Study of experimental leprosy in nude-mice inoculated with M. leprae--light and electron microscopic findings

Abstract

Since 1978, experimental leprosy in nude-mice has been studied at Leprosy Research Laboratory, Kyoto University School of Medicine, Japan, according to the method of Kohsaka in Osaka University. The main purpose of the experiment was to get leprosy bacilli of nude-mine inoculated with M. lepae for our studies of cultivation of leprosy bacilli and histopathological and biochemical researches.Fourty nude-mice used for the experiments were divided into 2 groups. Thirty nudemice in Group I were used for the experiment of inoculation with M. leprae. Ten nude-mice in Group II were used for the experiment of inoculation with M. lepraemurium. Nude-mice in Group II were bred in vinyl-isolator under SPF condition. Nudemice in Group II were bred under conventional condition. The materials and methods were summarized on Table I.Thirty nude-mice in Group I were inoculated with 107 M. leprae on each right hind foot-pad at 6 Feb. 1979. Seven out of 30 nude-mice died at early stages within 10 months after the inoculation. Twenty-three nude-mice were left alive after 10 months when right hind foot-pads became swollen. Eleven out of 23 nude-mice could be sacrificed between 12.5 months and 19 months after the inoculation as shown on Table 2. Twelve out of 23 nude-mice with the swelling of right hind foot-pads died between 10 months and 24.5 months after the inoculation. All spleens of all sacrificed 11 nudemice were swollen.Ten nude-mice in Group II were inoculated with 107 M. lepraemurium on each right hind foot-pad at 9 Oct. 1978. In this group, all nude-mice were sacrificed until 6 months after the inoculation. Each right hind foot-pad of the nude-mice became swollen at 1.5 months and the swelling became remarkable at 3 months after the inoculation.Light-miroscopic findings of the lesions of nude-mice inoulated with M. lepaae in Group I were shown on Plates 3, 4, 5 and 6. Large amount of bacilli and foamy structures were observed in the lesions of swollen right hind foot-pads and spleens as shown on Plates 3, 5 and 6. Many bacilli were observed inside peripheral nerve, especially inside axon as shown on Plate 4.Electron-microscopic findings of the lesions of nude-mice inoculated with M. leprae and M. lepraemurium were studied by ultra-thin sectioning, freeze-etching and shadowcasting methods.Almost all of bacilli in Group I were long and slender with band structure on the cell wall as shown on Plate 7. Spherical droplets (intracytoplasmic foamy structures) similar to those of human lepra cells were observed around bacilli inside the phagolysosomes of macrophages of nude-mice inoculated with M. leprae in Group I as shown on Plates 8, 9 and 10. On the contrary, crystalline materials similar to those of C 3H strain mice inoculated with M. lepraemurium were observed around bacilli inside the macrophages of nude-mice inoculated with M. lepraemurium in Group II as shown on Plates 11 and 12.These histopathological findings were clearly different between the lesions of nudemice inoculated with M. leprae and those of nude-mice inoculated with M. lepraemurium as shown on Table 3.