Selective induction of tumor necrosis receptor factor 6/decoy receptor 3 release by bacterial antigens in human monocytes and myeloid dendritic cells.

Tumor necrosis factor (TNF) receptor 6/decoy receptor 3 (TR6/DcR3) is an antiapoptosis soluble receptor of the TNF family produced by tumor cells. In this study, TR6 expression in human immune cells was investigated. TR6 mRNA and protein were detectable in selected antigen-presenting cells. Monocytes and myeloid-derived dendritic cells (MDC) released the protein exclusively following stimulation of Toll-like receptor 2 (TLR2) and TLR4 by gram-positive and gram-negative bacterial antigens. Plasmacytoid dendritic cells, activated by bacterial antigens via TLR9 or by viral infection, did not produce the protein. Similarly, activated T cells did not release TR6. The release of TR6 by MDC was dependent on the activation of p42/p44 mitogen-activated protein kinases, Src-like protein tyrosine kinases, and phosphatidylinositol 3-kinase, signaling pathways important for MDC maturation and survival. In agreement with the in vitro data, TR6 levels in serum were significantly elevated in patients with bacterial infections. Overall, these data suggest a novel role for TR6 in immune responses to bacteria.

Pharmacokinetic and pharmacodynamic studies of a human serum albumin-interferon-alpha fusion protein in cynomolgus monkeys.

Interferon-alpha (IFN-alpha) is indicated for the treatment of certain viral infections including hepatitis B and C, and cancers such as melanoma. The short circulating half-life of unmodified IFN-alpha makes frequent dosing (daily or three times weekly) over an extended period (6-12 months or more) necessary. To improve the pharmacokinetics of IFN-alpha and decrease dosing frequency, IFN-alpha was fused to human serum albumin producing a new protein, Albuferon. In vitro comparisons of Albuferon and IFN-alpha showed similar antiviral and antiproliferative activities, although Albuferon was less potent on a molar basis than IFN-alpha. Pharmacokinetic and pharmacodynamic properties of the fusion protein were enhanced in monkeys. After a single intravenous injection (30 microg/kg,) clearance was 0.9 ml/h/kg, and the terminal half-life was 68 h. After 30 microg/kg subcutaneous injection, apparent clearance (clearance divided by bioavailability) was 1.4 ml/h/kg, the terminal half-life was 93 h, and bioavailability was 64%. The rate of clearance of Albuferon was approximately 140-fold slower, and the half-life 18-fold longer, than for IFN-alpha given by the subcutaneous route in other monkey studies. Sera from Albuferon-treated monkeys demonstrated dose-related antiviral activity for > or =8 days based on an in vitro bioassay, whereas antiviral activity from IFN-alpha-treated animals was only slightly elevated relative to vehicle on day 0. Significant increases in 2',5'-oligoadenylate synthetase mRNA relative to IFN-alpha- or vehicle-treated animals were maintained for > or =10 days after subcutaneous dosing. The improved pharmacokinetics of Albuferon are accompanied by an improved pharmacodynamic response suggesting that Albuferon may offer the benefits of less frequent dosing and a potentially improved efficacy profile compared with IFN-alpha.