Immunotherapy of far-advanced lepromatous leprosy patients with low-dose convit vaccine along with multidrug therapy (Calcutta trial).

This report describes a promising mode of treatment of lepromin-unresponsive, far-advanced, lepromatous (LL) leprosy patients with antileprosy vaccines as an adjunct to multidrug therapy (MDT). The Trial Groups included 50 highly bacilliferous, lepromin-negative, untreated LL patients. They were given MDT for 2 years. Of them, 30 patients were administered a mixed antileprosy vaccine containing killed Mycobacterium leprae of human origin plus M. bovis BCG. The remaining 20 patients were given M. bovis BCG. Depending on the severity of lepromin unresponsiveness, they were given one to six inoculations at 3-month intervals. Another 20 similar LL patients were taken in the Control Group. They were given only MDT for 2 years. From the start of the study, all patients belonging to the Trial and Control Groups were followed every 3 months for clinical, bacteriological and immunological outcomes. Within 2 years all 50 patients of the Trial Groups and 19 of the 20 patients of the Control Group became clinically inactive and bacteriologically negative. However, the clinical cure and the falls of the bacterial and morphological indexes were much faster in those patients receiving the mixed vaccine therapy than in those patients who were given BCG plus MDT or only MDT. The immunological improvements in the patients of the Trial and Control Groups were assessed by: a) lepromin testing at the beginning of the study and at 3-month intervals and also by b) the in vitro leukocyte migration inhibition (LMI) test at both the beginning and end of the study. As the patients were given more and more vaccinations, the incidence of lepromin conversion increased, more so in the patients receiving the mixed vaccine. Thus, 63%, 15% and 5% of the patients became lepromin positive in those patients receiving the mixed vaccine, BCG, and MDT only, respectively. Lamentably, the vaccine-induced lepromin positivity was temporary and faded away within several months. At the beginning of the study, the LMI test against specific M. leprae antigen was negative in all patients of both the Trial and Control Groups. After the end of the chemo-immunotherapy schedule, the LMI test became positive in 50% and 20% of LL patients receiving the mixed vaccine and BCG, respectively. None of the Control Group could show LMI positivity after completion of the MDT schedule. These results show that treatment of LL patients with the mixed vaccine and MDT could quickly reverse the clinical course of the disease, remove immunologic anergy in some patients, and induce a rapid decrease in the bacterial load in them.