Genetic and Phenotypic Characterization of a Rabies Virus Strain Isolated from a Dog in Tokyo, Japan in the 1940s

Abstract

The rabies virus strain Komatsugawa (Koma), which was isolated from a dog in Tokyo in the 1940s before eradication of rabies in Japan in 1957, is known as the only existent Japanese field strain (street strain). Although this strain potentially provides a useful model to study rabies pathogenesis, little is known about its genetic and phenotypic properties. Notably, this strain underwent serial passages in rodents after isolation, indicating the possibility that it may have lost biological characteristics as a street strain. In this study, to evaluate the utility of the Koma strain for studying rabies pathogenesis, we examined the genetic properties and in vitro and in vivo phenotypes. Genome-wide genetic analyses showed that, consistent with previous findings from partial sequence analyses, the Koma strain is closely related to a Russian street strain within the Arctic-related phylogenetic clade. Phenotypic examinations in vitro revealed that the Koma strain and the representative street strains are less neurotropic than the laboratory strains. Examination by using a mouse model demonstrated that the Koma strain and the street strains are more neuroinvasive than the laboratory strains. These findings indicate that the Koma strain retains phenotypes similar to those of street strains, and is therefore useful for studying rabies pathogenesis.

Point Mutations in the Glycoprotein Ectodomain of Field Rabies Viruses Mediate Cell Culture Adaptation through Improved Virus Release in a Host Cell Dependent and Independent Manner

“…In cell culture, the broad panel of non-neuronal cell lines susceptible to laboratory RABV strains indicates the existence of more ubiquitous receptors, which support virus infection. Since field RABV isolates usually replicate poorly in cell culture [13,14], many cell culture-based approaches in RABV research include fixed viruses, which are adapted for improved replication by serial passages either in cell culture or non-natural host animals.…”

Establishment of a reverse genetics system for rabies virus strain Komatsugawa

“…The RABV strain Komatsugawa is the only existent Japanese street strain, which was isolated from a dog in Tokyo in the 1940s before eradication of rabies in Japan in 1957. Phylogenetic analyses previously revealed that this strain belongs to the Arctic-like clade [ 11 , 13 , 23 ], of which street strains have barely been characterized phenotypically. We recently demonstrated by comprehensive phenotypic analyses that, even though the Komatsugawa strain has experienced 19 brain-to-periphery passages in guinea pigs and more than 20 intracerebral passages in mice after the original isolation from a dog [ 19 ], this strain retains biological phenotypes including viral virulence that are similar to those of the representative street strains RABV-Dog and 1088 [ 23 ].…”

“…To construct a full-length genome plasmid of the Komatsugawa strain, a total of five cDNA fragments (1.5–3.8 kb in length) that collectively cover the whole viral genome (11,927 nt) were amplified by reverse transcription (RT)-polymerase chain reaction (PCR) from genomic RNA extracted from a wt Koma stock prepared in previous study [ 23 ]. These cDNA fragments were assembled on a pUC19 plasmid vector by stepwise cloning.…”