FIG. 3.

Influenza virus production in cells treated with PGA1. MDCK cells were treated with PGA1 and infected with the virus in the same way as for Fig. 2. (A) Virus production in the culture medium was assayed by measuring HA. In control cells without PGA1 (○), HA increased after 6 h and reached a plateau 24 h after infection. In cells treated with PGA1 (•), HA began to be detected 24 h after infection. (B) Phase-contrast images of cells infected with PGA1. MDCK cells treated with (b, d, and f) or without (a, c, and e) PGA1 were infected with the virus and cultured for 12 h (a and b), 24 h (c and d), or 48 h (e and f). CPE by infection was observed after 12 h in the cells without PGA1 treatment (arrows in panel a) and almost all of the cells had degenerated after 24 h (c and e). In the cells treated with PGA1, CPE was not seen at 12 h (b) but began to be observed from 24 h (arrows in panels d and f). Bar, 50 μm. (C) Expression of HSP70 in cells infected with PGA1. Total protein extracts were prepared from the infected cells in the presence (+) or absence (−) of PGA1 as shown in panels A and B and were blotted with anti-HSP70 antibody. HSP70 gradually decreased 12 h later in the presence of PGA1. (D) The intensities of the bands shown in panel C were measured by NIH Image software. The intensities were compared as relative percentages to that in the cells with PGA1 8 h after infection.