As the Chinese New Year approaches, the new crown virus has made a comeback and once again affects everyone's hearts. It is also destined to become a hot spot for exams in the past two years, so a thorough analysis of the various test sites that the new crown virus comes with is what students must do thing.
Today, Sister Centroid will take you to use biological knowledge to analyze the principles of the new coronavirus, hoping to help you.
1. Virus name:
2019-nCoV (n stands for new, CoV stands for Coronavirus coronavirus)
2. Biological classification:
Nidovirales
Coronaviridae (Coronaviridae)
Betacoronavirus (Betacoronavirus)
3. Introduction:
The highly pathogenic coronaviruses SARS-CoV and MERS-CoV, as well as the model virus MHV used to study the molecular virology of coronaviruses, belong to Betacoronavirus. This virus belongs to the +ssRNA virus (single-stranded positive-stranded RNA virus) with a length of about 30kb (1kb=1000bp, bp is the number of bases), and is one of the largest RNA viruses in the genome.
4. Structural features of virus genome:
The viral genome has a structure very similar to that of eukaryotic mRNA, that is, a methylated "cap" at the 5'end and a Poly(A) "tail" structure at the 3'end. It can be used as mRNA to translate into protein, and it can also be used as a template to synthesize negative-strand RNA, eliminating the RNA-DNA-RNA transcription process.
5. Virus replication process:
After the virus enters the human body, the outermost spike protein (Spike protein) binds to the specific receptors on the surface of human respiratory epithelial cells (ACE2 protein), enters the cell through cell endocytosis, and then directly uses the viral genome RNA As a translation template, viral RNA polymerase is expressed. Then use this enzyme to complete the transcription synthesis of negative-strand sub-genomic RNA (sub-genomic RNA), the synthesis of various structural protein mRNA, and the replication of viral genomic RNA. After the structural protein and genomic RNA have been replicated, they will be assembled at the endoplasmic reticulum of the host cell to generate new coronavirus particles, and secreted out of the cell through the Golgi apparatus to complete their cycle. (PS: Refer to the replication process of SARS virus in human cells)
6. Virus pathogenic mechanism:
The pneumonia caused by this new virus, like previous viral pneumonia, is essentially the immune system attacking itself.
After a virus invades the human body, the immune system will be mobilized, and when the enemy is annihilated, inflammation often occurs. In life, everyone's perception of "inflammation" is often negative. In fact, inflammatory response is a series of physiological reactions that occur when the body's immune system removes substances that it considers harmful. It is the normal response of the immune system to protect us, usually with "redness, heat, pain".
However, if the inflammatory response is too strong, it will cause too much autologous cell damage, and a large number of destroyed cells will release cellular contents, which will further provide more molecular signals to the immune system, further enhance the response, and eventually reach out of control degree. (Positive feedback regulation of inflammatory response, many processes are omitted here)
In some patients, a large amount of cell content is released into the blood, causing a broad and strong immune response, and a variety of cytokines are rapidly produced in large quantities. The result of excessive cytokine production is an extreme and exhaustive immune attack. While killing pathogens, more of its own cells are killed. This reaction caused by viral pneumonia mainly occurs in the endothelial cells of the vascular wall of the lung, which will cause a large number of activated immune cells to influx into the lungs, and at the same time, the permeability of the blood vessels will increase. Eventually, the patient will die of lung failure and acute respiratory distress syndrome. And hypovolemic shock.
7. Diagnostic criteria:
On the basis of meeting the criteria for suspected cases, samples such as sputum, throat swabs, and lower respiratory tract secretions are tested positive for 2019-nCoV nucleic acid by real-time fluorescent RT-PCR (RT-PCR or reverse transcription polymerase chain reaction). Confirmed.
8. Treatment methods:
At present, there are no specific antiviral drugs for coronavirus. The treatment is mainly symptomatic and supportive treatment. Symptomatic treatment is to supplement oxygen when the patient develops hypoxemia, and to correct the water and electrolyte balance when the water and electrolyte imbalance occurs. Supportive treatment is treatment that maintains and helps the body's functions, such as supplementing water, electrolytes, vitamins and nutrients. In response to autoimmune attacks on lung tissues, hormones (such as glucocorticoids) are used to suppress immunity to avoid further lung tissue damage, but this also suppresses the immune response and makes it difficult for the immune system to complete the formation of key autoantibodies in the course of viral infection. The side effects of using hormones, so the "New Coronavirus Pneumonia Diagnosis and Treatment Quick Guide" mentioned that unless there are special reasons, conventional corticosteroids should be avoided. Glucocorticoids can be used for short-term (3-5 days) according to the patient's dyspnea and chest imaging progress. You can try α-interferon atomized inhalation, lopinavir or ritonavir (broad-spectrum antiviral drug) and other drugs.
(PS: There is a schematic diagram behind the specific process of hormone suppression of immune function)
9. Preventive measures:
The most effective way at this stage is to avoid contact with the source of infection. But vaccination is still a powerful weapon for humans to deal with infectious diseases. Since the vaccinia vaccine eliminated smallpox 200 years ago, vaccines have become the ultimate magic weapon for humans to deal with many infectious diseases. At present, vaccines can be divided into six categories, namely, inactivated vaccines, live attenuated vaccines, DNA vaccines, antibody libraries, horse serum, and vaccines constructed using adenovirus vectors.
However, using inactivated coronavirus as an immunogen is potentially dangerous for humans. Moreover, inactivated bacterial vaccines need to cultivate a large number of viruses in vitro, without any leakage, and can only be mass-produced under the premise of foolproof, otherwise it will cause irreparable losses to production workers and the environment.
At present, my country has successfully developed a safe and reliable vaccine for the new crown. It is hoped that it can be popularized as soon as possible, and that the new crown virus will leave humanity as soon as possible.
More science contest details available in the center of mass physical official website View