IIT-M study predicts retained efficacy of spike protein vaccines against Covid-19 variants

Researchers with the Indian Institute of Technology-Madras (IIT-M) have found that spike protein vaccines may be effective against multiple variants of the Coronavirus (SARS COV-2), including Delta plus and Omicron.

While further experimental verification is called for, the study predicts T-cell immunity produced due to present vaccines may still be efficient in protecting the host against select SARS COV-2 variants.

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The results of the IIT Madras study suggest that the attack by selected variants – Delta plus, Gamma, Zeta, Mink and Omicron – may be dealt with by vaccine-induced T-cell responses despite the compromised neutralising antibodies responses.

The researchers set out to find out what would be the response like if the post-vaccination infections were caused by a variant other than the original Wuhan strain incorporated in vaccine preparations.

“In variants of SARS COV-2, there are molecular level changes to the spike protein of the virus, and these variations may include the regions of protein sequences that are recognized by T-cells called epitopes,” the institute said, adding that a research was carried out to get more clarity about the efficacy of vaccination against the variants of SARS COV- 2.

The results of the study Dr Vani Janakiraman, Assistant Professor, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, IIT-M, have recently been published in the reputed peer-reviewed journal BBA - Molecular Basis of Disease in a paper co-authored by S Sankaranarayanan and Mugdha Mohkhedkar and Janakiraman.

Janakiraman said the efficacy of vaccines, in this case, different forms of spike protein based vaccines, depends on whether it can trigger not only the antibody response but also the T cell response.

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Efficacy against multiple variants can be assessed by first analysing the epitope sequences of various variants for mutations and if they can effectively trigger T-cells induced in the immunization process, she said.

The vaccines could be considered effective against the variants if there are less mutated epitopes in their spike proteins and, if the mutated epitopes can still induce an immune response comparable to that elicited by original/native epitopes.

The IIT Madras team sought to investigate how many of the epitopes in the variants are mutated and whether the mutated epitopes can alter the immune response to vaccination in order to assess vaccine efficacy.

“We found that at least 90 per cent of both CD4+ and CD8+ epitopes were conserved in all variants except Omicron, but even in Omicron, nearly 75 per cent and 80 per cent of CD4+ and CD8+ epitopes were conserved. Additionally, the immunoinformatics tools also predicted the majorly retained ability of the epitopes to bind MHC molecules and hence trigger T cell responses,” she said.

This means that the changes to the epitopes are not so large enough to evade the T-cell immune response that the body learned through vaccination, Janakiraman said, adding that even in case of reduced neutralization by antibodies, variants may not become vaccine resistant.