May 10, 2021

The World of Antibodies: How do they shape up Diagnosis for COVID?

The last decade exposed humankind to various viral infections like SARS, MERS, Ebola, and now COVID-19. While some of them developed antibodies against the infections, there are still many people who have not been exposed to these infections and are potentially at high risk of getting infected. Not only that, the biggest concern lies if the immune response has already developed the memory cells to counter future interaction with these viruses. By virtue, the production of antibodies to infection is a standalone mechanism to fight the viral attack in a primitive response. Still, long-term protection can only be provided by a proper vaccine which can develop humoral immunity in the host body.

Currently, the whole world is working fast to develop the best vaccine to counter the resurgence of COVID infections. The countries are grappling with the idea of getting their population vaccinated. However, all this exercise still doesn’t guarantee long-term immunity. Typically in COVID-19 infection, the trigger of antibodies starts with the production of IgA and IgM. The former being the respiratory antibody as classical to the disease itself, while the latter serves as the primary antibody to the virus and remains active for a short period. Whether the infection is spreading or being checked depends on the production of secondary antibodies, i.e., IgG, which takes time to build up the immune system. Their titer itself can determine the course of the infection and the possible treatment plan for the individual.

The viral load decreases from the eighth day. Then the antibodies are produced, which are critical markers in understanding the immune development in an individual, and testing the same is ideal for sero-surveillance and seroprevalence. An individual infected with would develop anti-SARS-CoV-2 Spike Receptor Binding Domain (RBD) IgG, which will help build the immunity. Neutralizing Antibodies to the Spike-ACE2 receptor are produced by vaccination and develop humoral immunity in an individual. Neutralizing antibodies (NAb) are responsible for forming a defence mechanism against an invading pathogen in human cells. Their production is triggered by the immune system with the onset of infection in the body or by a vaccine response against infection and provides lifelong immunity against the disease. NAb(s) are produced by the B-cells of the immune system inside the Bone Marrow of an infected individual, and once they are created, they bind to specific pathogens. Neutralizing Antibodies help form passive immunity of an individual, i.e., to provide short-term immunity to the healthy individual against a disease that has not infected that person. This ensures that the individual can ward off the infection immediately. This can happen naturally from mothers to babies by breastfeeding, passing all the natural antibodies, or a vaccination program. Neutralizing Antibodies (or Late arriving IgG) are the key to reducing virus capture and spread of infection. These antibodies prevent the virus from attaching to the host cell. The prevalence of these antibodies (in High Titer) will determine if the individual has good humoral immunity if he/she can donate convalescent plasma and if the vaccination is successful.

NAb(s) are ideal as they provide no cross-reactivity with any other coronavirus infections. NAb(s) testing can help the patients segregate between Mild, moderate, and severe categories. The short-term to long-term immunity and the treatment regime can be specifically devised for an individual by testing NAb(s). Neutralizing antibodies are more applicable to be catered as the advanced Diagnostic and therapeutic marker to address the resurgence of COVID infections in the country.

From the inception of the pandemic in the country, J Mitra & Co. has been involved in catering to the need for Antibody testing for COVID-19 infection. It became the first company to indigenously develop and manufacture the COVID-19 (IgM+IgA+IgG) ELISA kit, followed by the COVID-19 Kawach IgG ELISA kit. Both these kits suited well for the early and the late stages of the infection, respectively. The second wave of COVID didn’t surprise albeit proved to be more challenging, and the idea was conceived to address the concern of utilizing the Neutralizing antibodies into the diagnostic approach, and hence the COVID-19 Neutralizing Antibody kit too was developed and has been effective with >95% Sensitivity and 100% Specificity.

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