The pre membrane and envelope protein is the crucial virulence determinant of Japanese encephalitis virus

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• Japanese encephalitis virus (JEV) causes severe neurological disease.
• The JEV vaccine strain SA14-14-2 exhibits reduced virulence compared to wild-type (WT) SA14.
• Amino acid mutations in the pre-membrane (prM) and envelope (E) proteins are suspected to cause this attenuation, but experimental evidence is limited.

Purpose of the Study:

• To investigate the role of the prM/E proteins as critical neurovirulence determinants of JEV.
• To experimentally validate the contribution of prM/E mutations to JEV vaccine strain attenuation.

Main Methods:

• Utilized infectious cDNA clones of JEV.
• Performed reciprocal genetic exchange of the prM/E genes between the WT SA14 and vaccine SA14-14-2 strains.
• Assessed the neurovirulence of the resulting JEV constructs in vivo.

Main Results:

• Replacing the vaccine strain's prM/E genes with those from the WT strain significantly increased JEV virulence to WT levels.
• Conversely, replacing the WT strain's prM/E genes with those from the vaccine strain significantly decreased JEV virulence to vaccine levels.
• These findings strongly implicate the prM/E proteins as major determinants of JEV neurovirulence.

Conclusions:

• The prM/E protein complex is a crucial determinant of Japanese encephalitis virus neurovirulence.
• While other viral proteins may contribute to a lesser extent, prM/E plays a primary role in modulating JEV virulence.
• This research provides critical experimental evidence for the mechanism of JEV vaccine strain attenuation.