LY6E blocks coronavirus fusion and confers immune control of viral disease

Zoonotic coronaviruses (CoVs) are significant threats to global health, as exemplified by the recent emergence of Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Host immune responses to CoV are complex and regulated in part through antiviral interferons. However, the interferon-stimulated gene products that inhibit CoV are not well characterized. Here, we show that interferon-inducible lymphocyte antigen 6 complex, locus E (LY6E) potently restricts cellular infection by multiple CoVs, including SARS-CoV, SARS-CoV-2, and Middle East respiratory syndrome coronavirus (MERS-CoV). Mechanistic studies revealed that LY6E inhibits CoV entry into cells by interfering with spike protein-mediated membrane fusion. Importantly, mice lacking Ly6e in hematopoietic cells were highly susceptible to murine CoV infection. Exacerbated viral pathogenesis in Ly6e knockout mice was accompanied by loss of hepatic and splenic immune cells and reduction in global antiviral gene pathways. Accordingly, we found that Ly6e directly protects primary B cells and dendritic cells from murine CoV infection. Our results demonstrate that LY6E is a critical antiviral immune effector that controls CoV infection and pathogenesis. These findings advance our understanding of immune-mediated control of CoV in vitro and in vivo, knowledge that could help inform strategies to combat infection by emerging CoV. Ly6etm1a ES cells were obtained from the EUCOMM consortium and microinjected into C57BL/6J blastocysts by the UTSW Transgenic Technology Center. Chimeric mice with germline transmission were bred to obtain Ly6etm1a/+ offspring. Ly6etm1a/+ mice were crossed with FLPe-expressing mice (B6N.129S4-Gt(ROSA)26Sortm1(FLP1)Dyn/J, #16226, Jackson Laboratories) to obtain Ly6efl/+ offspring, which were bred to homozygosity. Conditional Ly6efl/fl mice were bred to Vav1-iCre transgenic mice (B6.Cg-Commd10Tg(Vav1-icre)A2Kio/J, #008610, Jackson Laboratories) to obtain Ly6eΔHSC/+ (Ly6efl/+; Vav1-iCre) offspring. Ly6eΔHSC/+ mice were bred to obtain Ly6eΔHSC (Ly6efl/fl; Vav1-iCre) offspring, which harbor a deletion of exon 3 and 4 in hematopoietic stem cells (HSC). Experimental animals were obtained by crossing Ly6eΔHSC and Ly6efl/fl mice. Genotype was confirmed by PCR of genomic DNA in-house or outsourced to Transnetyx. Ablation of Ly6e was confirmed by qPCR in immune cells from spleen, liver, or bone marrow. Animal studies were carried out in specific-pathogen-free barrier facilities managed and maintained by the UTSW Animal Resource Center. All procedures used in this study complied with federal and institutional guidelines enforced by the UTSW Institutional Animal Care and Use Committee (IACUC).