Acceleration of scrapie disease in mice by an adenovirus.

Coinfected mice were examined for a possible interaction between the scrapie agent and an adenovirus. A low titer (10(2) TCD50) of mouse adenovirus (MAdV) caused a significant acceleration of clinical signs of scrapie in mice infected 128 days previously with scrapie. In this experiment, the coinfected mice died 19 days earlier than mice infected with scrapie alone. When a higher titer of MAdV (10(4)-10(5) PFU) was used, a more drastic acceleration of scrapie disease was seen in mice infected 85 and 110 days previously with scrapie. At 85 days, coinfection caused mice to die 37 days earlier than mice infected with scrapie alone, whereas at 110 days, coinfection caused mice to die 52 days earlier than mice infected with scrapie alone. MAdV alone caused no clinical disease in normal mice. The brains of coinfected mice and mice that had been infected with scrapie alone showed a histopathology consistent with scrapie. A possible explanation for these findings is that the replication of the scrapie agent is accelerated by adenovirus. Defective parvoviruses are known to be helped by adenoviruses. Spleens from coinfected mice but not from mice infected with MAdV alone yielded, in cultures of BALB 3T3 cells, infectious MAdV and one or two smaller agents with the dimension and shape of a parvovirus.