Characterisation and phylogenetic analysis of Murray Valley encephalitis virus (MVEV) from the Ralph Doherty collection.

Murray Valley encephalitis virus (MVEV) is a zoonotic flavivirus endemic to Australia and Papua New Guinea. A recent outbreak of MVEV has prompted renewed concerns regarding the potential for MVEV to generate disease outbreaks. Currently, nine full length sequences of MVEV are publicly available, divided into four genotypes (G1-G4). Herein, we sequenced MVEV isolates from the Ralph Doherty Virus Collection, a virus bank with Australian field isolates dating between the 1950s-1980s, and determined their phylogenetic relationship with existing isolates to provide insights into virus evolution and genetic diversity. Additionally, we characterised isolates from different genotypes both in vitro using human neuronal cells, and in vivo using C57BL/6J mice, to provide additional insight into MVEV pathogenicity and establish models of MVEV disease that recapitulate MVEV human disease. We found 15 new full length sequences of MVEV, which primarily clustered into the dominant genotype, G1. Additionally, we show MVEV can be lethal and neuroinvasive in C57BL/6J mice, recapitulating histological lesions identified in human infection. Overall, our study contributes significant genomic sequences to the current MVEV database and establishes mouse models of disease and infection which can be used for mechanistic studies and evaluation of new interventions.