Fig. 4.

Effect of furin-like protease activity on infectious particle production in astrocytes. (a) Furin activity in confluent monolayers of HBCAs and HBMECs. HBCA and HBMEC monolayers were lysed in assay buffer. The furin substrate pERTKR-amino-methylcoumarin (100 µM) was added to equal cellular amounts of lysate and fluorescence was measured every 20 s for 10 min. Values represent the mean±se relative fluorescence units (RFU) of at least three independent experiments. (b) HBCAs were infected with WNV-NY or WNV-MAD78 (m.o.i. 0.01) in the presence or absence of the furin inhibitor Dec-RVKR-CMK (50 µM). Culture supernatants were collected at 48 h post-infection. The concentration of total virus particles and infectious particles was determined using the ViroCyt virus counter and plaque assays on Vero cells, respectively. Values represent the mean±se number of particles/p.f.u. ml^–1 of at least three independent experiments. *P<0.05.