Molecular characterization and human T-cell responses to a member of a novel Mycobacterium tuberculosis mtb39 gene family

Davin C. Dillon, Mark R. Alderson, Craig H. Day, David M. Lewinsohn, Rhea Coler, Teresa Bement, Antonio Campos-Neto, Y. A.W. Skeiky, Ian M. Orme, Alan Roberts, Sean Steen, Wilfried Dalemans, Roberto Badaro, Steven G. Reed

Research output: Contribution to journalArticle

125 Scopus citations


We have used expression screening of a genomic Mycobacterium tuberculosis library with tuberculosis (TB) patient sera to identify novel genes that may be used diagnostically or in the development of a TB vaccine. Using this strategy, we have cloned a novel gene, termed mtb39a, that encodes a 39-kDa protein. Molecular characterization revealed that mtb39a is a member of a family of three highly related genes that are conserved among strains of M. tuberculosis and Mycobacterium bovis BCG but not in other mycobacterial species tested. Immunoblot analysis demonstrated the presence of Mtb39A in M. tuberculosis lysate but not in culture filtrate proteins (CFP), indicating that it is not a secreted antigen. This conclusion is strengthened by the observation that a human T-cell clone specific for purified recombinant Mtb39A protein recognized autologous dendritic cells infected with TB or pulsed with purified protein derivative (PPD) but did not respond to M. tuberculosis CFP. Purified recombinant Mtb39A elicited strong T-cell proliferative and gamma interferon responses in peripheral blood mononuclear cells from 9 of 12 PPD-positive individuals tested, and overlapping peptides were used to identify a minimum of 10 distinct T-cell epitopes. Additionally, mice immunized with mtb39a DNA have shown increased protection from M. tuberculosis challenge, as indicated by a reduction of bacterial load. The human T-cell responses and initial animal studies provide support for further evaluation of this antigen as a possible component of a subunit vaccine for M. tuberculosis.

Original languageEnglish (US)
Pages (from-to)2941-2950
Number of pages10
JournalInfection and Immunity
Issue number6
StatePublished - Jun 1999

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases

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