Immunogenicity and protective efficacy of a highly thermotolerant, trimeric SARS-CoV-2 receptor binding domain derivative

• Published in: bioRxiv 2021-06
• Main Authors: Malladi, Sameer Kumar, Patel, Unnatiben Rajeshbhai, Rajmani, Raju S, Singh, Randhir, Pandey, Suman, Kumar, Sahil, Khaleeq, Sara, Petrus Jansen Van Vuren, Riddell, Shane S, Goldie, Sarah, Savitha Gayathri, Chakraborty, Debajyoti, Kalita, Parismita, Pramanick, Ishika, Agarwal, Nupur, Reddy, Poorvi, Girish, Nidhi, Upadhyaya, Aditya, Mohammad Suhail Khan, Kanjo, Kawkab, Bhat, Madhuraj, Mani, Shailendra, Bhattacharyya, Sankar, Siddiqui, Samreen, Tyagi, Akansha, Jha, Sujeet, Pandey, Rajesh, Tripathi, Shashank, Dutta, Somnath, Mcauley, Alexander J, Nagendrakumar Balasubramanian Singanallur, Vasan, Seshadri S, Ringe, Rajesh P, Varadarajan, Raghavan
• Format: Article
• Language: English
• Subjects: Antibodies; Cartilage; Cartilage matrix protein; Cell lines; Coronaviruses; COVID-19; CpG islands; Immunization; Immunogenicity; Matrix protein; Molecular weight; Pandemics; Proteins; Severe acute respiratory syndrome coronavirus 2; Spike glycoprotein; Temperature tolerance; Trimers; Vaccines
• DOI: 10.1101/2021.01.13.426626

The Receptor Binding Domain (RBD) of SARS-CoV-2 is the primary target of neutralizing antibodies. We designed a trimeric, highly thermotolerant glycan engineered RBD by fusion to a heterologous, poorly immunogenic disulfide linked trimerization domain derived from cartilage matrix protein. The protein expressed at a yield of ~80-100 mg/liter in transiently transfected Expi293 cells, as well as CHO and HEK293 stable cell lines and formed homogeneous disulfide-linked trimers. When lyophilized, these possessed remarkable functional stability to transient thermal stress of upto 100 °C and were stable to long term storage of over 4 weeks at 37 °C unlike an alternative RBD-trimer with a different trimerization domain. Two intramuscular immunizations with a human-compatible SWE adjuvanted formulation, elicited antibodies with pseudoviral neutralizing titers in guinea pigs and mice that were 25-250 fold higher than corresponding values in human convalescent sera. Against the beta (B.1.351) variant of concern (VOC), pseudoviral neutralization titers for RBD trimer were ~ three-fold lower than against wildtype B.1 virus. RBD was also displayed on a designed ferritin-like Msdps2 nanoparticle. This showed decreased yield and immunogenicity relative to trimeric RBD. Replicative virus neutralization assays using mouse sera demonstrated that antibodies induced by the trimers neutralized all four VOC to date, namely B.1.1.7, B.1.351, P.1 and B.1.617.2 without significant differences. Trimeric RBD immunized hamsters were protected from viral challenge. The excellent immunogenicity, thermotolerance, and high yield of these immunogens suggest that they are a promising modality to combat COVID-19, including all SARS-CoV-2 VOC to date. Competing Interest Statement A provisional patent application has been filed for the RBD formulations described in this manuscript. R.V, S.K.M, S.P, R.S are inventors. R.V is a co-founder of Mynvax and S.P, R.S, U.R.P, N.A., P.R., M.B., N.G, and A.U are employees of Mynvax Private Limited. Footnotes * Additional data including nanoparticle RBD, B.1.1.7, B.1.351, P.1, B.1.617.2 variant neutralization and Hamster challenge studies showing protective efficacy of trimeric RBD immunogen.