BACKGROUND: Screening tuberculosis (TB) contacts is a priority for TB control; however, it remains inadequate in most regions of China.OBJECTIVE: To investigate the progression of latent TB infection (LTBI) using the interferon-gamma release assay (IGRA) in contacts of active TB patients.DESIGN: This longitudinal prospective observational study included 159 household contacts aged ≥14 years without preventive treatment who were followed up for 6 years to compare their conversion and reversion rates using the T-SPOT®.TB IGRA to diagnose LTBI.RESULTS: Among the 159 household contacts, LTBI positivity was 47.5%. Age was independently associated with LTBI (OR 3.6, 95%CI 1.81–7.14; P = 0.00). T-SPOT.TB conversion rates were respectively 29.4% and 18.8% at 3- and 6-year follow-up. The reversion rates were 9.4% of contacts during the 3-year follow-up period, which increased to 38.2% at the 6-year follow-up. A decreasing trend in spot-forming cells on T-SPOT.TB was observed in most patients at the 6-year follow-up.CONCLUSION: LTBI prevalence among household contacts was relatively high, particularly in elderly patients. Furthermore, serial IGRA testing was highly dynamic; however, this overall trend gradually decreased over time, even if preventive therapy was not prescribed.

ABSTRACT. Corn DNA was introduced into dry seeds of rice (cv. 'YuJing-6') by ion beam irradiation. Proteinase activities in rice seedling roots were subsequently analyzed by renaturation electrophoresis at pH 4.5, 7.0, and 8.5. Proteinase activity was more pronounced on gels at higher pH. Irradiation of rice seedling roots caused the loss of some proteinase bands at all pH conditions although a novel 50-kDa band was found at both pH 7.0 and 8.5. No new proteinase activity was detected at pH 4.5. However, novel bands and bands showing stronger activity were observed at pH 7.0 and 8.5. The data indicate that the expression of proteinases in rice seedling roots was altered following low energy ion beam mediated transformation with corn DNA.