To quantify HBV replication, medium was collected from day 8 to 13 post infection and secreted HBeAg was determined by enzyme-linked immunosorbent assay (ELISA (AxSym, Abbott)).

Primary hepatocytes were grown on coverslips, coated with 0.1 mg/mL collagen (Cell Systems). After incubation with peptide at 37°C, cells were washed in phosphate-buffered saline (PBS), fixed (4% paraformaldehyde [PFA]), and mounted in DAPI-containing mounting medium (VectaShield). Microscopy was performed on a Perkin Elmer spinning disk confocal microscope, using a 60× WI (NA 1.2) or 100× oil (NA 1.4) objective, a Hamamatsu C9100-50 camera, and the software Volocity (Perkin Elmer). Quantification of peptide binding was achieved by measurement of the gray values in 60 (Fig. DAPT clinical trial 5A) or 50 (Fig. 5B) circular Lumacaftor supplier selections in 3 or 10 representative pictures using ImageJ (NIH, Bethesda, MD). To analyze fluorescence recovery after photobleaching (FRAP), PMH were grown on collagen-coated chambered coverglass (LabTek). Cells were incubated with 400 nM HBVpreS/2-48myr-C-Atto565, diluted in Leiboviz (L-15) phenol red-free medium for 1

hour at 37°C, washed, and supplied with fresh L-15. As a control, cells were stained with 5 μL/mL Vybrant DiI (Invitrogen). Live cell microscopy at 37°C was performed in a heated chamber. Bleaching was achieved using the 568 nm laser, and recovery of fluorescence was monitored for 30 seconds with a frequency of 2 frames per second. The 4 × 105/mL freshly prepared or cryopreserved primary hepatocytes were incubated for 30 minutes at room temperature PAK6 with 200 nM of the respective peptide. After washing (PBS) flow cytometry was performed using a FACS Calibur and the software Cell Quest Pro (Becton-Dickinson).

Competition of binding was performed with a 100-fold excess of unlabeled HBVpreS/2-48myr or control peptides (HBVpreS/2-48myr(D11,13) and HBVpreS/1-48). Cell viability was assessed by propidium iodide. To exclude unspecific binding caused by nonparenchymal cells, hepatocyte preparations were controlled by uptake of acLDL (10 μg/mL for 2 hours at 37°C), a marker for endothelial cells. Myristoylated HBV-preS1 lipopeptides inhibit HBV infection of HepaRG cells.21 To investigate specific receptor-interaction, we synthesized a fluorescently labeled variant of HBVpreS/2-48myr (Fig. 1A) and performed binding assays with HepaRG cells. Cosynthetic coupling of one FITC-moiety per molecule HBVpreS/2-48myr-K-FITC was accomplished by introduction of a lysine at position 49. As a control, we synthesized a mutant lipopeptide in which the L-leucine at position 11 and the L-phenylalanine at position 13 were replaced by the respective D-enantiomers (HBVpreS/2-48myr(D11,13)-K-FITC). A second control peptide comprised the wildtype sequence but lacked the N-terminal myristoyl moiety (HBVpreS/1-48-K-FITC). Both peptides are inactive (HBVpreS/2-48myr(D11,13)) or drastically impaired in inhibitory activity (HBVpreS/1-48).