Adaptation of wild-type rabies virus on vaccine producing cell line and its quantification by peroxidase-based immunostaining.

Rabies lyssavirus, the causative agent of rabies (acute progressive encephalomyelitis) requires specific receptors on host cell to mediate neurotropism. Typically, cell lines used for rabies vaccine production are devoid of these receptors. In this study, we developed and optimized a protocol for adapting a locally isolated wild type rabies virus belonging to the Arctic-like lineage A1a, to a vaccine producing cell line, quantified its infectious titer using peroxidase-based immunostaining and virus neutralization was assessed using sera obtained from Abhayrab®-vaccinated individuals. The virus was initially propagated in mouse neuroblastoma cell line and gradually adapted to replicate in Vero E6 by serial passages. The adaptation was confirmed by cytopathic effect and the viral titer rose to as high as 1.72 × 107 FFU/mL. This is the first study to provide a detailed documentation of significant and typical cytopathic effect induced by an Arctic-like A1a lineage RABV in Vero E6 cells.