Abstract
Eidolon helvum bats are reservoir hosts for highly pathogenic lyssaviruses often showing limited disease upon natural infection. An enhanced antiviral interferon (IFN) response combined with reduced inflammation might be linked to the apparent virus tolerance in bats. Lyssavirus phosphoproteins inhibit the IFN response with virus strain-specific efficiency. To date, little is known regarding the lyssavirus P-dependent anti-IFN countermeasures in bats, mainly due to a lack of in vitro tools. By using E. helvum bat cell cultures in a newly established bat-specific IFN-promoter activation assay, we analyzed the IFN-ß inhibitory activity of multiple lyssavirus P in E. helvum compared to human cells. Initial virus infection studies with a recently isolated E. helvum-borne Lagos bat virus street strain from Ghana showed enhanced LBV propagation in an E. helvum lung cell line compared to human A549 lung cells at later time points suggesting effective viral countermeasures against cellular defense mechanisms. A direct comparison of the IFN-ß inhibitory activity of the LBV-GH P protein with other lyssavirus P proteins showed that LBV-GH P and RVP both strongly inhibited the bat IFN-β promotor activation (range 75-90%) in EidLu/20.2 and an E. helvum kidney cell line. Conversely, LBV-GH P blocked the activation of the human IFN-β promoter less efficiently compared to a prototypic Rabies virus P protein (range LBV P 52-68% vs RVP 71-95%) in two different human cell lines (HEK-293T, A549). The same pattern was seen for two prototypic LBV P variants suggesting an overall reduced LBV P IFN-ß inhibitory activity in human cells as compared to E. helvum bat cells. Increased IFN-ß inhibition by lyssavirus P in reservoir host cells might be a result of host-specific adaptation processes towards an enhanced IFN response in bat cells.
Highlights
The IFN-β promoter activation reporter assay in EidLu/20.2 and EidNi/41.3 bat cells was performed with the following adaptations: bat cells were transfected with 25 ng pRL-Simian virus 40 (SV40) plasmid (Promega) and 250 ng pGL4.10[luc2] plasmid including the R. aegyptiacus IFN-β promoter
We found a 10-fold higher IFN-β mRNA expression in EidLu/20.2 cells compared to A549 for both stimuli (Fig 1B)
As the pattern of IFN signaling inhibition by Rabies virus P protein (RVP) and Lagos bat virus (LBV) P was comparable between bat and human cells we focused our study on the inhibitory activity of lyssavirus P proteins on IFN-β induction
Summary
Lyssaviruses infect a wide range of mammals causing up to 50,000 fatal rabies cases in humans per year [1]. The well-studied Rabies virus (RABV) P protein (RVP) blocks several steps of the IFN pathway at the level of IFN induction and signaling, modulating pathogenicity in vitro and in vivo [12– 15]. Whereas some street strain lyssavirus-derived P proteins seem to have enhanced efficiency to block IFN induction in human cells [18], inhibition of IFN signaling by P proteins was shown to be highly conserved among lyssaviruses, including LBV [19]. Virus adaptation might promote intra-host transmission without severe damage to host bat cells but possibly result in high virulence in novel hosts [35] These initial findings encourage more in-depth functional analyses to elucidate the complex interactions of bat viruses in their natural host. Most experiments involving bat-associated viruses like LBV are performed in primate or rodent cells [18, 19]. Our data encourage further studies of the complex interplay of bat-associated viruses and host cells in the natural reservoir context
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
