Understanding Receptor-mediated Spillover of Rabies Virus Across Different Mammalian Hosts

Khalifa, Manar and Munir, Muhammad and Unterholzner, Leonie (2023) Understanding Receptor-mediated Spillover of Rabies Virus Across Different Mammalian Hosts. PhD thesis, Biomedical and Life Sciences.

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Abstract

Rabies is a lethal viral zoonotic disease causing up to 59,000 human deaths annually. Recent studies have identified several cellular receptors for rabies virus (RV) entry and internalization. However, none of these receptors was identified as indispensable for RV entry. To better understand the preference of RV receptors in vivo, we established a cellular model using a replication-competent vesicular stomatitis virus (VSV). In this model, the VSV-G surface glycoprotein was replaced with the RV-G (Rabies Virus Glycoprotein) surface glycoprotein fused with a green fluorescent protein (GFP). To investigate the specific role of RV receptors in promoting RV entry, we identified that HaCaT cell line is refractory for RV infection. By studying the role of RV receptors in HaCaT cells, we identified ITGB1, mGluR2, and nAChR as potential receptors for RV entry and replication. Consequently, further studies involved generating knockout (KO) cell lines corresponding to each of these receptors. Surprisingly, RV was still able to enter and replicate in the generated KO cell lines, yet the replication and entry of RV in KO cells lacking mGluR2 and ITGB1 were significantly reduced; respectively. These findings suggest that RV employ binding to these receptors in series rather than sequentially. To gain more understanding of whether RV employ similar receptor preference among human, dog, and bats. We utilized the rVSV-dG-RV-G-GFP in A549 (lung human cells), Pa-Br (brain bat cells), and MDCK (dog kidney cells) cell lines that over express receptor orthologs from their respective species. Our findings revealed distinct receptor utilization by RV depending on the cell type. In human cells, human ITGB1 increased virus entry, while the nAChR enhanced virus replication. In bat cells, ectopic expression of nAChR allowed enhanced virus entry and internalization. While MDCK cells over expressing ITGB1 enhanced the levels of virus entry and replication. These observations suggest that the RV receptor might be influenced by underlying pathways during the interaction between the virus and receptor in different cell lines. In conclusion, our study provides insights into the complex relationship between RV and its host receptors, uncovering distinct receptor preferences and emphasizing the significance of host-specific factors in virus entry and replication.