An appraisal of enzyme linked immunosorbent assay (ELISA) and serum antibody competition test (SACT) in leprosy.

Seventy-eight untreated leprosy patients, 104 treated patients and 105 healthy contacts were tested using two serological tests, SACT (serum antibody competition test based on competitive inhibition of monoclonal antibody binding to the MY2a determinant of M. leprae) and ELISA (measurement of IgM antibodies to the neoglycoproteins D-BSA and ND-BSA representing the phenolic-glycolipid antigen of M. leprae). The controls included normal healthy individuals, patients with sputum positive pulmonary tuberculosis, and active cases of rheumatoid arthritis from the department of rheumatology. The specificity of SACT was found to be very high. ELISA was found to be positive in two patients with rheumatoid arthritis, one each for D-BSA and ND-BSA ELISA. Both tests had a high sensitivity in BL and lepromatous patients. The sensitivity to both tests was considerably lower in tuberculoid and BT patients i.e., below 40%. Therefore the diagnostic value of a negative test in suspected cases of leprosy was very low employing either of the two tests. A proportion of patients with paucibacillary tuberculoid and BT leprosy were positive after six months or longer after therapy. Similarly a large number of BL and lepromatous patients were positive after considerably longer periods of treatment. The use of either tests for determining the duration of therapy is therefore limited. SACT appears to be more sensitive than ELISA with ND-BSA in detecting subclinical infection. The cumulative positivity of the two tests may be used as a measure of the infectivity of the disease in the community and for evaluating disease control methods.

Evidence for HTLV-III infection in prostitutes in Tamil Nadu (India).

PIP: Blood samples were collected from 102 female prostitutes housed in a custodial care institution in Tamil Nadu, India, to determine the presence of antibodies to human T-lymphotropic virus type III (HTLV-III). Both social and sexual histories were taken from 101 of the 102 women. Commercial test kits were used to test sera for antibody to HTLV-III. Reactive sera were tested for a 2nd time by the enzyme-linked immunoabsorbent assay (ELISA). Those repeatedly reactive sera were transported to the US, the National Institutes of Health, for western blot analysis. The sera from 11 of the study subjects were found to be repeatedly reactive in ELISA, and 10 were confirmed to have specific antibody to the virus by western blot analysis. Both infected and uninfected women were similar in age and of low socioeconomic status. The risk ratio for HTLV-III antibody was 8.2 in those women who had had sexual exposure to foreigners. None of the women were intravenous drug abusers, and all denied oral or rectal intercourse. On the basis of the stringent criteria used in the western blot analysis, it is believed that the 10 women have HTLV-III antibody. This emerges as the 1st report of evidence for HTLV-III infection in India. 10-40% of prostitutes in North America and Europe have HTLV-III antibody; the risk factors for infection appear to be intravenous drug use and penis-rectal intercourse. 54-88% of prostitutes in Central Africa have HTLV-III antibody, and the frequency of sexual contact with different partners is more important here as a risk-factor than the type of intercourse. As the prostitutes in this study in Indian did not use intravenous drugs and did not practice penis-rectal or penis-oral intercourse and had been prostitutes for shorter periods of time than the noninfected women and had fewer contacts, it is believed that HTLV-III infection has been introduced only recently into prostitutes in India. Sexual exposure to foreigners was a significant factor in the infected women.^ieng