Vaccination with Plasmid DNA Encoding Mycobacterial Antigen 85A Stimulates a CD4⁺and CD8⁺T-Cell Epitopic Repertoire Broader than That Stimulated byMycobacterium tuberculosisH37Rv Infection

Abstract

Vaccination of mice with plasmid DNA carrying the gene for the major secreted mycobacterial antigen 85A (Ag85A) fromMycobacterium tuberculosis is a powerful technique for generating robust specific Th1 helper T-cell responses, CD8+-mediated cytotoxicity, and protection against M. tuberculosis challenge (K. Huygen et al., Nat. Med. 2:893–898, 1996). We have now analyzed in more detail the antigen-specific immune CD4+- and CD8+-T-cell responses induced in BALB/c mice vaccinated with Ag85A DNA and have compared these responses to those generated by intravenous infection with M. tuberculosis. T-cell-epitope mapping, as measured by interleukin-2 and gamma interferon secretion from splenic T cells restimulated in vitro with synthetic 20-mer peptides spanning the complete mature sequence of Ag85A, demonstrated that DNA vaccination stimulated a stronger and broader T-cell response than did M. tuberculosis infection. Moreover, elevated cytotoxic T lymphocyte (CTL) activity against Ag85A-transfected and peptide-pulsed P815 target cells could be generated exclusively by vaccination with plasmid DNA, not following M. tuberculosis infection. By using DNA vaccination, three Ag85A CTL epitopes with predicted major histocompatibility complex class I binding motifs were defined. One of them was previously reported as a dominant, promiscuously recognized T-cell epitope in healthy humans with primary infections. These data strengthen the potential of DNA vaccination with respect to inducing antituberculous immunity in humans.

The Ag85B protein of Mycobacterium tuberculosis may turn a protective immune response induced by Ag85B-DNA vaccine into a potent but non-protective Th1immune response in mice

“…Therefore, the presence of effector/memory Ag85B-specific CD4 + and CD8 + T cells, along with anamnestic Ag85B presenting dendritic cells (DC) (Chiu et al, 2004), previously induced by DNA-85 vaccination, might have influenced the subsequent response to the exogenous Ag85B protein booster. In addition, the exclusive MHC class II antigen presentation of Ag85B protein was required, in view of the fact that the boosters with DNA, which are currently considered to elicit both MHC class I and class II immune responses (as demonstrated for Ag85A-encoding DNA; Denis et al, 1998), were ineffective in the generation of this phenomenon.…”

Cellular immune responses induced in cattle by heterologous prime–boost vaccination using recombinant viruses and bacille Calmette–Guérin

“…Ag85A and the 38 000-molecular weight protein, PstS-1, compared with M. tuberculosis-infected mice have been described. 28,[46][47][48] Interestingly, when the epitopes were mapped in the second experiment of this study (BCG ⁄MVA85A versus BCG ⁄BCG vaccination), a broader peptide repertoire was also demonstrated after MVA85A boosting compared with homologous revaccination with BCG ( Fig. 5).…”

CD4+ T cells contain Mycobacterium tuberculosis infection in the absence of CD8+ T cells in mice vaccinated with DNA encoding Ag85A

“…DNA-vaccinated C57BL/6 mice In Ag85A DNA-vaccinated BALB/c mice, we have previously demonstrated CD8 + T cell-mediated CTL activity against H-2 d targets pulsed with peptides from the Ag85A protein sequence [7]. Here we investigated whether the same occurred in C57BL/6 (H-2 b ) mice.…”