Genetic diversity accelerates canine distemper virus adaptation to ferrets

Area of Science:

• Virology
• Evolutionary Biology
• Host-Pathogen Interactions

Background:

• RNA viruses rapidly adapt to new hosts via quasispecies, generating diverse genomes.
• Minor genetic variants drive adaptation, leading to drug resistance and immune escape.
• Understanding viral adaptation is crucial for assessing cross-species transmission risks and vaccine/antiviral efficacy.

Purpose of the Study:

• To investigate the role of genetic memory in viral adaptation to new host environments.
• To compare the adaptation of a standard attenuated virus with a genetically engineered derivative in ferrets.

Main Methods:

• Passaging of an attenuated canine distemper virus (CDV) and its recombinant derivative through ferrets.
• Comparative analysis of viral genomes, mutation frequencies, and disease onset between the two virus groups.
• Identification of specific mutations and their contribution to pathogenesis.

Main Results:

• Both viruses adapted to ferrets, but the recombinant virus with reduced genetic diversity showed delayed disease onset.
• The non-recombinant virus utilized pre-existing low-frequency mutations for adaptation, while the recombinant evolved *de novo* mutations.
• A shared arginine mutation at position 519 in the nucleoprotein was identified as contributing to pathogenesis in ferrets.

Conclusions:

• Genetic diversity and pre-existing mutations ('genetic memory') facilitate rapid viral adaptation to new hosts.
• Genetic engineering that reduces initial diversity can delay adaptation and alter evolutionary pathways.
• Findings underscore the importance of genetic diversity for viral adaptation and inform the safety of live-attenuated vaccine development.