Herpes simplex virus type 1 infection of rat astrocytes in primary culture: effects of dibutyryl cyclic AMP.

Monolayer cultures of primary rat astrocytes grown with or without dibutyryl cyclic AMP (dBcAMP) for two weeks or longer were infected with round plaque-forming (Rd) or syncytia-forming (Syn) variants of herpes simplex virus type 1 (HSV-1). Infection with HSV-1 did not stimulate synthesis of glial fibrillary acidic protein (GFAP) or alter the general organization of the intermediate (glial) filaments in astrocyte cultures. However, the dBcAMP-treated astrocytes produced 10- to 100-fold lower titers of cell-free progeny HSV-1 than the untreated astrocyte cultures. Radiolabeled amino acid or glucosamine incorporated into acid precipitable cellular or viral glycoproteins was decreased by 10-25% in dBcAMP-treated astrocytes. Distinctive cell-rounding or syncytial cytopathology was produced by HSV-1 strains infecting untreated astrocytes, but the infected dBcAMP-treated astrocytes displayed only cell-rounding cytopathology. The dBcAMP-related effects on HSV-1 infection were specific to primary astrocyte cultures; they were not observed in HSV-1-infected human fibroblast cultures treated with dBcAMP. Comparison of HSV-1 infection of untreated versus dBcAMP-treated astrocytes suggests that the dBcAMP-induced "reactive" or differentiated state of the astrocyte can affect expression of virus-induced cytopathology and virus-specific polypeptide synthesis. The dBcAMP-treated primary astrocyte culture may afford a non-neoplastic, differentiated in vitro system for studying HSV-neural cell interactions.