LRP8 Identified as a Critical Receptor for Tick-Borne Encephalitis Virus via Genome-Wide CRISPR Screening

Tick-borne encephalitis (TBE) is a severe neurological infection caused by the tick-borne encephalitis virus (TBEV), with more than 10,000 clinical cases reported annually across Europe and Northeast Asia, and new endemic regions continuing to emerge. Although vaccines are available, coverage remains low, and no specific antiviral therapy exists. As an enveloped RNA virus, TBEV is closely related to other flaviviruses such as dengue and West Nile virus, but its host factors for viral entry remain largely unknown. In recent years, genomic screening technologies have uncovered various virus–host interactions, yet this represents the first comprehensive genome-wide screen for TBEV.

An international research collaboration led by Albert Einstein College of Medicine identified low-density lipoprotein receptor-related protein 8 (LRP8, also known as ApoER2) as a key receptor for TBEV through a genome-wide CRISPR-Cas9 screen. LRP8 is highly expressed in the brain and has been previously implicated as an entry factor for certain viruses, but its role in TBEV infection and potential as a therapeutic target remain unclear. This study demonstrates that LRP8 directly mediates TBEV attachment, internalization, and infection and develops a soluble LRP8-based decoy protein that blocks infection and protects animal models.

The researchers used the GeCKO v2 CRISPR-Cas9 library to screen for host factors required by the TBEV Sofjin strain in human A549 cells. Enriched genes were associated with the ER membrane complex, ER-associated degradation, lipophagy, and RNA replication—consistent with findings from other flavivirus screens. However, LRP8 emerged as the only highly enriched and unique hit (among 25 flavivirus datasets, LRP8 was the most distinct). Knockout (KO) of LRP8 markedly reduced TBEV infection, while overexpression enhanced it, confirming that LRP8 is a critical host factor.

After generating LRP8 knockout (KO) cell lines using CRISPR–Cas9, the team found that TBEV entry and infection were dramatically impaired—both for single-cycle RVP particles and live viruses (including European and Far Eastern strains). Re-expression of LRP8 rescued the infection, confirming that the defect was due to LRP8 loss. siRNA knockdown of LRP8 yielded similar results. Conversely, overexpressing LRP8 increased infection by approximately 2–10 fold, suggesting that LRP8 promotes TBEV entry and replication.

Further analysis revealed that LRP8 did not significantly affect infection by other flaviviruses (e.g., dengue, West Nile virus) but specifically facilitated TBEV infection. It also promoted Semliki Forest virus (SFV) entry, consistent with its known role as a partial alphavirus receptor. Therefore, LRP8 was confirmed as a TBEV-specific host entry receptor.

In A549 cells, LRP8 knockout led to severely reduced viral attachment, whereas overexpression of full-length LRP8 (containing the LA1–2 domains) markedly enhanced surface binding and endocytosis. Confocal imaging showed that after incubation at 37°C, viral E protein signals shifted from the cell surface to the cytoplasm and co-localized with the early endosome marker EEA1, indicating that LRP8 mediates both viral attachment and internalization. In contrast, an LRP8 mutant containing only the LA1 domain failed to restore these processes. Collectively, these data show that LRP8 interacts with TBEV E protein via its LA1–2 domain to facilitate viral attachment and endocytic entry, representing a key early step in infection.

Based on the specific binding of LA1–2 to the E protein, the researchers engineered a soluble LRP8(LA1–2)–Fc decoy protein. This decoy inhibited TBEV RVP entry in a dose-dependent manner at nanomolar concentrations and significantly reduced infection in hepatocytes and neuronal cells. In vivo, pre-mixing TBEV with LRP8(LA1–2)–Fc or administering the decoy prior to infection completely protected mice from lethal challenge, with brain viral titers dropping below the detection limit and no detectable viral RNA signals. These findings indicate that the LRP8–E interaction is essential for infection both in vitro and in vivo, and its disruption provides strong protection. This offers direct evidence supporting LRP8-targeted antiviral strategies.

Low-density lipoprotein receptor-related protein 8 (LRP8, also known as ApoER2; gene symbol LRP8) is a member of the LDLR family predominantly expressed in the brain. It mediates apolipoprotein E and Reelin signaling, contributing to neuronal development and synaptic plasticity. Structurally, it contains ligand-binding repeats (7 LA domains), EGF-like domains, a β-propeller, an O-linked glycosylation region, a transmembrane domain, and a cytoplasmic tail. Physiologically, it regulates lipid metabolism and neuronal signaling; pathologically, it can be hijacked by certain viruses (e.g., alphaviruses) as an entry receptor. As a therapeutic target, the development of soluble decoys or blocking agents that disrupt viral binding without impairing physiological functions represents a promising antiviral strategy against TBEV and related viruses.

abinScience, founded in Strasbourg, France, leverages the region’s strong research and innovation ecosystem to focus on the development and production of high-quality life science reagents. abinScience adheres to the vision of “Empowering Bioscience Discovery,” providing efficient and reliable experimental solutions to global researchers and advancing cutting-edge life science studies. The LRP8 and TBEV-related proteins featured in this research are also available as abinScience's ready-to-use research tools to support related studies.

The following table lists LRP8 and TBEV-related proteins and antibodies available from abinScience: