Ebola virus defective interfering particles and persistent infection

Ebola virus (Zaire subtype) is associated with high mortality disease outbr eaks that commonly involve human to human transmission. Surviving patients can show evidence of prolonged virus persistence. The potential for Ebola v irus to generate defective interfering (DI) particles and establish persist ent: infections in tissue culture was investigated. It was found that seria l undiluted virus passages quickly resulted in production of an evolving po pulation of virus minireplicons possessing both deletion and copyback type DI genome rearrangements. The tenth undiluted virus passage resulted in the establishment of virus persistently infected cell lines. Following one or two crises, these cells were stably maintained for several months with cont inuous shedding of infectious virus. An analysis of the estimated genome le ngths of a selected set of the Ebola virus minireplicons and standard filov iruses revealed no obvious genome length rule, such as "the rule of six" fo und for the phylogenetically related Paramyxovirinae subfamily viruses. Min imal promoters for Ebola virus replication were found to be contained withi n 156 and 177 nucleotide regions of the genomic and antigenomic RNA 3' term ini, respectively, based on the length of authentic termini retained in the naturally occurring minireplicons analyzed. In addition, using UV-irradiat ed preparations of virus released from persistently infected cells, it was demonstrated that Ebola virus DI particles could potentially be used as nat ural minireplicons to assay standard virus support functions.