Body immunity, SOP will curb Covid-19 spread

Whether it’s a mutant or normal SARS-CoV-2 virus, if we strictly follow the SOP, we can break the chain of infection. - NSTP file pic, for illustration purposes onlyWhether it’s a mutant or normal SARS-CoV-2 virus, if we strictly follow the SOP, we can break the chain of infection. – NSTP file pic, for illustration purposes only

WE have begun a new year, and the Covid-19 virus is still with us. Research has shown that the virus is caused by SARS-CoV-2 RNA virus which has a genome comprising around 30,000 bases.

The single-stranded ribonucleic acid (RNA) genetic material is made of building blocks A, G, U and C, i.e. adenine, guanine, uracil and cytosine bases.

Simply put, building blocks in various combination codes make up amino acids and a protein is made up of several amino acids.

The spike protein present in the SARS-CoV-2 virus is made of 1,273 amino acids. Any change in the combination can cause a change in the protein, which is commonly called a mutation.

Since SARSCoV-2 virus genome is made of single-stranded RNA, the mutation rate is slightly higher than bacteria. So far, several mutations have been reported in SARS-CoV-2. Most of the speculation about this virus variant are based on genome sequence and epidemiological data without experimental evidence, hence it is hard to conclude the infectivity of this virus.

Though the United Kingdom variant is proposed to have increased transmission rate by genomic epidemiological studies, thorough biological and virological studies need to be conducted to understand these specific mutations role in transmission, disease severity and mortality.

Our immune system can only recognise a short stretch of amino acids (eight to 15 in number) in the spike protein, called epitopes, and elicit an immune response. As the spike protein has 1,273 amino acids, it has numerous epitopes that can be targeted by our immune system.

However, there are three perspectives why we should not worry about the mutations in SARSCoV-2. First is the vaccine perspective. Most of the vaccines that are being developed for Covid-19 uses spike protein or its gene as the target.

Since spike protein of this virus has numerous epitopes, change in just one amino acid in a few locations will not significantly change our immune response to a vaccine.

It is analogous to shooting an object that has 100 targets, if we miss two targets, we still have 98 targets to “shoot” and clear the virus.

Currently the two major vaccines being licensed are RNA based vaccines. The sequence of RNA molecule in the vaccine is essentially synthesised in the laboratory, based on the genome sequence of the SARS-CoV-2 virus and encapsulated with lipid molecules.

The modified RNA molecule can be easily synthesised in a lab in a very short time, in the event of major mutations in the spike gene.

We can draw some comfort that it is unlikely that a sporadic mutation of spike gene can alter the immune efficiency of forthcoming vaccines for Covid-19.

Nevertheless, we should also monitor all possible variants of this virus by sequencing. Then we have the diagnostic perspective.

The molecular diagnostic test for Covid-19 is done by real-time polymerase chain reaction (PCR) method to detect N1 and RP genes or any sequence among the 30,000 bases.

Generally, multiple genes are targeted by this test, even if one gene is mutated the other gene can be detected by this method.

Even if the spike gene is used as a target, the location of the primers can be changed based on the mutations prevalence in the region. Hence, the impact on the diagnostic accuracy of Covid-19 due to spike mutation can be avoided by choosing the correct region of the genes in the realtime PCR test.

Finally, the containment perspective. This is the strict following of the standard operating procedures (SOP) by every person.

Observing the new norms, such as wearing masks, washing hands frequently, using hand sanitisers, maintaining social distancing, and minimising non-essential travels, are a must.

Even if the mutation allows the faster spread of the virus, strict SOP will break the chain of the spread of the virus.

There is plenty of good news on the horizon concerning Covid-19 vaccine, and how the mutations may not be as dangerous as they appear.

Let us trust our immunity — if one epitope is mutated, there are other sites (epitopes) our immunity can attack the virus.

Whether it’s a mutant or normal SARS-CoV-2 virus, if we strictly follow the SOP, we can break the chain of infection.

By Dr Ravichandran Manickam.

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