Serologic response of study subjects by indirect ELISA to the recombinant antigens. A. Levels of HspX IgM and IgG antibodies in serum from HCW uninfected (n = 159), LTBI (n = 211) and recent LTBI (n = 43). B. Levels of GlcB IgM and IgG antibodies in serum from HCW uninfected, LTBI and recent LTBI. Horizontal bars represent the mean antibody levels in the groups. IgM levels in recent LTBI were significantly higher than in those uninfected and LTBI (P < 0.0001).