ABSTRACT
Although the World Health Organization recommends the use of in vitro techniques to qualify rabies vaccine lot release, very limited proposals have been made to arrive at a harmonized approach for wide scale usage. The present study proposed and evaluated the use of a novel avidin-biotin ELISA as an alternative to these in vivo tests in rabies vaccine manufacture. This assay utilized a neutralizing pan reactive monoclonal antibody (mAb) reactive with the conserved site-II of the natively folded rabies glycoprotein. Linear regression analysis of the in vitro glycoprotein estimates with the in vivo potency values, showed a good correlation (r(2)=0.8) with veterinary vaccines, but a poor correlation (r(2)=0.2) with human vaccines. However, we could qualitatively arrive at cut-off glycoprotein estimates from the ELISA, above which all the vaccines were declared to be protective by mouse challenge studies (>2.5IU/dose).
