## 3 Results
### SH-SY5Y Cells Can Be Transduced by Many Viral Envelope Proteins but Not by GP of Filoviruses  
The genus _Ebolavirus_ comprises five species: _Zaire ebolavirus_ (Ebola virus (EBOV)), _Sudan ebolavirus_ (Sudan virus (SUDV)), _Reston ebolavirus_ (Reston virus (RESTV)), _Bundibugyo ebolavirus_ (Bundibugyo virus (BDBV)), and _Tai Forest ebolavirus_ (Tai Forest virus (TAFV)) [1]. Moreover, a new filovirus species, _Lloviu cuevavirus_ (Lloviu virus (LLOV)), was discovered in Spain in 2011 [58]. We asked whether the GPs of these viruses could mediate productive entry in SH-SY5Y cells. To test this, we transduced either HEK293T or SH-SY5Y cells with pseudoparticles bearing no viral envelope protein (NoEnvpp) or GPs from the respective _Ebola_ species or _Lloviu cuevavirus_. For EBOV, we used GPs of 1976 Mayinga strain, 2014 Makona strain (WT), and the cell entry-enhancing Makona variant A82V [59; 60]. VSV-Gpp served as positive control (Figure 3A). Consistent with our other results, HEK293T cells but not the SH-SY5Y cells were susceptible to transduction mediated by all GPs (Figure 3A). To determine whether SH-SYSY cells were susceptible to transduction driven by other viral GPs, we generated pseudoparticles encoding for GFP and bearing Chikungunya virus envelope proteins (CHIKV E1-E3), severe acute respiratory syndrome virus S protein (SARS-S), Lassa virus GPC (LASV-GPC), Rabies virus G protein (RABV-G), or VSV-G GPs (Figure 3B). Filovirus susceptible Huh-7.5 and HEK293T cells (Figure 1A-B) as well as resistant SH-SYSY and Jurkat cells were transduced at a MOI of 0.1. While Huh-7.5 cells were susceptible to all pseudoparticles tested, Jurkat cells were effectively transduced only with VSV-Gpp. HEK293T cells were susceptible to all pseudoparticles with the exception of SARSpp, which could only transduce Huh-7.5 cells. LASVpp efficiently transduced epithelial Huh-7.5 and HEK293T cells. SH-SYSY cells were susceptible not only to VSV-Gpp, but also to transduction driven by RABV-G and CHIKV E1-E3. In addition, marginal transduction was detected with LASV-GPC pseudoparticles. In summary, SH-SYSY cells are resistant to transduction driven by filovirus GPs but not by the majority of the other viral glycoproteins tested. Figure 2: SH-SYSY is resistant to EBOV and VSVAG-EBOVGP infection. (**A,B**) Authentic filovirus infection. Susceptible HEK293T, SK-N-BE(2)-C as well as resistant SK-N-MC and SH-SYSY cells were infected with EBOV or MARV or mock-infected for 1 h at a MOI of 0.1. Seventy-two hpi, cells were fixed and stained for EBOV and MARV NP (**A**) using DAPI as counterstainedaining. Images acquired with a 40\(\times\) objective (**B**) In parallel, remaining cells were lysed, and analyzed by immune-blotting for virus NP. \(\alpha\)-tubulin was used as internal control. Images and blots are representative of three independent infections. (**C,D**) rVSVAG-EBOV infection. HEK293T and SH-SYSY cells were infected with rVSV bearing EBOV Mayinga GP for 1 h at 37 °C. Fresh media was added and cells further incubated for 48 h. A 10\(\times\) objective was used for image acquisition (**C**) 48 hpi. GP-specific cell rounding and detachment. (**D**) Cell supernatant was collected 24 hpi and viral titers determined by TCID50. Figure 3: SH-SY5Y cells are resistant to pseudoparticles bearing either Ebolavirus species GPs but susceptible to pseudoparticles bearing glycoproteins of other virus families. (**A**) SH-SY5Y cell susceptibility to Ebolavirus species and entry-enhancing variant GPs. HEK293T and SH-SY5Y cells were transduced for 6 h with denoted pseudoparticles encoding for a firefly luciferase reporter gene. After 72 h, 100 uL of cell lysates were measured for luciferase activity. Unspecific entry was determined by NoEnvpp RLU values. Data are the log10 RLU mean values of 3 independent transductions with 9 individual values. Error bars represent SD. (**B**) Cell–virus specificity analysis.