Brucella abortus induces intracellular retention of MHC-I molecules in human macrophages down-modulating cytotoxic CD8+ T cell responses.

BARRIONUEVO P., DELPINO M. V., POZNER R., VELáSQUEZ L. N., CASSATARO J., GIAMBARTOLOMEI G. H.

CELLULAR MICROBIOLOGY (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 vol. 15 p. 487 - 502

1462-5814

Brucella abortus elicits a vigorous Th1 immune response which activates cytotoxic T lymphocytes. However, B. abortus persists in its hosts in the presence of CD8+ T cells, establishing a chronic infection. Here, we report that B. abortus infection of human monocytes/macrophages inhibited the IFN-ã-induced MHC-I cell surface expression. This phenomenon was dependent on metabolically active viable bacteria. MHC-I down-modulation correlated with the development of diminished CD8+ cytotoxic T cell response as evidenced by the reduced expression of the activation marker CD107a on CD8+ T lymphocytes and a diminished percentage of IFN-ã-producing CD8+ T cells. Inhibition of MHC-I expression was not due to changes in protein synthesis. Rather, we observed that upon B. abortus infection MHC-I molecules were retained within the Golgi apparatus. Overall, these results describe a novel mechanism based on the intracellular sequestration of MHC-I molecules whereby B. abortus would avoid CD8+ cytotoxic T cell responses, evading their immunological surveillance.