Identification and Characterization of Protective T Cells in hsp65 DNA-Vaccinated and Mycobacterium tuberculosis -Infected Mice

Abstract

ABSTRACT Immunization by intramuscular injection of plasmid DNA expressing mycobacterial 65-kDa heat shock protein (hsp65) protects mice against challenge with virulent Mycobacterium tuberculosis H37Rv. During infection or after immunization, CD4 + /CD8 − and CD8 + /CD4 − hsp65-reactive T cells increased equally in spleens. During infection, the majority of these cells were weakly CD44 positive (CD44 lo ) and produced interleukin 4 (IL-4) whereas after immunization the majority were highly CD44 positive (CD44 hi ) and produced gamma interferon (IFN-γ). In adoptive transfer of protection to naive mice, the total CD8 + /CD4 − cell population purified from spleens of immunized mice was more protective than that from infected mice. When the cells were separated into CD4 + /CD8 − and CD8 + /CD4 − types and then into CD44 hi and CD44 lo types, CD44 lo cells were essentially unable to transfer protection, the most protective CD44 hi cells were CD8 + /CD4 − , and those from immunized mice were much more protective than those from infected mice. Thus, whereas the CD44 lo IL-4-producing phenotype prevailed during infection, protection was associated with the CD8 + /CD44 hi IFN-γ-producing phenotype that predominated after immunization. This conclusion was confirmed and extended by analysis of 16 hsp65-reactive T-cell clones from infected mice and 16 from immunized mice; the most protective clones, in addition, displayed antigen-specific cytotoxicity.