NEW DELHI: India’s first images of the SARS-CoV2 under a microscope are in — it’s round like other coronaviruses, about 70 to 80 nanometre (a human hair is about 80,000 nanometre) and has a cobbled surface structure.
The findings have been published in the ‘Indian Journal of Medical Sciences’ based on a report by the National Institute of Virology in Pune, the nodal testing centre for Covid-19 in India.
The specimen for these images were taken from the throat swab of a woman in Kerala, India’s first confirmed Covid-19 case. “A total of seven negative stained virus particles having morphodiagnostic features of a coronavirus-like particle could be imaged in the fields scanned,” the paper has said. “One particular virus particle was very well preserved.”
Studying the structure is crucial to understanding the origin and, eventually, develop vaccines to counter it. In the long run, it also helps understand its evolutionary relationship with other viruses. In this sample, two structural features specific to the novel coronavirus were observed.
When compared to other human viruses and coronaviruses, the report said, this sample had a shorter envelope (within which lies a long strand of RNA genome), at about 15 nanometre. However, that can be confirmed only when a sample is taken from a cell culture, it added.
The other feature was that peplomers, spike proteins on its surface that give it the name ‘coronavirus’ because of the crown-like structure, were found to have aggregated. In the common flu virus, these appear triangular in shape. Five distinct peplomers were imaged and a ‘stalk’ connecting the peplomer to the surface of the virus. The spikes are how the virus latch on to human cells and enter them. Further studies into the structure of the stalk could help understand the genomic structure of the virus.
The technique they used, electron microscopy, had been used by Hong Kong researchers to study the structure of the virus. “No detailed studies on ultrastructural cytopathology are available till date,” the paper said.