Background: Infection of mice with mouse-adapted strains of influenza virus has been widely used to establish mouse pneumonia models. Intranasal inoculation is the traditional route for constructing an influenza virus-induced pneumonia mouse model, while intratracheal inoculation has been gradually applied in recent years. In this article, the pathogenicity of influenza virus-induced pneumonia mouse models following intranasal and aerosolized intratracheal inoculation were compared.

Methods: By comparing the two ways of influenza inoculation, intranasal and intratracheal, a variety of indices such as survival rate, body weight change, viral titer and load, pathological change, lung wet/dry ratio, and inflammatory factors were investigated. Meanwhile, the transcriptome was applied for the initial exploration of the mechanism underlying the variations in the results between the two inoculation methods.

Results: The findings suggest that aerosolized intratracheal infection leads to more severe lung injury and higher viral loads in the lungs compared to intranasal infection, which may be influenced by the initial site of infection, sialic acid receptor distribution, and host innate immunity.

Conclusion: Intratracheal inoculation is a better method for modelling severe pneumonia in mice than intranasal infection.