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BackgroundA novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in the Chinese capital Wuhan in 2019. Since late 2019, SARS-CoV-2 has been responsible for a global pandemic that has resulted in 205,338,159 confirmed cases of infection and 4,333,094 deaths as of August 11, 2021, according to the World Health Organization. Currently, there are no approved antiviral drugs and vaccines against SARS-CoV-2. Several strategies to develop SARS-CoV-2 vaccines rely on different technologies such as DNA- and RNA-based formulations, recombinant subunits with viral particles, viral vectors, and purified inactivated viral formulations with or without adjuvant. MethodHere we report the development of an inactivated SARS-CoV-2 vaccine candidate and show that its efficacy and safety in preclinical studies warrant further clinical evaluation. For this purpose, a vaccine candidate was manufactured by using microcarrier based cell culture methods in a disposable wave bioreactor, purified by using ultrafiltration and multimodal chromatography system, and their effect and possible side effects on different doses were evaluated using qRT-PCR, Western Blotting, antigen ELISA, histopathology, serum neutralization test in Balb/c mice. ResultsMicrocarrier-based production in disposable wave bioreactors (SARTORIUS Biostat RM20, Germany) was very efficient for vaccine production. Each dose of the vaccine candidate contains about 340 –400 ng viral spike protein. TEM analysis verified the viral replication in VERO cells and showed intact, oval-shaped particles with diameters of 90 to 110 nm of the virus after the final purification step. The preliminary results in mice showed that the NtAb titers reached the peak post-priming and boosting in 21 days. The titers were respectively 1/ 595, 1 /791, and 1/1048 in 4, 6, and 10 μg groups. In transgenic ferrets, the inactivated vaccine doses were well tolerated in all dose groups with no vaccine-related serious adverse effects. ConclusionsIn conclusion, two different doses (4 and 6 micrograms) of the inactivated SARS-CoV-2 candidate vaccine administered twice were shown to be effective and safe in preclinical studies. All analytical studies have shown that the quality control parameters of the vaccine candidate meet the requirements for inactivated viral vaccines. |
