Immunomodulation of the Innate Host Response by Mesenchymal-Derived Versican during Influenza A Virus Infection

ABSTRACT Viral and bacterial lung infections place a significant burden on public health. Versican, an extracellular matrix (ECM) chondroitin sulfate proteoglycan, coordinates the innate immune response in multiple experimental models. Versican’s potential as an immunomodulatory molecule makes it a promising therapeutic target for controlling the host’s immune response to lung infection. However, versican’s contribution to lung inflammation, injury, and immune cell activity during influenza A virus (IAV) infection represents a critical knowledge gap. To address our central hypothesis that mesenchymal-derived versican is pro-inflammatory and enhances the innate immune response to IAV infection, we generated a tamoxifen-inducible mouse deficient in mesenchymal-derived versican (B6. Col1a2-Cre ERT+/- /Vcan tm1.1Cwf , Col1a2/Vcan -/- ). We report that mesenchymal-derived versican plays a critical role in neutrophil, monocyte, and dendritic cell migration into the lungs and airways early in IAV infection. Intriguingly, mesenchymal-derived versican deficiency had the most substantial negative impact on neutrophil emigration into the lungs. We found that neutrophils were less adhesive to the ECM of Col1a2/Vcan -/- mouse lung fibroblasts (mLFs), which had a significant decrease in versican compared to wild-type mLFs. Additionally, Col1a2/Vcan -/- mLFs treated with poly(I:C) in vitro have reduced cell-associated hyaluronan. These findings suggest that fibroblast-derived versican is necessary for adhesion to lung fibroblasts by neutrophils as they transit into the lung interstitium and airways from the pulmonary vasculature. Our findings demonstrate that mesenchymal-derived versican is a key regulator of the early host immune responses to IAV. NEW & NOTEWORTHY We report the novel finding that mesenchymal-derived versican is critical for neutrophil, monocyte, and dendritic cell migration into the lungs and airways early in influenza A virus infection. Additionally, a differentiated neutrophil-cell line is less adherent to versican-deficient fibroblasts, and versican-deficient fibroblasts have significantly reduced cell-associated hyaluronan (HA) content in vitro . These findings suggest that mesenchymal-derived versican and cell-associated HA are necessary for the adhesion of neutrophils and monocytes to lung fibroblasts.