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New tools are urgently needed for the detection of latent tuberculosis (TB). We evaluated the diagnostic potential of 2 novel Mycobacterium tuberculosis complex--specific candidate antigens (Rv2653 and Rv2654) and investigated T cell recognition during natural infection in humans and experimental infection in guinea pigs. Peripheral blood mononuclear cells stimulated with peptide pools covering the full length of Rv2654 induced interferon-γ release in 10 of 19 patients with TB. Neither Rv2654 single peptides nor Rv2654 pools were recognized by bacille Calmette-Guérin--vaccinated donors. However, peptides from Rv2653 were recognized by both patients group. The cross-reactive epitope(s) in Rv2653 were located in a 36--amino acid stretch in the center of the molecule. Rv2654 also induced M. tuberculosis--specific skin-test responses in 3 of 4 aerosol-infected guinea pigs. Rv2654 is a strongly recognized T cell antigen that is highly specific for TB and has potential as a novel cell-mediated immuni--based TB diagnostic agent. [ABSTRACT FROM AUTHOR]

In recent years, there has been considerable focus on the discovery and characterization of proteins derived from Mycobacterium tuberculosis leading to the identification of a number of candidate antigens for use in vaccine development or for diagnostic purposes. Previous experiments have demonstrated an important immunological role for proteins encoded by the RD1 region, which is absent from all strains of bacillus Calmette–Guérin (BCG) but present in the genomes of virulent M. bovis and M. tuberculosis. Herein, we have studied human T-cell responses to the antigen encoded by the putative open reading frame ( rv3878) of the RD1 region. Immunoblot analysis revealed that rv3878 was expressed and the native protein was designated TB27.4. Immunological evaluations demonstrate that TB27.4 elicits a prominent immune response in human tuberculosis patients with a dominant region in the C-terminal part of the molecule. In contrast, very limited responses were seen in M. bovis BCG-vaccinated donors. This study therefore emphasizes the diagnostic potential of proteins encoded by the RD1 region. [ABSTRACT FROM AUTHOR]