Publication date: Jul 25, 2025

Viral pneumonia is a common clinical infectious disease in which host immunity plays a pivotal role in its onset and progression. A compromised adaptive immune response, particularly involving CD8 T cells, is a fundamental pathophysiological feature of viral pneumonia. The Xuanfei Baidu Formula (XFBD), recognized as one of the “three medicines and three prescriptions” for the effective clinical management of Coronavirus Disease 2019 (COVID-19) in China, has been shown to enhance lymphocyte counts in patients with pneumonia. However, the pharmacological mechanisms and active compounds of XFBD in modulating T-cell therapy for viral pneumonia remain unclear. This study aims to elucidate the pharmacological mechanisms and therapeutic components of XFBD in modulating adaptive immune CD8 T cells, thereby providing an experimental basis for its clinical application. A murine model of pneumonia was established through intranasal administration of Influenza A Virus (IAV) and the Delta variant of SARS-CoV-2. Treatment with XFBD or oseltamivir was conducted over a period of 5 or 7 days. Lung protection was evaluated by measuring pulmonary viral titers, inflammatory factors, and conducting histopathological examinations. Clinical data analysis involved assessing alterations in the quantity and functionality of T cells in patients infected with influenza and COVID-19. The therapeutic potential of XFBD in modulating T cell activity was ascertained in TCRbetadelta mice. Flow cytometry was employed to analyze changes in T cells and functional factors of CD8 T cells in both lung tissue and blood samples. Transcriptomic analysis and western blot were utilized to identify XFBD targets involved in the regulation of CD8 T cells. High-performance liquid chromatography (HPLC) was used to characterize XFBD and its principal components, while molecular docking studies elucidated the molecular mechanisms of key compounds. Primary CD8 T cells were stimulated with CD3/CD28 to develop an in vitro activation model. The active compounds in XFBD that influence CD8 T cell proliferation via the MAPK pathway were evaluated using Carboxyfluorescein Succinimidyl Ester (CFSE) assay. Our research findings indicate that XFBD can alleviate lung inflammation and ameliorate damage caused by immune imbalances induced by viral infections. XFBD significantly improves the condition of viral pneumonia by enhancing the infiltration and functionality of T cells, particularly CD8 T cells, within the lungs. The therapeutic efficacy of XFBD is substantially reduced in T cell-deficient mice. XFBD primarily influences CD8 T cell proliferation, which is associated with the mitogen-activated protein kinase (MAPK) signaling pathway. Tissue distribution and molecular binding experiments identified polydatin and naringenin as the key compounds that facilitate CD8 T cell proliferation through the MAPK signaling pathway. In conclusion, we found that XFBD regulates CD8 T cell proliferation through the MAPK signaling pathway, thereby combating viral infection, which helps explain the theory and scientific principle of drug action and provides a scientific basis for the clinical application of XFBD.

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Original Article