Cytolytic T-cell responses to human dendritic cells and macrophages infected with Mycobacterium bovis BCG and recombinant BCG secreting listeriolysin

Cytolytic T-cell responses from 63 normal blood donors were monitored in a Mycobacterium bovis BCG infection system in vitro. We wanted to know whethe r cultured dendritic cells were capable of potentiating the cytolytic T-cel l responses to M. bovis BCG. Infected cultured dendritic cells were up to t en times more effective antigen-presenting cells than macrophages in prolif erative assays, while cytolytic T-cell induction did not differ significant ly between dendritic cells and macrophages. Separated CD4(+) and CD8(+) T-c ell subsets contributed equally to lysis of infected targets. Experiments c omparing wild-type M, bovis BCG strain with two new recombinant M, bovis BC G strains secreting listeriolysin revealed statistically significantly high er maximal lysis values for recombinant M. bovis BCG. We conclude from our in vitro infection system with mycobacteria that dendritic cells are superi or to macrophages in proliferative assays bur equal to macrophages in their ability to induce cytolytic T-cell responses. Moreover, our data suggest t hat recombinant M, bovis BCG vaccine strains secreting listeriolysin improv e cytolytic T-cell responses. (C) Elsevier, Paris.