TY - JOUR T1 - Design of a highly thermotolerant, immunogenic SARS-CoV-2 spike fragment JF - bioRxiv DO - 10.1101/2020.08.15.252437 SP - 2020.08.15.252437 AU - Sameer Kumar Malladi AU - Randhir Singh AU - Suman Pandey AU - Savitha Gayathri AU - Kawkab Kanjo AU - Shahbaz Ahmed AU - Mohammad Suhail Khan AU - Parismita Kalita AU - Nidhi Girish AU - Aditya Upadhyaya AU - Poorvi Reddy AU - Ishika Pramanick AU - Munmun Bhasin AU - Shailendra Mani AU - Sankar Bhattacharyya AU - Jeswin Joseph AU - Karthika Thankamani AU - V. Stalin Raj AU - Somnath Dutta AU - Ramandeep Singh AU - Gautham Nadig AU - Raghavan Varadarajan Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/08/16/2020.08.15.252437.abstract N2 - Virtually all SARS-CoV-2 vaccines currently in clinical testing are stored in a refrigerated or frozen state prior to use. This is a major impediment to deployment in resource-poor settings. Several use viral vectors or mRNA. In contrast to protein subunit vaccines, there is limited manufacturing expertise for these novel, nucleic acid based modalities, especially in the developing world. Neutralizing antibodies, the clearest known correlate of protection against SARS-CoV-2, are primarily directed against the Receptor Binding Domain (RBD) of the viral spike protein. We describe a monomeric, glycan engineered RBD protein fragment that is expressed at a purified yield of 200mg/L in unoptimized, mammalian cell culture and in contrast to a stabilized spike ectodomain, is tolerant of exposure to temperatures as high as 100°C when lyophilized, and upto 70°C in solution. In prime:boost guinea pig immunizations, when formulated with the MF59 like adjuvant AddaVax™, the RBD derivative elicited neutralizing antibodies with an endpoint geometric mean titer of ~415 against replicative virus, comparing favourably with several vaccine formulations currently in the clinic. These features of high yield, extreme thermotolerance and satisfactory immunogenicity suggest that such RBD subunit vaccine formulations hold great promise to combat COVID-19.Competing Interest StatementA provisional patent application has been filed for the RBD formulations described in this manuscript. S.K.M, S.A., R.V, S.P, R.S are inventors. G.N, R.V are founders of Mynvax and S.P, R.S, N.G, A.U, and PR are employees of Mynvax Private Limited. ER -