While intensive efforts continue to focus on the development of an effective vaccine against coronavirus infection, plasma therapy is currently being widely explored as an interim strategy to treat Covid-19. Neutralising antibodies, typically of IgG subclass, are important for blocking viral infection, and hence are considered key components for the success of plasma therapy. Individuals with plasma-neutralising antibodies at sufficiently high levels are generally considered most suitable donors for successful plasma therapy. Measurement of neutralising antibodies in routine clinical samples, however, remains a challenge. While recent studies from the Indian Council of Medical Research suggest little benefit from plasma therapy, there is not enough information on whether all the donors selected for plasma therapy had sufficient titers of neutralising antibodies to donate plasma, and whether these titers reflected in all recipients that received the transfusion. A new study, led by Dr Anmol Chandele and Dr Kaja Murali Krishna of ICGEB-Emory Vaccine Center at the International Centre for Genetic Engineering and Biotechnology, New Delhi, in collaboration with ICMR-National Institute of Malaria Research, Department of Biotechnology and the Emory Vaccine Center, Atlanta, gives new hope to improve plasma therapy regimen in India. This study- published as a pre-print - finds that while a vast majority of the 42 Covid-19 recovered individuals examined had IgG, nearly half of them did not have appreciable levels of neutralising antibodies. Only 7 of the 42 Covid-19 recovered individuals examined had sufficiently high levels of neutralising antibodies that may be most suitable to increase success of plasma therapy. Interestingly, this study finds that the levels of IgG antibodies that bind to the receptor binding domain (RBD) of the SARS-CoV-2 serve as good surrogate measurement to estimate neutralising antibody titers, said the study authors.
