IISc pitches heat-stable vaccine candidate against current, future SARS-CoV-2 variants

Bengaluru: Researchers at the Indian Institute of Science (IISc) have developed a synthetic antigen that can be manufactured as a potential Covid-19 vaccine candidate.

Developed by the institute’s Molecular Biophysics Unit (MBU), the new vaccine candidate was found effective against all current strains of SARS-CoV-2 and can be adapted for protection against future variants, IISc said on Wednesday.

Unlike many vaccines in the market that require mandatory cold storage, the antigen can be stored at room temperature for a month, making the distribution and storage of these vaccine candidates much more economical.

This marks a significant turn in the efforts taken up by Raghavan Varadarajan, professor at MBU, and his collaborators, since the beginning of the pandemic toward developing a heat-tolerant vaccine against current and future strains. Their study has been published in the journal npj Vaccines.

The virus’ rapid mutation has steadily depleted the efficacy of current vaccines. After analysing various proteins found in the virus, the researchers selected two parts of SARS-CoV-2's spike protein – the S2 subunit and the Receptor Binding Domain (RBD) – for designing their vaccine candidate.

The S2 subunit mutates much less than the S1 subunit, which is the target of most current vaccines. Scientists have also known that the RBD can provoke a strong immune response in the host. 

These features were factored in as the team combined the two components, to create a hybrid protein called RS2.

The researchers used mammalian cell lines to study the expression of the hybrid protein. Nidhi Mittal, PhD student at MBU and first author of the study, said the protein showed very high levels of expression, indicating that it can be produced in large quantities.

In mice and hamster models, the hybrid protein was found to trigger a strong immune response and provide better protection than vaccines containing the whole spike protein.

Since 2000, Varadarajan’s team has been working on several viral vaccines. They have leveraged this expertise to design their current vaccine candidate in collaboration with the startup Mynvax, which was, until recently, incubated at IISc.