Integrin- v 6, a Putative Receptor for Foot-and-Mouth Disease Virus, Is Constitutively Expressed in Ruminant Airways

Evolved functions of integrin-alpha(v)beta(6) include roles in epithelial cell-extracellular matrix protein interactions and in the binding and activation of latent TGF-beta(1). Integrin-alpha(v)beta(6) is also exploited as a receptor by foot-and-mouth disease virus (FMDV) and may play a significant role in its transmission and pathogenesis. The ovine beta(6) integrin subunit was cloned and sequenced (EMBL accession no. AJ439062). Screening of normal ovine tissues by RT-PCR and immunocytochemistry confirmed that integrin-alpha(v)beta(6) is restricted to sheep epithelial cells. Integrin-alpha(v)beta(6) expression was detected in epithelia of the airways, oral cavity, gastrointestinal tract, kidney, sweat glands, hair follicle sheaths, and the epidermis of pedal coronary band (PB) but not of normal skin. Consistent with FMDVtropism, integrin-alpha(v)beta(6) was detected within the basal layers of the stratified squamous epithelium of the oral mucosa and PB. In addition, integrin-alpha(v)beta(6) appears to be constitutively expressed in the normal airways of both cattle and sheep. The latter finding suggests that ruminant airway epithelium presents a highly accessible target for initiation of infection with FMDV by inhalation.