Susceptibility of severe combined immunodeficient mice to Mycobacterium leprae

The susceptibility of severe combined immunodeficient (SCID) mice to human leprosy bacilli was investigated. Nude mice were used as controls. SCID mice were found to be highly susceptible to Mycobacterium leprae and the progress of infection was comparatively 2-3 months earlier than observed in the nude mice. After reaching a maximum of approximately 1 x 10(9) acid fast bacilli/foot pad at about 8 months postinfection the number of bacilli gradually decreased. The progress of infection in nude mice was different from that found in SCID mice. The multiplication of M. leprae in the foot pads of nude mice continued and reached approximately 2.0 x 10(10) bacilli/foot pad and then nearly remained the same. The results indicate that SCID mice can be used as a suitable model for screening antileprosy drugs while nude mice should be involved in the production of M. leprae for use in other fields of leprosy research.