Immunoreactivity and diagnostic value of Mycobacterium tuberculosis PstS1 and HspX
Objective 
To evaluate the humoral and cellular immunoreactivity of recombinant Mycobacterium tuberculosis (M.tuberculosis) PstS1 and HspX protein antigens in order to provide reference for immunodiagnosis of tuberculosis and screening of candidates for vaccine antigens. 
 
 
Methods 
Purified recombinant M. tuberculosis PstS1 and HspX proteins were obtained using molecular cloning expression and Ni2+ affinity chromatography. Blood samples and epidemiological data of healthy individuals and patients with M. tuberculosis infection were collected. Specific IgG antibodies and IFN-γ-producing antigen-specific T cells were respectively detected by enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunospot assay (ELISPOT) with the recombinant proteins used as antigens. The humoral and cellular immunoreactivity of the recombinant PstS1 and HspX proteins were assessed with statistical analysis of data. 
 
 
Results 
Both the recombinant PstS1 and HspX proteins could induce the secretion of IFN-γ by more specific effector T cells in patient with M. tuberculosis infection, and the differences between the infection and healthy control groups were statistically significant (P<0.05). The specificity and sensitivity of the recombinant PstS1 and HspX as the diagnostic antigens of ELISPOT were 92.11% (35/38) and 65.96% (31/47), and 68.42% (26/38) and 91.49% (43/47), respectively. The two proteins also possessed some humoral immunoreactivity, but statistically significant difference was only observed in the HspX-specific antibody level between the two groups (P<0.05). 
 
 
Conclusions 
Both the recombinant PstS1 and HspX proteins had good cellular immunoreactivity and were the immunodominant antigens of cellular immunity. They performed well in cellular immunodiagnosis and were good potential candidate antigens for anti-tuberculosis vaccines. 
 
 
Key words: 
Mycobacterium tuberculosis; PstS1; HspX; Immunodominant antigens