| Summary: | Histoplasma capsulatum var. capsulatum é um fungo dimórfico causador da histoplasmose, doença sistêmica e grave em imunossuprimidos. Tem sido relatada a atividade hemaglutinante do fungo e de casos de histoplasmose disseminada associada a autohemofagocitose. O objetivo do presente trabalho foi analisar e caracterizar parcialmente o(s) componente(s) solúvel(eis) com atividade hemaglutinante. Inicialmente foram obtidos cell free antigen (CFA) de H. capsulatum var. capsulatum (isolado IMT/HC 128) e anticorpos policlonais de camundongos a componentes ligantes às hemácias (anti-Ea-CFA). Para análise de atividade hemaglutinante foram utilizados eritrócitos de camundongo incubados com amostras de CFA (E-CFA), com CFA previamente aquecida a 56 ºC durante 30 minutos (E-CFAa) ou tratada com PBS (E-PBS). Os anticorpos anti-Ea-CFA foram testados quanto a sua capacidade em inibir a hemaglutinação e para análise das frações de CFA por ELISA. As frações foram obtidas por cromatografia de CFA em coluna de gel filtração (Sephadex G-75/120 e G-200). Adicionalmente foi realizada a análise de hemofagocitose, incubando-se hemácias autólogas sensibilizadas ou não com CFA e células peritoneais de camundongos BALB/c aderentes ao vidro. Os resultados obtidos demonstraram aglutinação positiva com E-CFA e negativa com E-CFAa ou E-PBS. Os anticorpos policlonais obtidos apresentaram a capacidade de inibir a atividade hemaglutinante e de interagir com as frações cromatográficas de alta MM. O ensaio de hemofagocitose demonstrou positividade com E-CFA e negativa com E-PBS. Concluímos que o fungo H. capsulatum var. capsulatum libera componente solúvel, termolábil, com atividade hemaglutinante e este trabalho evidencia pela primeira vez a indução da autohemofagocitose por componentes solúveis de H. capsulatum var. capsulatum e análise indireta utilizando anticorpos sugerem que os componentes responsáveis pela interação com as hemácias apresentam alta MM. === Histoplasma capsulatum var. capsulatum is a thermally dimorphic fungus that causes histoplasmosis, a quite common systemic disease which can have serious or fatal outcomes, especially among immunocompromised patients. Both fungal hemagglutination activity and cases of reactive hemophagocytic syndrome (RHS) have been reported in the disseminated form of disease. The objective of the present study was to detect and partially characterize soluble components of H. capsulatum var. capsulatum with hemagglutinin activity. Initially, cell-free antigen (CFA) was obtained from H. capsulatum var. capsulatum (isolate IMT/HC128) and mouse polyclonal antibodies were raised against red blood cells (RBC) binding CFA components (anti-RBC-CFA). To analyze hemagglutination, RBC were incubated with CFA (RBC-CFA), with heated CFA (56 ºC, 30 min) (CFA-hCFA) and with PBS (CFA-PBS) as a control. The anti-RBC-CFA antibodies were assayed for hemagglutination inhibition by pre-incubation with CFA and used to analyze chromatographic fractions (Sephadex G - 75/120 and Sephadex G-200) by immunoenzymatic assay (ELISA). Additionally, hemophagocytosis was analyzed by icubating BALB/c mouse peritoneal phagocytic cells with autologous RBC, sensitized or not with CFA. Hemagglutinin activity was observed with RBC-CFA but not with RBC-hCFA or RBC-PBS. The anti-RBC-CFA antibodies inhibited hemagglutination and reacted with high molecular mass (MM) CFA fractions. Hemophagocytosis was observed with RBC-CFA but not with RBC-PBS. In conclusion, the (37 °C) yeast form of H. capsulatum var. capsulatum releases thermolabile soluble components with hemagglutinin activity and it has been demonstrated for the first time that soluble components of the same fungus induce autohemophagocytosis. Also, the indirect analysis with antibodies suggests that high MM components are responsible for the interaction with the red blood cells.
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