Relationships between PGL-1 antigen in serum, tissue and viability of Mycobacterium leprae as determined by mouse footpad assay in multibacillary patients during short-term clinical trial.

In connection with a 56-day controlled clinical trial for comparing the therapeutic effects between pefloxacin and ofloxacin in 21 lepromatous patients, we have studied the relationships between PGL-1 antigen level in serum and in skin and serum PGL-1 antibody titre on the one hand, and the viability of Mycobacterium leprae, as measured by serial mouse footpad inoculations, and other bactericidal parameters on the other. Before and during treatment, significant correlation was found between serum PGL-1 level and the morphological index (MI), and with the number of viable organisms per mg skin tissue. However, neither serum PGL-1 antibody titre nor skin PGL-1 antigen level showed significant change during the 56-day trial. Because the reduction of serum PGL-1 level was well correlated but less pronounced as compared with the evolution of viable organisms during treatment, the serum PGL-1 antigen assay may be useful as an early indicator of response to chemotherapy in short-term clinical trial, but it is unlikely to replace mouse footpad inoculation for the evaluation of viability of M. leprae.