By Trang Truong and Yidan Gao
Worldwide healthcare efforts have led to the recovery of millions of patients infected with the SARS-CoV-2 virus over the course of 2020. However, recent discoveries of new strains of the SARS-CoV-2 virus have raised concerns about the infectivity of the disease and whether these new, mutated forms of the virus pose a deadlier threat. This article will address the implications of such mutations upon viral transmission rates, fatality, and vaccine development.
At the molecular level, the SARS-CoV-2 virus is made of ribonucleic acid (RNA). RNA consists of individual units called nucleic acids (much like the DNA in our own cells). The specific nucleic acid sequence for SARS-CoV-2 encodes amino acids that make up the protein forming the virus. Think of this nucleic acid sequence as the virus’ “barcode”: when the virus infects our own cells, it hijacks our cells’ machinery and uses this barcode to replicate, churning more copies of the infectious viral protein.
This nucleic acid sequence is not static, however; it can change through mutations. Mutations can occur because of many reasons, one of which are errors in viral gene replication. Proteins involved in viral gene replication are very error-prone, creating mistakes in the replicated genetic materials. When this sequence changes, the final protein product of the virus is modified as well, resulting in new versions of the virus. These mutations can affect many characteristics of the virus and make it harder for our immune system to recognize and fight them.
Notably, the discovery of a mutation at position 23,403 of the SARS-CoV-2 nucleic acid sequence made headlines because the mutation changed the part of the virus protein that is responsible for attaching to human cells: the virus’ spike. Specifically, the virus’ genome changed from an A to a G at this nucleic acid position. This mutation led to the amino acid at position 614 of the viral spike to change from an aspartic (abbreviated as D) acid to a glycine (G). Reflective of the mutation, this new strain of the SARS-CoV-2 virus is called the G614 strain. This new mutated version of SARS-CoV-2 quickly became the prevalent strain of the virus across the world, constituting over 75% of approximately 12,000 tested sequences by the end of May.
With the rise of this new form of the virus, researchers are concerned that the infectivity of SARS-CoV-2 may increase. In a study published in July 2020, scientists observed that the new mutant G614 strain spread more quickly than the original D614 strain. This suggests that the mutation affecting the virus’ spike may make the disease more infectious than before, as this mutation facilitates the spike protein processing after the virus attaches to human cell receptors, allowing for better viral entry. Another study published in Cell demonstrated that this new G614 strain of SARS-CoV-2 appeared to infect human and non-human primate cell-lines more easily than the previous D614 strain; however, it is important to remember that the results from cell culture work may not directly reflect the transmission events in a normal environment. Research is continuously being conducted, and more studies are needed before we can come to concrete conclusions.
Fortunately, despite the possible increase in infectivity, the mutant G614 strain of the virus does not initially seem to be any deadlier than the previous D614 strain of SARS-CoV-2. This hypothesis is being studied however as a couple of other studies in the Journal of Human Genetics and International Journal of Clinical Practice have reported greater fatality rates associated with the mutated strain. More research needs to be performed in this area to know for sure. However, the G614 strain does not appear to be more difficult to treat; the rate of fatalities resulting from COVID-19 has remained about the same in the US (approximately 1%) despite the mutant G614 strain becoming more prevalent.
With the mutation changing the protein structure of the virus, there may be some worry that the new G614 strain hinders the process of developing a vaccine for COVID-19. Vaccines are used to prime our bodies to produce antibodies capable of recognizing foreign pathogens (such as the SARS-CoV-2 virus). With the mutated G614 strain becoming the novel prevalent strain, some may be worried that any previous work done on developing a vaccine is rendered useless since it was all based on the original D614 strain. Reassuringly though, preliminary research indicates that the antibodies produced in response to the D614 strain of SARS-CoV-2 appear to be able to recognize the new G614 strain as well. Furthermore, many of the vaccines in development are designed to generate antibodies that recognize to a different part of the SARS-CoV-2 virus’ spike, separate from where the G614 mutation is found. In other words, a vaccine that works against the old D614 strain should still be effective against the new G614 strain. With these findings and research processes, researchers are not overly concerned about the mutated virus inhibiting the development of a vaccine.
The fight against COVID-19 is constantly shifting with new discoveries being made everyday. The more information that medical professionals and researchers gather about the virus, the better prepared they are to treat patients and create potential vaccines and therapeutics. The rise of the new mutated G614 strain of the SARS-CoV-2 virus is just another curve ball in this long battle; luckily, it does not seem to affect our current medical efforts too much. In addition to vaccine development and medical interventions, simple behavioral changes, such as social distancing and hand washing, can still make a huge difference in protecting us from the virus, regardless of its mutations. Staying up-to-date on the latest developments in the fight against COVID-19 is also critical during this pandemic; for more information on various COVID-19 topics such as vaccine development and post-recovery life, please follow the Students vs Pandemic blog post page!
Results from ongoing research and the current understanding of COVID-19 are constantly evolving. This post contains information that was last updated on September 11, 2020.