Respiratory microbiota, host immunity, respiratory viral infections and malignant tumors

Abstract

In recent years, the role of the respiratory tract microbiota in respiratory tract infections has attracted considerable attention. Respiratory microbiota have important effects on respiratory physiology, immune regulation, and the occurrence and development of various respiratory viral infectious diseases. The microbial composition in the different parts of the respiratory tract, such as the nose, oropharynx, and lower respiratory tract, varies. Under physiological conditions, the respiratory microbiota remains relatively stable; however, when this homeostatic balance is disrupted, respiratory microbiota imbalance occurs, increasing the risk of infection. An increasing number of studies have revealed the complex relationship between bacterial dysregulation and respiratory viral infections. Dysregulation of the respiratory tract microbiota plays an important role in both innate and adaptive immune responses. In this study, changes in respiratory microbes and their interactions with host immunity, respiratory viral infections and malignant tumors were reviewed. Future studies should further explore the interaction mechanism between respiratory microbiota and host immunity, develop new diagnostic and therapeutic strategies, and improve the current level of clinical treatment for respiratory diseases.

Keywords: airway dysbiosis; immune; interaction; respiratory tract microbiota; viral infection.

Figure 1

Overview of the respiratory tract microbiota dysbiosis and immunity. Respiratory tract microbiota dysbiosis leads to activation of immune cells. The immune cells then migrate into the tissue and produce pro-inflammatory cytokines, which ultimately contribute to the local inflam-matory response. In addition, changes in the cytokine environment promote pathological fibrotic remodeling, NETosis, and apoptosis. However, this also maintains the pulmonary immune balance through the differentiation of Tregs and Th17 cells. The arrows indicate changes in the relative abundance of immune cell subsets and bacterial species.

Figure 2

In a healthy state major phyla originating from the microbiota of nasal, oral, and lung in the human respiratory tract and changes of respiratory tract microbiota during respiratory viral infections.