Role of the indigenous microbiota in maintaining the virus-specific CD8 memory T cells in the lung of mice infected with murine cytomegalovirus.

The potent role of indigenous microbiota in maintaining murine CMV (MCMV)-specific memory T cells, which were measured by multimer staining, was investigated using germfree (GF) mice. When the BALB/c mice bred under specific pathogen-free (SPF) conditions were i.p. infected with 0.2 LD(50) of MCMV, high frequencies of CD69(+)/CD44(+) MCMV-specific CD8 T cells were noted in the lungs even at 6-12 mo after infection (11.1 +/- 3.2 and 9.8 +/- 0.9%, respectively). In contrast, even though the viral load and expression levels of mRNA of such cytokines as IL-2, IL-7, IL-15, and IFN-gamma in the lungs of MCMV-infected GF mice were comparable to those of infected SPF mice, the frequencies of MCMV-specific CD8 T cells in the lungs of infected GF mice were kept lower than 1% at 6-12 mo after infection. In addition, the reconstitution of microbiota of MCMV-infected GF mice by orally administering a fecal suspension prepared from SPF mice restored the frequencies of both CD8(+)/multimer(+) and CD8(+)/multimer(-) T cells to levels similar to those found in SPF mice. These results suggested the indigenous microbiota to play a crucial role in the expansion and maintenance of viral-specific CD8 memory T cells, probably by cross-reactivity between the antigenic epitope of the MCMV-specific memory T cells and the variety of peptides derived from the members of the microbiota. Such cross-reactivity may thus be a major feature of those cells.

Therapeutic effect of a traditional Chinese medicine, ren-shen-yang-rong-tang (Japanese name: Ninjin'yoeito) on nitric oxide-mediated lung injury in a mouse infected with murine cytomegalovirus.

The therapeutic effect of a traditional Chinese medicine ren-shen-yang-rong-tang (Japanese name: Ninjin'yoeito, NYT) on murine cytomegalovirus (MCMV)-associated pneumonitis was examined. In MCMV-pneumonitis, IFN-gamma-induced nitric oxide (NO) mediates its pathogenesis. When mice, which had been infected with 0.2LD(50) of MCMV at 28 days previously, were intraperitoneally injected with anti-CD3 monoclonal antibody (mAb), MCMV-pneumonitis was induced in the lung, where high amounts of IFN-gamma-producing cells thereafter accumulated, accompanied by an elevation in the NO level in the serum and abundant expression of inducible NO synthase (iNOS) mRNA, thus resulting in all mice eventually dying. When the mice were orally treated with NYT (1000 mg/kg/day) once on the day of mAb injection and once the day after, the expression level of iNOS-mRNA was suppressed and NO level in the serum decreased. The survival rate improved from 0% to 57.1%. The pathological findings of the lungs in the NYT-treated mice were comparable to those of the uninfected controls. In contrast, NYT itself did not affect either the ratio of IFN-gamma-producing cells or MCMV titer. As a result, NYT had a therapeutic effect on MCMV-pneumonitis by decreasing the degree of inflammation mediated by the IFN-gamma-induced NO. It is also interesting to note that only two oral administrations of NYT had a therapeutic effect on viral disease.

Deficiency of inducible nitric oxide synthase exacerbates hepatic fibrosis in mice fed high-fat diet.

The role of inducible nitric oxide synthase (iNOS) in the progression of fibrosis during nonalcoholic steatohepatitis remains to be elucidated. This study examined the role of iNOS in the progression of fibrosis during steatohepatitis by comparing iNOS knockout (iNOS(-/-)) and wild-type (iNOS(+/+)) mice that were fed a high-fat diet. Severe fatty metamorphosis developed in the liver of iNOS(+/+) and iNOS(-/-) mice. Fibrotic changes were marked in iNOS(-/-) mice. Gelatin zymography showed that pro MMP-2 and pro MMP-9 protein expressions were more highly induced in iNOS(+/+) mice than in iNOS(-/-) mice. Active forms of MMP-2 and MMP-9 were clearly present only in the liver tissue of iNOS(+/+) mice. In situ zymography showed strong gelatinolytic activities in the liver tissue of iNOS(+/+) mice, but only spotty activity in iNOS(-/-)mice. iNOS may attenuate the progression of liver fibrosis in steatohepatitis, in part by inducing MMP-2 and MMP-9 expression and augmenting their activity.