Abstract: We report the results of detecting M.lepraespecific antigen-phenolic glycolipid I (PGL-I) with modified M-Dot-ELISA in sera from 75 cases of household contacts (HC)of leprosy patients, which were all seropositive by Gelatin Particle Agglutination Test (MLPA)and ELISA.The results indicate that:(1) 16/75 (21.3%) are antigen positive.The rates of positivity in HC of MB patients are much higher than those in HC of PB patients,the difference (P<0.01) between them is significant.(2) Positive rates and levels of PGL-I in HCs are associated with levels of antibody against PGL-I in sera from HCs.There are significant differences in antigen positive rates and levels between weak and strong antibody positive groups of HC (P<0.01).(3)The sera from 40 normal controls and 10 nonleprosy patients with positive anti-PGL-I antibody by MLPA and ELISA are antigen negative.

Key words: Leprosy, Contacts, Antigens, bacterial