Résumé
Our original aim was to determine whether dBcAMP-induced activation of cultured astrocytes affected the course of subsequent viral infection. After 2 h exposure of 2-day-old first subculture of mouse astrocytes to dBcAMP 1 mM, cell monolayers grown in glass coverslips of Leighton tubes were inoculated with 10(3) PFU of Theiler virus-GDVII strain (TMEV-GDVII). At 9 days post-infection (pi), viral infectivity persisted in supernatants from dBcAMP-treated cultures, but was no longer detectable in non-stimulated controls. The relatively spared astroglial monolayer at day 1 pi, hardly affected by progressive viral cytolytic effect, was chosen for immunolabeled cell count, whether by viral antigen or GFAP. To this end, 20 fields for each coverslip were digitalized at 250x final magnification. In dBcAMP treated cultures, viral antigen(+) cells were fewer and lower in percentage versus infected cultures lacking stimulation. As regards GFAP staining, stimulation or infection per se induced a greater number and percentage of labeled astrocytes. According to morphometric characterization, such increase was due to a greater number of process-bearing astrocytes. It may be concluded that, regardless of previous dBcAMP treatment, early TMEV-GDVII infection enhanced immunocytochemical and morphological differentiation in cultured astrocytes.