Introduction
The coronavirus SARS CoV-2 that causes COVID-19 is spreading like wild-fire across our globe. Scientists around the world are striving towards developing a vaccine in order to prevent more people from getting infected. However, there is also one other important job that is the need of the hour: Finding faster and effective methods for virus testing. At present, there are 2 types of virus tests: PCR technique and immunoassays. Let’s take a closer look at why we need these tests.
Why do we need PCR and immunoassays?
PCR test (Polymerase chain reaction test) and immunoassays are crucial in viral testing. PCR tests for whether the patient is infected with the virus while immunoassays tests for whether the patient has already been infected with the virus. Since virologists need to collect data about the virus from patients, both these tests are critical.
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The first PCR technique was discovered by Kary Mullis in the mid-1980s. The PCR technique primarily targets the virus’ genetic material. PCR amplifies small amounts of genetic information in the virus to large enough quantities so that it can be readily observed. Researchers sequence the genome of a new virus for the PCR to identify sections/regions that are unique to that specific virus. A PCR test begins by collecting a sample-blood(for hepatitis), feces(for poliovirus), or nose and throat(for coronaviruses)-from the patient. Let’s take the example of the novel coronavirus.
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Genetic information can be transcribed via DNA or RNA. The SARS CoV-2 virus uses RNA. Such RNA viruses must be reverse transcribed into a strand of complementary DNA(cDNA) before running the PCR. During the PCR test, if the virus is identified, substances called ‘complementary primers’ will identify its unique regions of code. This information is then copied by enzymes. This “amplified” genetic material is detected with probes containing fluorescent dye. The sample is tested positive for the virus if the PCR machine senses fluorescence.
On the other hand, immunoassays show if someone has been previously infected. The first immunoassay was described by Solomon Berson and Rosalyn Yalow in 1959. Immunoassays work by tapping into the body’s adaptive immune system/memory of the virus. This process targets specific antibodies that were generated by the immune system in order to fight the virus. Immunoassays may detect IgG and IgM antibodies. Since IgG circulates through the body for a longer period of time after infection, it is reliable and often used for immunoassays. Additionally, before performing immunoassays, scientists expose a blood sample of a patient to the virus. If antibodies in the blood bind to the virus, the sample tests positive and that the individual has been exposed to the virus.
So here it is. Next time you go to the doctor for a COVID-19 test. Think about the type of test they are using. This is just the beginning of the world of virology.
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