Double blind trial on the effect of certain soluble cytoplasmic mycobacterial antigens on the late reactivity to lepromin.

Two hundred forty-four children between six months and 59 months of age from nursery schools and playgrounds in Ribeirão Preto, São Paulo, Brazil, were randomly allocated into five groups. These received: 1) intradermal BCG; 2) placebo; 3) antigen F, containing soluble cytoplasmic components of the mycobacteria Mycobacterium tuberculosis, M. aquae, and M. lepraemurium; 4) antigen G, containing soluble cytoplasmic components of M. piscium, and M. balnei, and 5) antigen H, containing soluble cytoplasmic components of M. leprae. BCG preinjected children had the highest proportion of positive late lepromin reactions. The injection of antigens F, G, or H had no effect on the late lepromin reactions. These findings contrasted with those observed in our earlier trial in which the injection of antigens X (containing soluble cytoplasmic components of the mycobacteria M. avium and M. gallinarum), Y (M. simiae, M. gallinarum, and M. avium), and Z (M. leprae, M. simiae, and M. borstelense) had caused significantly lower positive late lepromin reactions. By comparing the data of the present investigation with the findings of the first trial, it appears that the antigens obtained from M. borstelense and from either M. avium or M. gallinarum could have been instrumental in the impairment of lepromin activity observed in the first trial.

Impairment of reactivity to lepromin by mycobacterial antigens related to, or identical with, Mycobacterium leprae.

Three hundred and twenty young children were injected with Bacillus Calmette-Guerin (BCG) saline, or with one of the mycobacterial cytoplasmic antigens related with Mycobacterium leprae. At an appropriate time thereafter they were tested for dermal hypersensitivity to the antigens and for reactions to lepromin. Whereas all the antigens induced cell-mediated immunity, the incidence and intensity of late response to lepromin were significantly reduced in children preinjected with the cytoplasmic mycobacterial antigens, as contrasted with increased lepromin reactivity in the BCG group and with the findings in saline-injected children.