Gamma-ray-enhanced reactivation of irradiated adenovirus in Xeroderma pigmentosum and Cockayne syndrome fibroblasts.

A gamma-ray-enhanced reactivation (gamma RER) of uv-irradiated as well as of gamma-irradiated human adenovirus type 2 (Ad 2) was detected following infection of normal, Xeroderma pigmentosum (XP), and Cockayne syndrome (CS) fibroblasts that had been preirradiated with gamma rays. Gamma-irradiated or nonirradiated fibroblasts were infected with either nonirradiated or irradiated Ad 2, and 48 hr after infection cells were examined for the presence of viral structural antigens (Vag) using immunofluorescent staining. Results obtained using seven different normal fibroblast strains showed that irradiation of host monolayers with 1 krad immediately prior to infection resulted in a gamma RER factor +/- SE of 4.5 +/- 1.6 for uv-irradiated virus and 4.3 +/- 1.3 for gamma-irradiated virus. CS fibroblasts, as well as excision repair-deficient XP fibroblasts from complementation groups A and D, were all found to be capable of expressing gamma RER of irradiated Ad 2. XP variant cells expressed lower levels of gamma RER compared to most normal strains, suggesting a possible role for cellular postreplication repair in the mechanism responsible for ER in human cells. An excision-deficient XP fibroblast strain belonging to complementation group A, but derived from a patient afflicted with the severe De Sanctis-Cacchione form of XP, although proficient in gamma RER of gamma-irradiated Ad 2, yielded barely detectable levels of gamma RER for uv-irradiated Ad 2.