Reciprocal interference between specific CJD and scrapie agents in neural cell cultures.

Infection of mice with an attenuated Creutzfeldt-Jakob disease agent (SY-CJD) interferes with superinfection by a more virulent human-derived CJD agent (FU-CJD) and does not require pathological prion protein (PrPres). Using a rapid coculture system, we found that a neural cell line free of immune system cells similarly supported substantial CJD agent interference without PrPres. In addition, SY-CJD prevented superinfection by sheep-derived Chandler (Ch) and 22L scrapie agents. However, only 22L and not Ch prevented FU-CJD infection, even though both scrapie strains provoked abundant PrPres. This relationship between particular strains of sheep- and human-derived agents is likely to affect their prevalence and epidemic spread.