Porcine adenovirus serotype 3 internalization is independent of CAR and α vβ 3 or α vβ 5 integrin

Abstract

Nonhuman adenoviruses including porcine adenovirus serotype 3 (PAd3) are emerging vectors for gene delivery. PAd3 efficiently transduces human and murine cells in culture, and circumvents preexisting humoral immunity in humans. The coxsackievirus–adenovirus receptor (CAR) serves as a primary receptor and α vβ 3 or α vβ 5 integrin as a secondary receptor for several human adenovirus (HAd) subtypes including HAd5. In this study, we deduced the role of CAR, α vβ 3 or α vβ 5 integrin in PAd3 internalization. Transduction experiments were conducted in human mammary epithelial (MCF-10A) cells using replication-defective PAd-GFP (PAd3 vector expressing green fluorescent protein [GFP]) and HAd-GFP (HAd5 vector expressing GFP). MCF-10A cells were treated with or without anti-human CAR, or anti-α vβ 3 or anti-α vβ 5 integrin antibodies prior to infection with HAd-GFP or PAd-GFP. Significant ( P < 0.05) inhibition in transduction by HAd-GFP was observed in antibody-treated cells as compared to untreated cells, whereas transduction by PAd-GFP remained to similar levels irrespective of the treatment. To study the adenoviral fiber knob-mediated virus interference, MCF-10A cells were treated with or without the recombinant HAd5 or PAd3 knob followed by infection with HAd-GFP or PAd-GFP. Significant ( P < 0.05) inhibition was observed only in transduction of the homologous vector. These results suggested that PAd3 internalization was CAR- as well as α vβ 3 or α vβ 5 integrin-independent and the primary receptor for HAd5 and PAd3 were distinct. CAR- and α vβ 3 or α vβ 5 integrin-independent entry of PAd3 vectors may have implications in targeting cell types that are not efficiently transduced by other adenoviral vectors.