New insights into the role of N-glycosylation involved in molecular immune checkpoint regulation by human cytomegalovirus glycoproteins with the implication in cancer therapy

Abstract

Abstract The regulation of immune checkpoint molecules, such as BTLA or TIGIT, on immune cells occurs during persistent viral infections. These pathways are important for preventing immune-driven pathology but can also limit immune-mediated clearance of the infection. The recent success of immune checkpoint blockade in cancer therapy suggests that targeting these pathways would also be effective for preventing and treating a range of infectious diseases. Here, we report our current study of immune checkpoint pathways in the pathogenesis of human cytomegalovirus and discuss the potential for therapeutically targeting these pathways in this setting. Human cytomegalovirus (HCMV) belongs to the beta herpes virus family that has co-evolved with the host immune system. UL144 and UL141 are found exclusively in clinical HCMV strains; while UL144 encodes a structural homologue of the herpesvirus entry mediator HVEM (target of BTLA), UL141 mimics TIGIT immunoreceptor. UL144 plays a role in virus-mediated immune evasion by transmitting inhibitory signals to downregulate T-cell responses and UL141 play significant role in NK cell evasion mechanism. Their sequences show considerable number of N-linked glycosylation sites located mostly in extracellular part. Many of them are not present in other viral species that suggest this glycosylation is important in human setting and may play a role in ligand-binding recognition. Here, we present characterization of recombinant HCMV glycoproteins by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and intact protein analysis. The individual glycan profiles followed protein-binding studies showed specific function of glycosylation in immune recognition.