Establishment and Characterization of a Piglet Model for Pulmonary Heat-Induced Cough and Asthma Syndrome

Porcine lung-heat cough and asthma syndrome is mainly caused by mixed infections of viruses, bacteria and other pathogens. It is characterized by disturbed lung movement and accumulated heat in the lung, with typical clinical signs including fever, cough, purulent nasal discharge and dyspnea. To construct an exploratory model mimicking its clinical features, twelve healthy piglets were randomly divided into a control group (mock-infected) and three Influenza A virus subtype (H1N1)-infected groups (high-dose, medium-dose and low-dose virus challenge). Piglets in the three challenged groups were intranasally inoculated with H1N1 influenza virus at high, medium, or low doses, while the control group received mock inoculation with DMEM. Clinical symptoms were monitored throughout the experiment. On day 8 post infection(dpi), samples of the heart, liver, spleen, lung, kidney, trachea and various intestinal segments were collected for histopathological observation and viral load detection. We conducted disease target enrichment analysis to screen core targets in lung tissues after H1N1 infection, and further verified the results via Western blot. H1N1 infection induced typical symptoms in piglets, such as fever, purulent nasal discharge, cough, dyspnea, decreased feed intake, reduced average daily gain, elevated feed conversion ratio and listlessness. Obvious pathological lesions were found in the trachea, lung, liver and kidney, and H1N1 virus was detected in tracheal and lung tissues. Enrichment analysis revealed that the Phosphatidylinositol 3-kinase–protein kinase B (PI3K–Akt) signaling pathway participates in lung injury progression induced by H1N1 infection. Further molecular detection indicated that H1N1 infection was associated with changes in PI3K–Akt signaling while upregulating Class III PI3K, simultaneously accompanied by alterations in autophagy- and apoptosis-related markers and potentially associated with pulmonary injury. The established piglet model is largely consistent with the diagnostic criteria for porcine lung-heat cough and asthma pattern stated in the Technical Guidelines for Clinical Research of Traditional Chinese Veterinary Medicine for Porcine Lung-Heat Cough and Asthma Syndrome issued by the Ministry of Agriculture and Rural Affairs of China. In summary, this study established an exploratory model of H1N1-induced lung-heat cough and asthma in piglets. The observed phenotypic and molecular characteristics provide preliminary evidence for subsequent investigations into the disease mechanism.