Effect of alphavirus infection on mouse embryos (original) (raw)

The Pathogenicity of the A7, M9 and L10 Strains of Semliki Forest Virus for Weanling Mice and Primary Mouse Brain Cell Cultures

Journal of General Virology, 1985

The multiplication of the M9, A7 and L10 strains of Semliki Forest virus (SFV), both in weanling mice and primary mouse brain cell cultures, was compared. Following both intraperitoneal (i.p.) and intracerebral (i.c.) injection, the virulent L10 strain multiplied to higher titre in the mouse central nervous system (CNS) than did the less virulent'M9 and A7 strains, whereas M9 multiplied to higher titre than A7. By the i.c. route, all three virus strains multiplied to higher titre than following i.p. injection. Multiplication of A7 and M9 in oligodendrocytes, but not neurons, was detected following i.c. injection. All three virus strains showed a tropism for cultured mouse glial cells rather than neurons. The L10 strain multiplied better in neurons than did A7 or M9. It is concluded that the mechanism of acute demyelination induced by the M9 and A7 strains is similar. Based on this and previous studies, it is proposed that infection of glial cells triggers immune-mediated demyelination. The virulence of the L10 strain is due to its ability to exceed a lethal threshold of damage to neurons before immune intervention can occur.

Infection of Cultured Early Mouse Embryos with Semliki Forest and Rubella Viruses

Journal of General Virology, 1986

Early mouse embryos at the four-to eight-cell stage or the blastocyst stage could be infected with the A7 strain of Semliki Forest virus (SFV) after the removal of the zona pellucida, either by Pronase treatment or following hatching of blastocysts. With SFV, rapid virus production and eventual cytolysis resulted from infection at either stage. For four-to eight-cell embryos the cytopathic effect was delayed and a proportion of embryos developed to the blastocyst stage. Four-and eight-cell embryos could not be infected with rubella virus (RV), even after removal of the zona pellucida. RV infection of zona-free blastocysts resulted in a productive but non-cytolytic infection which did not affect embryonic development to the early egg-cylinder stage. RV did not multiply in inner cell mass cells isolated from embryos at the blastocyst stage, although SFV did multiply in such cells. 0000-6974 © 1986 SGM

Multiplication of virulent and demyelinating Semliki Forest virus in the mouse central nervous system: consequences in BALB/c and SJL mice

Journal of General Virology, 1990

The sites of multiplication in the mouse central nervous system (CNS) of the virulent L10 strain of Semliki Forest virus (SFV) and the L10-SFV-derived demyelinating M9 mutant were determined using both BALB/c and SJL mouse strains. In situ hybridization (ISH), using a cRNA probe to an SFV non-structural sequence, and immunogold-silver staining (IGSS), using polyclonal anti-SFV rabbit IgG, were the techniques utilized. For L10-SFV, viral RNA and antigen were detected in neurons and glial cells of both mouse strains. For BALB/c mice infected with M9-SFV, both neuronal and glial cell infection was less extensive than that obtained with L10. ISH or IGSS were generally not sensitive enough to detect viral RNA and antigen, respectively, in M9-SFV-infected SJL mice. M9-SFV multiplied to a similar titre in primary cultures of glial cells derived from either BALB/c or SJL mice. Following infection with M9-SFV, small plaques of demyelination in the CNS and occasional small aggregates of mononuclear leukocytes in the leptomeninges persisted for up to 12 months in SJL mice but not BALB/c mice. This was not associated with detectable persistence of infectious virus, viral antigen or viral RNA in the CNS.

