Delta and its sub lineages reduce Covaxin antibodies: ICMR study
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In news According to a study by scientists at the Indian Council of Medical Research-National Institute of Virology, antibodies produced in response to Covaxin were reduced when tested against the Delta variant and its sub lineages but continued to be high enough to remain protective,
This demonstrates the possible role of memory cells in immune boosting with post-infection or infection after immunisation.
What is Adaptive response?
When infected by a virus, non-specific immune response in the form of macrophages, neutrophils and other cells tend to prevent the virus from causing symptoms.
Soon after, the body makes antibodies specific to the virus called the immunoglobulins — IgG and IgM, called the adaptive response.
In addition, cellular immunity kicks in when the body makes T cells that destroy cells that have been infected by the virus.
The combination of adaptive response and cellular immunity may prevent progression to severe illness or re-infection by the same virus.
This process is often measured by the presence of antibodies in blood.
Besides T cells, people infected with coronavirus also make memory B cells, which rapidly produce antibodies when required.
If they find the virus again, they remember and start to make antibodies very, very quickly.
Even when the antibodies were present at low levels, it was sufficient to neutralise the virus.
Most convalescent plasmas obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity yet have antibodies with potent antiviral activity were found in all these individuals.
Also, pre-existing memory T cells may only reduce COVID-19 severity, do not prevent infection
How the memory T cells may help reduce the severity of the disease?
The cross-reactive memory T cells on activation would help in the development of plasma cells, antibody production, and in the development of killer T cells that would kill virus infected cells.
Cross-reactivity refers to a situation in which an antibody reacts to a substance other than its corresponding antigen.
The latter reduces the reservoirs of infection.
This would most likely reduce disease severity.
Why do antibodies reduce over time?
B cells are responsible for releasing antibodies into the blood.
When an infection or vaccination occurs, some of them will metamorphose into specialised antibody-production factories, known as plasma cells.
Antibodies are proteins, and like any other protein will be naturally broken down and removed from the body within a few months at most.
For longer-term protection, we need to produce antibodies for ourselves.
Once the infection or vaccine has been completely removed, memory B cells no longer replenish the plasma cell population, which then declines.
