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Articles by Miguel Viveiros
Total Records ( 3 ) for Miguel Viveiros
  Diane J. Ordway , Miguel Viveiros , Fernando A. Ventura , Ian M. Orme , Hazel M. Dockrell and Leonard Amaral
  The majority of tuberculosis (TB) exists in the world’s poorest countries, where costly biosafety level three facilities for containment of infectious TB patients and diagnostic facilities are not affordable. Health care workers (HCWs), in countries with high burdens of tuberculosis (TB) are at risk of nosocomially acquired TB, as there are increased numbers of cases of TB on open hospital wards and minimal or absent TB infection control. This setting provides a means to study development of immune profiles associated with human exposure to Mycobacterium tuberculosis (Mtb). Individuals with multiple exposures to Mtb develop a Th1 response, involving IFN-γ. However early expression of a Th2 response, consisting of IL-4, was found to be associated with development of active TB disease. A Th2 response was confined to T cells of the CD8 and γδ T cell phenotype which can result in reduced bactericidal function of mycobacterial infected cells. The facets of the immune response which are responsible for failure of elimination of intracellular Mtb leading to active disease are poorly understood.
  Marta Martins , Miguel Viveiros , Diane Ordway , Jette E. Kristiansen , Joseph Molnar and Leonard Amaral
  Marta Martins , Miguel Viveiros , Diane Ordway , Jette E. Kristiansen , Joseph Molnar and Leonard Amaral
  Killing of bacteria by neutrophils is dependent upon the availability of potassium. Although macrophages derived from human peripheral blood monocytes have little killing activity of their own, they can be transformed into effective killers of Staphylococcus aureus and Mycobacterium tuberculosis by in vitro exposure of the macrophage to clinically relevant concentrations of phenohiazines, namely, thioridazine or chlorpromazine. Because transport mechanisms dependent upon the availability of calcium are inhibited by these agents, the possibility that other agents which have similar activity also have the ability to enhance the killing of bacteria by the macrophage derived from peripheral blood monocytes was investigated. In this study we show that the presence of increasing concentrations of ouabain, reserpine or verapamil in the medium enhances the killing of Staphylococcus aureus. Because these concentrations have no activity on the replication or killing of the bacterium, killing is deemed to be due to the macrophage itself. A model is presented which describes the mechanism by which these agents and phenothiazines indirectly activate lysosomal enzymes as a result of the inhibition of potassium efflux pumps that would normally pump the ion from the phagocytic vacuole to the cytoplasm of the macrophage.
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