The Indian variant B.1.617 can "modestly" evade the neutralising antibodies produced after vaccination, but its two mutations do not have an additive impact on loss of sensitivity, according to a molecular study of the variant conducted by Indian SARS-CoV-2 Genomic Consortia in collaboration with researchers from UK.
The variant is called "double mutant" because of it the mutations, E484Q and L452R. The yet-to-be peer-reviewed article uploaded on biorxiv shows that immune evasion of the "double mutant" variant is less than variants with E484K that caused ten-fold reduction in neutralisation as compared to the variant that was in circulation last year.
"What we found was a reduction in the ability of the antibodies to neutralise this variant, but they weren't ineffective. There are infections reported in vaccinated individuals but all vaccines protect against severe disease," said Dr Anurag Agarwal, one of the authors of the paper and director of Institute of Genomics and Integrative Biology (IGIB).
He added, "Breakthroughs are being seen with both (all) vaccines though. In vast majority, disease is mild."
The researchers also found that the variant was more transmissible in laboratory setting, corroborated by the data of breakthrough infections – infection after complete vaccination – from a Delhi hospital. Of the 33 healthcare workers who got the infection, almost half were caused by B.1.617 variant.
"The dominance of B.1.617 could be explained by prevalence of this lineage in community infection or simply reflect transmission between healthcare workers. The data nonetheless raise the possibility of a transmission advantage of B.1.617 in vaccinated individuals," the article said.
In addition, the mutation P681R – also found on the spike protein of the virus that attaches with the human receptors to infect a person – makes the virus more infective.
"The P681R mutation increases the formation of syncytium (a single cell with several nuclei) makes the virus better equipped to enter the human cell, replicate for longer, and lead to a higher viral load. Basically, the viral cells fuse together, creating a larger space for the virus to replicate and making it difficult for the antibodies to destroy them. So, if 10 copies of the neutralising antibodies were needed to destroy the previous virus, the body may need to create 15 copies for this. This also means that the virus will stay in the body longer and transmit to others," said Dr Rajesh Pandey, senior scientist at IGIB.
The researchers conducted the experiments using a pseudovirus with the key mutations of the Sars-CoV-2 and sera from people who had received the Pfizer/BioNTech vaccine.