Structure-function investigation of a new VUI-202012/01 SARS-CoV-2 variant
The SARS-CoV-2 (Severe Acute Respiratory Syndrome-Coronavirus) has accumulated multiple mutations during its global circulation. Recently, a new strain of SARS-CoV-2 (VUI 202012/01) had been identified leading to sudden spike in COVID-19 cases in South-East England. The strain has accumulated 23 mutations which have been linked to its immune evasion and higher transmission capabilities. Here, we have highlighted structural-function impact of crucial mutations occurring in spike (S), ORF8 and nucleocapsid (N) protein of SARS-CoV-2. Some of these mutations might confer higher fitness to SARS-CoV-2. SummarySince initial outbreak of COVID-19 in Wuhan city of central China, its causative agent; SARS-CoV-2 virus has claimed more than 1.7 million lives out of 77 million populations and still counting. As a result of global research efforts involving public-private-partnerships, more than 0.2 million complete genome sequences have been made available through Global Initiative on Sharing All Influenza Data (GISAID). Similar to previously characterized coronaviruses (CoVs), the positive-sense single-stranded RNA SARS-CoV-2 genome codes for ORF1ab non-structural proteins (nsp(s)) followed by ten or more structural/nsps [1, 2]. The structural proteins include crucial spike (S), nucleocapsid (N), membrane (M), and envelope (E) proteins. The S protein mediates initial contacts with human hosts while the E and M proteins function in viral assembly and budding. In recent reports on evolution of SARS-CoV-2, three lineage defining non-synonymous mutations; namely D614G in S protein (Clade G), G251V in ORF3a (Clade V) and L84S in ORF 8 (Clade S) were observed [2-4]. The latest pioneering works by Plante et al and Hou et al have shown that compared to ancestral strain, the ubiquitous D614G variant (clade G) of SARS-CoV-2 exhibits efficient replication in upper respiratory tract epithelial cells and transmission, thereby conferring higher fitness [5, 6]. As per latest WHO reports on COVID-19, a new strain referred as SARS-CoV-2 VUI 202012/01 (Variant Under Investigation, year 2020, month 12, variant 01) had been identified as a part of virological and epidemiological analysis, due to sudden rise in COVID-19 detected cases in South-East England [7]. Preliminary reports from UK suggested higher transmissibility (increase by 40-70%) of this strain, escalating Ro (basic reproduction number) of virus to 1.5-1.7 [7, 8]. This apparent fast spreading variant inculcates 23 mutations; 13 non-synonymous, 6 synonymous and 4 amino acid deletions [7]. In the current scenario, where immunization programs have already commenced in nations highly affected by COVID-19, advent of this new strain variant has raised concerns worldwide on its possible role in disease severity and antibody responses. The mutations also could also have significant impact on diagnostic assays owing to S gene target failures.