Recently, the Shanghai Municipal Center for Disease Control and Prevention conducted genetic sequencing monitoring of confirmed cases of new coronary pneumonia imported from the United Kingdom and found that the gene sequence of the new coronavirus in one case was B.1.1.7 subtype, which was similar to the mutant virus gene reported in the UK recently. On January 2, the Guangdong Provincial Center for Disease Control and Prevention also found a B.1.1.7 mutant in a confirmed imported case in the UK, which is highly similar to the mutant virus reported in the UK. At present, mutated viruses have been detected in many countries, and WHO has also notified several other variants.
How is the mutant virus currently diagnosed? Does this increase the infectiousness of the disease? Is the new crown vaccine developed in many countries effective?
On January 3, Lu Hongzhou, Secretary of the Party Committee of the Shanghai Public Health Clinical Center and Professor of the Department of Infectious Diseases of Huashan Hospital Affiliated to Fudan University, said in an interview with the Red Star News reporter that there is no evidence to prove the overseas discovery. Viral mutations increase pathogenicity. Still need more laboratory cell experiments and animal experiments to further confirm its infectivity.
What caused the virus to mutate?
Immunity vulnerable people or the key to mutation
What is the mutation of the new coronavirus? According to Lu Hongzhou, virus mutation refers to changes in the genetic material of a virus due to various reasons, such as base mutations in its genetic material DNA/RNA. Various factors such as chemistry and physics can induce various mutations. These mutations are often beneficial in viruses, such as HIV-1 virus, which has a mutation rate of one in 30,000. Such high mutations often lead to changes in drug resistance, which increase the difficulty of treatment, the difficulty of vaccine development, and the weakening of protection.
He added that viruses, as the simplest living organisms, are more prone to mutation due to their simple genetic material structure. These mutations mainly occur in the process of genome proliferation and replication. Due to immune pressure (such as changes in the cellular immune microenvironment where the virus exists) or the characteristics of the virus itself (such as errors in the replication and shearing of genetic material, lack of accurate replication capabilities), mutations occur all the time. Therefore, mutation can be said to be a strategy or way of survival for viruses to respond to environmental choices. This mutation is long and slow in the natural environment (such as the formation of new quasispecies) and can be accelerated with the increase of environmental pressure.
Lu Hongzhou introduced that the coronavirus (Sars-CoV-2) has changed once or twice a month since the beginning of the pandemic. The mutation rate of the mutant new coronavirus (B.1.1.7) found abroad this time is relatively fast . There are a total of multiple different gene mutation points in the genetic code of this virus mutation, including 6 synonymous mutations, 3 deletion mutations and 14 non-synonymous mutations, and its evolution is farther than the root. Among them, 8 gene mutation points occurred on the spike protein, the important structural protein of the virus. It is worth noting that the 501Y.V2 mutation occurs in the RBD receptor binding region, which leads to a tighter binding to the human cell receptor ACE2.
WHO has also notified several other variants, such as D614G, which can make the virus more contagious; the mink-related variant “Cluster 5” may be related to the reduction of natural infections or immune protection after vaccination. The scope is related to the duration. VOC 202012/01 variant, it can make the virus more contagious.
What kind of environmental changes caused the virus to mutate? According to Lu Hongzhou, according to the “Science” point of view, immunity to vulnerable populations may be the key to major mutations in the new coronavirus. These immune vulnerable populations may provide opportunities for the evolution of the new coronavirus, and the mutation of the new coronavirus will also aggravate the primary diseases of this population. It can be said that external environmental pressures, such as treatment strategies, vaccine strategies, and the host’s own immune environment can all be the cause of mutations.
▲On December 29, 2020, a man wearing a mask walked by in front of the Houses of Parliament in London, England. Picture from Xinhua News Agency
What are the characteristics of this overseas virus mutation?
The spread is wider, and the pathogenicity needs to be studied
Mutated viruses have been detected in many countries, but are there no virus mutations in countries where there is no report? Lu Hongzhou said that it is not because the virus mutation does not exist in the area, but because of the limitation of the detection methods and the strength of the detection.
