Type I Interferon Reaction to Viral Infection in Interferon-Competent, Immortalized Cell Lines from the African Fruit Bat Eidolon helvum

Abstract

Bats harbor several highly pathogenic zoonotic viruses including Rabies, Marburg, and henipaviruses, without overt clinical symptoms in the animals. It has been suspected that bats might have evolved particularly effective mechanisms to suppress viral replication. Here, we investigated interferon (IFN) response, -induction, -secretion and -signaling in epithelial-like cells of the relevant and abundant African fruit bat species, Eidolon helvum (E. helvum). Immortalized cell lines were generated; their potential to induce and react on IFN was confirmed, and biological assays were adapted to application in bat cell cultures, enabling comparison of landmark IFN properties with that of common mammalian cell lines. E. helvum cells were fully capable of reacting to viral and artificial IFN stimuli. E. helvum cells showed highest IFN mRNA induction, highly productive IFN protein secretion, and evidence of efficient IFN stimulated gene induction. In an Alphavirus infection model, O'nyong-nyong virus exhibited strong IFN induction but evaded the IFN response by translational rather than transcriptional shutoff, similar to other Alphavirus infections. These novel IFN-competent cell lines will allow comparative research on zoonotic, bat-borne viruses in order to model mechanisms of viral maintenance and emergence in bat reservoirs.

Evolution and Antiviral Specificities of Interferon-Induced Mx Proteins of Bats against Ebola, Influenza, and Other RNA Viruses

“…Infection with RVFV clone 13 induced comparable levels of Mx1 in all bat cells used in our study, including CarLu cells (data not shown). Accordingly, the accumulation of Mx1 argues for a virus-induced type I or type III IFN production and upregulation of Mx1 as described previously (17,21). Therefore, bat Mx1 expression can be used as a reliable marker for the detection of type I and type III IFN activity during virus infection and IFN treatment.…”

“…Bat cell cultures were obtained from the cell culture collection of the Institute of Virology, University of Bonn. All bat cell cultures were immortalized by lentiviral transduction with the simian virus 40 (SV40) large T antigen and tested negative for mycoplasma, SV5, lyssavirus, and filovirus contaminations as described previously (17). The species type of the cell cultures was confirmed by amplification of the COX1 gene, encoding cytochrome c, as previously described (69).…”

“…The species type of the cell cultures was confirmed by amplification of the COX1 gene, encoding cytochrome c, as previously described (69). Cultures of human embryonic kidney (HEK) 293T cells, human cervical carcinoma HeLa cells, Madin-Darby canine kidney epithelial cells (MDCK II), Carollia perspicillata CarLu/1 (70), Myotis daubentonii MyDauNi/2c (17), Pipistrellus pipistrellus PipNi/1 (17), Eidolon helvum EidNi/41 (17), Hypsignathus monstrosus HypNi/1 (71), and Rousettus aegyptiacus RoNi/7 (17) cells were cultivated in Dulbecco's modified Eagle's medium (DMEM) with 5 to 15% fetal calf serum (FCS) at 37°C.…”

“…These cytokines activate their respective receptors and induce an intracellular antiviral state, thereby suppressing virus replication. Critical components of this innate antiviral defense system have also been described for bats (17)(18)(19)(20)(21)(22). Moreover, constant elevated expression of type I IFNs in Pteropus alecto was recently described, and thus constitutive expression of ISGs might contribute to an early stringent control of invading viral pathogens in bats (23).…”

Unlocking bat immunology: establishment of Pteropus alecto bone marrow-derived dendritic cells and macrophages

“…To this end, various non-immune bat cell lines, originating from either insectivorous or fruit-bats and covering multiple species, had been constructed including Pteropus, Eidolon, Hypsignathus, Rousettus, Epomops, Myotis and Tadarida bats11121314. These cell lines, either primary or immortalized, supported bat viral infection studies and basic host responses.…”