Leishmania major: solid phase radioimmunoassay for antibody detection in human cutaneous leishmaniasis.

A radioimmunoassay for the quantitative determination of antileishmanial antibody in sera from patients suffering from cutaneous leishmaniasis was developed. The assay, using as antigen either the soluble fraction from freeze-thawed sonicated Leishmania major (LRC-L137) promastigotes or a carbohydrate-lipid containing fraction obtained by extraction with hexane-isopropanol, was shown to be sensitive and reproducible. The sera of 95 patients were examined. These were from patients with cutaneous leishmaniasis (26 from the Jordan Valley and 13 from Sinai), kala-azar (9), malaria (24), schistosomiasis (10), toxoplasmosis (5), and leprosy (8); controls were 37 normal human sera. No significant antigen dependent differences were observed using sera from cutaneous leishmaniasis patients, although differences in the immunological response were observed between the two populations of these patients. Antileishmanial activity was not detected in sera from patients with malaria, schistosomiasis, or toxoplasmosis. Although sera from leprosy patients crossreacted with the carbohydrate-lipid containing fraction, it was nevertheless more strain specific than freeze thawed sonicated L. major.

Immunologic shin titration in leprosy patients and contacts.

A method of studying delayed-type hypersensitivity was developed with specific antigen in leprosy patients and contacts, measuring the dose-response curve at different lepromin concentrations. This "immunologictitration" is highly efficient for discriminating the degree of hypersensitivity reactions among the groups tested. With respect to the Fernandez reaction, the results obtained showed that there was a similar behavior in all groups studied, except in the tuberculoid group which had a more intense response, four times higher than that yielded by contacts of lepromatous patients. In the Mitsuda reaction, a similar behavior was also found among the different groups, except with respect to the reactivity intensity of contacts of lepromatous patients. Here it was demonstrated that this group had a significant depression in response to M. leprae antigen when compared with that from the other groups, independent of the degree of consanguinity or closeness to bacilliferous cases. In order to explain this immunosuppression in contacts of lepromatous patients, a hypothesis is proposed. It is suggested that changes could occur in M. leprae derived from lepromatous patients, diminishing their capacity to produce an adequate immune response.