Lu Hongzhou introduced that compared with influenza, which is also a respiratory virus, the rate of change of the new coronavirus is slower. However, a large number of mutation sites were detected in the mutations of the new coronavirus gene found overseas. Compared with the previous mutation of the new coronavirus, the scope of the spread of this mutation is also wider. The report pointed out that the mutant virus has 70% higher transmission than the original strain, and the binding rate of S protein to human ACE2 receptor has also increased by 100 times. It is worth pointing out that the accuracy of the data still requires more epidemiology. The precise results of the investigation also require more laboratory cell experiments and animal experiments to further confirm its infectivity.
Does the virus mutation cause the disease to worsen? In this regard, Lu Hongzhou believes that so far, the new mutation of the new coronavirus does not seem to cause the infected person to have more severe illness than the previous virus infected person. There is no evidence that this new virus mutation causes an increase in pathogenicity. This aspect still needs more research. At present, even if the new mutations of these viruses are truly more infectious, the overall course of the epidemic will not change as a result.
Lu Hongzhou emphasized that, at the very least, under my country’s continued strict prevention and control strategy, its impact on the overall course of the epidemic is still optimistic. The overall process of the epidemic is also affected by the protective measures in the public health strategy and the promotion of vaccines. Therefore, the people do not need to panic while not taking it lightly.
Virus mutation does not affect current detection methods
But put forward more requirements on testing methods
How to diagnose the new coronavirus mutation? Lu Hongzhou introduced that, first of all, the current mainstream nucleic acid detection reagents in my country are aimed at dual target genes, namely N gene and ORF1ab gene, which are more effective than single target gene amplification. The S protein gene mutation of this new mutant strain that is currently emerging overseas, and the remaining detection methods will not affect the sensitivity and specificity of nucleic acid reagents.
“During the COVID-19 pandemic, scientists from various countries have sequenced the Sars-CoV-2 genome. The continuous updating of sequencing methods has improved our grasp of the mystery of the viral genome.” The new crown variant strain cannot yet be differentiated and diagnosed. From the perspective of scientific research and medical diagnosis, the virus mutation puts forward more requirements for detection methods. However, on the basis of conventional nucleic acid detection technology-PCR positive and clinical diagnosis positive, high-throughput genome/transcriptome sequencing technology is used to determine the mutation characteristics of the new coronavirus. The mutation sites were further verified by sanger sequencing the PCR products of the genome fragments. Through the combined use of a variety of detection methods, to promote further understanding of the genetic code of the virus.
It is not yet confirmed that the vaccine is not effective against virus mutation
Still need to take protective measures
my country’s new crown vaccine has been approved for marketing, and Beijing, Shanghai and other places have started vaccination work. In the face of the mutation of the new coronavirus, is vaccination effective? In this regard, Lu Hongzhou introduced that after the vaccine is injected, the human immune system will respond to the entire virus, including the production of antibodies, and even the mobilization of cellular immunity to achieve anti-viral effects. Antibodies are not only for the part where the mutation occurred. Therefore, it has not been confirmed that the current vaccine is not effective against this new virus mutation B.1.1.7. More laboratory results are yet to be verified, and we take a positive attitude towards this.
According to the Beijing Youth Daily, Wang Huaqing, chief expert and chief physician of the China Centers for Disease Control and Prevention’s immunization program, said that according to the latest information released by the WHO, the vaccine effect has not been seen to be affected by the virus mutation, and the WHO has been paying attention to this issue.
Lu Hongzhou said that from the perspective of the development of influenza vaccines, the emergence of virus mutations also promotes the continuous advancement of vaccine development. Viral mutations can also promote the continuous update and development of more effective and safer vaccines. Judging from the current situation, we still recommend and encourage people to vaccinate to reduce the risk of infection.
So, what to do with isolation and protection in the face of mutated new coronavirus? In this regard, Lu Hongzhou said that major scientific issues such as virus mutation and what kind of mutation will cause disease aggravation still need more research data to answer. Therefore, it is necessary to resolutely resist the spread of mutant strains in a wider range. He reminded that people still need to maintain strict physical isolation measures, such as maintaining a certain social distancing, personal protection, such as wearing a good mask when traveling, and paying attention to hand cleaning and disinfection.
Lu Hongzhou added that for the emergence of significant changes, basic research should be actively promoted at the scientific research level, and medical diagnosis technology and training should be continuously improved. The prevention and control system of “early detection, early reporting, early isolation, and early treatment” is still an effective public health strategy to stop the spread of epidemics.