There have been cases of reinfection of SARS-CoV-2 across the globe and including a particular case where it had occurred despite the presence of neutralising antibodies. The study then showed the presence of a mutation in the structural spike protein of the coronavirus as it has happened in most cases of reinfection.
However, there is also evidence of SARS-CoV-2 or COVID-19 refinfection without any mutations to the spike protein, a joint study by scientists of CSIR-Centre for Cellular & Molecular Biology (CCMB) and doctors at the Apollo Hospitals here indicated on Wednesday.
The study reported two cases – one clear case and another possible case of COVID reinfection detected during routine surveillance. No difference in the spike protein of the virus was noticed in these cases when the samples were sequenced to establish the genetic diversity of the virus.
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First case was a 61-year-old male healthcare worker, who had tested positive for COVID-19 on Aug 31 last year following contract tracing. After an episode of asymptomatic infection and home quarantine, he tested negative subsequently. Although he had no travel history in between, complained of weakness in second week of November and developed a cough two days later.
He again tested positive for the virus on Nov.14. There were no other symptoms during this period and it was a mild disease overall. Genetic sequencing had revealed the presence of 10 unique variations between the viral genomes of both cases. However, no variation was observed in the 'spike protein' which binds to the host cells to spread the virus.
Second case is that of a 38-year-old male admitted to the hospital with symptoms of headache, fever and tested positive on Nov.4. The patient was symptom-free after a day, but on Nov.22, fever surfaced again. Sample collected on that day tested positive for COVID-19. Other than five days of fever following the test, there were no symptoms during the second episode.
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Genetic analysis revealed the presence of three unique variations between both the episodes, and a large number of shared variants including that of the spike protein. If the first case had 10 unique variations between the viral strains; the second remains a bit unclear with three unique variations in 18 days, higher than expected, possibly due to prolonged viral shedding and accelerated viral evolution due to immuno-compromised state, it explained.
“Our study provides rare evidence but distinct possibility of reinfection without changes in the spike protein, and highlights the need for further research to understand COVID-19 reinfections ," said scientists including Onkar Kulkarni, Suneetha Narreddy, Lamuk Zaveri, Irawathy Goud Kalal, KarthikBharadwaj Tallapaka and Divya Tej Sowpati.
CCMB Director Rakesh Mishra said there were a lot many unknowns about COVID-19 and deep research including continued genome sequencing is necessary to understand why this virus is behaving differently. “Reinfection in particular needs to monitored and studied extensively as it will have implications in vaccine effect, herd immunity and multiple waves of infection,” he added.
It was published in reputed journal 'Clinical Infectious Diseases'. https://doi.org/10.1093/cid/ciab136 .