H5N1,病毒感染 z-bo 2020-08-11 472

　　Avian influenza (AI) is an acute, highly contact, and severe infectious disease of poultry caused by type A influenza viruses (AIV), which can cause infection or disease syndromes in poultry. The virus belongs to the Orthomyxoviridae family and the influenza virus genus. It contains neuraminidase and hemagglutinin, can agglutinate the red blood cells of certain animals, and is pathogenic to the digestive tract and respiratory system. Poultry such as chickens, turkeys, ducks and quails, as well as wild birds, waterfowls, seabirds, etc. can be infected, while domestic chickens and turkeys cause the most serious harm. Foreign reports have found 88 species of poisoned birds. According to its pathogenicity to susceptible chickens, avian influenza viruses can be divided into highly pathogenic AIV (such as H5N1, etc.) and low pathogenic AIV (such as H9N2, etc.). Turkeys, chickens, ducks and geese are susceptible to avian influenza virus in their natural state and are the most commonly used experimental animals. Other experimental animals that can be used for artificial inoculation of AIV include: ferrets, cats, hamsters, mice, monkeys, mink and pigs.

　　1 Rodent model

　　(1) Copy method SPF ICR mice or NIH mice aged 4-6 weeks. First, inoculate the virus aseptically into the allantoic cavity of 10-day-old chicken embryos. The virus strain is A/Goose/Guangdong/NH/2003 (H5N1). After activation and propagation, the hemagglutination titer of the virus can reach 1:256 . After the mice were anesthetized, they were inoculated with AIV through their nasal cavity with an inoculation volume of 0.1ml/mouse, and then compared and analyzed by model animal body temperature, weight, clinical symptoms, pathological changes, virus isolation and antibody determination. After inoculation, the lungs of ICR and NIH mice can be seen to the naked eye, with congestion and edema, the lung volume becomes larger, and the surface of the lung tissue is slightly consolidated, showing spotty congestion; pathological observation under the microscope shows that the lung interstitial congestion, blood vessels There is inflammatory cell infiltration around; congestion in the bronchioles, necrosis and shedding of epithelial cells in the mucosa of the tube wall.

　　(2) Model features The respiratory tract of the body is the main route of infection of the AIV virus. Sensitive animals may have obvious pathological changes in the bronchus and lung tissues; some animals may still have humoral immune responses, and nearly 1/2 of the infected mice can detect AIV Antibodies, and the first appearance of antibodies is the 6th day after vaccination. Some animals have virus replication. Most ICR and NIH model mice are isolated from AIV. ICR and NIH mice are most sensitive to AIV and are more suitable as small animal models of AIV.

　　(3) Comparative medical vaccination and infection. Both ICR mice and NIH mice have more obvious clinical symptoms, manifested as unresponsiveness, loss of appetite, shortness of breath, wrinkles, arched back and other phenomena, and they are getting worse; body weight and body temperature All showed a decreasing trend, with typical clinical symptoms and pathological changes. The main symptoms of human infection with avian influenza virus are fever, and most of the body temperature continues to be above 39°C, which may be accompanied by nasal congestion, cough, sore throat, headache, muscle aches and general malaise. During the experiment, nearly half of the mice died. The clinical symptoms of model animals and humans are not exactly the same, but the histopathological changes are basically similar. So far, the main routes of artificial infection are nasal cavity, trachea, conjunctiva, subcutaneous, muscle, etc. The incidence and clinical symptoms of model animals are affected by many factors (animal susceptibility, virus virulence, inoculation route, animal age, etc.) .

　　2 Non-human primate model

　　(1) Replication method "Cricothyrocentesis" is used to inoculate the virus. The rhesus monkey takes the supine position, tilts the head back as far as possible, and determines the position of the cricothyroid membrane between the thyroid cartilage and cricoid cartilage; at the midclavicular line, insert the needle toward the foot at an angle of 35°～45° with the skin. Use size 16 The injection needle is pierced into the cricothyroid membrane to enter the tracheal cavity, and the avian influenza H5N1 virus cultured in chicken embryos is injected through the trachea (the virus hemagglutination titer is more than 1:256, and the strain is ACGoose/Guangdong/11961H5N1) to infect rhesus monkeys. Observe the constant The clinical signs that appear after the river monkeys are infected, the dynamic changes of peripheral blood white blood cells are detected by microscopic counting, the changes of avian influenza virus specific antibodies are detected by ELISA, and the peripheral blood T lymphocytes and their subgroups are detected by flow cytometry Dynamic changes. Model animals are mainly pulmonary injuries with multiple organ diseases. Lung lesions are mainly manifested as diffuse alveolar injury, which has experienced an exudative phase, a proliferative phase, and a fibrotic phase; pathological changes such as degeneration and necrosis have also been observed in the liver, kidney, and central nervous system.

　　(2) Features of the model: Animals have acute onset after virus inoculation. The clinical manifestations are fever, dyspnea, lethargy, decreased activity, decreased appetite, cough and cyanosis, etc. The lungs of the model animals can be heard dry and wet. . Microscopic histopathological observations are mainly lung pathological changes, accompanied by multiple organ disease; lung tissue lesions are mainly manifested as diffuse alveolar injury, which can occur successively in the exudative phase, proliferative phase and fibrotic phase; in the liver, kidneys and central nervous system Pathological changes such as degeneration and necrosis can also be seen in the nervous system. The virus replicates only in the respiratory system of model animals, not in tissues and organs other than the respiratory tract; bronchial epithelial cells, alveolar epithelial cells and lung macrophages in the lungs are the main cell types invaded by avian influenza viruses. In the early stage of vaccination and infection, the total number of white blood cells and lymphocytes in the peripheral blood of model animals may briefly decrease, while the number of neutrophils first increases and then decreases, but they all gradually return to normal levels after the 7th day of infection. On the 7th to 11th day after infection, the body's antibody level continued to rise rapidly; after the 11th day of infection, the antibody level showed a gradual and slow rise (up to 50 days after infection was observed). After infection, the cellular immune function of the model animal is impaired, which is manifested as a short-term decline in CD3+ T lymphocytes, CD3+ CD4+ T lymphocytes and CD3+ CD8+ T lymphocytes, but this cellular immune function damage is reversible until infection After the 7th day, it can gradually return to normal.

　　(3) Comparative medicine The clinical characteristics, pathological changes, peripheral blood picture, and immune response of rhesus monkeys after infection are similar to those of severe cases of human avian influenza, and their clinical symptoms and lung tissue pathological changes are smaller than NIH mouse models and ICR The mouse model is more typical and can provide an animal model that is most similar to humans for the pathogenic mechanism of human avian influenza virus infection, drug treatment and vaccine evaluation.