Proteomic basis of antigenic shift of Coronavirus from animal to human hosts

Coronaviruses are RNA viruses which were first identified as chicken infections way back in the year 1920 from North America. Of the seven Human Coronavirus species, three viz. SARS-CoV-1, MERS-CoV and SARS-CoV-2 have caused severe diseases. Low titre of neutralizing antibodies was seen in case of SARS-COV-2 as found in the previous infection of 2002-2003 i.e. SARS-CoV-1. When the genome profile of the current SARS-CoV-2 was compared with the older strains, it showed forty percent similarity with the MERS CoV. This indicates that origin of SARS-CoV-2 is basically from the non-human reservoirs viz. bat, camel, bovine, mice, snake etc. We aimed to study the number of nucleotide substitutions throughout the course of evolution in the coronaviruses. Clustal Omega multiple alignment tool was used for studying mutations in nucleotide and amino acid sequences. The structure of spike protein was designed using Swiss modelling and then interactions were studied by PyMOL. On comparing the results of genome sequences in animal reservoirs, it was seen that in the Receptor Binding Domain (RBD) of the Spike Protein of SARS-CoV-2, number of mutations have taken place enabling the zoonotic strain to find its way to internalize into human cells by using human Angiotensin Converting Enzyme 2 (ACE-2) as host receptor. Open Reading frame (ORF) region of SARS-CoV-2 had shown more number of mutation in coronavirus as compared to viral genome in bats. These mutations in Coronavirus of bats have enabled them as a serious diseases causing pathogens to humans.