On 16 August 2020, Malaysia's health ministry announced that D614G, a mutation of SARS-CoV-2 virus which causes Covid-19, has been detected in at least three of the 45 cases in a cluster that started from a restaurant owner returning from India and breached his 14-day home quarantine. The D614G mutation was first detected in February in Europe and since then has become the dominant variant of SARS-CoV-2, found in swab samples across the world. As per some researchers, the mutation is deemed to have given the virus some kind of biological edge enabling its global spread.
What is D614G
- Sars-Cov-2 is the official name of the virus that causes the disease Covid-19. And D614G is a mutation of Sars-Cov-2.
- D614G is situated within the protein making up the virus's "spike" it uses to break into our cells. This mutation changes the amino acid at position 614, from D (aspartic acid) to G (glycine) — so, D-614-G.
- Sars-Cov-2 has undergone several mutations since the pandemic emerged in December 2019. However, only one of these mutations has so far been singled out as possibly altering Sars-Cov-2 behaviour, namely D614G.
- The mutation appeared sometime after the initial Wuhan outbreak, probably in Italy. This strain was seen in as many as 97% of samples around the world.
How does a variant become dominant
- Dr. Bette Korber, a computational biologist & population geneticist said that the fact the D614G variant now appears to be dominant everywhere, including in China, indicates it may have become better at spreading between people than the original version. Whenever the two versions were in circulation at the same time, the new variant took over.
- In his research paper published in July, Dr Korber had said that the D614G variant is so dominant, it is now the pandemic. And it has been for some time - perhaps even since the start of the epidemic in places like the UK and the east coast of the US.
- So, while evidence is mounting that this mutation is not neutral, it doesn't necessarily change how we should think about the virus and its spread, he wrote.
Does D614G increase Covid-19 transmissibility
- All viruses mutate constantly because they are replicating constantly. But while some changes help the virus reproduce, others may hinder it and some changes might make no difference at all.
- In lab tests conducted by Scripps University in Florida, the mutated virus was better at entering human cells than those without the variation. Changes to the spike protein the virus uses to latch on to human cells seem to allow it to "stick together better and function more efficiently".
- In another study conducted by the New York Genome Center and New York University, the researchers said that their findings point to the mutated virus being more transmissible than the original version "at least in the lab" but said it remains unclear how representative the lab results are of transmission in real patients.
- Two studies published in Cell, by Dr. Korber and a second study by WHO Collaborating Center in China, too gave similar outcomes that D164G, the dominant strain of SARS-CoV-2 seems to be 10-fold more infectious than the original Wuhan-1 strain.
- However, Cell also published a research review in July, by Dr Nathan D. Grubaugh, an assistant professor of epidemiology of microbial diseases at Yale School of Public Health who remarked that such studies suggest, but not prove increased viral transmissibility.
Can mutation impact vaccine research
- Earlier it was speculated if we will need to develop separate vaccines for different variants. However, most of the vaccines in development are based on a different region of the spike so this should not have an impact on their development.
- Although the D614G mutation happens in the viral spike protein, it does not change the receptor-binding domain (RBD) at the tip of the spike protein.
- The RBD binds to the ACE2 receptor on human cells; it is also the main target of the immune system. In essence, the D614G mutation alters the spike protein, but not the critical RBD immunogenic part.
- A WHO study in China also showed that the G614 variant remained susceptible to neutralization by antibodies isolated from infected patients.
- Moreover, given how most of the circulating SARS-CoV-2 around the world is the D614G variant now, one vaccine is likely to do the work, suggest researchers.