Protein expression by a Beijing strain differs from that of another clinical isolate and Mycobacterium tuberculosis H37Rv

1 MRC Centre for Molecular and Cellular Biology, Department of Medical Biochemistry, University of Stellenbosch Medical School, PO Box 19063, Tygerberg, 7505, South Africa 2 GlaxoSmithKline Research and Development, Stevenage, Hertfordshire SG1 2NY, UK Correspondence Paul van Helden pvh{at}sun.ac.za The Beijing strain family has often been associated with tuberculosis (TB) outbreaks and drug resistance worldwide. In this study the authors have compared the protein expression and antigen recognition profiles of a local Beijing strain with a less prevalent clinical isolate belonging to the family 23 strain lineage, and the laboratory strain Mycobacterium tuberculosis H37Rv. Using two-dimensional electrophoresis, liquid chromatography tandem mass spectrometry and Western blot analysis several proteins were identified as quantitatively increased or decreased in both clinical strains compared to H37Rv. Remarkably, the Beijing strain showed increased expression of -crystallin and decreased expression of Hsp65, PstS1, and the 47 kDa protein compared to the other clinical strain and H37Rv. One- and two-dimensional Western blot analysis of antigens expressed by the three strains, using plasma from TB patients, confirmed differential antigen expression by strains and patient-to-patient variation in humoral immunity. These observed protein differences could aid the elucidation of mechanisms underlying the success of the Beijing strain family, measured by global dissemination, compared to other M. tuberculosis strains. Abbreviations: 1D, one-dimensional; 2D, two-dimensional; BCG, Mycobacterium bovis bacille Calmette–Guérin; BCIP, 5-bromo-4-chloro-indolyl-phosphatase; CF, culture filtrate; F11, family 11; F23, family 23; ICD, isocitrate dehydrogenase; IPG, immobilized pH gradient; LC/MS/MS, liquid chromatography tandem mass spectrometry; NBT, nitro blue tetrazolium; TB, tuberculosis; WCL, whole-cell lysate