Vaccine with an adjuvant may boost immune system's response against COVID-19, claim researchers
Adjuvants are substances that are used in combination with a vaccine to produce a more robust immune response than what the vaccine alone would provide
There is an urgent need for a COVID-19 vaccine as almost 14 million people globally have been infected with the SARS-CoV-2 virus and the case count has crossed one million (10 lakhs) in India, the second most populous country in the world.
While research is still underway to understand the human immune system's response to the virus, it's known that those infected with the COVID-19 causing virus are able to develop antibodies in their body. Some scientists believe that the antibody response in people can be improved by using an adjuvanted flu-vaccine.
In a recent study, published in the journal Proceedings of the National Academy of Sciences on 13 July, 2020, scientists compared the antibody responses in the body after vaccination with an adjuvanted vaccine and non-adjuvanted vaccine.
What is an adjuvant?
Vaccines contain either inactivated or live-attenuated (less potent) microorganisms, which are injected into the body so that the immune system of our body fights it and forms antibodies against it in the process. Adjuvants are substances that are used in combination with a vaccine to produce a more robust immune response than what the vaccine alone would provide.
The need for the adjuvant
Previous studies have shown that whenever the body encounters any unfamiliar flu-causing virus (like the one seen during 2009 H1N1 pandemic), the immune system of the body works more actively and neutralises a broader range of viruses. During this fight, the antibodies, produced by the immune system, align themselves towards the stem of the viral hemagglutinin protein (the protein structure present on the surface of the virus which increases its power of infection) than the head. The scientists also found that the immune system, especially the memory B cells, can recognise the flu virus when it enters the body the second time as the stem structure of this virus protein does not change much — unlike the head, which changes every year.
So when another flu virus, H5N1 (the bird flu) is encountered by the human body, scientists found that the stem region of the virus was familiar, but the head had changed. While the vaccine was still effective, the extent of its effectiveness, however, was limited. So, the scientists decided to use an adjuvant to increase the potency of the vaccine.
The study: Adjuvanted vaccine vs non-adjuvanted vaccine
Dr Ali Ellebedy, the lead of the study, along with his team examined the effect of AS03-adjuvanted H5N1 avian influenza virus against the non-adjuvanted inactivated vaccine. In this study, the scientists tested 50 healthy young adults who were exposed to some flu viruses and vaccines earlier in their lives. These patients were given two doses of both AS03-adjuvanted and non-adjuvanted three weeks apart.
AS03 is an adjuvant which is composed of α-tocopherol, squalene and polysorbate 80 in an oil-in-water emulsion.
After a week of getting the first dose of the adjuvanted vaccine, the immune system of the body recruited the antibodies towards the stem of the virus. They believed that this happened because of the pre-existing memory B cells of the immune system. However, after the second dose, the fresh naive B cells were deployed against the head of the virus.
The scientists stated in the study that in order to gain immunity against the SARS-CoV-2 virus, the use of adjuvant vaccine can help in bringing out the naive B cells which can provide a better immune response by working along with the pre-existing memory B cells in the body.
For more information, read our article on COVID-19 vaccine: Potential targets and types of vaccines.
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