Design of a highly thermotolerant, immunogenic SARS-CoV-2 spike fragment immunogen

• Published in: bioRxiv
• Main Authors: Malladi, Sameer Kumar, Singh, Randhir, Pandey, Suman, Savitha Gayathri, Kanjo, Kawkab, Shahbaz, Ahmed, Mohammad Suhail Khan, Kalita, Parismita, Girish, Nidhi, Upadhyaya, Aditya, Reddy, Poorvi, Pramanick, Ishika, Bhasin, Munmun, Mani, Shailendra, Bhattacharyya, Sankar, Jeswin, Joseph, Thankamani, Karthika, V Stalin Raj, Dutta, Somnath, Singh, Ramandeep, Nadig, Gautham, Varadarajan, Raghavan
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 06.10.2020
• Subjects: Antibodies; Cell culture; COVID-19; Immunization; Immunogenicity; mRNA; Patent applications; Proteins; Severe acute respiratory syndrome coronavirus 2; Spike protein; Temperature tolerance; Vaccines
• DOI: 10.1101/2020.08.15.252437

Abstract 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 214mg/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, upto 70°C in solution and stable for over four weeks at 37°C. 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 Statement A 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. Footnotes * Figure 4G, 4H added; Supplementary Figure 1, 2, 3 available