Differences in fusogenicity and mouse neurovirulence of Japanese encephalitis viruses.
The fusogenic capacity in AP-61 cell monolayers of 10 strains of Japanese encephalitis (JE) virus from different geographic locations was compared. One strain, isolated from Beijing (JE-Bei), did not fuse AP-61 cells after replication (fusion from within; FFWI), whereas all other strains fused these cells by 72 h post-infection. JE-Bei also readily established a non-cytolytic persistent infection in AP-61 cells. Differences in the envelope proteins of fusogenic and non-fusogenic virus were detected by haemagglutination-inhibition tests and by antigenic analysis using monoclonal antibodies. Yields of infectious virus in either AP-61 or Vero cell cultures were similar if JE-Bei was compared with the fusogenic strain (JE-Sar) but yields of haemagglutinin were 50-100 fold higher with the non-fusogenic virus, implying excessive generation of non-infectious particles. When added directly to AP-61 cell monolayers at pH6, only JE-Bei produced significant fusion from without (FFWO) presumably reflecting the larger quantity of antigen. Cell monolayers persistently infected with JE-Bei or monolayers treated with UV-inactivated JE-Bei, were resistant to superinfection with JE, West Nile and dengue 2 viruses but were susceptible to infection with the alphavirus Sindbis. When administered intracerebrally (I/C) to newborn and weanling mice, the viruses were equally neurovirulent. However, fusogenic JE-Sar was significantly more neurovirulent than JE-Bei for weanling mice after intraperitoneal (I/P) or subcutaneous (S/C) inoculation. Mice given non-fusogenic JE-Bei, resisted the peritoneal challenge with fusogenic JE-Sar, and West Nile but not Semliki Forest virus when given 6 h after the first virus. The potential significance of cell fusion by JE virus and interference through over production of non-infectious virus, is discussed in the context of JE virus virulence.
Higgs
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NERC Institute of Virology and Environmental Microbiology, Oxford, England.
Gould
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D000330:Aedes; D000818:Animals; D000956:Antigens, Viral / Q000276:immunology; D001921:Brain / Q000382:microbiology; D002459:Cell Fusion; D002460:Cell Line; D003465:Culex / Q000382:microbiology; D004664:Encephalitis Virus, Japanese / Q000302:isolation & purification / Q000472:pathogenicity*; D004672:Encephalitis, Japanese / Q000382:microbiology*; D006386:Hemagglutination Tests; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D013045:Species Specificity; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000378:metabolism; D014762:Viral Interference; D010948:Viral Plaque Assay
D000956:Antigens, Viral; D014759:Viral Envelope Proteins