Editors' ChoiceEbola virus

Going live with a live Ebola assay

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Science Translational Medicine  18 Oct 2017:
Vol. 9, Issue 412, eaap8169
DOI: 10.1126/scitranslmed.aap8169

Abstract

A new reporter cell line can be used to detect live, infectious Ebola virus.

During the Ebola virus outbreak of 2014–2016, there were nearly 30,000 cases of Ebola hemorrhagic fever in Guinea, Liberia, and Sierra Leone with reported case-fatality rates of up to 67%. According to the WHO, there are over 10,000 people who survived Ebola infection during this outbreak. The long-term impact for survivors is still unclear, including the natural history of the virus beyond the initial infection. For how long and with what chronicity people have Ebola virus in bodily fluids—and if this virus is infective—are being investigated. Laboratory assays that quickly and sensitively identify infectious virus are crucial for risk assessment for people with Ebola and in epidemiologic investigations.

In a recent publication, Kainulainen and colleagues describe a reporter cell line to detect infectious Ebola virus. This line has improved sensitivity and earlier detection of infection compared with the current standard, which detects virus at days 7 and 14 via immunofluorescence. The authors created an Ebola virus “minigenome” of single-stranded, negative-sense RNA recognized by Ebola virus machinery with a downstream green fluorescent protein sequence, which they transfected into Vero E6 cells. When Ebola virus infects the cells, the fluorescent protein sequence is transcribed by the Ebola replication complex; detection of fluorescence corresponds to live and infective Ebola virus. Five Ebola virus types induced fluorescence at 3 days after infection of the modified cells, while Marburg virus did not.

To determine if the reporter cell line would detect infectious virus from clinical samples, the authors studied whole blood, EDTA-anticoagulated blood, and serum spiked with stock virus. Live virus was detected consistently from 3 and 4 days after infection in samples spiked with Ebola and Sudan types, respectively. Clinical serum, plasma, and blood samples collected during outbreak investigations were also tested for infectious virus. Live virus was detectable in the six specimens tested, although there was variability between samples in time of positivity, consistent with variable collection, storage conditions, and viral burden. These results are very exciting; an assay that allows more rapid and potentially high-throughput assessment for viral infectivity would expand capacity for more in-depth studies of shedding of live virus in bodily fluids prior to, during, and after acute Ebola infections.

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