ABSTRACT
To investigate biological characteristics of the IVpi-189 progeny virus derived from the culture of influenza A virus as a live-attenuated vaccine candidate. Persistent infection of a cultured cell line with influenza A virus (MDCK-IVpi) was established by incubating continuously influenza virus-infected cells at a lower temperature. The infectious progeny virus derived from MDCK-IVpi cells at the 189rd subculture was designated as the IVpi-189 strain of influenza virus. The cytopathic effect induced by IVpi-189 virus was observed under different temperature conditions. The production of infectious progeny virus was examined at 38 and 32 degrees C by plaque titration of cell-associated and released virus. IVpi-189 virus showed cytopathic effect as strong as that of IVwt in infected cell line of MDCK at 32 degrees C. However, when culture temperature was raised to 38 degrees C, the cytopathic effect induced by IVpi-189 virus was delayed and less pronounced. Virus growth in IVpi-189 virus-infected cells at 38 degrees C was significantly reduced as compared with that of IVwt virus, although both viruses yielded nearly equivalent high titers of cell-associated and released virus at 32 degrees C. The reasons of the decreased proliferative ability of IVpi-189 virus at high culture temperature were unrelated with virus inactivation or the release of progeny virus, but associated with the decreased replication of infectious progeny virus in the infected cells. IVpi-189 virus derived from MDCK cells infected persistently with influenza A virus showed biological characteristics as a potential live-attenuated vaccine candidate.
Subject(s)
Animals , Dogs , Humans , Cell Line , Cytopathogenic Effect, Viral , Influenza A virus , Genetics , Physiology , Temperature , Virus Cultivation , Methods , Virus ReplicationABSTRACT
Risk factors for developing hemolytic uremic syndrome among patients with enterohemorrhagic <i>Escherichia coli</i> O157: H7 (EHEC) infection include age. The young, especially those under the age of five, face an increased risk, as do the elderly. In the present study, we evaluated the protective effects of Hochu-ekki-to (HET) on intraperitoneal infection with EHEC, using immunosuppressant, dexamethasone (Dex)-treated mice.<br>It was found that HET induced improvement of Dex-induced leukopenia. Similarly, the IgM-plaque forming cell responses to sheep red blood cell (SRBC) were restored by the administration of HET to the normal-mice level in Dex-treated mice. Consequently, HET was administered orally into the Dex-treated mice before infection with EHEC to observe the therapeutic effect. With the oral administration of 500mg/kg/head of HET into the Dex-treated mice, prolonged survival was shown: the 50% survival time in the HET-administered mice was four days, compared with one day in the non-administered controls. In addition, the number of bacteria in the liver was reduced by the administration of HET in the Dex-treated mice.<br>The results indicate that orally administered-HET protects against EHEC infection in Dex-treated mice, and such protective effects appear to be due to the restorative effects of HET against the Dex-induced immunosuppression.