Diagnostic Potential of a PPE Protein Derived from Mycobacterium tuberculosis Beijing/K Strain

Purpose@#The prevalence of Mycobacterium tuberculosis (M. tb) and the status of M. bovis BCG vaccination may affect host immune responses to M.tb antigens. Understanding of the predominant local M. tb strain and immune signatures induced by its strain-specific antigens may contribute to an improved diagnosis of tuberculosis (TB). The aim of this study was to determine immune responses to M. tb antigen which was identified from the hyper-virulent Beijing/K strain in South Korea. @*Materials and Methods@#Pulmonary TB patients (n=52) and healthy subjects (n=92) including individuals with latent TB infection (n=31) were recruited, and QuantiFERON-TB Gold In-Tube tests were performed. The Beijing/K-antigen specific immune signatures were examined by diluted whole blood assays and multiplex bead arrays in a setting where nationwide BCG vaccination is employed. @*Results@#Statistical analyses demonstrated that three [C-X-C motif chemokine (CXCL10), interleukin (IL)-6, interferon (IFN)-α] of 17 cytokines/chemokines distinguished active cases from healthy controls following stimulation with the Beijing/K-specific antigen. IFN-α also differentiated between active diseases and latent TB infection (p<0.01),and the detection rate of TB was dramatically increased in combination with IL-6 and CXCL10 at the highest levels of specificity (95–100%). @*Conclusion@#Our data indicate that immune signatures to the M. tb Beijing/K-specific antigen can provide useful information for improved TB diagnostics. The antigen may be developed as a diagnostic marker or a vaccine candidate, particularly in regions where the M. tb Beijing/K strain is endemic.

A Feasibility Study for Diagnosis of Latent Tuberculosis Infection Using an IGRA Point-of-Care Platform in South Korea

PURPOSE: This study aimed to evaluate ichroma™ IGRA-TB, a novel point-of-care platform for assaying IFN-γ release, and to compare it with QuantiFERON-TB Gold In-Tube (QFT-GIT) for identifying Mycobacterium tuberculosis (M. tb) infection. MATERIALS AND METHODS: We recruited 60 healthy subjects, and blood samples were obtained in QFT-GIT blood collection tubes. The blood collection tubes were incubated at 37℃, and culture supernatant was harvested after 18–24 hours. IFN-γ responses were assessed by the ichroma™ IGRA-TB cartridge and the QFT-GIT IFN-γ enzyme-linked immunosorbent assay. Three active TB patients were recruited as a positive control for M. tb infection. RESULTS: The area under the receiver operating characteristic curve of the ichroma™ IGRA-TB test for differentiating between infected and non-infected individuals was 0.9706 (p < 0.001). Inconsistent positivity between the two tests was found in three participants who showed weak positive IFN-γ responses ( < 1.0 IU/mL) with QFT-GIT. However, the two tests had excellent agreement (95.2%, κ=0.91, p < 0.001), and a very strong positive correlation was observed between the IFN-γ values of both tests (r=0.91, p < 0.001). CONCLUSION: The diagnostic accuracy demonstrated in this study indicates that the ichroma™ IGRA-TB test could be used as a rapid diagnostic method for detecting latent TB infection. It may be particularly beneficial in resource-limited places that require cost-effective laboratory diagnostics.

The Current Status of BCG Vaccination in Young Children in South Korea / 결핵및호흡기질환

BACKGROUND: Delivery of Bacille Calmette-Gurein (BCG) Tokyo vaccine, with the multipuncture device, has been much preferred over BCG Pasteur, with the intradermal method, possibly due to the easier manner of administration, a desire to avoid any trouble with scars, as well as side effects and higher profits to providers in South Korea. METHODS: To determine BCG scar status in 0~6 year old children vaccinated with two BCG vaccines (Pasteur BCG vaccine with intradermal method and BCG Tokyo vaccine with percutaneous method), the data from the national BCG scar survey in 2006 was analyzed. RESULTS: Based on the national survey, the high proportion that were vaccinated with BCG Tokyo vaccines with the multipuncture method (64.5%) was noted in 0~6 year old Korean children. From inspection of scar formation, as an indicator of vaccination, the median number of the visible pin scars from the percutaneous method was 16 (interquartile range, 12~18) in the Korean children, and pin scars decreased as the age of the children increased (p<0.001). CONCLUSION: The findings in this survey clearly showed a growing preference of parents for the BCG Tokyo vaccines by the multipuncture method in South Korea.