Development and validation of a real-time RT-PCR assay for the quantification of rabies virus as quality control of inactivated rabies vaccines

Abstract Rabies is an infectious viral disease, characterized as a neglected zoonosis, responsible for nearly 60,000 deaths annually. The virus is transmitted mainly by dogs in Africa and Asia, and wildlife in Europe and the Americas, to all mammals’ species, causing severe encephalitis almost always fatal after the onset of neurological symptoms. Human rabies can be prevented through extensive vaccination of dogs and pre/post-prophylaxis treatments in humans with inactivated rabies vaccines. The vaccine manufacture involves a series of quality control assays using laboratory animals, which are mandatory to exclude the presence of viable residual virus. The quality controls must be carried out in various steps during the vaccine production, which demands the use of a large number of animals. In this study, we standardized a real-time quantitative RT-PCR duplex assay to be used during intermediate stages of the vaccine production. This assay was done for the quantification of vaccine strain rabies virus, targeting rabies nucleoprotein, and β-actin mRNA of BHK-21 cells as an internal endogenous control. The results showed specific amplification, with the analytical sensitivity ranged from 10 1 to 10 6 TCID 50 /mL with high repeatability rate for the quantification of rabies virus in inactivated vaccine samples. Global organizations are engaged to develop new approaches to determine viable residual virus, and this assay can be applied in combination with traditional in vitro methods for the release of intermediate batches of vaccines during the production process, keeping the in vivo tests only for final release.