SARS-CoV2 Spike Protein Expression as an Identification in Quality Control Testing for Adenovector Based COVID-19 Vaccine

Quality control testing of the vaccine for lot release is of paramount importance in public health. A recent pandemic caused by SARS-CoV2 virus brought together all spheres of vaccine to combat the virus. The scientific advancement in the development of vaccines facilitated the scientists to develop the vaccine against SARS-CoV2 in a record time. The Covid-19 virus exploited the ACE2 (Angiotensin Converting Enzyme 2) receptor, a surface protein on the mammalian cells for gaining an entry into the host cells. The viral surface protein that interacted with ACE2 receptor is Spike protein of SARS-CoV2. Thus, in the development of vaccine and assessing its quality, spike protein of SARS-CoV2 became an attractive immunodominant antigen. In National Institute of Biologicals, an apex body in the testing of biologicals in India, received the adenovector based Covid-19 vaccine, a finished product for quality evaluation. Due to the lack of pharmacopeial monograph, the testing of the vaccine was done as per manufacturer’s specifications and methods. The routine assays of identification employed by the manufacturer do not reflect the expression of spike protein which is required for the immune system to get activated. In this report, we showed the determination of spike protein expression by immunoblotting and immunofluorescence for identification parameter in the quality testing of Covid-19 vaccine. We determined the translation of SARS-CoV2 spike gene cloned into an adenovector. The results from these experiments clearly indicated the expression of spike protein upon infection of mammalian cells with viral particles and suggested that the expression of immunodominant spike protein of SARS-CoV2 may be employed by quality control laboratories as a parameter for identification. The study suggested that determination of the expression of spike protein is pertinent in order to identify the adenovector based vaccines against Covid-19.