Focus: GS-III Disaster Management

Why in news?

  • German researchers plan to regularly test over 100,000 people to see if they have overcome infection with coronavirus (COVID-19) to track its spread, an institute behind the plan confirmed on 27th March 2020.
  • You could give immune people something similar to a vaccination certificate that could allow them exceptions from limits on their activities.

Issues with the move

  • But even if the study is approved, initial readings might not be completely reliable.
  • Tests currently available can show false positives for coronavirus antibodies, as 90% of adults already have immunity against common, harmless viruses from the same family.
HOW DO THE TESTS FOR CORONAVIRUS WORK? ISSUES WITH TESTING REAGENT ISSUES High demand and issues with reagents have delayed testing in some countries. TIME-CONSUMING It takesa few hours to get results from the test, limiting haw rnany tests can be done. HOW CURRENT TESTS WORK A swab is taken of the inside of a patient's nose or the back of their throat. This sample is then sent to a lab to test VIRUS RNA The RNA of the virus is extracted and purified. An enzyme, reverse transcriptase, converts the RNA to DNA. The DNA is mixed with primers, sections Of DNA designed to bind to characteristic parts Of the virus DNA. Repeatedly heating then cooling DNA with these primers and a DNA- building enzyme makes millions of copies of virus ONA. DYES Fluorescent dye molecules bind to the virus DNA as it is copied. Binding makes them give off more light, which is used to confirm the presence of the virus in the sample, In some cases sample degradation or contamination can affect the results. FUTURE TESTS The current tests are good for diagnosing an infection - but they can't tell us if someone has had it and then recovered. Tests that look for antibodies against the virus can do this. POSITIVE AND NEGATIVE TESTS The fluorescence increases as more copies of the virus DNA are produced. If it crosses a certain threshold, the test is positive. If the virus isn't present, no ONA copies are made and the threshold isn't reached. Inthis case, the test is negative. POSITIVE Threshold Copying cycles NEGATIVE Threshold Copying cycles INFECTION ANTIBODIES Produced by the immune m. They remain in the blood some time after infection, NEUTRALISATION Tests that look for proteins on the surface of the virus are also in development. These testsare faster, but Less accurate. @Andy Brunning/Compound Interest 2020 - www.compoundchem.com I Twitter: @compoundchem I FB: www.facebook.com/compoundchem c, This graphic is shared under a Creative Commons Attribution- NonCommercial-NoDerivatives 14_0 licence,

What are antibodies?

  • Antibodies, also known as immunoglobulins, are Y-shaped proteins that are produced by the immune system to help stop intruders from harming the body.
  • When an intruder enters the body, the immune system springs into action.
  • These invaders, which are called antigens, can be viruses, bacteria, or other chemicals.
  • When an antigen is found in the body, the immune system will create antibodies to mark the antigen for the body to destroy.

Function of Antibodies

  • The antibodies act sort of like the immune system’s scouts.
  • They find antigens, stick to them, and identify for the immune system the exact type of antigen so that it can be destroyed.
  • Each antibody is made for one and only one antigen, and it’s fitted with special receptors that will only bind to that antigen.
  • For instance, a specific antibody is created to help destroy the chickenpox virus. Only that particular antibody will attack a chickenpox virus.

How does antibody test work?

  •  Antibody tests look to see if someone has been exposed to a specific antigen, like a virus.
  • The British tests are designed to work in one of two ways. They either detect human antibodies in blood using an antigen designed to be similar to a feature of the virus. Or conversely, the test detects the virus in blood using a antibody designed to trap the virus.



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