Molecular characterization of M1146, an American isolate of Ljungan virus (LV) reveals the presence of a new LV genotype.

Ljungan virus (LV) is a suspected human pathogen recently isolated from bank voles in Sweden. This study describes the genetic characterization of a virus, M1146, which was isolated in 1962 from another vole species (Microtus montanus), trapped in Oregon, USA. Based on antigenic properties, M1146 was postulated previously as a putative member of the family PICORNAVIRIDAE: The near complete genomic sequence verifies that M1146 is a member of the Picornaviridae, most closely related to LVs isolated in Sweden. The strain M1146 possesses typical LV genomic organization, including a cluster of two 2A homologues. There are significant differences throughout the capsid protein region, while the non-structural region of M1146 is closely related to the Swedish LV genomes. Genetic and phylogenetic analyses show that M1146 represents a new genotype within the distinct LV cluster. Isolation of LV from both Swedish and American voles trapped over a period of 30 years suggests a continuous worldwide presence.