As the coronavirus Delta variant B.1.617.2 has further mutated to 'Delta plus', virologists are concerned whether this new variant will evade pre-existing immunity better than either Delta or Beta.
The genome sequencing of Delta plus revealed K417N mutation in the Delta genomic background. The World Health Organisation (WHO) termed the Delta variant as a 'variant of concern' (VOC) and said it is more powerful than the Alpha variant that has lineage B.1.1.7.
Experts stressed on need for more studies on the 'plus variant' before reaching any conclusion. Leading Virologist Dr. Shahid Jameel told ANI, "The B.1.617.2 or Delta variant of concern has acquired another mutation - K417N - within the receptor-binding domain of the spike protein. This new variant is called Delta+ or AY.1. This change is of note since this mutation is also found in the B.1.351 or Beta variant of concern."
"So, in a sense, this is the coming together of changes earlier found in two different variants of concern, which are so far the best adapted to immune escape. Whether this new variant will evade pre-existing immunity better than either Delta or Beta remains to be seen. Therefore, it is a cause for worry but not panic. More studies are needed," says Dr Jameel. Till date, 202 sequences corresponding to this variant have been found in 11 countries with the highest numbers of cases being reported from the USA (82) and within it the state of California (62).
India reported eight cases of Delta 'plus' variant with three cases coming from Tamil Nadu and one each from Odisha, Karnataka, Andhra Pradesh, Gujarat, and Maharashtra. Regarding its chances of causing a surge, the virologist said, "This has to be watched carefully. Remember that even B.1.617, the precursor of Delta VoC was also seen in very low numbers in India in December 2020 and surged within the next 8 to 12 weeks."
On vaccination efficacy, regarding this variant, Dr. Jameel said, "The Indian vaccines have shown three to eightfold reduced efficacy against the Delta and Beta VOCs. Whether this coming together of key mutations would be neutral, additive or more than the sum of both remains to be seen." Two mutations in the Delta variant L452R and P681R make it more infectious and transmissible.
"L452R allows the virus to bind better to the ACE2 receptor. P681R allows better cleavage of the S1/S2 junction in the Spike protein, which is required for the virus to enter cells," he explained. Till date there are no studies on the transmissibility or immune escape potential of the mutated Delta plus variant.