Leprosy in hypertensive nude rats (SHR/NCrj-rnu)

Since more than a decade ago, we have attempted to develop spontaneously hypertensive rats carrying the nude gene that permits high multiplication of Mycobacterium leprae. A congenic strain carrying nude (rnu) and hypertensive genes was produced using SHR/NCrj females and F344/NJcl-rnu males. Cross-intercross was carried out 12 times to establish the hypertensive nude rat congenic strain. As a result of the genetic monitoring test with NE12F2 generation rats, the genetic profile of the SHR/NCrj-rnu rats was the same as that of the SHR/NCrj rats except for the rnu gene. We have successfully developed a hypertensive congenic nude rat strain (SHR.F344Hfh11; SHR/NCrj-rnu). An increase in the blood pressure in nude rats was found to begin at a slightly delayed age when compared with their hairy litter mates. Both female and male rats showed the highest blood pressure at approximately 20 weeks of age--166 +/- 1.4 and 197 +/- 11 mm Hg in nude rats and 175 +/- 11 and 193 +/- 3.2 mm Hg in their hairy litter mates in female and male rats, respectively. In the present study, comparisons were made on the susceptibility to M. leprae in hypertensive SHR/NCrj-rnu and normotensive F344/NJcl-rnu rats. We have reconfirmed that hypertensive SHR/NCrj-rnu rats of the NE12F3 generation were highly susceptible to M. leprae. In the SHR/NCrj-rnu rats of both sexes excellent massive swelling due to multiplication of M. leprae was observed and, also, nodular lesions were produced in uninoculated fore feet and lips while those sites in the F344/NJcl-rnu rats showed only a slight swelling of the inoculated feet with mild nodular lesions. Although mild lymphocyte proliferation was seen only in the M. leprae-inoculated site with numerous bacilli and partial necrosis in the SHR/NCrj-rnu rats, at noninoculated sites, multiplication of M. leprae was only observed in the cells of the mononuclear phagocyte system. However, in F344/NJcl-rnu rats, lymphocyte proliferation with a few neutrophils was seen at the site of inoculated hind foot pads and everywhere at the site of multiplication of M. leprae. There was a wide difference in the susceptibility to M. leprae between the SHR/NCrj-rnu and the F344/NJcl-rnu rats.

Susceptibility to Mycobacterium leprae of ALY (Alymphoplasia) mice and IFN-gamma induction in the culture supernatant of spleen cells

The aly/aly (alymphoplasia) mice from a mutation of a colony of the C57BL/6J mouse strain, which has a systemic absence of lymph nodes and Peyer's patches, are deficient in both T- and B-cell-mediated immune functions. We have undertaken a comparison of susceptibility to Mycobacterium leprae of ALY (aly/aly, aly/+) mice with C57BL/6J mice. The aly/aly mouse was found to have an excellent high susceptibility to M. leprae with no distinction between female and male. The aly/+ mouse also was more susceptible to M. leprae at an earlier stage than the C57BL/6J mouse. Therefore, we examined and compared the cytokine gene expression and gamma interferon (IFN-gamma) induction in the splenocytes of ALY mice. The expression of interleukin 4 (IL-4), IL-10 and IL-12 mRNA was weakly stimulated with ML-lysate in inoculated aly/aly mice but IL-2, IL-6, IGIF/IL-18 and IFN-gamma mRNA were not observed. None of the cytokine genes used appeared, except the mRNA for IL-1-alpha, when uninfected cultured spleen cells were stimulated with ML-lysate. Also, IFN-gamma production was not induced. However, the appearance of these cytokine genes was observed when stimulated with concanavalin A (ConA), and IFN-gamma production was also induced in the culture supernatant by aly/+ and even aly/aly mice stimulated with ConA. To examine the reason why IFN-gamma cannot be produced by splenocytes of ALY mice inoculated with M. leprae, we detected cytokine gene expression and IFN-gamma induction in the presence of recombinant murine IL-12 or IGIF/IL-18. IL-2 mRNA expression was detected in all of the mice tested in the presence of IL-12 but not in aly/aly mice under IGIF/IL-18, and iNOS mRNA expression was not observed in aly/aly mice under IL-12 or IGIF/IL-18. IL-4 and IL-10 mRNA were detected by aly/aly mice only by exposure to IGIF/IL-18. In culture, the supernatant with ML antigens of the aly/aly mice did not produce IFN-gamma in spite of the presence of IL-12 and IGIF/IL-18, while IFN-gamma was weakly induced in aly/+ mice stimulated with ML-lysate and in the presence of IGIF/IL-18. Nevertheless, IFN-gamma production was observed in splenocytes of the aly/aly mice stimulated with ConA and also with IGIF/IL-18 plus anti-CD3 antibody. Our results suggest that ALY mice might be showing a high susceptibility to M. leprae because of deficient priming for activation of T cells with the leprosy bacilli infection. Moreover, it is possible that the phagocytic activities of the macrophages of ALY mice are also impaired.