The antigen-specific memory CD8+ T-cell response induced by BCG in cattle resides in the CD8+γ/δTCR-CD45RO+ T-cell population

Tuberculosis (TB) remains a worldwide leading cause of death among infectious diseases. Development of safer and more efficacious vaccines requires a basic understanding of the protective mechanisms induced by BCG. Here we show that vaccination of cattle with BCG induces CD8(+)gamma/delta TCR-CD45RO(+) T-cells that can produce IFN-gamma, up-regulate transcription and expression of perforin, lyse BCG-infected monocyte-derived macrophages (MoM phi) and contribute to a reduction in the number of intracellular mycobacteria. We also observed BCG-induced CD8(+) responses in vivo. After infection of cattle with Mycobacterium bovis, CD8(+)gamma/delta TCR-CD45RO(+) cells responded more strongly to M. bovis-infected MoM phi than to BCG-infected MoM phi. These results indicate that the antigen-specific CD8(+) memory response resides in the CD8(+)gamma/delta TCR-CD45RO(+) cell population. (C) 2008 Elsevier Ltd. All rights reserved.