The Society for Promotion of Science of Science & Technology in India (SPSTI), jointly with Chandigarh Chapter of the National Academy of Sciences India (NASI), Chandigarh Chapter of the Indian National Science Academy (INSA) and Indian National Young Academy of Sciences (INYAS) with support from Haryana State Council for Science, Innovation and Technology, Government of Haryana have organized another series of Expository Lectures on current state of Covid-19 pandemic to spread awareness on issues involved so as to enhance the confidence of the general public in facing this pandemic. The third lecture of the second series was conducted on May 28, 2021 at 11.00 am pm through online mode on “Covid-19: Infection & Immunity”. The session was attended by more than 60 participants on the zoom and about 52 viewed the same on the Facebook page of SPSTI.

The session steered with introduction of the series by Prf. Arun K. Grover, to educate masses about how to deal with the consequences of pandemic as it has been affecting every walk of life. Prof. R. K. Kohli welcomed the attendees and the speaker Prof. Agrewala. Prof. Javed N. Agrewala is Dean Research & Professor, Immunology Laboratory, IIT Ropar.

The talk emphasized on how to prevent infection and bolster immunity against COVID-19, which is an extremely contagious virus that infects chiefly through the nasal route by aerosols. The best protection provided against any infection to the majority of the population is by the body’s own immune system, which comprises natural and acquired immunity. He explains there are various microorganisms in our environment which have been affecting us continuously but our innate immunity provides defence against these. There are many types of cells present in our body performing different functions to protect the individual. The structure of these cells is very complicated with almost 10⁸ receptors on the membrane and to these receptors in cells binds different molecules including pathogens, enzymes, hormones, etc. This binding triggers a sequence of signaling effects. Different cells in the body like macrophages engulf the foreign body, process it and present it to other cells. B-cells produce antibodies which are highly antigen specific and can recognize 10¹⁸ antigens, as soon any antigens enter the body, they start producing antibodies. They further lead to developing memory cells. T-cells also develops cytokines which fight against these foreign bodies. Cytotoxic t-cells recognize the cancerous cells and kill the infected cell. The lymph node also helps to maintain immunity against disease with educating the immune response of the body to recognize self and non-self cells. He explains it is not only the viruses and bacteria against which the immune system provides defence but also eliminates many toxins, carcinogens, etc. from the body.  Immune system is of two kinds, first is the innate immune system which is non-specific but fast and includes macrophages, natural killer T-cells, T-cells, dendritic cells, eosinophils, basophils, etc. these provide the first line of defence and if the foreign body escape innate immunity, adaptive immunity comes to play including b-cells, t-cells and natural killer T-cells producing antibodies to fight against these.

He elaborated that the majority of people are extremely strong to eliminate pathogens without inflicting any disease symptoms who get naturally vaccinated. Other individual’s immunity is powerful enough not to allow the pathogens to afflict disease symptoms, but is extremely weak to eliminate and remain asymptomatic, who becomes carriers, but in in minor population population, immunity is sufficiently weak to kill the pathogens and they become sick and require vaccine and drugs. So, the vaccine is induced to boost the immunity to provide protection. He explained vaccine is a biological preparation that improves immunity to a particular disease and contains an agent that resembles a disease causing organism and stimulates the body immune system to recognize it as a foreign and destroy and remember it forever, to afflict response against it in future. But he also emphasized that vaccines should impart the right type of immunity else it may increase the disease. He shared the results of a study where people who were vaccinated with different dosage BCG with different age groups. After 10 years of follow up the result showed that among individuals vaccinated with BCG had 50 people out of 1 lakh infected with TB while in placebo group 48 people out of 1 lakh were infected. He also shared that vaccines should not induce autoimmunity and maintain balance between autoimmunity and tolerance. He shared maintaining proper measures of hygiene and civil engineering can help to eliminate certain diseases completely.

Talking about SARS-CoV-2 he says it is a zoonotic virus coming from bats that have entered humans and uses human machinery to replicate and infect the host. Infection is transmitted through cough and sneeze, and the aerosols with size less than 5 microns can travel up to distance of 6-10 feet or more and hence those who are asymptomatic are more dangerous. The advocate wearing a mask is to protect oneself and others and the disposable masks should be properly disposed, they can remain on mask for up to 7 days. He also explained in detail the complete life cycle of SARS-CoV-2 in the human body and how the human body reacts against it. He says viruses have a tendency to hyperactivate the immune system. The immune system activates the first line of defence and when it proves inefficient the adaptive immunity comes to play but in order to destroy the virus, being hyperactivated it does more damage to the immune system. He explained that it takes at least 5 days for viruses to get into our secretion when innate immunity starts getting activate leading to mild and moderate symptoms for protection from infection and it takes almost 7 days for humoral immunity to start appearing and hence it is advisable to get RT-PCR test done after 5 days. Also, as we age there is an imbalance in how the immune system performs, which is leading to a greater number of cases among aged individuals. He suggested to take seasonal fruits and vegetables and regular exercise as it helps to naturally boost the immunity.

He further explained about various types of vaccines like inactivate, subunit, mRNA, etc., explaining the differences in various vaccines against Covid-19. He finally wrapped up the session explaining how a Covid-19 infected cell expresses different receptors. The vaccine binds to these receptors, initiating a cascade of reactions by the immune system, releasing cytokines that recognize viruses and kill them.

The session was much appreciated by the audience and followed with questions about vaccination as combination of two different vaccines, need to develop vaccine, increasing false negative RT-PCR reports, efficacy of protein and mRNA based vaccine, herd immunity and many more. Answering these queries Prof. Agrewala emphasized that one must get the booster dose of the same vaccine only, as it would help to generate a memory response, which equips the immune system better to fight against the infection. Shri Dharam Vir, IAS (Retd.) & President SPSTI thanked the speaker as well as the attendees. The information about future lectures in the series will be available on the SPSTI webpage and these lectures can be accessed on the SPSTI official website and Facebook page.