Phagocytosis of splenetic neutrophils of mice enhanced by orally administered peptidoglycan from Bifidobacterium thermophilum.

A preparation of peptidoglycan (PG) of swine Bifidobacterium thermophilum was orally administered to SPF-BALB/C and ICR mice and its effect on phagocytosis splenetic neutrophils from PG administered mice was measured by chemiluminescent response (CL) and fluorometric analysis and the result was compared with that of non-treated mice. PG stimulated phagocytosis of neutrophils in a dose-dependent manner, whereas dosage exceeding the optimum concentration (500 microgram) inhibited phagocytosis. The maximum effect on phagocytosis of neutrophils was observed at 3 days after administration of PG 500 microgram. The result of fluorometric analysis was almost similar to that of CL. These results indicate that orally administered PG enhances the activity of the phagocytosis of splenetic neutrophils from mice.

Characterization of DBT cell clones derived from cells persistently infected with the JHM strain of mouse hepatitis virus.

Twelve clones derived from the cells persistently infected with the JHM strain (JHMV) of mouse hepatitis virus (MHV) were established from mouse astrocytoma-derived DBT cells and characterized. All the cell clones were resistant to superinfection with MHV. Only one of the persistently infected cell clone synthesized viral RNA and proteins and produced virus particles. Viral RNA was detectable in some other cell clones without production of viral protein nor the virus. No cell clones exhibited contact fusion activity. The results suggested that such variety of cell clones might have resulted from persistent infection with JHMV.

Inhibition of viral multiplication in cells chronically infected with mouse hepatitis virus by antisense RNA against the polymerase gene.

Recently, we showed that the antisense RNA containing a hammerhead ribozyme sequence against the polymerase gene of mouse hepatitis virus (MHV) inhibited viral multiplication in acute infection [10]. In the present study, we examined the inhibitory effects of an antisense RNA on viral multiplication in chronic MHV infection. In cell line LR-2, in which the 926-nucleotide (nt) antisense RNA containing a ribozyme sequence against the polymerase gene was expressed constitutively at a high level, chronic MHV infection was established through the maintenance of infection over 100 days postinfection (d.p.i.). After 200 d.p.i., no infectious progeny virus was observed in the culture medium of chronically MHV infected LR-2 cells. Our present results showed that the anitsense RNA could also inhibit viral multiplication in chronic MHV infection.

Changes in the nucleosomal structure of the Marek's disease virus genome in lymphoblastoid cell line MDCC-MSB1 induced by 5-azacytidine.

Marek's disease virus (MDV) DNA in latently infected lymphoblastoid cell lines is considerably methylated. Treatment of the MDV-derived lymphoblastoid cell lines MDCC-MSB1 (MSB1) and MDCC-RP1 (RP1) with 5-azacytidine (5-AzC) results in hypomethylation of MDV DNA. An increase in mRNA from certain portions of MDV DNA, including the BamHI-H region, was observed in 5-AzC-treated MSB1 cells, but not in the agent-treated RP1 cells. After the treatment of cells with 5-AzC, a site hypersensitive to digestion with DNaseI appeared in the BamHI-H region of MDV DNA in MSB1 but not in RP1. These results suggested that the enhancement of mRNA synthesis by 5-AzC is associated with changes in the nucleosomal structure of MDV DNA in lymphoblastoid cell line MSB1.

Inhibition of viral multiplication in acute and chronic stages of infection by ribozymes targeted against the polymerase gene of mouse hepatitis virus.

Two hammerhead ribozymes targeted against the polymerase gene of mouse hepatitis virus (MHV), which consisted of 22-nucleotide (nt) ribozyme core sequences and antisense sequences of different lengths, 243-nt (S-ribozyme) and 926-nt (L-ribozyme), were tested for their++ inhibitory effects on viral multiplication. Vectors that expressed the ribozymes were transfected into mouse DBT cells and several resulting cell lines constitutively expressing the ribozymes were selected and examined for intracellular MHV multiplication in acute and chronic stages of infection. The production of infectious progeny viral particles was significantly reduced in the transfected cell lines expressing either the S-ribozyme or L-ribozyme in acute infection. Although the in vitro cleavage process of the L-ribozyme was slower than that of the S-ribozyme, no difference was observed in inhibitory effects on MHV multiplication between S- and L-ribozymes in the transfected cells. In the transfected cells expressing L-ribozymes, production of viral particles was also inhibited in the chronic stage of MHV infection.

