The Tyrosine Kinase Receptor EphA2 in Alveolar Macrophages Provides a Protective Role in Host Defense Against Pneumocystis Pneumonia

BACKGROUND: Alveolar macrophages (AMs) are central to host defense against Pneumocystis, mediating organism clearance while also contributing to lung inflammation. EphA2, a transmembrane receptor that binds fungal β-glucans, has emerged as a regulator of host-pathogen interactions, but its role in AM responses during Pneumocystis pneumonia (PCP) is unknown. METHODS: We evaluated AM inflammatory responses to Pneumocystis β-glucans in the presence and absence of EphA2. In vivo studies used a CD4-depleted mouse model of PCP comparing wild-type and EphA2-deficient (EphA2-/-) mice. Lung cytokine responses and organism burden were assessed. Additionally, EphA2 signaling was pharmacologically inhibited using ALW-II-41-27 during trimethoprim-sulfamethoxazole treatment. RESULTS: EphA2 deficiency significantly reduced AM proinflammatory cytokine responses to Pneumocystis β-glucans. In CD4-depleted PCP mice, EphA2-/- animals demonstrated decreased lung inflammatory cytokines, but increased organism burden compared to controls. Pharmacologic inhibition of EphA2 during antimicrobial therapy significantly suppressed lung inflammation. CONCLUSIONS: EphA2 signaling plays a critical role in AM-mediated host defense against Pneumocystis by promoting inflammatory responses necessary for organism control. However, this pathway also contributes to lung inflammation. Targeting EphA2 may represent a novel strategy to modulate inflammation during severe PCP while preserving antimicrobial defense.