| Background:Streptococcus Pneumoniae(S.pn)is one of the main pathogens causing pneumonia in infants and the elderly,and pneumonia caused by S.pn infection is the leading cause of death in children under 5 years of age,and one of the leading causes of infant and young monkey death in artificial breeding experimental monkey farms.However,there is currently a lack of effective vaccines for the prevention and treatment of S.pn infections,as well as reliable animal models for vaccine evaluation.Objective:Use RT-PCR and microbial culture method to screen the S.pn carrying status in the nasopharyngeal swab samples in the rhesus monkey population,select the negative infant monkeys as the model construction object,and infect them through a combination of nose drops and aerosolization The standard strain of Streptococcus pneumoniae S.pn-19F is to construct the S.pn infection model of the infant rhesus monkey.Use blood routine and biochemical tester to detect the level of white blood cells,red blood cells,hemoglobin,neutrophils,lymphocytes,immunoglobulin,Creactive protein,procalcitonin and cytokines in the blood of the model monkey,and the S.pn load of nasopharyngeal swabs,feces,and blood were measured;In addition,use HE staining,pathological sections and tissue smears to analyze pathological changes in the respiratory,nerve,immune,and digestive systems and S.pn infection in the tissues;Comprehensive evaluation of the reliability of the Rhesus monkey S.pn infection model in this study.Finally,based on this model,the safety and immunogenicity of the 23valent pneumococcal polysaccharide vaccine(PPV23)were evaluated.Select S.pn antibody-negative 1-year-old healthy rhesus monkeys to inoculate PPV23 vaccine by intramuscular injection,and observe the animal’s body temperature,weight and possible side effects at the injection site after inoculation;And through the blood routine and biochemical detector to measure and analyze the blood related indicators at 0,7,14,21,28,35,41 and 49 days;The concentration of coated antigen,enzyme-labeled antibody and the dilution of serum to be tested were determined by checkerboard assay,and the level of S.pn-specific IgG antibody in serum was detected by enzyme-linked immunosorbent assay.Results:The first part of the results:(1)RT-PCR and bacterial culture results showed that 4 baby monkey nasopharyngeal swab samples were positive,detection rate of 20%(4/20),adult and elderly rhesus monkey detection rate of 0%.The S.pn strain in the positive sample was isolated,and its colony was gray-white convex,surrounded by grass-green hemolytic ring,and umbilical fossa shape,and other typical characteristics of Streptococcus pneumoniae.In addition,the optochin test,bile dissolution test,and inulin fermentation test The identification results all showed that the isolate was S.pn.(2)Model baby monkeys developed severe pneumonia symptoms on the 11th day of infection S.pn-19F:shortness of breath(90 times/min),abdominal breathing,wheezing,chest hearing and wet tone.(3)The results of the blood routine showed a significant decrease in red blood cells,hemoglobin and lymphocytes,and a significant increase in white blood cells,neutrophils and immunoglobulin;(4)RT-PCR test results showed that the bacterial load in nasopharyngeal swabs and feces was as high as 106 CFU/mL;(5)Cytokines such as IL-6,IL-8,IL-10,TNFa and INF γ show a changing trend;(6)Histopathological results show that S.pn-19F infection can cause severe pathological changes in the lungs.In addition,the brain,spleen,olfactory bulb and other organs have different degrees of pathological changes.The second part of the results:(1)The body temperature of the experimental monkeys increased within 4 days after being vaccinated,up to 40.9℃,and gradually returned to normal on the 5th day;The weight shows a normal trend of slow growth.There were no adverse reactions such as swelling,erythema,and local induration at the vaccination site.The blood routine and blood biochemical indexes all changed within the normal range.(2)The checkerboard method determines that the best antigen dilution is 4μg/mL,and specific IgG antibodies are detected one week after vaccination,the 2-fold growth rate(P/N)of antibodies of 23 serotypes is 75%in the first week,100%from the second week.The antibody titer reached a peak value of 6.2 after 4 weeks of immunization;the antibody titer reached the highest value of 1:12800 2 weeks after vaccination;the antibody level on the 14th day was the highest,and the maximum GMT reached 219.79.Conclusion:This study found that infant monkeys are the main carrier group of S.pn.In addition,this study successfully constructed an S.pn-19F infection rhesus monkey model,and a relatively complete bacterial infection process and typical symptoms of pneumonia infection appeared.Rhesus monkeys inoculated with PPV23 may have transient high fever,but no other side effects and no damage to the liver and kidneys;In addition,the vaccine can induce a significant immune response in infant monkeys one week after vaccination,indicating that the Rhesus monkeys inoculated with human PPV23 vaccine can produce higher safety and better immunogenicity. |
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