The correlation between subclinical stage of leprosy and antibody level of IDALLE L-ESAT 6 on Household Contact in Endemic leprosy area

Leprosy is an infectious disease caused by M. leprae. One of a high-risk group of leprosy is people who live at home together with the lepers. Since a long ago, it had been known that there was a certain subclinical stage in leprosy. In this case, the leper doesn’t show the clinical symptoms of leprosy, but it can be found the antibody against the leprosy bacillus, especially Phenolic Glycolipid-1 in his/her blood serum. Moreover, this research aimed at analyzing the correlation between the occurrence of subclinical stage of leprosy and the antibody against protective epitopes of IDALLE L-ESAT 6, which was discovered by Kurdi et al. (2010) in a group of healthy nurse who had treated the lepers more than 10 years. This observational research utilized cross sectional approach. The total sample was 95 people of household contact in a house with the lepers at Brondong sub-district, Lamongan district, East Java, Indonesia. Subclinical stage of leprosy was measured based on titter of IgM anti PGL-1 by utilizing ELISA method. In addition, a level of protective antibody of IgG anti IDALLE L-ESAT 6 was also measured by utilizing ELISA method. The results showed that 48 samples were seropositive household contact PGL-1 (1286.6 ± 756.428 U / ml) and 47 samples were seronegative household contact PGL-1 (287, 06 ±152,084 U/ml). The mean of IgG anti IDALLE L-ESAT 6 at PGL-1 seropositive household contact was 344.80 U / ml, whereas, PGL-1 seronegative household contact was 508.09 U / ml. However, it was found that cut off of antibody anti IDALLE L-ESAT 6 was in 348 U/ml with 50% percentile calculation. By applying simple logistic regression analysis, it was known that there was a correlation between the occurrence of subclinical stage of leprosy and the level of IDALLE L-ESAT 6, the higher antibody level toward the IDALLE L-ESAT 6, in household contact the higher protection against M. leprae. Therefore, it would not grow to be subclinical stage of leprosy.