Over the last month and a half, CSIR-Centre for Cellular and Molecular Biology (CCMB) has establishedstable cultures of COVID-19 causing coronavirus, SARS-CoV-2 from patients’ samples.A team of researchers led by the Virologist in CCMB, Dr. Krishnan H Harshan have isolated infectious viruses from several isolates. The ability to culture the virus in lab enables CCMB to work towards vaccine development and testing potential drugsto fight COVID-19. It also makes them a potential donor of the culture to other authorized centres that can continue growing the virus for their own use.
This virus is known to infect epithelial cells in human respiratory tract. The viruses infect these cells by interacting with receptor proteins called the ACE-2 following which the virus is internalized by a process namely endocytosis. Virus RNA is later released into the cytoplasm of the cells where it makes viral proteins first and then starts to replicate the genomic RNA. Thus, the virus uses resources from these cells to make more copies of itself. Therefore the virus needs a set of host factors that allow it to replicate. “Currently, primary epithelial cellsgenerated from human origins do not grow for many generationsin labs, which is keyto culturing viruses continuously. And hence, CCMB and other labs who are growing the virus need an ‘immortal’ cell line”, says Dr Krishnan. They use Vero cells – kidney epithelial cell lines from green African monkey, which express ACE-2 proteins and carry a mutation that allows them to proliferate indefinitely.