Comparison of the immunogenicity of vaccines prepared from viable Mycobacterium bovis BCG, heat-killed Mycobacterium leprae, and a mixture of the two for normal and M. leprae-tolerant mice

Intradermal vaccines consisting of viable Mycobacterium bovis BCG, heat-killed Mycobacterium leprae, or mixtures of the two were titrated in mice in doses of 10(5.2), 10(5.8), 10(6.4), 10(7.0), and 10(7.6) acid-fast bacilli. The immune response was measured by sensitization (48 to 72 h foot pad enlargement on challenge with 10(7.0) heat-killed M. leprae) and by protection against infection with a viable M. leprae challenge. There was increasing response with increasing dose of vaccine, and overall the responses to the three vaccines were similar. At the lowest dose, however, the combination of BCG and M. leprae gave superior protection. The local reaction to the vaccines in the lower dose range was less severe with the M. leprae vaccine. In another experiment, the three vaccines were compared in normal mice and in mice that had been rendered tolerant by intravenous injection of M. leprae. The tolerant mice developed no measurable sensitization on vaccination with M. leprae, but they developed partial but distinct sensitization on vaccination with BCG, alone or in combination with M. leprae. The tolerant mice developed little or no protection with any of the vaccines, however..

Searches among mycobacterial cultures for antileprosy vaccines

All mycobacteria species share some antigens, so there may be cultivable mycobacterial cultures that can provide vaccine protection against leprosy. Vaccine protection against Mycobacterium leprae infections in mice has been demonstrated for M. leprae itself, as living or heat-killed suspensions, and for Mycobacterium bovis (BCG), as living suspensions. Results are reported here with 17 other cultures. The mycobacterial suspensions were injected intradermally, and the mice were challenged in the footpad with infectious suspensions of M. leprae. In two experiments the mice were also challenged by footpad injections of 10(7) heat-killed M. leprae so the footpad enlargment could be measured. That some mycobacterial suspensions were immunogenic for some of their own antigens was suggested by reactions at the vaccine site and enlargement of the regional lymph nodes. Some mycobacterial suspensions also stimulated footpad enlargement on challenge by homologous suspensions or by challenge with M. leprae suspensions. Consistent protection against infectious challenge with M. leprae was observed only with BCG and M. leprae, however...

Heat stability of Mycobacterium leprae immunogenicity

The protection provided to mice by vaccines administered intradermally was measured after footpad challenge with Mycobacterium leprae. The protection offered by M. leprae suspensions was not decreased when the vaccines were killed by 60 degrees C heat or at the higher temperatures tested, which included 215 degrees C (autoclave). Even highly purified suspensions retained their immunogenicity. In contrast, the vaccine protection provided by intradermal M. bovis (strain BCG) was markedly reduced when heated to 60 degrees C. The enlargement of the lymph nodes regional to the intradermal vaccines was measured and found generally to parallel the vaccine protection provided by M. leprae and by BCG.

Lack of protection afforded by ribonucleic acid preparations from Mycobacterium tuberculosis against Mycobacterium leprae infections in mice

Mycobacterial ribonucleic acid preparations from H37Ra, an attenuated strain of Mycobacterium tuberculosis, provide their usual marked protection against M. tuberculosis challenge; however, they provided no protection against Mycobacterium leprae challenge. Suspensions of intact H37Ra were not effective against M. leprae. Suspensions of BCG gave their usual distinct protection against M. leprae challenge.

Immunology and animal experimentation in leprosy

The immunological status of leprosy patients is reflected in the clinical picture. Figure 1 and 2 illustrate the lepromatous variety.

Rapid bactericidal effect of rifampin on Mycobacterium leprae

Rifampin was rapidly bactericial for Mycobacterium leprae. Leprosy responds very slowly to current therapy, so there is a special need for more rapidly effective drugs. In mice rifampin exerted a bactericidal-type effect with single administration by gavage; the effect increased with dosage in the range 10 to 40 mg/kg of body weight. Five patients with lepromatous disease were treated with 600 mg rifampin daily, and the viability of the bacilli in their skin lesions was tested by inoculation of mice. Infectivity for mice had completely disappeared in the 1st specimen collected after the start of therapy - at 7 days in 4 patients and 14 days in 1. In 4 control patients treated with dapsone, infectivity for mice was lost much more slowly and in 1 was still present, though decreased, 112 days after the start of treatment. The slower loss of infectivity with dapsone is in accord with our previous experience in which the same methods were used.

Kinetic testing of drugs against Mycobacterium leprae in mice. Activity of cephaloridine, rifampin, streptovaricin, vadrine, and viomycin

A series of drugs that had been found active against Mycobacterium leprae in mice by the continous method of drug administration was tested by the kinetic method. Vadrine and vyomivin were found inactive. Cephaloridine, streptovaricin, and rifampin gave bactericidal-type results. In a second experiment, rifampin was found to have distinct bactericidal effect when given for only 2 days. The plasma levels of rifampin that were associated with bactericidal effect in mice were in the range reported for man receiving acceptable dosages of rifampin. Cephaloridine and, especially, rifampin merit further investigation in clinical trials in leprosy patients, either as single drugs or in combination with other active drugs. The combination of rifampin and dapsone (DDS) or acedapsone (DADDS) appear to provide the advantages of tboth drugs.