OBJECTIVETo identify mouse acute pneumonia model induced by influenza virus adapted strains (FM1 strain) using RT-PCR, gene clone and sequence analysis and pathological examination of lung tissues.

METHODSAcute pneumonia was induced by intranasal drip of FM1 strain. The lungs were collected after 3, 5 and 7 days. RT-PCR was used to detect the viral load. Amplified PCR products were cloned and sequenced. Pathological and histological changes to the lungs were observed.

RESULTSThere were no abnormalities in the alveoli, alveolar sacs and alveolar septa and no inflammatory cell infiltration was found in normal mice. In the model group, we found disappearance of alveoli, alveolar sacs, alveolar ducts and alveolar septa, thickening of the alveolar septal and bronchiolar walls, and infiltration of inflammatory cells after 3, 5 and 7 days of influenza virus (IV) infection. Compared with the normal group, pathological changes at various time points were significantly increased (P<0.01). Viral nucleic acid can be detected in the lung tissue of the model group at various time points, and the pathological changes of the lung tissue were positively correlated with viral load. Sequence analysis demonstrated that there was 99.1% consistency between RT-PCR products of lung tissues in the model group and the known IV cDNA sequence (P<0.01).

CONCLUSIONSGene clone and sequence analysis may be used to identify acute mouse pneumonia model induced by FM1 strain.