Mechanisms of SP-A and Its Genetic Variants in Regulating Lung Innate Immunity

My research aims to elucidate the molecular mechanisms by which surfactant protein-A (SP-A) variants regulate innate immune responses in the lung microenvironment, with the long-term goal of developing novel therapies for acute and chronic lung diseases. Respiratory Syncytial Virus (RSV) is the leading cause of viral mortality in children worldwide. Despite the availability of recent vaccines, uptake remains low, and ~8% of vaccinated children still develop severe disease. Age at initial infection is an independent risk factor for RSV severity, yet the mechanisms driving increased susceptibility remain unclear. RSV severity varies due to complex interactions between the virus and host immune responses, underscoring the need to understand the heterogeneity of host immune responses to develop effective therapies. SP-A, a C-type lectin critical for lung innate immunity, has been implicated in RSV pathogenesis with our previous findings linking young age and the SFTPA2-1A0 variant to severe RSV in children. While SP-A enhances RSV clearance, its precise antiviral mechanisms remain unknown. Toll-like receptors (TLRs), key mediators of innate immunity, are modulated by both SP-A and RSV, suggesting a link between SP-A, TLR signaling, and RSV pathogenesis. Our preliminary data show that neonatal SFTPA2-1A0 mice exhibit a diminished antiviral response compared to wild-type mice in bulk RNA studies, while SP-A attenuates RSV-induced TLR expression in epithelial (A549) cells, and the 1A0 variant has reduced RSV-binding affinity. Based on these strong preliminary findings, we hypothesize that RSV severity in children with the 1A0 variant results from impaired modulation of TLR pathways, leading to delayed viral clearance and excessive inflammation, which can be restored by exogenous SP-A. However, bulk studies fail to capture the complexity of the host immune response to RSV. To address this gap, we will use single-cell RNA sequencing and spatial transcriptomics to delineate the heterogeneity of host immune responses in infected versus bystander cells and generate a high-resolution, unbiased, spatially resolved gene expression map of neonatal lungs (Aim 1), while Aim 2 will elucidate the mechanism of SP-A-mediated TLR regulation in RSV pathogenesis through binding and endocytic assays, advanced imaging, and siRNA/CRISPR approaches in epithelial cells, clarifying how the SFTPA2-1A0 variant affects these processes. These studies will provide a mechanistic understanding of the association between SP-A genetic variants and RSV severity, laying the foundation for future research, including an R01 application, to develop and test personalized, variant-specific therapies for RSV infection. Importantly, this proposal will uncover fundamental aspects of SP-A-mediated regulation of TLR signaling, which may also be relevant to other respiratory viral infections, addressing the broader threat of emerging viral pandemics. Project Number: 1R03HL183266-01 | Fiscal Year: 2026 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Chintan Gandhi | Institution: PENNSYLVANIA STATE UNIV HERSHEY MED CTR, HERSHEY, PA | Award Amount: $105,705 | Activity Code: R03 | Study Section: Special Emphasis Panel[ZRG1 RCCS-P (92)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R03HL18326601