Global initiatives have made substantial progress toward replacing the in vivo rabies vaccine potency test (NIH method) with in vitro methodologies for quantifying immunodominant glycoprotein (GP) in rabies vaccine. A sandwich ELISA approach based on a neutralising rabies GP site III directed human monoclonal antibody (RAB-1) and a polyclonal GP specific antibody recognising the intact form of viral GP is described here.The assay was able to distinguish between vaccine samples that were potent and those that were not.

The assay was found to be linear over the 0.07–2.25 IU/mL range, with LOD and LLOQ values of 0.035 and 0.070 IU/mL, respectively. The assay was able to quantify the GP content of rabies vaccines generated from rabies vaccine strains, such as Pittman-Moore, Pasteur, and Flury LEP, with reasonable precision, and it also agreed well with NIH potency estimations. Using biolayer interferometry, the binding kinetics of RAB-1 with intact and modified vaccination samples were also studied (BLI). In quality control testing of human rabies vaccines, the new method could be utilised instead of the NIH approach.

Reference: https://www.tandfonline.com/doi/full/10.1080/21645515.2019.1709350