A Review on D 614G Mutation with Bangladesh Scenario

With the COVID-19 pandemic, disparities between the infection rate and death rate in different countries become a major concern. In some countries, lower mortality rate compared to others can be explained by better testing capacity and intensive care facilities. Complete SARS-CoV-2 genome sequences from different countries of the world are continually submitted to Global Initiative for Sharing All Influenza Data using Next Generation Sequencing method. A SARS-CoV-2 variant with a D 614G Mutation in the spike (S) protein has become the most dominant form in the global pandemic. There are a number of ongoing studies trying to relate this mutation with the infectivity, mortality, transmissibility of the virus and its impact on vaccine development. This review aims to accumulate the major findings from some of these studies and focus its future implication. Some studies suggested D 614G strain has increased binding capacity, it affects more cells at a faster rate, so has a high transmissibility. Patients infected with this strain were found with high viral load. But still now there is no such evidence that this strain produces more severe disease as well as increased mortality. The structural change of spike protein produced by D 614G mutation was minor and did not hamper the vaccine efficacy. Some studies showed antibodies produced against D614 strain can neutralize G614 strain and vice versa. Whenever a mutation occurs in spike protein there are always chances of affecting the infectivity, transmissibility, vaccine efficacy. Therefore, more studies are required to find out the overall effect of D 614G mutation.

Genomic characterization of SARS-CoV-2 identified in a reemerging COVID-19 outbreak in Beijing's Xinfadi market in 2020

After 56 days without coronavirus disease 2019(COVID-19)cases,reemergent cases were reported in Beijing,China on June 11,2020.Here,we report the genetic characteristics of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)sequenced from the clinical specimens of 4 human cases and 2 environmental samples.The nucleotide similarity among six SARS-CoV-2 genomes ranged from 99.98%to 99.99%.Compared with the reference strain of SARS-CoV-2(GenBank No.NC_045512),all six genome sequences shared the same substitutions at nt241(C→T),nt3037(C→T),nt14408(C→T),nt23403(A→G),nt28881(G→A),nt28882(G→A),and nt28883(G→C),which are the characteristic nucleotide substitutions of L-lineage European branch I.This was also proved by themaximum likelihood phylogenetic tree based on the full-length genome of SARS-CoV-2.They also have a unique shared nucleotide substitution,nt6026(C→T),which is the characteristic nucleotide substitution of SARS-CoV-2 in Beijing's Xinfadi outbreak.It is noteworthy that there is an amino acid D614Gmutation caused by nt23403 substitution in all six genomes,which may enhance the virus's infectivity in humans and help it become the leading strain of the virus to spread around the world today.It is necessary to continuously monitor the genetic variation of SARS-CoV-2,focusing on the influence of key mutation sites of SARS-CoV-2 on viral transmission,clinical manifestations,severity,and course of disease.