Bengaluru: In what could be a major boost to fight future SARS-COV-2 infections, researchers from CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, have developed a "safe and highly effective" protein subunit-based vaccine candidate offering "near-complete protection" in preclinical studies.
Newer variants of SARS-CoV-2 capable of evading the human immune response continue to emerge, although not of pandemic-proportions such as those detected in 2020 and 2021. Most existing Covid vaccines currently in human use are based on messenger ribonucleic acid (mRNA), inactivated Covid virus or non-replicating virus vectors.
Recently published in the international journal Vaccine (Elsevier), CSIR-IMTECH’s paper reported the development and pre-clinical assessment of an engineered antigen IMT-CVAX, which is a recombinant prefusion-stabilised trimeric spike protein, to tackle Severe Acute Respiratory Syndrome-related Coronavirus 2 (SARS-CoV-2) infections.
The project was funded by the Council of Scientific and Industrial Research (CSIR), New Delhi, and the team was headed by principal scientist Dr Ravi P N Mishra.
Dr Mishra told DH that this was a "first-of-its-kind study", completely based on indigenous resources for antigen designing and production, characterisation, and preclinical assessment of efficacy.
Dr Sanjeev Khosla, Director, CSIR-IMTECH, said that the idea was to generate scientific know-how and set up an indigenous technology platform for the development of vaccine proof of the concept, either for Covid variants or similar pathogens, so that we have readiness for any exigencies or pandemic-like situations in the future.
How is IMT-CVAX different?
Protein subunit-based vaccines have a documented ease of large-scale production and transportation, efficient storage in standard refrigerators, compatibility with approved adjuvants, and safe administration to individuals across age groups, making them well-suited for mass immunisation programmes.
The IMTECH team used the SARS-CoV-2 spike protein — one of four structural proteins encoded in the virus that is the major virulence factor enabling pathogens to infect the host (human) and stabilised it to use as the antigen IMT-CVAX.
It elicited robust anti-spike IgG antibodies in mice, effectively neutralising various virus variants, including Delta, one of the most common variants during the Covid second wave in 2021.
Vaccine testing
Vaccine efficacy was tested at the viral biosafety level 3 laboratory at CIDR, IISc, where it was found that it provided hamsters "excellent protection" against the SARS-CoV-2 infection, compared to control groups that did not receive the vaccine.
Dr Shashank Tripathi, Assistant Professor, CIDR, said: "We tested seven SARS-CoV-2 vaccine candidates in our lab using the Hamster model during Covid-19 pandemic. IMT-CVAX emerged as the best performing vaccine."
The NII’s vaccine immunologist, Dr Nimesh Gupta, and his team evaluated the immunological effectiveness of the adjuvanted IMT-CVAX and found that the vaccine generates potent humoral immunity by inducing a robust T-cell-mediated germinal centre response. Germinal centres, located in lymphoid organs, are critical for developing protective immunity.
Efficacious vaccine candidate
The study's authors concluded that the adjuvanted IMT-CVAX is an "efficacious vaccine candidate" to offer broad and long-lasting immunity against any future SARS-COV-2 infections, showing no visible adverse side-effects in mice and hamsters.
"It is imperative to have a robust expression system and bioprocess for generating high quality and quantity antigen that meets the prerequisites of clinical development to ensure a rapid response to any potential pandemics," noted Dr Mishra.
The CSIR-IMTECH team has also filed international patents in the effort to protect the innovation and secure the intellectual property.
About the vaccine
Funded by: Council of Scientific and Industrial Research (CSIR), New Delhi.
Team lead: Dr Ravi P N Mishra, Principal Scientist, CSIR-IMTECH, Chandigarh.
Collaborators: The Centre for Infectious Disease Research (CIDR), IISc, Bengaluru and National Institute of Immunology (NII), New Delhi.