Multigenic relation to the attenuation of rabies virus

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• The Nishigahara strain of rabies virus causes lethal infections in adult mice after intracerebral inoculation.
• The RC-HL strain, derived from the Nishigahara strain, exhibits an attenuated phenotype, failing to cause lethal infections in adult mice.
• Previous studies showed a chimeric virus R(G) (Nishigahara G-ORF in RC-HL background) was virulent, suggesting the G gene's role.

Purpose of the Study:

• To investigate the role of the G gene from the attenuated RC-HL strain in rabies virus virulence.
• To determine if the G gene of the RC-HL strain is the sole determinant of its attenuated phenotype.
• To identify the genetic basis of attenuation in the RC-HL rabies virus strain.

Main Methods:

• Established a reverse genetics system for the Nishigahara strain.
• Generated chimeric viruses by swapping open reading frames (ORFs) of specific genes (G, N, P, M, L) between Nishigahara and RC-HL strains.
• Inoculated adult mice intracerebrally with wild-type and chimeric viruses to assess virulence and neuropathic symptoms.

Main Results:

• A chimeric virus Ni(G) (RC-HL G-ORF in Nishigahara background) was virulent, indicating the G-ORF alone from RC-HL does not confer attenuation.
• Chimeric viruses containing only a single gene (G, N, P, M, or L) from the RC-HL strain were not attenuated.
• Chimeric viruses with the G-ORF and at least one additional ORF from the RC-HL strain exhibited attenuation.

Conclusions:

• The attenuated phenotype of the RC-HL rabies virus strain is not solely determined by its G gene.
• Attenuation is a multigenic trait, requiring the combined contribution of multiple genes from the RC-HL strain.
• Understanding the genetic basis of rabies virus attenuation is crucial for developing safer vaccine strains.