posted on 2021-07-14, 18:09authored bySameer
Kumar Malladi, Unnatiben Rajeshbhai Patel, Raju S. Rajmani, Randhir Singh, Suman Pandey, Sahil Kumar, Sara Khaleeq, Petrus Jansen van Vuren, Shane Riddell, Sarah Goldie, Savitha Gayathri, Debajyoti Chakraborty, Parismita Kalita, Ishika Pramanick, Nupur Agarwal, Poorvi Reddy, Nidhi Girish, Aditya Upadhyaya, Mohammad Suhail Khan, Kawkab Kanjo, Madhuraj Bhat, Shailendra Mani, Sankar Bhattacharyya, Samreen Siddiqui, Akansha Tyagi, Sujeet Jha, Rajesh Pandey, Shashank Tripathi, Somnath Dutta, Alexander J. McAuley, Nagendrakumar
Balasubramanian Singanallur, Seshadri S. Vasan, Rajesh P. Ringe, Raghavan Varadarajan
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/L 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 up to 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
∼3-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.