Prokaryotic expression of the Mycobacterium tuberculosis PhoY2 gene and its diagnostic utility in various populations infected with tuberculosis

Early and timely diagnosis is crucial for reducing the transmission of tuberculosis.In this study, we constructed and expressed PhoY2, a persistent infection related antigen of Mycobacterium tuberculosis and evaluated its potential as a diagnostic target through population experiments.The immunogenicity of the recombinant PhoY2 (rPhoY2) protein in M. tuberculosis infected individuals was evaluated using whole blood interferon-gamma (IFN-) release assay (WBIA) and serum specific antibody detection.Further, the diagnostic value, sensitivity, and specificity of rPhoY2-WBIA and anti-rPhoY2 specific antibody in different M. tuberculosis infected populations were analyzed using receiver operating characteristic.The results indicated that rPhoY2 can stimulate specific IFN- production in active tuberculosis (ATB) and latent tuberculosis infection (LTBI), levels of which were significantly higher than that in healthy controls (HCs).The anti-rPhoY2 specific IgG levels of LTBI were significantly higher than those of ATB and HCs.The cutoff value of rPhoY2-WBIA for diagnosing M. tuberculosis infection is 309.2 pg/ml with a sensitivity of 72.2% and a specificity of 93.7%.The cutoff value of anti-rPhoY2 specific IgG for diagnosing LTBI is 0.1765 with 61.5% sensitivity and 75% specificity.The agreement rate between rPhoY2-WBIA combined with specific antibodies and clinical diagnosis for the three populations is 69.9%.In summary, the combination of rPhoY2-WBIA and specific antibody detection has certain value in distinguishing different populations infected with M. tuberculosis, especially in excluding the infection with high specificity.However, its sensitivity should be further enhanced for differentiating ATB and LTBI.