Anionic pulmonary surfactant lipid treatment inhibits rhinovirus A infection of the human airway epithelium
Rhinoviruses (RVs) are major instigators of acute exacerbations of asthma, COPD and other respiratory diseases. RVs are categorized into three species (RV-A, RV-B, and RV-C), which comprise more than 160 serotypes, making it difficult to develop an effective vaccine. Currently no effective treatment for RV infection is available. Pulmonary surfactant is an extracellular complex of lipids and proteins that plays a central role in regulating innate immunity in the lung. The minor pulmonary surfactant lipids, palmitoyl-oleoyl-phosphatidylglycerol (POPG) and phosphatidylinositol (PI), are potent regulators of inflammatory processes, and exert antiviral activity against respiratory syncytial virus (RSV) and influenza A viruses (IAV). In the current study, we examined the potencies of POPG and PI against rhinovirus A16 (RV-A16) in primary human airway epithelial cells (AECs) differentiated at an air-liquid interface (ALI). After AECs were infected with RV-A16, PI reduced viral RNA copy number by 80% and downregulated (55-65%) expression of antiviral genes (MDA5, IRF7 and IFN-lambda). In contrast, POPG only slightly decreased MDA5 (24%) and IRF7 (11%) gene expression but did not inhibit IFN-lambda gene expression or RV-A16 replication in AECs. However, both POPG and PI inhibited (50-80%) IL6 and CXCL11 gene expression and protein secretion. PI treatment dramatically attenuated global gene expression changes induced by RV-A16 infection in AECs. Cell type enrichment analysis of viral regulated genes opposed by PI treatment revealed that PI inhibited viral induction of goblet cell metaplasia and virus-induced downregulation of ciliated, club, and ionocyte cell types. Notably, PI treament altered the ability of RV-A16 to regulate expression of some phosphatidylinositol 4-kinase (PI4K), acyl-CoA binding domain containing (ACBD) and low density lipoprotein receptor (LDLR) genes that play critical roles in the formation and functioning of replication organelles (ROs) required for RV replication in host cells. These data suggest PI can be used as a potent, non-toxic antiviral agent for RV infection prophylaxis and treatment. Overall design: To examine anti-viral effects of the phospholipids, palmitoyl-oleoyl-phosphatidylglycerol (POPG) and phosphatidylinositol (PI) against the RV-A16 virus or the control lipid palmitoyl-oleoyl-phosphatidylcholine (POPC), we generated three replicate ALI samples from each of three tracheal donors (T22, T51, T56) treated in each of the following ways: (1) mock (i.e., Control), (2) lipid only (PI, POPG, or PC), (3) RV-A16 infection alone at 4hr or 48hr (RV-A16_4hr, RV-A16_48h, respectively), or (4) lipid pretreatment followed by RV-A16 infection (RV-A16+PI, RVA-16+POPG, RV-A16+PC).