How COVID-19 Variants Get More Infectious And Resistant To Antibodies

All viruses, including SARS-CoV-2 -- the virus that causes COVID-19 -- constantly change through mutation and become more diverse. Think of it as like the branching out of trees, with each branch slightly different than the others. Scientists can compare and label them according to the differences.

Representational Image

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These small differences, or variants, may sometimes emerge and disappear; other times, new variants persist. And some of it may affect the virus¡¯s properties, allowing it to spread more easily, heighten the severity of the associated disease or make it resistant to treatments or vaccines.

Scientists have been tracking and documenting these variations since the onset of the pandemic and have categorised them into Variants of Concern (VOC) and Variants of Interest (VOI) depending on how easily and quickly they spread compared to other variants, leading to more cases of COVID-19. This includes the Delta variant, or B.1.617.2, which was first identified in India and has largely been credited for driving the second wave of coronavirus infections.

Why does coronavirus mutate?

A team of US researchers has now identified how multiple mutations on the SARS-CoV-2 spike protein independently create variants that are more transmissible and potentially resistant to antibodies.

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Covid-19 variant | Photo: Reuters/Representational image

¡°The spike on the surface of the virus helps SARS-CoV-2 enter into host cells,¡± said senior author Priyamvada Acharya from Duke Human Vaccine Institute in a press note.

¡°Changes on the spike protein determine transmissibility of the virus -- how far and quickly it spreads,¡± she explained. ¡°Some variations of the SARS-CoV-2 spike are occurring at different times and different places throughout the world, but have similar results, and it¡¯s important to understand the mechanics of these spike mutations as we work to fight this pandemic.¡±

Creating mimics of virus to study its behaviour

The study, published in journal Science, saw the researchers combine structural biology and computation analyses to identify changes in the virus¡¯s spike protein. Cryo-electron microscopy allowed atomic level visualization, while binding assays enabled the team to create mimics of the live virus that directly correlated with its function in host cells.

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Rory Henderson, the co-corresponding author, said that the skeleton of the spike allowed the researchers to visualise how the spike was moving, and how this movement changes with mutations.

¡°The different variant spikes are not moving the same way, but they accomplish the same task. The variants first appearing in South Africa and Brazil use one mechanism, while the UK and the mink variants use another mechanism,¡± he added.

Are current vaccines efficient against new variants?

According to the study, all the variants showed increased ability to bind to the host, notably via the human angiotensin-converting enzyme 2 (ACE2) receptors of human cells in the nose, lungs and other areas of the body. The changes also created viruses that were less susceptible to antibodies, raising concerns that continued accumulation of spike mutations may reduce the efficiency of current vaccines.

A doctor attends to a baby who tested positive for Covid-19 coronavirus at a hospital | Photo: AFP/Representational image

But the government has said that both the Covishield and Covaxin vaccines work against SARS-CoV-2 variants Alpha, Beta, Gamma and Delta, while effectiveness tests against the Delta Plus variant will be available in the next week.

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According to international data, presented by ICMR Director General Balram Bhargava, Bharat Biotech's Covaxin remains equally effective against the Alpha variant, though against Beta and Delta variant its neutralising capabilities reduce threefold. Covishield's capabilities reduce 2.5 to 9 fold against Alpha and two-fold against Delta, while Pfizer and Moderna's capabilities reduce significantly against the Delta variant.

The two vaccines, #COVISHIELD and #Covaxin work against the Alpha, Beta, Gamma, and Delta variants of SARS-CoV2.

Laboratory tests are ongoing to check the vaccine effect on the Delta Plus variant - DG, @ICMRDELHI#IndiaFightsCorona #Unite2FightCorona pic.twitter.com/fAwHDMNQBc

¡ª PIB India (@PIB_India) June 25, 2021

Notably, drug makers Moderna and Pfizer-BioNTech have said they are developing additional booster shots to fight against the worrisome COVID-19 variants.

Additional COVID-19 precautions required?

Experts say that as of now, none of the new coronavirus variants call for any new prevention strategies. The Indian government continues to follow the same public health intervention, irrespective of the variants, that include ¡°cluster containment, isolation and treatment of cases, quarantining of contacts and ramping up vaccinations.¡±

The importance of human behaviour couldn¡¯t be stressed enough: more the infected people, greater are chances for a mutation to occur. People need to follow basic COVID-appopriate strategy, including masking, physical distancing, frequently washing hands and limiting gatherings of people in close proximity with poor ventilation to limit the spread of the virus.

Scientists work on Covid-19 samples to find variations of the virus | Photo: AFP/Representational image

Experts recommend that the larger public and health officials shouldn¡¯t overreact to these variations in the novel coronavirus and continue to be watchful as well as ensure that testing, treatment and vaccines are still effective.

Scientists, meanwhile, continue to monitor these mutations to track potential vaccine escape, increased transmissibility and disease severity.