Influenza A virus activates cellular Tropomyosin receptor kinase A (TrkA) signaling to promote viral replication and lung inflammation

Abstract

Influenza A virus (IAV) infection causes acute respiratory disease with potential severe and deadly complications. Viral pathogenesis is not only due to the direct cytopathic effect of viral infections but also to the exacerbated host inflammatory responses. Influenza viral infection can activate various host signaling pathways that function to activate or inhibit viral replication. Our previous studies have shown that a receptor tyrosine kinase TrkA plays an important role in the replication of influenza viruses in vitro, but its biological roles and functional mechanisms in influenza viral infection have not been characterized. Here we show that IAV infection strongly activates TrkA in vitro and in vivo. Using a chemical-genetic approach to specifically control TrkA kinase activity through a small molecule compound 1NMPP1 in a TrkA knock-in (TrkA KI) mouse model, we show that 1NMPP1-mediated TrkA inhibition completely protected mice from a lethal IAV infection by significantly reducing viral loads and lung inflammation. Using primary lung cells isolated from the TrkA KI mice, we show that specific TrkA inhibition reduced IAV viral RNA synthesis in airway epithelial cells (AECs) but not in alveolar macrophages (AMs). Transcriptomic analysis confirmed the cell-type-specific role of TrkA in viral RNA synthesis, and identified distinct gene expression patterns under the TrkA regulation in IAV-infected AECs and AMs. Among the TrkA-activated targets are various proinflammatory cytokines and chemokines such as IL6, IL-1β, IFNs, CCL-5, and CXCL9, supporting the role of TrkA in mediating lung inflammation. Indeed, while TrkA inhibitor 1NMPP1 administered after the peak of IAV replication had no effect on viral load, it was able to decrease lung inflammation and provided partial protection in mice. Taken together, our results have demonstrated for the first time an important biological role of TrkA signaling in IAV infection, identified its cell-type-specific contribution to viral replication, and revealed its functional mechanism in virus-induced lung inflammation. This study suggests TrkA as a novel host target for therapeutic development against influenza viral disease.

Intestinal microbiota analysis and network pharmacology reveal the mechanism by which Lianhua Qingwen capsule improves the immune function of mice infected with influenza A virus

“…Animal experiments have also confirmed that LHQW can reduce the viral load in the lungs of mice with viral pneumonia, reduce the expression of inflammatory factors in the lungs, and improve lung injury (Xia et al, 2020;Su et al, 2022). It is well known that viral clearance in the lung depends mainly on lymphocytes and macrophages (Bedi et al, 2022;Cammann et al, 2022;Harris and Borg, 2022;McGee et al, 2022;Verma et al, 2022;Wei et al, 2022;Zhang H. et al, 2022;Zhang M. et al, 2022); however, the present findings do not clarify how LHQW reduces the viral load in the lung and improves lung injury with viral pneumonia.…”

Pathogenicity and virulence of influenza

“…Receptor-tyrosine kinases (RTKs) and their downstream signalling pathways (Raf/MEK/ERK, phosphatidylinositol − 3-kinase (PI3K)/Akt, JAK/STAT, PLC-γ1, NF-κB) have been found to facilitate viral replication through different mechanisms [ 189 ]. Influenza virus infection activates many RTKs, such as epidermal growth factor receptor (EGFR), c-Met, and tropomyosin receptor kinase A (TrkA), possibly through clustering of lipid rafts induced by multivalent virus binding [ 190 , 191 ]. Activated EGFR and c-Met promote efficient viral uptake [ 190 ].…”

“…TrkA is another RTK activated by influenza virus infection but has post-entry functional roles in the viral replication cycle [ 191 ]. TrkA and its high-affinity ligand, nerve growth factor (NGF), are essential for neuron cell development and functions [ 197 ].…”

“…TrkA inhibitors block influenza virus replication at multiple steps after viral entry, viral RNA synthesis, vRNP nuclear export, and viral budding and release [ 201 , 202 ]. Using a TrkA F592A knock-in mouse model to specifically control TrkA kinase activity [ 203 ], Verma et al showed that TrkA not only promotes influenza virus replication in airway epithelial cells but also contributes to airway inflammation and lung pathology by activating the expression of proinflammatory cytokines/chemokines in infected cells [ 191 ]. Thus, targeting TrkA could be an effective treatment against influenza viral diseases by blocking both viral replication and airway inflammation.…”

“…Influenza viruses not only antagonize antiviral responses but also hijack the activated signalling network to efficiently accomplish different steps of the viral life cycle (pro-viral role). Thus, targeting the pro-vial and/or proinflammatory pathways in the influenza virus-infected cells can be developed as effective anti-influenza therapeutics [ 191 , 210–212 , 227 ], which, unlike inhibitors of single viral or host targets, generally has a high barrier to resistance [ 193 , 201 , 210 ]. The roles of host signalling pathways in viral replication and disease severity, however, can be virus- and cell-type-specific and need to be carefully evaluated for therapeutic development.…”