Published on June 19, 2021
AHMEDABAD: Rajesh Bhatt, Ahmedabad chief fire officer, bucked the general perception that if you get infected with Covid-19 once, there are less chances of second infection due to development of antibodies. The CFO got infected a second time in April, barely 30 days after he had contracted Covid-19 the first time.
The later infection during the deadly second wave saw Bhatt needing 13-day hospitalization due to a severe lung infection. In the first infection, he was cured after home quarantine. Contracting Covid-19 despite having perceptible immunity against the virus through prior infection or vaccination had left many citizens in Ahmedabad and across Gujarat puzzled.
And though the reinfections were not widely reported and the majority of those infected got away with a milder infection, a study by computer simulation by a group of researchers at Gujarat Biotechnology Research Centre (GBRC) may hold a key to understanding the phenomenon.
‘Immune escape not very widespread yet’
A paper, titled ‘E156G and Arg158, Phe-157/del mutation in NTD of spike protein in B.1.617.2 lineage of SARS-CoV-2 leads to immune evasion through antibody escape’ currently in preprint and peer-review, claims that the changes in Delta variant (B.1.167.2) made it ‘escape’ the antibodies gained by the body either through earlier infection or through intervention like vaccination.
‘B.1.617.2 variant 16 carried E156G and Arg158, Phe-157/del mutations in N-terminal domain (NTD) of spike protein. These mutations revealed more rigidity and reduced flexibility compared to spike protein of Wuhan isolate (original/ wildtype virus) … Results of the present study demonstrate the possible case of immune escape and thereby fitness advantage of the new variant and further warrants demonstration through experimental evidence,’ mentioned the study.
Simplifying the find for laymen, researchers said that the variant had two amino acids (Arg158 and Phe-157/del) missing, whereas E156G got mutated on the spike protein of the virus. Spike protein of Covid reports the maximum changes as it binds with the human cells to proliferate further. These changes in the variant helped it escape the antibodies as it didn’t match the copy of the virus they had in memory.
‘Our study showed possible case of immune escape by demonstrating reduce binding of mutant spike compared to Wuhan isolate with reported antibody known to bind NTD of spike protein, thereby providing insights into the structural basis and highlight the impact of the key mutations for the higher transmissibility, pathogenicity and virulence,’ mentioned the paper.
The researchers advocated better monitoring and identification of the new variants through genomic sequencing to check for its transmission, virulence and altered antigenicity. The state government has recently announced genomic sequencing of 1,000 samples every month as part of its third wave action plan.
But experts said that the ‘immune escape’ is not very widespread yet. Dr Amit Prajapati, a city-based critical care specialist, said that they have reported only a few cases of severe second-time infections in April-May. “At our facility, we have reported only one case where the patient had tested positive after both the doses of vaccination. Thus, the findings should be seen more as a warning that we must not lower our guards even after developing antibodies,” he said.