Demonstration of in vivo expression of a hypothetical open reading frame (ORF-14) encoded by the RD1 region of Mycobacterium tuberculosis.

Previously we identified a novel antigenic open reading frame (ORF), designated as ORF-14, on the RD1 region of Mycobacterium tuberculosis that was not originally predicted by Mahairas or by annotation of the M. tuberculosis H37 Rv genome. Here we show that anti-ORF-14 antibodies either from mice immunized with recombinant ORF-14 protein or isolated from serum samples from tuberculosis patients, react with a protein in culture filtrate but not in cytoplasmic or cell wall fractions from M. tuberculosis. Our data indicate that the ORF-14 protein is expressed as a secreted protein, representing one more secreted protein antigen not previously identified by genomics.