Detection of phenolic glycolipid I of Mycobacterium leprae in sera from leprosy patients before and after start of multidrug therapy

A total of 100 untreated new leprosy patients were recruited prospectively and examined for the presence of phenolic glycolipid I (PGL-I) antigen in t heir serum specimens by dot enzyme-linked immunosorbent assay (ELISA) using rabbit anti-PGL-I antiserum. The presence of circulating PGL-I antigen was closely related to the bacterial indices (BI) of the patients. The PGL-I a ntigen was detectable in 27 (93.1%) of 29 patients with a BI of 4.0 or abov e and in 15 (68.2%) of 22 patients with a BI of 3.0 to 3.9. However, none o f the 37 patients with a BI of less than 1.9 had detectable PGL-I antigen b y the methods used in this study. The level of PGL-I in serum declined rapi dly by about 90% 1 month after the start of multidrug therapy. This study s howed clearly that anti-PGL-I IgM antibodies and circulating PGL-I antigen levels reflect the bacterial loads in untreated leprosy patients. The serol ogical parameters based on the PGL-I antigen may therefore be useful in the assessment of leprosy patients at the time of diagnosis and possibly in mo nitoring patients following chemotherapy.