Rhinovirus Regulation of IL-1 Receptor Antagonist In Vivo and In Vitro: A Potential Mechanism of Symptom Resolution

Abstract

Rhinovirus (RV) upper respiratory tract infections are prototypic transient inflammatory responses. To address the mechanism of disease resolution in these infections, we determined if RV stimulated the production of the IL-1 receptor antagonist (IL-1ra) in vivo and in vitro. In contrast to IL-1α and IL-1β, immunoreactive IL-1ra was readily detected in the nasal washings of normal human volunteers. Symptomatic RV infection caused a small increase in IL-1α, a modest increase in IL-1β, and an impressive increase in IL-1ra. Maximal induction of IL-1α and IL-1β was transiently noted 48 h after RV infection. In contrast, maximal induction of IL-1ra was prolonged appearing 48–72 h after RV infection. These time points corresponded to the periods of peak symptomatology and the onset of symptom resolution, respectively. Western analysis of nasal washings demonstrated that RV stimulated the accumulation of intracellular IL-1ra type I in all and secreted IL-1ra in a subset of volunteers. Unstimulated normal respiratory epithelial cells contained intracellular IL-1ra type I mRNA and protein. RV infection increased the intracellular levels and extracellular transport of this IL-1ra moiety without causing significant changes in the levels of IL-1ra mRNA. IL-1ra may play an important role in the resolution of RV respiratory infections. RV stimulates epithelial cell IL-1ra elaboration, at least in part, via a novel translational and/or posttranslational mechanism.