The Indian variant of SARS-CoV-2 (B1.617) causes worse lung disease in hamsters than earlier versions of the coronavirus, the Indian Council of Medical Research has said in a new study days after the Union Health Ministry described it as a “variant of concern.”
Carried out on hamsters, the ICMR study shows maximal body weight loss and higher viral load in animals infected with B1.617, causing pronounced lung lesions in hamsters compared to the B1 variant.
This demonstrates the pathogenic or disease-causing potential of B1.617 in an animal model as the virus has been reported from human samples in at least 17 states and union territories with a significant presence in Maharashtra, West Bengal, Karnataka, Delhi and Gujarat.
Scientists at the National Institute of Virology, Pune, ICMR headquarters and a couple of other institutes studied the effects of B1.617 variants which have been associated with a surge of cases spreading rapidly not only in Maharashtra but in other states and abroad too.
The variant became known as the double mutant because of two genetic mutations (L452R and E484Q) but subsequently, a third mutation (P681R) was also seen. The tiny genetic changes possibly enhance the virus's transmissibility with the likelihood of escaping the immunity.
The scientists inoculated two groups of Syrian golden hamsters (nine each) intranasally with SARS CoV-2 isolates, B1 (D614G) and B1.617 respectively. The animals were monitored daily for the clinical signs and body weight.
The hamsters infected with B1.617 demonstrated increased body weight loss compared to the B1 variant. Also, they displayed pronounced lung lesions and haemorrhage.
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"This study demonstrates B1.617's higher pathogenicity in hamsters, which is evident with reduced body weight, higher viral load in lungs and pronounced lung lesions as compared to B1 variant. It caused pronounced lung lesions demonstrating the pathogenic potential,” the ICMR team reported in a paper, which is yet to be peer-reviewed and appeared in a preprint server.
The study comes a day after Public Health England also classified B1.617 as a “variant of concern” because it was more transmissible. Last week the health ministry too described it as a “variant of concern” nearly two months after Indian scientists flagged how it was driving the second surge in Maharashtra.
"In some of the districts, B1.617 comprises nearly 60% of all cases,” said Shahid Jameel, a senior virologist and head of the Trivedi School of Biosciences at Ashoka University who was not associated with the Indian SARS-CoV-2 genetic sequencing initiative.
Out of the 18,000 plus genetic sequencing of the virus carried out till May 4 by a consortium of 10 science laboratories (INSACOG), more than 1,500 samples carried the double mutation variant.