In vivo studies of pathogenic, immunogenic and protective properties of Roma strain rabies virus recovered from a persistently infected BHK21 cell line.

Rabies virus strain Roma was adapted to grow in BHK21 cells and a persistently infected cell line was established. The cell line released infectious virus only irregularly and at low titers. We report in this work experiments carried out in mice on pathogenicity, immunogenicity and protective properties of the virus recovered at different phases of the persistent infection. The adapted virus strain was only weakly pathogenic when injected intracerebrally and apathogenic when given intramuscularly. Dose-response curves in mice of virus produced by the persistently infected cell line were irregular, often with deaths occurring at low but not at high virus doses. Moreover, the symptoms of rabies differed from the course of disease induced by unadapted Roma strain rabies virus. Sera of survivors of a first non lethal inoculation were tested for the presence of rabies virus neutralizing antibodies and these mice were challenged with virulent CVS rabies virus. Animals having survived the highest viral doses had the highest antibody titers and resisted a challenge with the standard challenge virus.