【Animal Modeling】-Influenza virus model preparation technology
动物造模,流感病毒模型
z-bo
2023-02-28
670
1. According to its pathogenicity to poultry, avian influenza can be divided into three levels: high pathogenicity, low pathogenicity and non-pathogenicity. Among them, highly pathogenic avian influenza has two subtypes, H5 and H7, but not all H5 and H7 are virulent strains. Studies have shown that when rapid mutations between poultry are for 6-9 months, the originally low pathogenic avian influenza virus strains (H5N2, H7N7, H9N2) can become highly pathogenic (H5N1). Human highly pathogenic avian influenza is an acute human respiratory infection caused by a specific subtype of highly pathogenic avian influenza virus. The symptoms caused by H5N1 avian flu are severe and the mortality rate is high.
Water Wild waterfowl are the genetic "repository" of influenza viruses. Currently, 16 HA and 9 NA subtype influenza viruses have been isolated from poultry. These antigens are used in various combinations to produce a very diverse strain. Human highly pathogenic avian influenza comes from poultry, especially poultry. From the perspective of genetic evolution, the virus strains isolated from the human avian influenza in Hong Kong in 1997 and the avian influenza in Southeast Asia from 2003 to the present are highly related to the H5N1 subtype virus of chickens. The avian influenza virus is a type A influenza virus. It can be isolated from passage cells of chicken embryo and canine kidney. Poultry, especially wild waterfowl, are natural reservoirs of avian influenza viruses. Poultry are mainly chickens and ducks. Sometimes it can cause infections in marine and land mammals, such as whales, dolphins, pigs and horses. According to reports, in cats such as tigers, highly pathogenic H and N are sometimes isolated. virus. It is rare in humans. Ferrets are sensitive hosts of avian influenza viruses, and mice can get sick and sick.
(1) Epidemic overview: In 1997, a total of 18 people in Hong Kong were infected with the avian influenza virus, and 6 of them died. Since then, there have been reports that the avian influenza subtypes and H5N1 subtypes infected with H9N2 and H7N7 were again infected in humans, and the relationship between avian influenza and human avian influenza began to attract attention. Since mid-December 2003, H5N1 highly pathogenic avian influenza has occurred in more than 10 Asian countries such as Japan and China, and human highly pathogenic avian influenza infections have also occurred in Vietnam, Thailand, Cambodia and Indonesia. The symptoms caused by H7N7 infection are relatively mild, mainly keratoconjunctivitis and mild respiratory symptoms. Looking back at history, the first reported incidents of avian influenza infection occurred in the 1970s and 1980s, and occurred in some H7N7 infected patients with self-limiting conjunctivitis. (2) Pathogenicity: The pathogenicity of highly pathogenic avian influenza is relatively clear in poultry, and is mainly related to the amount of basic amino acids bound between the heavy and light chains of hemagglutinin. .. Most current cases of highly pathogenic avian influenza H5N1 identified by the World Health Organization have a history of contact with affected poultry, and only one case of human-to-human transmission has limited evidence. The latest data show that in late 2004 and 2005, 112 cases of human highly pathogenic avian influenza occurred in Asian countries and regions, of which 57 cases were fatal. The existing highly pathogenic avian influenza has limited ability to be introduced into animals.
(3) Clinical symptoms: The incubation period of viral infection is usually 2 to 4 days, with an average of 3 days. Detoxification begins the day before the onset of the disease. Children take longer to detoxify than adults. Immunosuppressed patients may detoxify for more than a month. The clinical manifestations are acute, and the early manifestations are similar to common flu, mainly fever. Most body temperatures are above 38°C, accompanied by a history of fever for 1-7 days (usually 3-4 days), and may be accompanied by a runny nose, nasal congestion, cough and sore throat. Headache and general malaise, some patients may have symptoms such as nausea, diarrhea and sparse water samples. The condition of severely ill patients can progress rapidly and may lead to a variety of complications, including pneumonia, acute respiratory distress syndrome, pulmonary hemorrhage, pleural effusion, pancytopenia, renal failure, sepsis, shock, and Reye's syndrome.
(4) Route of infection: A large number of epidemiological investigation results show that the route of infection of the disease is through contact and close contact with air droplets, aerosols, and patient respiratory secretions. The routes of infection are as follows: (1) Mainly inhaled through human secretions or excrement of infected poultry; (2) Direct contact with affected poultry, human digestive tract, respiratory tract, skin damage and conjunctival infection ③ Existing data does not support infection The vertical existence of worms; ④ Transmission through multiple channels in poultry, these channels include air droplets, water sources, contact, vertical transmission, human mechanical transmission and mosquito bites. It is contagious.
