Seropositivity to anti-phenolic glycolipid-I in leprosy cases, contacts and no known contacts of leprosy in an endemic and a non-endemic area in northeast Brazil

The seroprevalence rates of IgM anti-phenolic glycolipid-I (PGL-I) antibodies in four study groups with differing exposure to Mycobacterium leprae in Ceará, Brazil were investigated between March 2005 and August 2006. The first three groups in a high prevalence area included 144 cases of leprosy, their 380 contacts and 317 participants with no known lep- rosy contact. The fourth group in a low prevalence area consisted of 87 participants with no known leprosy contact living in an area in which no cases of leprosy had been reported in the previous 6 months. Seropositivity and levels of IgM antibodies to PGL-I were investi- gated using ELISA. The seropositivity levels of anti-PGL-I among the different clinical forms ofleprosycaseswere61%forlepromatous,25%fortuberculoidand27%indeterminate.The levels of anti-PGL-I antibodies in the endemic area differentiated leprosy cases from non- cases. However, the seropositivity was similar among contact cases (15.8%) and no known leprosycontactcasesfromhigh(15.1%)andlow(13.8%)prevalenceareas.Theseropositivity of both contacts and no known contacts was much higher than previously reported among no known contacts in other endemic areas. The study indicates that anti-PGL-I antibod- ies are not useful as immunological markers of household leprosy contacts and no known leprosy contacts in endemic are