tuberculosis (Gioffréet al., 2005; Senaratne et al., 2008). Like mce3 mutants of M. tuberculosis, mice infected with RD1 mutants had increased survival with reduced virulence and pathogenesis, as compared with wild-type M. tuberculosis (Hsu et al., 2003; Lewis et al., 2003). Furthermore, immunological characterization of RD1 proteins in humans using overlapping synthetic peptides in cell-mediated immunity (CMI) assays has identified three major proteins (ESAT-6, CFP10 and PPE68) with potentials for the diagnosis and development of new vaccines against TB (Okkels et al., 2003; Mustafa,

2005a, b; Hanif et al., 2008; Mustafa et al., 2008). However, mce3 operon containing RD15 region has not yet been characterized Cabozantinib supplier for identification ZD1839 molecular weight of antigens useful in diagnostic or vaccine applications. It has been suggested that CMI responses are responsible for both protection and pathogenesis

in TB (Dietrich et al., 2006; Mustafa, 2009c). Protective CMI primarily involves interferon (IFN)-γ release by antigen-activated CD4+ T-helper (Th) type 1 cells, which activates macrophages to destroy intracellular mycobacteria (Flynn, 2004). The central role of IFN-γ in the protection against TB has been suggested by many studies in both animals and humans (Flynn, 2004; Al-Attiyah et al., 2006a; Dietrich et al., 2006; Mustafa et al., 2006). On the other hand, the Th2 responses, characterized by the secretion of interleukin (IL)-4, IL-5 and anti-inflammatory cytokine IL-10, are associated with a lack of protection (Bai et al., 2004; Flynn, 2004). In particular, IL-10 is associated with reduced resistance and chronic progressive TB in the murine model (Turner et al., 2002). Furthermore, IFN-γ : IL-10 ratios provide a useful objective marker of disease activity in TB and can be important in disease management (Salina from & Morozova,

2004; Jamil et al., 2007). In response to mycobacterial antigens, high IFN-γ : IL-10 ratios correlate strongly with protection and TB cure, whereas low ratios correlate with disease severity and pathology (Salina & Morozova, 2004; Jamil et al., 2007). Therefore, the ability to stimulate strong IFN-γ release and higher IFN-γ : IL-10 ratios were used in this study as criteria for the identification of M. tuberculosis-specific protective antigens encoded by genes in RD15. In this study we have characterized the proteins of RD15 for CMI responses by determining their Th1 (antigen-induced proliferation and IFN-γ secretion) and anti-inflammatory (IL-10 secretion) reactivity using peripheral blood mononuclear cells (PBMC) obtained from TB patients and healthy subjects. Furthermore, IFN-γ : IL-10 ratios were calculated to determine the Th1 vs. anti-inflammatory bias of the responses.