Host-specific vascular endothelial cell responses to : a comparative study in red foxes () and domestic dogs.

Introduction: Canine angiostrongylosis, caused by , affects dogs and red foxes, with dogs developing cardiopulmonary and coagulation disorders, while foxes remain mostly subclinical.

Methods: This study examined aortic endothelial cell responses from both species to adult full somatic antigen extracts, first-stage larval (L1) antigen, and adult excretory-secretory products (ESP). Differential gene expression of interleukins (IL) -6, -10, and -33, intercellular adhesion molecule 1 (ICAM-1), vascular adhesion molecule 1 (VCAM-1), endothelial selectin (E-selectin), platelet selectin (P-selectin), vascular endothelial growth factor (VEGF), and monocyte chemoattractant protein 1 (MCP-1) was assessed via reverse transcription quantitative PCR (RT qPCR) after four and 24 hours of antigen exposure.

Results: Four hours post ESP stimulation, IL-10 increased in dogs (1.8-fold) but decreased in foxes (0.4-fold). IL-33 declined in both, (0.9-fold vs. 0.7-fold, respectively). VCAM-1 was upregulated more in foxes (3.5-fold vs. 1.2 in dogs). Following adult antigen exposure, P-selectin, ICAM-1, and VCAM-1 increased in fox more than in dog cells (1.4, 1.7, and 3.1-fold vs. 0.9, 0.5, and 0.7-fold, respectively). L1 antigen downregulated IL-10 and MCP-1 in dogs (0.7 and 0.8-fold) but upregulated them in foxes (2.1 and 1.1-fold). Twenty-four hours after ESP stimulation, ICAM-1 decreased in dogs (0.8-fold) but increased in foxes (1.4-fold). VCAM-1 was downregulated in dogs (0.6-fold) but upregulated in foxes (12.9-fold). Adult antigen exposure upregulated P-selectin in both species, more in foxes (4.8-fold) than in dogs (1.9-fold). ICAM-1 was downregulated in dogs (0.8-fold) but upregulated 7.5-fold in foxes. L1 antigen stimulation caused the most substantial differences between species: IL-6 was upregulated more in dogs (4.7-fold) than foxes (1.2-fold). E-Selectin was upregulated in dogs (12.8-fold) but downregulated in foxes (0.2-fold). P-selectin increased more in dogs (10.0-fold) than in foxes (1.7-fold). ICAM-1 was downregulated in dogs (0.6-fold) but upregulated in foxes (2.6-fold), as was VCAM-1 (0.7-fold and 3.1-fold). VEGF was upregulated 9.5-fold in dogs after adult antigen exposure, and 7.6-fold after L1 antigen exposure, while it remained rather unchanged in foxes (0.9-fold and 1.0-fold, respectively).

Discussion: These findings corroborate that foxes have developed mechanisms for a regulated immune response following exposure, while dogs exhibit a higher pro-inflammatory reaction, contributing to severe clinical outcomes. Host-parasite co-evolution may explain differences in the pathogenesis and clinical presentation of canid angiostrongylosis.