Molecular basis of Sindbis virus neurovirulence in mice

Journal of …, 1988

We examined a variety of strains of Sindbis virus for the genetic changes responsible for differences in neurovirulence in mice. SVlA (a low passage of the AR339 strain of Sindbis virus), a neuroadapted Sindbis virus (NSV), and two laboratory strains of Sindbis virus (HRSP and TotollOl) were examined. NSV causes severe encephalomyelitis with hind-limb paralysis and high mortality after intracerebral inoculation in weanling mice. In contrast, SV1A causes only mild, nonfatal disease in weanling mice; however, in suckling mice, SVlA causes a fatal encephalomyelitis after either intracerebral or subcutaneous inoculation. The two laboratory strains used have a greatly reduced neurovirulence for suckling mice and are aviruleit for weanling mice. The nucleotide sequences and encoded amino acid sequences of the structural glycoproteins of these four strains were compared. Hybrid genomes were constructed by replacing restriction fragments in a full-length cDNA clone of Sindbis virus, from which infectious RNA can be transcribed in vitro, with fragments froni cDNA clones of the various strains. These recombinant viruses allowed us to test the importance of each amino acid difference between the various strains for neurovirulence in weanling and suckling mice. Glycoproteins E2 and El were of paramount importance for neurovirulence in adult mice. Recombinant viruses containing the nonstructural protein region and the capsid protein region from an avirulent strain and the El and E2 glycoprotein regions from NSV were virulent, although they were less virulent than NSV. Furthermore, changes in either E2 (His-55 in NSV to Gln in SV1A) or El (Ala-72 in NSV to Val in SVlA and Asp-313 in NSV to Gly in SVIA) reduced virulence. For virulence in suckling mice, we found that a number of changes in E2 and El can lead to decreased virulence and that in fact, a gradient of virulence exists.

Pathogenesis of a Newly Isolated Rat Virus in Newborn and Juvenile Rats

Experimental Animals, 1991

The pathogenesis of the UT-1 strain, a newly isolated rat virus (RV), in juvenile and newborn rats was examined. Intracerebrally (ic) inoculated newborns developed severe pantropic infections resulting in emaciation, stunted growth, diarrhea, dehydration and icterus, and died 13 to 15 days after the inoculation. Newborns inoculated intraperitoneally (ip) developed similar, but milder diseases. The virus replicated in all the organs tested, which was followed by severe viremia. Histopathologically, diffuse vacuolation and necrosis of the hepatocytes were observed in the liver. Juvenile rats inoculated with the virus showed neither clinical signs nor histopathologic lesions, although viral recovery and antibody production were observed. Thus, we conclude that the UT-1 strain of RV caused asymptomatic infections in juvenile rats, and fatal infections with hepatic lesions in newborn rats. KEY WORDS : jovenile rat, newborn rat, pathogenesis, rat virus Rat virus (RV), a member of the family Parvoviridae, is one of the common viruses in laboratory rat colonies and often causes asymptomatic infections in adult rats, and severe diseases in fetal and newborn rats [1, 7, 11,14-16]. Little attention, however, has been paid to the RV infection in laboratory rat colonies in Japan, since there has been no information about it. We have isolated new RV strains in Japan from asymptomatic adult rats and have found the Japanese isolates to have hemagglutination patterns differing from those of the RV-13 prototype strain [5].

Semliki Forest virus neurovirulence mutants have altered cytopathogenicity for central nervous system cells

Infection and Immunity

We have analyzed the pathogenicity and host range properties of four neurovirulence mutants of Semliki Forest virus which, unlike the wild type (WT), allow the survival of weanling mice injected intraperitoneally with 102 PFU. The mutant M9 showed a sustained multiplication in the brains of infected mice. It produced paralysis in 35%, and 8% died. Demyelination occurred in 94% of the surviving mice and was associated with the destruction of oligodendrocytes. All of the mutants showed a restricted ability to multiply in BHK, C1300 (neuroblastoma), and G26-24 (oligodendroglioma) cells as compared with the WT, and this was not associated with differential interferon production or action. C1300 cells infected with the mutants survived, whereas WT-infected cells were killed. In G26-24 cells all of the mutants and the WT produced a rapid cytopathic effect which was inhibited by pretreatment with 10 U of mouse interferon. Extensive RNA synthesis was detected for all of the mutants and the WT in BHK and C1300 cells, but it was only detectable in G26-24 cells in small amounts early in the infection. The mutant M4 had a defect in the nucleocapsid assembly, whereas M9 had a defect in total RNA synthesis. M136 was defective in the synthesis of 26S RNA, and M103 showed defective synthesis of viral core protein in C1300 cells. It is concluded that C1300 cells can tolerate viral RNA synthesis by a defective virus without showing a cytopathic effect, but the fully virulent WT virus is cytopathic. G26-24 cells are sensitive to small amounts of viral RNA synthesis. These properties of the WT and mutant viruses correlate with changes produced in the neurons and oligodendrocytes of the central nervous system: the virulence of the WT is due to its ability to destroy both neurons and oligodendrocytes, whereas the demyelination produced by the mutants M9 and M136 is due to the destruction of oligodendrocytes alone.