Immunosuppressed (IS) patients, such as recipients of hematopoietic stem cell transplantation, occasionally develop severe and fatal adenovirus (Ad) infections. Here, we analyzed the potential of a virus receptor trap based on a soluble coxsackievirus and Ad receptor (sCAR) for inhibition of Ad infection. In vitro, a dimeric fusion protein, sCAR-Fc, consisting of the extracellular domain of CAR and the Fc portion of human IgG1 and a monomeric sCAR lacking the Fc domain, were expressed in cell culture. More sCAR was secreted into the cell culture supernatant than sCAR-Fc, but it had lower Ad neutralization activity than sCAR-Fc. Further investigations showed that sCAR-Fc reduced the Ad infection by a 100-fold and Ad-induced cytotoxicity by ~20-fold. Not only was Ad infection inhibited by sCAR-Fc applied prior to infection, it also inhibited infection when used to treat ongoing Ad infection. In vivo, sCAR-Fc was delivered to IS mice by an AAV9 vector, resulting in persistent and high (>40 μg ml(-1)) sCAR-Fc serum levels. The sCAR-Fc serum concentration was sufficient to significantly inhibit hepatic and cardiac wild-type Ad5 infection. Treatment with sCAR-Fc did not induce side effects. Thus, sCAR-Fc virus receptor trap may be a promising novel therapeutic for treatment of Ad infections.