Reston and Zaire Ebolavirus Life cycle and host cellular response : a comparative study

Ebolaviruses are negative strand RNA viruses which are known to cause Ebola virus disease (EVD) with a fatal outcome in primates. All five species of Ebolavirus can infect humans, but only four lead to EVD. The Ebolavirus with the most provoked outbreaks and highest fatality rate (above 80%) is Zaire ebolavirus (EBOV), while the one without any provoke symptoms in humans is Reston ebolavirus (RESTV). In order to determine the features which lead to the different outcomes from EBOV and RESTV the cellular response against these viruses, and the divergence between RESTV and EBOV life cycle inside human cells was investigated. To study the cellular response RNA of two human cell lines (HuH7 and THP1) infected with RESTV, EBOV and uninfected (Mock) at two different time points was analyzed. Using whole transcriptome screening with smallRNAseq, Microarray, de novo annotation and expression profiles it was possible to elucidate that the cellular response against RESTV and EBOV infection differs the most at 3 h p.i., this was consistent in HuH7 and THP1 cell lines. The transcriptomic study showed RESTV and EBOV stimulate a distinct set of genes related to cellular entry. Also, the transcriptomic data suggests EBOV transcribes and replicates faster than RESTV, supported by cellular components like snoRNAs, while RESTV is similar to Mock in this aspect. This finding was backed with an entry assay which showed EBOV releases its content into the cytosol faster than RESTV, pointing to differences in entry pathway or a better time controlled response from the cell against RESTV. To understand the life cycle of RESTV and EBOV in human cells transcription/replication, inclusion bodies, nucleocapsid (NC) transport, viral particle formation, and infection was studied. Selected genes which were differentially expressed between RESTV and EBOV infected cells were further analyzed on the virus life cycle context.