Enhancement of the human T cell response to culture filtrate fractions of Mycobacterium tuberculosis by microspheres.

An improved method of assessment of the human immune response against Mycobacterium tuberculosis antigens will assist the development of new vaccines or diagnostic reagents. In this study, we have analyzed human T cell responses to culture filtrate fractions (CFF) of actively replicating M. tuberculosis strain H37Rv using peripheral blood mononuclear cells from healthy PPD skin test positive and negative individuals. Adsorption of CFF onto polystyrene microspheres, that were approximately the size of the M. tuberculosis (bead-adsorbed antigens, BAA) significantly enhanced IFN-gamma production compared to soluble antigens (SA) in PPD skin test positive individuals in an antigen-specific manner. Further, BAA induced activation of both CD4(+) and CD8(+) T cell subsets. However, CD4(+) responses in general were higher and their antigenic repertoire was wider than the CD8(+) responses. By contrast, CD8(+) responses were strongest to the lower molecular weight BAA. When CFF were chemically coupled to carboxyl modified microspheres (bead-coupled antigens, BCA), induction of IFN-gamma was similar to BAA. Enhancement of T cell responses to particulate M. tuberculosis antigens may prove useful in vaccine design strategies.