Neurovirulence and neuroinvasiveness of Murray Valley encephalitis virus mutants selected by passage in a monkey kidney cell line

• Published in: Journal of general virology 1995-04, Vol.76 (4), p.865-872
• Main Authors: McMinn, P. C, Marshall, I. D, Dalgarno, L
• Format: Article
• Language: English
• Subjects: Aedes - cytology; Animals; Brain - virology; Cell Fusion; Cell Line; Cercopithecus aethiops; Encephalitis Virus, Murray Valley - isolation & purification; Encephalitis Virus, Murray Valley - pathogenicity; Encephalitis, Arbovirus - virology; Hemagglutination; Hydrogen-Ion Concentration; Mice; Murray Valley encephalitis virus; Mutagenesis; Sequence Analysis, DNA; Tumor Cells, Cultured; Vero Cells; Virulence
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/0022-1317-76-4-865

Division of Biochemistry and Molecular Biology, School of Life Sciences, Faculty of Science, Australian National University, Canberra ACT 0200, Australia Variants of the prototype Murray Valley encephalitis virus (MVE-1-51) were selected by serial plaque purification and amplification in monkey kidney (Vero) cells. Four clones (C1–C4) at passage levels two and nine (P2 and P9) were examined in 21-day-old Swiss outbred mice for neuroinvasiveness (assessed from LD 50 values after intraperitoneal inoculation) and neurovirulence (LD 50 values after intracranial inoculation). The growth characteristics of the clones were determined in intracranially inoculated mouse brain and in mouse neuroblastoma, Vero and mosquito (C6/36) cell lines. Genomic RNA of the cloned virus stocks was sequenced through the structural protein genes (E, prM/M and C) and the 5' untranslated region. Clone C2P2 was of high neuroinvasiveness whereas C2P9 was of low neuroinvasiveness; there were also decreased yields of C2P9 in C6/36 cells compared to C2P2 and MVE-1-51. These changes were associated with the substitution of valine for phenylalanine at amino acid position 141 of the C2P9 E protein. Clone C4P2 was of high neurovirulence and low neuroinvasiveness; C4P9 was of low neurovirulence, a change accompanied by a further reduction in neuroinvasiveness. Concomitantly, C4P9 showed a pronounced reduction in growth rates and yields in 21-day-old Swiss mouse brain, in mouse neuroblastoma cells and in C6/36 cells compared to parental virus. The phenotypic changes in clone 4 appear to be due to mutation(s) within non-structural protein genes. * Author for correspondence. Present address: Department of Microbiology, Prince of Wales Hospital, High Street, Randwick, NSW 2031, Australia. Fax [phone]. Received 31 August 1994; accepted 7 December 1994.