4. Discussion
The absence of basic research and translational technology has been
highlighted since the 2014-2016 EBOV epidemic in West Africa, the reason
for which is BSL-4 facility restrictions. It is a priority to develop a
safe method for EBOV research with low BSL restrictions and definite
applicability.
Although the result of the neutralization assay is a gold standard for
antibody detection, BSL-4 laboratories are not available for many
research groups. In this situation, many groups developed an increasing
number of agents, which are single replication cycle pseudotyped
viruses, for hazardous pathogens based on the lentivirus system
(Chen et al., 2018;
Qiu et al., 2013;
Zhao et al., 2013). In addition, the
efficient expression of the luciferase reporter gene in infected cells
was demonstrated after GP-mediated infection (Fig. 2b, 2c), indicating
the infection efficiency. These features make pseudotyped EBOV a safe
and quantifiable tool for antiviral drug discovery and neutralizing
activity evaluation.
Among the viral proteins, GPs are considered the major pathogenicity
factor (Panina et al., 2017). EBOV entry
into target cells is initiated by the interaction between the viral GP
and receptors on the surface of target cells. As a result, the GP of
EBOV was selected to construct the pseudotyped EBOV in this study. As
expected, GP endowed the pseudotyped EBOV with similar infectivity of
authentic EBOV, as indicated by the result that the pseudotyped EBOV
could infect different target cells in this study, except C3/36 cells
from mosquitoes (Fig. 2a).
All assays involving live EBOV have to be performed under BSL-4
conditions because of the high lethality of EBOV, which limits the
application of these assays. However, the pseudotyped EBOV generated
from our two-plasmid system has only a single infection cycle (Fig. 2d,
2e), so that it cannot cause mass infection and death. In addition,
based on the pseudotyped EBOV, we developed a neutralization assay to
evaluate the neutralizing activity of the antibody products. As our data
show (Fig. 3a), the pseudotyped EBOV neutralization assay can
successfully be used for neutralizing activity evaluation, having the
consistent results with an authentic EBOV-based neutralization assay in
neutralizing antibody detection, confirming its potential application
value in antiviral drug discovery and neutralizing antibody evaluation.