CSIR-Centre for Cellular and Molecular Biology (CCMB) has established stable cultures of COVID-19 from patients’ samples in the last one-and-a-half months.
Virologist Krishnan H. Harshan and his research team have isolated infectious viruses from several isolates. The ability to culture in the lab enables to work towards vaccine development and testing potential drugs to fight COVID-19, said director Rakesh Mishra.
“The premier research institution could become a potential donor of the culture to other authorised centres that can continue growing the virus for their own use,” he said, pointing out that the virus is known to infect epithelial cells in human respiratory tract. It makes viral proteins first and then starts to replicate the genomic RNA to make more copies of itself.
This meant the virus needs a set of host factors to replicate. “Currently, primary epithelial cells generated from human origins do not grow for many generations in labs, which is key to culturing viruses continuously. CCMB and other labs are growing the virus through an ‘immortal’ cell line using kidney epithelial cell lines from Green African monkey and carry a mutation allowing them to proliferate indefinitely,” said Dr. Krishnan.
This ‘cultured SARS-CoV-2’ can help in making vaccines, antigens, test drugs and so on. Vaccines trigger immune response in host organism that can be used as protection from infection from viruses. Usually, proteins specific to such pathogens are good candidates as vaccines as they trigger antibody response in the host that could be long-term or short-term. Such killed viruses are used as vaccines in several cases like polio.
Though the inactivated virus cannot initiate infection, their structural proteins trigger antibody production. The efficacy of inactivated SARS-CoV-2 as vaccine candidate is currently being investigated by several groups. Inactivated viruses can trigger antibody response in other mammalian hosts like mice, horses and camels. Antibodies generated in these can be purified and processed for injecting into humans to trigger antiviral response and limit the infection. These antibodies are not vaccines, but can be considered as antidote against the virus, he said.
Lab culture of virus will also help in testing of antibodies because neutralising antibodies can bind to viruses preventing them from infecting cells. These antibodies can be generated in other mammals and their neutralising capacity is studied by incubating with infectious virus to check for the prevention of infection successfully, he said.
Drug-screening too will be possible as a quick way to identify a good drug is to ‘repurpose’ those already being used in humans for other infections since they had already undergone clinical trials. So, if found to be having anti-SARS-CoV-2 effects, they can be quickly tested in humans for limiting COVID, he pointed out.
“We can now isolate and maintain viral strains. We are working towards producing viruses in huge quantities that can be inactivated to be used in vaccine development and antibody production. We have also started testing potential drugs with DRDO and others. We hope such systems are replicated at multiple research institutes and private companies to become a useful resource in the fight against this pandemic and for future preparedness,” he added.