2.A (H1N1) The influenza A H1N1 epidemic was called "swine flu" when it first occurred in Mexico, and some reporters even suspected that it was related to a terrorist attack. it is. Nowadays, as the epidemic spreads, people's understanding of H1N1 flu is deepening. The epidemic is serious, but it can be prevented, controlled and cured. H1N1 flu symptoms are similar to other flu symptoms, such as high fever, cough, fatigue and loss of appetite. Sudden fever, cough, myalgia and fatigue are the main symptoms of this case found in the United States. Some patients also experience diarrhea and vomiting. The cases found in Mexico also showed symptoms such as red eyes, headaches and runny nose. The most common influenza A virus is the H1N1 subtype, but there are other subtypes (H1N2, H3N1, H3N2, etc.). Like the A (H1N1) influenza virus, pigs can also be infected with avian and human seasonal influenza viruses. It was originally thought that the A (H1N1) influenza virus was transmitted from humans to pigs. Sometimes pigs can be infected with multiple virus subtypes at the same time, and the genes of these viruses can be recombined or reclassified. This may cause influenza viruses to contain genes from multiple sources, which are called recombinant viruses. Generally speaking, influenza A viruses are species-specific, but they can cross population barriers and cause human diseases.
Human infections are caused by pigs carrying viruses and diseases. Pigs are in close contact with people, so be vigilant. Humans usually get A (H1N1) influenza virus from infected pigs, but sometimes they have no contact with pigs or have never been in contact with the environment in which they live. Although human-to-human transmission may have occurred in the past, it is still limited to those in close contact with the patient and those living in closed environments. This approach changed this perception. So far, human infections with influenza A (H1N1) virus are rare, and influenza A (H1N1) virus does not usually spread from person to person. In February 1976, an influenza outbreak caused by the A (H1N1) strain broke out in a training camp in Fort Dix, New Jersey, USA. The disease infected about 200 people and caused one death. Influenza and pathogenicity analysis showed that A (H1N1) influenza virus was transmitted directly from pigs to humans. From December 2005 to January this year, only 12 cases of H1N1 influenza were infected in the United States, 11 of which were in direct contact with pigs.
In the United States and Mexico, the vast majority of patients have never been in contact with pigs of this epidemic. The virus has been confirmed to spread from person to person. Scientists pointed out that sneezing, coughing and physical contact can spread the new A (H1N1) influenza virus to people. At this stage, the Mexican government has eliminated the possibility of infection caused by eating pork. due to
A (H1N1) influenza virus can grow in chicken embryos, so chicken embryos can be used for allantoic or amniotic cavity inoculation to isolate the virus. In addition to chicken embryos, a variety of cell culture systems, such as chicken embryo fibroblasts, porcine testis cells, fetal bovine kidney cells and dog kidney cells, can also be used to propagate isolated viruses.
Pig is the natural host of the virus. Like all influenza viruses, A (H1N1) influenza viruses are constantly changing. Pigs are a mixture of influenza viruses and can be infected with avian influenza, seasonal influenza viruses and A (H1N1) influenza viruses. When different types of influenza viruses infect pigs, these viruses recombine and a new type of mixed virus emerges, namely A (H1N1) influenza virus, human seasonal influenza virus and avian influenza virus. Over the years, A (H1N1) influenza virus has undergone many changes. At present, four major subtypes of type A virus have been isolated from pigs: H1N1, H1N2, H3N2 and H3N1. However, most influenza viruses isolated from pigs recently are H1N1 viruses.
Generally speaking, influenza viruses are host-specific and it is difficult to spread from one animal to another. More and more information shows that pigs play an important role as a "mixer" of influenza viruses in the process of crossing species barriers and infecting new hosts. Since human epithelial cells have sialic acid 2, 6-galactoside and sialic acid 2, 3-lactoside, human influenza virus can bind to the former and avian influenza virus can bind to the latter. Influenza and avian influenza viruses can infect and become viable vectors for genetic recombination between strains.
The source of H1N1 influenza is mainly sick pigs and pigs carrying pigs. It has been confirmed that people infected with the H1N1 influenza virus can also be infected with the virus. The main route of infection is respiratory infection, but it can also be spread through contact with infected pigs and their feces, the surrounding polluted environment and aerosols. The pandemic was infected with the new H1N1 influenza A virus (H1N1). It contains the genes of human influenza virus, North American avian influenza virus and three A H1N1 viruses from North America, Europe and Asia. Segmented. The virus has been confirmed to be spread from person to person, and infection can cause symptoms such as fever, lack of energy, loss of appetite and cough. Scientists pointed out that sneezing, coughing and physical contact can spread the new A (H1N1) influenza virus to people. Another major feature of this A (H1N1) influenza virus is that it is highly aggressive to young people. At present, most confirmed A (H1N1) influenza deaths are 25-45 years old. Yes. According to the characteristics of influenza viruses, disease transmission can occur through dense air droplets, contact with sick pigs, patient respiratory secretions, and close contact. The route of infection is as follows. ①Mainly inhale the secretions and excrements of infected pigs and humans ②After direct contact with pigs and humans, it spreads to the human digestive tract, respiratory tract, skin damage, and conjunctiva. ③Existing data does not support the existence of vertical transmission; ④ Multi-channel transmission between pigs and people. It can be spread through water droplets, water sources, close contact, vertical transmission, mechanical transmission from the human body, and mosquito bites.
