Explained: What is recombinant protein-based technology used for making vaccines

Reliance Life Sciences to conduct trial of recombinant protein-based Covid vaccine

HEALTH-CORONAVIRUS/ISRAEL Representational image | Reuters

Mukesh Ambani-helmed Reliance has now stepped into COVID-19 vaccine manufacturing. On Thursday, the drug regulator approved Reliance Life Sciences' application to conduct phase one clinical trials of its two-dosed Covid-19 vaccine which is based on the recombinant protein-based technology. The approval was given after the subject expert committee (SEC) reviewed its application during a meeting. The vaccine will be developed at the company's Navi Mumbai facility.

Currently, there are six vaccines to have received emergency use authorisation. Serum Institute’s Covishield, Bharat Biotech's Covaxin, Russia’s Sputnik V, Moderna’s, Johnson & Johnson’s, and Cadila’s that was approved last week.

While it will be interesting to see how the vaccine made by Reliance Life Sciences will play out in the market, it is the recombinant protein-based technology which it uses in the making of its vaccine that makes it stand out from the rest of the players as of now.  As per a paper published in the Brazilian journal of medical and biological research, most current vaccines in use in the present times owe their success to their ability to target pathogens that have low antigenic variability and for which protection depends on immunity generated by antibodies. This is the case for polio, tetanus, diphtheria, measles, and hepatitis B, among others. As a consequence, vaccines capable of generating neutralising antibodies against these pathogens were successful.

Now what the recombinant protein technology does is that it allows the targeting of immune responses focused against few protective antigens. The classical example of recombinant protein vaccines currently in use in humans is the vaccine against hepatitis B virus infection which is a chronic liver disease occurring worldwide, including India. Back then it was the 1980s when an era of genetic engineering had dawned and recombinant DNA technology—which enables DNA from two or more sources to be combined—was harnessed to develop the first recombinant protein vaccine. The vaccine antigen is a hepatitis B virus protein produced by yeast cells into which the genetic code for the viral protein has been inserted.

Recombinant vaccines rely on the capacity of one or multiple antigens to induce immunity against the pathogen, when administered in the presence of adjuvants - a substance which enhances the body's immune response to an antigen. These vaccines help in negating several potential concerns such as the reversal of the toxoids to their toxigenic forms, for example as it happens in the case of diphtheria or tetanus toxoid vaccines. Another fundamental issue overcome by this technology is the complexity involved in obtaining sufficient quantities of purified antigenic components.

According to NIH, rather than delivering DNA or mRNA directly to cells, some vaccines use a harmless virus or bacterium as a vector, or carrier, to introduce genetic material into cells. Several such recombinant vector vaccines are approved to protect animals from infectious diseases, including rabies and distemper. Many of these veterinary vaccines are based on a technology developed by NIAID researchers in the 1980s that uses weakened versions of a poxvirus to deliver the pathogen’s genetic material. Today, NIAID-supported scientists are developing and evaluating recombinant vectored vaccines to protect humans from viruses such as HIV, Zika virus and Ebola virus.

"However, one of the main challenges in the development of these new strategies of immunisation consists of designing vaccines that elicit the appropriate kind of immune response to confer immunity mainly to intracellular pathogens and especially to those that establish chronic, often lifelong infections. For this, the knowledge of the biology of highly conserved antigens involved in pathogenesis and of the immune mechanisms that should be elicited for protection must be obtained to rationally design vaccine strategies that can overcome the low protective immunity naturally generated by infection," reads the paper.