Enhancement of cytotoxic activity of lymphocytes in mice by oral administration of peptidoglycan (PG) derived from Bifidobacterium thermophilum.

A preparation of peptidoglycan (PG) of Bifidobacterium thermophilum (B. thermophilum) of swine was orally administered to SPF-C57BL/6CrSlc mice in order to confirm the enhancement of the cytotoxic activity of natural killer cells (NK), intraperitoneal cytotoxic T lymphocytes (CTL) and lymphocytes stimulated by concanavalin A (Con A-stimulated lymphocytes). The NK cells from the spleen and the mesenteric lymph node (MLN) of mice that were continuously fed with PG-mixed feed for three weeks showed a significantly higher rate of cytolysis than those from the control group. However, a single oral administration of PG had no significant effect on NK activity. The activity of peritoneally sensitized CTL of the mice that were continuously fed with PG-mixed feed was assayed. The PG-mixed feed administered group showed a higher CTL activity than that of the control group. The cytotoxic activity of Con A-stimulated lymphocytes in the PG-mixed feed administered group was higher than that of the control group. These results indicate that the cytotoxic activity of mice was enhanced by orally administered PG.

Targeted pituitary tumorigenesis using the human thyrotropin beta-subunit chain promoter in transgenic mice.

We have generated transgenic mice that express the simian virus 40 (SV40) large T antigen under the control of a 1109 bp 5'-flanking sequence of the human thyrotropin beta-subunit (TSH beta) gene. The hybrid gene, termed TTP-1, was microinjected into fertilized mouse eggs and 11 transgenic mice were obtained. One of the transgenic mice, a female, a phenotypical dwarf, developed a pituitary tumor and wasted away from 7 to 9 weeks after birth. To establish the transgenic mouse line, her ovaries were transferred to a normal female, whose ovaries were removed beforehand. To examine the tissue specificity of transgene expression, mRNA of SV40 large T antigen was monitored in various tissues from the transgenic mice by the reverse transcriptase-polymerase chain reaction analysis, and was detected only in the pituitary. Histological and immunohistochemical analyses showed that the pituitary tumors of the transgenic mice were composed of poorly differentiated pituitary cells expressing SV40 large T antigen. These results indicated that the 1109 bp sequence of the human TSH beta 5'-flanking region is essential for pituitary-specific expression of SV40 large T antigen in transgenic mice, which exhibited a dwarf phenotype and developed pituitary tumors. The tumors were composed of undifferentiated cells and did not produce thyrotropin. These transgenic mice should provide a valuable animal model for studying the pathogenesis of anterior pituitary tumors.

In vivo and in vitro transcription of small mRNAs containing a leader sequence from mouse hepatitis virus strain JHM.

Two additional small RNAs, named mRNA8 and 9, are transcribed from mouse hepatitis virus (MHV) in virus-infected mouse DBT cells. This report shows that the small mRNAs (mRNA8 and 9) were observed at 3 hr post infection (p.i.) in DBT cells infected with the JHM strain of MHV. This result suggested that products from mRNA8 and 9 may play a role in the early stage of the viral replication cycle in the infected DBT cells. The mRNA8 is initiated from a perfectly conserved intergenic site, but mRNA9 is from an imperfectly conserved intergenic sequence. Since mRNA8 and 9 were found in the liver and brain of an infected mouse, it was suggested that the imperfect intergenic sequence of MHV may serve as an initiation site for leader-primed transcription in vivo.

Inhibition of viral multiplication by hammerhead ribozymes targeted against the polymerase gene of mouse hepatitis virus.

