Objective To explore novel methods for efficient respiratory viral infection of organoids by microinjection and polarity inversion techniques.Methods Lung tissue samples were obtained from 8-week-old male C57BL/6 mouse,and respiratory epithelial cells were extracted to establish a transwell organoid culture model.The green fluorescent protein(GFP)labeled influenza virus PR8(GFP-PR8)was quantitatively injected into organoids by improving the traditional microinjection platform,and morphologic changes in organoids and the immunofluorescence staining characteristics of tight junction proteins and microtubule proteins were observed.Polarity inversion apical-out(AO)was induced by suspension culture,and the morphological characteristics of polarity inversion was determined by HE staining.Normal and inverted organoids were infected with PR8,and the infection efficiency and expression differences of key pathway genes under different virus concentrations were observed.Results Ordinary organoids showed a significant increase in volume after microinjection.Following PR8 injection,the efficiency of infection was significantly higher in the apical region of organoids,accompanied by noticeable damage,as evidenced by significant down-regulation of tight junction proteins and microtubule protein expression.After suspension culture of the organoids,the polarity of ciliated cells gradually inverted outward over time,and the proportion of AO organoids stabilized on the 6th day.The efficiency of viral infection significantly increased in the inverted organoids,accompanied by significant cellular damage.After PR8 infection at 0.01 MOI,AO organoids showed significant changes in the inflammatory pathway and differentiation-related genes,with the opposite trend observed after higher concentration of PR8 infection.Conclusion Both polarity inversion and microinjection techniques significantly enhance the efficiency of influenza virus infection in organoids,thereby facilitating organoid widespread application in the field of respiratory tract infections.