As the world battles with hyper-infectious delta COVID-19, scientists are urged to understand the basis of its biological behavior. The delta variant not only spreads ferociously but is also more transmissible. Reduced vaccine effectiveness against this variant has been found, which means even a “fully vaccinated person” is at risk. Currently, the Delta variant is the predominant strain of COVID-19 in many countries.  

 Many research studies have found that an amino-acid modification in the delta is the key player that contributed to the swift spread. Researchers say many people are spreading the virus even before they come to know they are infected. That is one of the main reasons that lead to the rapid spread of the virus. Epidemiological studies proved that the Delta variant (B.1.617.2) is at least 40% more transmissible than the Alpha variant identified in the United Kingdom in late 2020. 

 A team of researchers led by Pei-Young-Shi explained why the hyper-infectious delta variant replaced other SARS-COv2 strains in a short span of time. “The key hallmark of Delta seems to be ramping up to the next notch. We thought Alpha was very pretty bad and very good at spreading but delta seems to be even more” says Pei-Young-Shi, a virologist at the University of Texas Medical Branch in Galveston. 

 Shi’s team and various other teams have zeroed in on a mutation that changes a single amino acid in the SARS-Cov-2 spike protein (the viral molecule that is responsible for recognizing and invading cells). The change is called P681R. It is named so because it swapped proline, an amino acid at position 681 on the spike protein, with another arginine. This single change in the mutation has the power to resuscitate Delta’s entry into the cells. 


 Delta was not the first SARS-Cov-2 variant to gain a mutation. The Alpha variant also has a different amino-acid change at the same location as Delta. Pei-Young’s team found that the spike protein is cut much more efficiently in Delta than in Alpha particles. Later other results were reported by Wendy Barclay, a virologist at Imperial College London. Wendy and her team also compared delta with an earlier strain. Both the experiments proved that the P681R is responsible for spike spread.  

 The researchers also experimented between P681R and Delta’s violent infectivity and spread. Pei-Young-Shi and his team found that in cultured human airway epithelial cells were infected with equal numbers of Alpha and Delta. The researchers found that the Delta’s advantage vanished when the researchers eliminated the P681R. It is said that the mutation can also speed up the spread of SARS-Cov-2 from cell to cell. 

 The study says that P681R is the main reason for the Delta variant’s key rapid transmission and infectivity. However, P681R is not the only mutation responsible for the delta variant spread. P681R is also present in Kappa!