects were compared to those observed in cured cutaneous leishmaniasis (CCL) patients, who controlled the disease after antimonial therapy. All of them have shown maintenance of specific long-term immune responses characterized by expansion of higher proportions of CD4+ as compared to CD8+ Leishmania reactive T-lymphocytes. Asymptomatic subjects had lower indexes of in vitro Leishmania induced lymphoproliferative responses and interferon-gamma (IFN-gamma) production in comparison to CCL patients. On the other hand, interleukin (IL-10) production was much higher in asymptomatics than in CCL, while no differences in IL-5 levels were found. In conclusion, long lived T-cell responses achieved by asymptomatic individuals differed from those who had developed symptomatic leishmaniasis in terms of intensity of lymphocyte activation (proliferation or IFN-gamma) and regulatory mechanisms (IL-10). The absence of the disease in asymptomatics could be explained by their intrinsic ability to create a balance between immunoregulatory (IL-10) and effector cytokines (IFN-gamma), leading to parasite destruction without producing skin tissue damage. The establishment of profiles of cell-mediated immune responses associated with resistance against Leishmania infection is likely to make new inroads into understanding the long-lived immune protection against the disease.

Atypical Mucocutaneous Leishmaniasis Caused by Leishmania braziliensis in an Acquired Immunodeficiency Syndrome Patient: T-cell Responses and Remission of Lesions Associated with Antigen Immunotherapy

An atypical case of acquired immunodeficiency syndrome-associated mucocutaneous lesions due to Leishmania braziliensis is described. Many vacuolated macrophages laden with amastigote forms of the parasite were found in the lesions. Leishmanin skin test and serology for leishmaniasis were both negative. The patient was resistant to therapy with conventional drugs (antimonial and amphotericin B). Interestingly, remission of lesions was achieved after an alternative combined therapy of antimonial associated with immunotherapy (whole promastigote antigens). Peripheral blood mononuclear cells were separated and stimulated in vitro with Leishmania antigens to test the lymphoproliferative responses (LPR). Before the combined immunochemotherapy, the LPR to leishmanial antigens was negligible (stimulation index - SI=1.4). After the first course of combined therapy it became positive (SI=4.17). The antigen responding cells were predominantly T-cells (47.5 percent) most of them with CD8+ phenotype (33 percent). Very low CD4+ cells (2.2 percent) percentages were detected. The increased T-cell responsiveness to leishmanial antigens after combined therapy was accompanied by interferon-g (IFN-g) production as observed in the cell culture supernatants. In this patient, healing of the leishmaniasis lesions was associated with the induction of a specific T-cell immune response, characterized by the production of IFN-g and the predominance of the CD8+ phenotype among the Leishmania-reactive T-cells

Leishmanioses: reaçäo de imunofluorescência indireta para pesquisa de anticorpos IgM em fraçöes de soros separados por cromatografia de gel filtraçäo / Leishmaniasis: indirect immunofluorescent test to detect IgM antibodies in serum fractions separated by gel filtraction cromatography

Um total de 143 soros de pacientes (120 da forma cutânea localizada, seis da mucocutânea e 17 com leishmaniose visceral), provenientes de ambulatórios ou de hospitais do Grande Rio de Janeiro, suspeitos de leishmaniose tegumentar ou visceral americanas, foi submetido às reaçöes de imunofluorescência indireta (RIFI-IgM e IgG). Estes soros foram selecionados porque se apresentavam com RIFI-IgG de títulos elevados ou eram RIFI-IgM reagentes no soro. Como existe a possibilidade de falsos resultados de IgM näo reagentes na presença de títulos elevados de IgG e falsos IgM reagentes, devido à presença de fator reumatóide (autoanticorpos IgM anti-IgG), utilizou-se a separaçäo das fraçöes IgM e IgG do soro destes pacientes. Para isro, procedeu-se a separaçäo destas imunoglobulinas em coluna de Sephacryl S-300, nos casos em que os soros eram IgM negativo e IgG maior ou igual a 360, com a finalidade de se detectar falsos negativos e, em soros IgM reagentes, falsos positivos. Nestes últimos, também realizou-se a prova do látex para fator reumatóide. Deste modo a RIFI-IgM da fraçäo IgM separada no Sephacryl permitiu evidenciar apenas um soro - de paciente da forma cutânea localizada (0,7 por cento) - falso negativo por provável competiçäo com títulos de anticorpos IgG elevados. Por outro lado, permitiu o encontro de 23 (16,1 por cento) soros RIFI-IgM falso-reagentes para leishmanioses, devido à presença de fator reumatóide (seis soros eram de leishmaniose mucocutânea e os 17 restantes de leishmaniose visceral). Em outros indivíduos da forma cutânea localizada (8,4 por cento) a RIFI-IgM do soro e a RIFI da fraçäo IgM eram reagentes, embora também tivessem positivos (maior ou igual a 20 U/ml) à prova do látex, como os outros 23 indivíduos anteriores. Os 107 indivíduos restantes (74,8 por cento) foram RIFI-IgM reagentes no soro e na fraçäo IgM, mas, entretanto, todos eram negativos para fator reumatóide. Todas as RIFI-IgM das fraçöes IgM eram näo-reagentes. Os resultados demonstram a utilidade da presente metodologia na obtençäo de maior confiabilidade nos testes de RIFI-IgM para leishmanioses