低滴度流感病毒-金黄色葡萄球菌共感染模型建立及对肺泡气血屏障的影响OA

Objective Establish a mouse model of co-infection with low-titer influenza virus and Staphylococcus aureus(H1N1-S.aureus)to recapitulate the mixed infection commonly observed in clinical practice,and investigate the effects on the alveolar-blood barrier in mice.Methods After pathogenicity screening of influenza virus and Staphylococcus aureus at different titers,a low-titer influenza-S.aureus co-infection mouse model was established in male BALB/c mice by intranasal administration of influenza virus(0.1 TCID50,20 μL)on day 0 and Staphylococcus aureus(1× 106 CFU,20 μL)on day 3.Using this model,host tissue damage and changes in alveolar adhesion and tight junction proteins were compared.Starting at 24 h after co-infection,the treatment was administered orally for three consecutive days.Hematoxylin and eosin(HE)staining was used to evaluate lung histopathological damage.The relative expression level of the influenza virus M gene in lung tissue was detected using reverse transcription quantitative PCR(RT-qPCR).The bacterial load in mouse lung tissue was determined by the spread plate method.Additionally,the gene and protein expression levels of air-blood barrier adhesion proteins and tight junction proteins in lung tissue were examined.Results Co-infection with a low titer of influenza virus(0.10 TCID50)and S.aureus(1 × 106 CFU)led to severe symptoms.In the H1N1-S.aaureus group,the mice exhibited a significant decrease in body mass,a marked reduction in the thymus index(P＜0.05),and a significant increase in the lung index(P＜0.05).The relative expression level of the M gene was significantly higher compared with the H1N1 group(P＜0.05),and the bacterial load was significantly higher compared with the S.aureus group(P＜0.05).Relative to the co-infection control group,the H1N1-S.aaureus group showed significantly decreased expression levels of Cadherin 5,ZO1,Claudin-5,and Occludin genes in lung tissue(P＜0.05),along with markedly elevated expression levels of the inflammatory cytokines IL-6,IL-1β,TNF-α and IFN-γ in lung tissue.Intervention with Chaihuguizhi decoction effectively alleviated the body mass loss trend in H1 N 1-S.aaureus group,reduced the expression levels of pulmonary inflammatory cytokines,and ameliorated lung inflammation.Conclusions In this study,we established a mouse model reflecting the characteristics of common clinical co-infections,and the pathogenic microbial replication and inflammatory factor damage were significantly higher than those in the separate infection group,and the intervention of the Chinese herbal medicine compound Chaihuguizhi decoction was able to attenuate the pathologic damage in the co-infection model.