We designed and constructed two hammerhead ribozymes targeted against the polymerase gene of mouse hepatitis virus (MHV). They consisted of a 22-nucleotide (nt) ribozyme core sequence and antisense sequences of different lengths, 243-nt (S-ribozyme) and 926-nt (L-ribozyme). In cell-free reactions, the constructed ribozymes cleaved the target RNA at a specific site. Vectors that directed the expression of ribozymes by a promoter of human elongation factor 1 alpha were introduced into DBT cells, and the resulting several cell lines constitutively expressing the ribozymes were selected by Northern blot analysis and examined for intracellular multiplication of MHV. The production of infectious progeny virus particles was significantly reduced in the transfected cell lines expressing either S-ribozyme or L-ribozyme. Although the in vitro cleavage process of L-ribozyme was slower than that of S-ribozyme, no difference was observed in inhibitory effects on MHV multiplication between S- and L-ribozymes in the transfected cells.

The inhibitory effects of MgSO4 on the multiplication and transcription of mouse hepatitis virus.

The multiplication of mouse hepatitis virus (MHV) was inhibited by the treatment of infected cells with MgSO4 at concentrations higher than 50 mM. The inhibition of viral multiplication was more effective with the treatment of cells at the early stage of infection using MgSO4 than at the late stage. Viral adsorption to the cells was not inhibited by MgSO4 and pretreatment of the cells with MgSO4 did not show an inhibitory effect on the RNA synthesis of MHV. The synthesis of viral RNA was inhibited more effectively by the treatment of infected cells with MgSO4 at 0-2 and 2-4 h postinfection (p.i.) than at 4-6 h p.i. The present study suggests that the stage at which viral multiplication is susceptible to MgSO4 may be the early stage of viral transcription and that Mg2+ may be a useful tool for the analysis of the early stage of MHV infection.

A high frequency of induction of chromosome aberrations in the bone marrow cells of LEC strain rats by X-irradiation.

LEC strain rats, which have been known to develop hereditarily spontaneous fulminant hepatitis 4 to 5 months after birth, are highly sensitive to whole-body X-irradiation when compared to WKAH strain rats. The present results showed that the frequencies of all types of chromosome aberrations induced by X-irradiation in the bone marrow cells of LEC rats were approximately 2- to 3-fold higher than those of WKAH rats, though no significant difference was observed in the frequency of spontaneous chromosome aberrations between LEC and WKAH rats.

Enhanced resistance of mice to Escherichia coli infection induced by administration of peptidoglycan derived from Bifidobacterium thermophilum.

Peptidoglycan (PG) of Bifidobacterium thermophilum (B. thermophilum) from swine were orally administered to SPF-ICR mice in order to confirm the enhancement of the defence activity of the mice against Escherichia coli (E. coli) infection. It was found that the survival rates of the PG-administered group were significantly higher than those of the non-treated control group after the single oral administration of PG. And the proper concentration at which PG enhanced defence activity most effectively was found to be 500 micrograms per mouse. The number of E. coli in the peripheral blood, liver and spleen of the PG-administered group at 24 hr after the inoculation was significantly smaller than that in the control group. Liver weight per body weight in the PG treated group significantly increased in comparison with that of the non-treated group. The number of blastoid plasmacytes in the spleen of the PG-administered mice was found to be greater than that in the control group. These results indicate that the defence activity of mice against E. coli infection was accelerated by PG treatment.

Enhancement of mRNA synthesis from Marek's disease virus genome in the lymphoblastoid cell line, MDCC-MSB1, by 5-azacytidine.

Marek's disease virus (MDV) DNA in latently infected lymphoblastoid cell lines is considerably methylated. A treatment of the MDV-derived lymphoblastoid cell line, MDCC-MSB1 (MSB1), with 5-azacytidine (5-AzC) resulted in a hypomethylation of MDV DNA and an increase in mRNA from certain portions of the MDV DNA. These results suggest methylation of MDV DNA as being one of the factors associated with a repression of transcription of MDV DNA in the lymphoblastoid cell line, MSB1.

Both antisense and sense RNAs against the nucleocapsid protein gene inhibit the multiplication of mouse hepatitis virus.

DBT cells and several transfected cell lines which express antisense or sense RNA against the nucleocapsid protein gene of mouse hepatitis virus (MHV) were examined for the yields of MHV. The transfected cells showed 95 and 99% reduction of virus yield at 9 and 12 hr postinfection (p.i.) as compared with untransfected DBT cells. A remarkable decrease in MHV-specific RNA synthesis was observed in both transfected cell lines at 3.5 hr p.i. The result suggested that both antisense and sense RNAs inhibited viral replication at the initial stage of infection.

