Around November 2002, some diseases with unknown etiology and severe respiratory symptoms were discovered in Guangzhou Province, China. The disease has also been discovered in Hong Kong, Vietnam and other places and spread to many countries around the world. In 2003, the disease was discovered in Vietnam by the Italian physician Wobyna, who suggested it be named SARS (se-vereacuterespiratory syndrome) and issued an “alert” to the World Health Organization. However, Dr. Wobyna died of SARS. After collective research by scientists from ten countries (including my country), the World Health Organization had announced that the pathogen of SARS was a new type of coronavirus on April 16, 2003. As a pathogen, the virus complies with Kock’s three laws, that is, the virus can be isolated from most patients; the virus can be subcultured in vitro; after the virus is inoculated with monkeys, monkeys show typical symptoms of SARS, and the same can be isolated from infected animals virus. Although since February to March 2003, the new coronavirus has been isolated and the whole genome sequenced, but the results of monkey experiments conducted by the Dutch laboratory finally confirmed that this virus is the pathogen of SARS. After confirming that the coronavirus is the causative agent of SARS, scientists have not ruled out the co-infection of individual patients with other microorganisms. Because co-infected microorganisms generally fail to show that the corresponding antibody titer in the infected person has increased by more than 4 times, it cannot be the main pathogen of the disease.
- General characteristics of coronavirus
In 1961, Kendall and others inoculated the nasal washing liquid of young students with colds in human embryo tracheal organ culture, and isolated a virus through human test and interference test. In 1967, another scholar used this method to isolate 6 strains of viruses. The prototype representative strain was OCA3. The appearance of this virus was found to resemble the corona (solarcorona) under the electron microscope. In 1968, it was proposed to be named Coronavirus, which translates as coronavirus. Coronavirus is generally difficult to cultivate, and it often needs to be blindly passaged before it can be successfully isolated and cultivated. In addition to entering the trachea, coronaviruses can also grow in embryonic lungs and embryonic intestinal cells, and can also cause intestinal infections. Human intestinal coronavirus is more difficult to cultivate than respiratory coronavirus. Adding a small amount of trypsin (5mg) to cell culture medium can promote virus reproduction.
According to the special morphological structure of this virus in 1975, the International Commission on Viruses, which can cause natural infections in a variety of animals (cats, mice, cows, dogs, rabbits, pigs), and can involve different organs. The virus family Coronavirus family. This virus is a single positive-stranded RNA virus, which has a high mismatch rate during virus replication.
The gene of the human coronavirus 229E strain is 27277 nucleotides, with a leader sequence at the 5’end, followed by the RNA polymerase gene (composed of two overlapping reading frames), and the surface glycoprotein gene is also called thorn Spike coding gene (S), followed by ORF 4a, ORF4b, whose function is unknown, followed by ORF5, which is probably a structural protein, also known as SM protein, similar to the M2 protein of influenza virus, and later is membrane Protein M; its 3’end is N (nucleocapsid protein), where S, M, and N are all structural proteins.
Second, the characteristics of the new coronavirus
Since the Shanghai Municipal Health Bureau organized the Shanghai Pathogen Research Group in early April 2003, scholars have begun research on the SARS virus. Successfully established RTPCR method and immunofluorescence antibody detection method. The study of SARS virus has gone through a complicated process of eliminating known pathogens. Some laboratories in Canada initially ruled out potentially involved viruses (influenza, parainfluenza, type 1, 2, 3, adenovirus, respiratory syncytial virus) from clinical specimens, and later performed immunopurification through autopsy to exclude some rare ones Viruses, mycoplasma and chlamydia, etc. German and French laboratories also use primers against different pathogens for polymerase chain reaction (PCR) amplification. Laboratories in the United States and Hong Kong also use PCR reactions to eliminate all known viruses. In terms of virus culture, chicken embryo inoculation, cell culture and suckling mouse inoculation are carried out. The Canadian university first inoculated the cells with the patient’s respiratory secretions. In the presence of lesions, the use of the patient’s convalescent serum can inhibit the emergence of virus lesions and virus proliferation.
The current research on the new coronavirus is still in progress. According to the genome analysis of several virus strains sequenced, the genome of the SARS virus does not belong to the known coronavirus groups 1, 2, and 3. The virus can multiply in the passage cells FRhK-4 cells, vero and other cells, and the cytopathic caused is part of the cytopathic disease, and the virus can be obtained after a group shrinkage, a vacuole disease or a blind passage. At present, several strains of viruses have been isolated worldwide and can be passaged stably in cell lines. It is understood that some strains have a decreased ability to cause cytopathic effects on cells with passage. Therefore, obtaining these strains is not only meaningful for analyzing the differences in the genomes of strains in different countries and regions, and understanding the trend of virus mutation, but also has important value for drug screening and research and development of vaccines.
- Research progress on anti-SARS virus
Although no drugs have been screened to specifically inhibit SARS virus, it is said that interferon-a and viral protease inhibitors have certain effects on it. At present, although it has been reported that SARS virus has stronger resistance than other coronaviruses, it can be killed at 56°C for 30 minutes. Peracetic acid, chlorine-containing preparations, formaldehyde and 75% alcohol can effectively kill the virus. As the SARS virus is a virus with a membrane, its resistance is lower than that of a virus without an envelope. Surface active substances such as soap can also inactivate the virus. At present, international vaccine research believes that inactivated vaccines should be the first choice, and the effectiveness of inactivated vaccines in porcine coronavirus infection has been confirmed. In addition, live attenuated vaccines, recombinant antigen vaccines and DNA vaccines are areas that can be studied. So far, although the genomes of multiple strains have mutated, they are limited to a few nucleotides, which have not yet affected the antigenicity and immunogenicity of the virus. Research on this aspect is still in progress. At present, RT-PCR technology can detect viral nucleic acid, but there are still different opinions as a means of diagnosis. It is understood that RT-PCR positive can only occur in 40% to 60% of SARS patients. ELISA or immunofluorescence can be used to detect the anti-SARS IgG of patients, and the diagnosis rate can reach more than 95%. However, it needs to be positive at least 2 weeks after the onset, so it has certain limitations. Through the concerted efforts of all people, we believe that in the near future, mankind will control the SARS virus and achieve a major victory in the prevention and treatment of SARS.