Activating NK- receptors, homing selectins and inhibitory Siglecs recognize EBOLA-GP and HPV-L1NK

Abstract

The Ebola virus glycoprotein (EBOV)-GP is extensively glycosylated. Its expression induces a physical alteration of surface adhesion molecules, which causes cell rounding and detachment of the infected cells. This phenomenon likely plays a crucial role in viral pathogenicity. In this study, we show that such morphological changes are cell line-dependent as well as dependent on the surface proteins that interact with EBOV-GP in cis and trans. We have generated data showing that natural killer (NK) cell receptors (NCRs: NKp44 and NKp46), selectins (CD62E/P/L) and inhibitory Siglecs function as receptors for Ebola-GP and human papilloma virus (HPV-L1). We used HEK293 cells transfected with Ebola-GP and recombinant fusion proteins containing the extracellular domain of each of these receptors linked to the Fc of human IgG1, which showed significant differences in their virus-binding behavior compared to HEK293 cells transfected with empty vector. Further, to demonstrate that EBOV-GP is a ligand for NKp44 and other NK-receptors, and to investigate their role in immune escape, we also used human HEK-293, HeLa- and hamster CHO-GP-transfectants. Our data show that the NK receptors NKp44 and NKp46 play a key role in recognizing EBOV (Ebolavirus) and strongly suggest that other inhibitory (Siglec-7, Siglec-5) and non-inhibitory homing receptors (P-Selectin, L-Selectin, E-Selectin, and DC-SIGNR/DC-SIGN) take part in the interaction with virus particles. In addition, we show that NKp44, and NKp46, Siglec-7, and -5, and P-, L-, E-selectins as well as of and DC-SIGNR/DC-SIGN bind to the artificial viral envelope of a lentiviral vector that contains EBOV-GP. Altogether we prove that NCRs and a range of other inhibitory and activating receptors can interact with viral envelope/capsid proteins and that such interaction could play an important role in the elimination of virus infected cells. Our findings could be used to develop new strategies for prevention and treatment of infections by these viruses.Author summaryThe innate immune system is able to recognize specifically certain virus components. Here we show that activating NK-cell receptors (NKp44, and NKp46) are involved in such interaction by using HEK293 and CHOK1 cells transfected with the Ebola virus glycoprotein (EBOV-GP) and by binding studies with purified EBOV-GP. In detail, we have found moderate to strong affinity of Siglecs (Siglec-7, and -5), selectins (P-, L-, E-Selectin) and DC-SIGNR/DC-SIGN to purified EBOV-GP, and to cells transfected with EBOV-GP as well as to the envelope of a lentiviral vector carrying the EBOV-GP. Our findings show that NKp44, and NKp46, Siglec-7, and -5, as well as P-and L-selectins have a strong affinity to EBOV-G.