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The isolation and characterisation of viral agents from the central nervous system of cats

Flower, Robert Lewis Powell (1988) The isolation and characterisation of viral agents from the central nervous system of cats. PhD thesis, Murdoch University.

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The thesis describes the isolation and characterisation of viral agents from the central nervous system (CNS) of cats, and an investigation of the prevalence of antibody to the agents isolated from the CNS, and to paramyxoviruses, 1n sera from randomly selected cats and from cats with demyelinating lesions.

Inclusions in demyelinating lesions in the CNS of cats contained tubular structures that were morphologically similar to paramyxovirus nucleocapsids. Virus isolates were obtained using a cocultivation technique, similar to that previously used to recover paramyxoviruses from persistent infections of the CNS; measles virus from the CNS of patients with subacute sclerosing panencephalitis, and canine distemper virus from CNS of dogs with old dog encephalitis. In this study, explant cultures of cat CNS tissue were established and subsequently cocultured with Vero and Crandell feline kidney cell lines. Three types of agent were isolated: feline panleukopenia virus, feline syncytia forming virus (FeSV), and an non-cytopathic virus-like agent which produced cytoplasmic inclusions, containing paramyxovirus nucleocapsid-like structures, in cocultered cells. The morphology of the paramyxovirus nucleocapsid-like structures in the cocultured cell s closely resembled the morphology observed i n inclusions found in areas of demyelination in the CNS of cats.

The feline panleukopenia viral isolates were not studied further, as feline panleukopenia virus is well characterised, and production of demyelinating lesions of this type in adult cats infected with panleukopenia virus has not been reported.

The FeSV isolates were shown to have physico-chemical characteristics typical of those previously described for these agents, and were shov/n to have a wide host range in vitro. Three antigenic types of FeSV were differentiated on the basis of a serum neutralisation test. A serological survey demonstrated that FeSV was widespread in the cat population and provided evidence of a change in the prevalence of infection with the major serotypes over a four year period. Mice infected with FeSV developed a persistent infection. No demyelinating lesions or neurological signs were observed in FeSV-infected mice. The prevalence of antibody to FeSV was similar in cats with demyelinating lesions and in randomly selected cats, no structures similar to those present in the CNS of cats v/ith demyelinating lesions were detected in FeSV infected cells, and no demyelinating lesions were detected in mice inoculated with FeSV. These negative findings suggested that FeSV was unlikely to be a primary aetiological agent of the demyelinating condition described in cats.

Two cocultured cell lines designated CCA147 and MV631, derived from CMS explants cocultured with Vero and CRFK cells respectivly, were studied in detail. No evidence of a lytic cytopathic effect was observed in these cells, and there was no evidence of budding or conclusive evidence of haernadsorption. Attempts to induce a lytic cytopathic effect by fusion of CCA147 and MV631 cell lines with cells susceptible to paramyxovirus infection, or by inhibition of DNA synthesis, were unsuccessful. CCA147 and MV631 cells reacted differently with lectins and the possibility that this altered reactivity reflects changes in the membrane is discussed. The susceptibility of CCA147 and MV631 cells to infection v/ith other viruses (measles virus and FeSV) was reduced. Similar reductions in sensitivity to infection have previously been reported in cells persistently infected v/ith paramyxoviruses. Antisera produced to CCA147 and to MV631 cells, and extensively absorbed with normal cell antigens. specifically reacted in an immunoperoxidase test with the nucleocapsid-1ike structures in these cells and also stained tubular structures in measles virus-infected Vero cells. These antisera reacted in an ELISA test with measles virus-infected Vero cells, but not normal Vero cells.

Antisera to measles virus and canine distemper virus reacted weakly with CCA147 and MV631 cells. These results suggested that the agent present in CCA147 and MV631 cells may be antigenically related to paramyxoviruses of the morbi11ivirus group.

Neurological signs and dernyelinating lesions occurred in some strains of mice after intracerebral infection with viable CCA147 cells. Inclusions containing nucleocapsid-1ike structures, resembling those observed in CCA147 and MV631 cells and in the CNS of cats, were detected within inclusions in lesions in the CNS of infected mice.

A serological survey for antibody to paramyxoviruses in cats provided evidence of antibody to the Sendai strain of parainfluenza virus type 1, to parainfluenza viruses type 2 and 3, mumps virus, respiratory syncytial virus and measles virus. There was an association between the occurrence of dernyelinating lesions in cats and the detection of antibody to measles virus, there was also an association between detection of antibody to measles virus and detection of antibody to the structures present in CCA147 and MV631 cells.

The results obtained in this study provide indirect evidence that CCA147 and MV631 cells were persistently infected with a virus-like agent derived from the CNS of cats, that the agent is possibly antigenically related to paramyxoviruses of the rnorbi 11 ivirus group and that this agent may be involved in the production of dernyel inating lesions.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary Studies
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Wilcox, Graham
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