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CD40 is a receptor with numerous functions in the activation of antigen presenting cells (APCs), particularly dendritic cells (DC). Using phage display technology, we identified linear peptides containing a novel FPGN/S consensus sequence that enhances the binding of phage to a purified murine CD40-immunoglobulin (Ig) fusion protein (CD40-Ig), but not to Ig alone. To examine the ability the FPGN/S peptides to enhance adenoviral infection of CD40-positive cells, we used bifunctional peptides consisting of an FPGN-containing peptide covalently linked to an adenoviral knob-binding peptide (KBP). One of these, FPGN2-KBP, was able to enhance adenoviral infection of both murine and human DCs in a dose-dependent manner. FPGN2-KBP also improved infection of murine B cell blasts, a murine B lymphoma cell line (L10A), and immortalized human B cells. To demonstrate that enhancement of adenoviral infection depended on the presence of CD40, we analyzed infection of the breast cancer line, SKBR3, that does not express CD40 or the adenovirus cellular receptor, CAR. Infection of SKBR3 cells was enhanced by FPGN2-KBP following transient transfection with a plasmid vector that expresses murine CD40, but not when the cells were mock-transfected. In conclusion, we have isolated a peptide that binds to murine CD40, and promotes the uptake of adenoviruses into CD40-expressing cells of both murine and human origin, suggesting that it may have potential applications for antigen delivery to CD40-positive antigen-presenting cells.

Acute hyperoxic lung injury remains a major factor in the development of chronic lung disease in neonates. A critical step in the repair of acute lung injury is the proliferation of type II alveolar epithelial cells. Type II cell proliferation is stimulated by keratinocyte growth factor (KGF), an epithelial cell-specific mitogen. We sought to investigate KGF mRNA expression in relation to type II cell proliferation during hyperoxic lung injury. We studied a previously described newborn (NB) rabbit model of acute and chronic hyperoxic injury [C. T. D’Angio, J. N. Finkelstein, M. B. LoMonaco, A. Paxhia, S. A. Wright, R. B. Baggs, R. H. Notter, and R. M. Ryan. Am. J. Physiol. 272 ( Lung Cell. Mol. Physiol. 16): L720–L730, 1997]. NB rabbits were placed in 100% O2for 9 days and then recovered in 60% O2. RT-PCR was used to synthesize and amplify a 267-bp fragment of rabbit KGF cDNA from whole lung RNA. KGF mRNA expression was analyzed by ribonuclease protection assay, and mRNA abundance was quantified by phosphorimaging. Proliferating cell nuclear antigen immunohistochemistry was used on lung sections to identify proliferating cells. The rabbit partial cDNA sequenced was >95% homologous to human cDNA, and all amino acids were conserved. Whole lung KGF mRNA expression was increased 12-fold after 6 days of hyperoxia compared with control lungs, and remained increased throughout the 100% O2exposure period. Proliferating cell nuclear antigen immunohistochemistry showed an increase in type II cell proliferation after 8–12 days of hyperoxia. NB rabbits exposed to hyperoxic injury exhibit increased whole lung KGF mRNA expression preceding type II cell proliferation. KGF may be an important mitogen in the regulation of alveolar epithelial repair after hyperoxic lung injury.