Radiation hypersensitivity of LEC strain rats controlled by a single autosomal recessive gene.

LEC strain rats (LEC rats), which are known to develop hereditarily spontaneous fulminant hepatitis 4-5 months after birth, were highly sensitive to whole-body X-irradiation when compared to WKAH strain rats. The radiosensitivity of F1 hybrids of LEC and WKAH rats was similar to that of WKAH rats and significantly lower than that of LEC rats. Segregation data of backcross hybrids (F1 x LEC and LEC x F1) suggested that the hypersensitivity of LEC rats to whole-body irradiation is controlled by a single autosomal recessive gene. The radiosensitivity of fibroblasts from LEC rats was higher than that of fibroblasts from WKAH rats. The repair process of DNA double-strand breaks in LEC cells was slower than that in WKAH cells. LEC rats could provide a useful animal model to assist in understanding the mechanism of radiation-induced DNA damage and repair.

Transgenic mice with antisense RNA against the nucleocapsid protein mRNA of mouse hepatitis virus.

In this study transgenic mice which expressed antisense RNA against the nucleocapsid protein gene of mouse hepatitis virus (MHV) under the control of RSV LTR were produced. These transgenic mice were able to transmit the foreign gene to their progeny in a Mendelian fashion. Antisense RNA was detected in various tissues from the transgenic mice including liver and brain, the target organs of MHV infection. One strain of transgenic mice derived from founder mouse No. 19 was more resistant to the lethal challenge of MHV than non-transgenic mice. The results of the present study show the ability of antisense RNA against the viral gene to protect against viral infection in vivo.

High level expression of human alpha-fetoprotein in transgenic mice.

Transgenic mice were produced by the microinjection of the cDNA of human alpha-fetoprotein (AFP) under control of the enhancer/promoter of the human beta-actin gene. Among the 4 mouse lines where the transgene were stable transmitted to the progeny, 3 produced human AFP. The expression was not developmental stage-specific nor tissue-specific as predicted from the properties of enhancer/promoter. The serum human AFP levels of adult mice were 30-600-fold higher than those of mouse AFP. These mice could be useful for the studies of possible biological functions of AFP during development as well as in malignancies.

Hypersensitivity of LEC strain rats in radiation-induced acute bone-marrow death.

LEC strain rats, which have been known to develop hereditarily spontaneous fulminant hepatitis 4 to 5 months after birth, were highly sensitive to whole-body X ray-irradiation as compared to WKAH strain rats. Radiation-induced acute bone-marrow death occurred at doses higher than 2.0 Gy in LEC rats, and at doses higher than 7.4 Gy in WKAH rats, respectively. By probit analysis of survival data, it was shown that the LD50/30 value for LEC rats was 3.0 Gy which was significantly lower than that (7.8 Gy) of WKAH rats. Histopathological examinations of the bone marrows from both strains after irradiation at a dose of 4.0 Gy revealed that a number of hemopoietic cells were recovered in WKAH rats on day 8 after irradiation, but not in LEC rats. These results suggested the hypersensitivity of LEC rats to ionizing radiation in connection with acute bone-marrow death.

Inhibition of mouse hepatitis virus multiplication by antisense oligonucleotide, antisense RNA, sense RNA and ribozyme.

Antisense nucleic acids against specific sequences of mouse hepatitis virus (MHV)-RNAs were tested for their inhibitory effects on viral multiplication in mouse DBT cells. An antisense oligonucleotide containing a sequence complementary to leader RNA was synthesized and shown to induce a significant inhibitory effect on the multiplication of MHV-JHM. A vector which expressed the antisense or sense mRNA7 of MHV was transfected into DBT cells. A decreased multiplication of MHV was observed in both cell lines. The transfected cell line which expressed ribozyme against the 5'-end of the MHV genome was established. The rate of inhibition of MHV-multiplication and the quantity of synthesized virus-specific mRNAs in this transfected cell line were the same for both antisense and sense RNA. These results show that antisense nucleic acids might be eligible for use as antiviral agents against MHV multiplication.