Glycoprotein H and α4β1 Integrins Determine the Entry Pathway of Alphaherpesviruses

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Here, we report that cell surface MHC-I in EHV-1-infected cells is internalized and degraded in the lysosomal compartment in a pUL56-dependent fashion. pUL56-induced MHC-I endocytosis required dynamin and tyrosine kinase but was independent of clathrin and caveolin-1, the main constituents of the clathrin-and raft/caveola-mediated endocytosis pathways, respectively. Downregulation of cell surface MHC-I was significantly inhibited by the ubiquitin-activating enzyme E1 inhibitor PYR41, indicating that ubiquitination is essential for the process. Finally, we show that downregulation is not specific for MHC-I and that other molecules, including CD46 and CD63, are also removed from the cell surface in a pUL56-dependent fashion. IMPORTANCEWe show that alphaherpesvirus induces MHC-I downregulation through endocytosis, which is mediated by pUL56. The dynamin-dependent endocytic pathway is responsible for MHC-I internalization in infected cells. Furthermore, we discovered that this endocytic process can be disrupted by the inhibiting ubiquitin-activating E1 enzyme, which is indispensable for ubiquitination. Finally, pUL56 action extends to a number of cell surface molecules that are significant for host immunity. Therefore, the protein may exert a more general immunomodulatory effect.

Section: Discussionmentioning

confidence: 99%

Major Histocompatibility Complex Class I Downregulation Induced by Equine Herpesvirus Type 1 pUL56 Is through Dynamin-Dependent Endocytosis

Huang

Lehmann

Said

et al. 2014

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“…Those were BACs of EHV-1 strain Ab4 (33) and EHV-4 strain TH20p (34), as well as modified BACs EHV-1_gB4, EHV-4_gB1, revertant EHV-1_gB1r (20), EHV1_gD4, EHV-4_gD1 (35), EHV-1⌬US3, and EHV-1 that contained US3 of EHV-4 (EHV-1_US3_4) in lieu of authentic US3, fully rescuing the parental EHV-1 phenotype and functioning as revertant for this study (A. Proft and W. Azab, unpublished data). monomeric red fluorescent protein (mRFP1)-labeled EHV-1 was previously constructed by inserting mRFP1 into VP26 of EHV-1 strain RacL11 (36). Viruses were grown on equine dermal (ED) cells.…”

Section: Methodsmentioning

confidence: 99%

Role of gB and pUS3 in Equine Herpesvirus 1 Transfer between Peripheral Blood Mononuclear Cells and Endothelial Cells: a DynamicIn VitroModel

Spiesschaert

Goldenbogen

Taferner

et al. 2015

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Infected peripheral blood mononuclear cells (PBMC) effectively transport equine herpesvirus type 1 (EHV-1), but not EHV-4, to endothelial cells (EC) lining the blood vessels of the pregnant uterus or central nervous system, a process that can result in abortion or myeloencephalopathy. We examined, using a dynamic in vitro model, the differences between EHV-1 and EHV-4 infection of PBMC and PBMC-EC interactions. In order to evaluate viral transfer between infected PBMC and EC, cocultivation assays were performed. Only EHV-1 was transferred from PBMC to EC, and viral glycoprotein B (gB) was shown to be mainly responsible for this form of cell-to-cell transfer. For addressing the more dynamic aspects of PBMC-EC interaction, infected PBMC were perfused through a flow channel containing EC in the presence of neutralizing antibodies. By simulating capillary blood flow and analyzing the behavior of infected PBMC through live fluorescence imaging and automated cell tracking, we observed that EHV-1 was able to maintain tethering and rolling of infected PBMC on EC more effectively than EHV-4. Deletion of US3 reduced the ability of infected PBMC to tether and roll compared to that of cells infected with parental virus, which resulted in a significant reduction in virus transfer from PBMC to EC. Taking the results together, we conclude that systemic spread and EC infection by EHV-1, but not EHV-4, is caused by its ability to infect and/or reprogram mononuclear cells with respect to their tethering and rolling behavior on EC and consequent virus transfer. IMPORTANCEEHV-1 is widespread throughout the world and causes substantial economic losses through outbreaks of respiratory disease, abortion, and myeloencephalopathy. Despite many years of research, no fully protective vaccines have been developed, and several aspects of viral pathogenesis still need to be uncovered. In the current study, we investigated the molecular mechanisms that facilitate the cell-associated viremia, which is arguably the most important aspect of EHV-1 pathogenesis. The newly discovered functions of gB and pUS3 add new facets to their previously reported roles. Due to the conserved nature of cell-associated viremia among numerous herpesviruses, these results are also very relevant for viruses such as varicella-zoster virus, pseudorabies virus, human cytomegalovirus, and others. In addition, the constructed mutant and recombinant viruses exhibit potent in vitro replication but have significant defects in certain stages of the disease course. These viruses therefore show much promise as candidates for future live vaccines. E quine herpesvirus type 1 (EHV-1) and EHV-4 are members of the Herpesviridae family and Alphaherpesvirinae subfamily (1, 2). After initial replication in the upper respiratory tract, EHV-1 infects immune cells and migrates past the epithelial basement membrane to the lymph nodes and bloodstream (1-4). As a result, EHV-1 is able to spread throughout the body, where it infects endothelial cells (EC), causing vascular lesions an...

“…While the specific role of lipid rafts in alphaherpesvirus entry is not known, pseudorabies virus (PRV) localizes in juxtaposition with GM1, a lipid raft marker (49), and herpes simplex virus 1 (HSV-1) gB associates with lipid rafts during virus entry (50). Additionally, cholesterol is important for entry of alphaherpesviruses (49)(50)(51)(52)(53). BoHV-1 requires cell membrane cholesterol for entry into Madin-Darby bovine kidney (MDBK) cells and viral envelope cholesterol for infectivity (54).…”

mentioning

confidence: 99%

Role of Sphingomyelin in Alphaherpesvirus Entry

Pastenkos

Miller

Pritchard

et al. 2019

Bovine herpesvirus 1 (BoHV-1) is an alphaherpesvirus that causes disease in cattle populations worldwide. Sphingomyelin (SM) is the most abundant sphingolipid in the mammalian cell membrane, where it preferentially associates with cholesterol to form lipid raft domains. SM is a substrate for the lysosome-resident enzyme acid sphingomyelinase, which plays a role in cell membrane repair following injury. Treatment of cells with noncytotoxic concentrations of Staphylococcus aureus-derived sphingomyelinase successfully reduced cell surface-exposed sphingomyelin but did not significantly inhibit BoHV-1 entry and infection, as measured by the beta-galactosidase reporter assay. Interestingly, entry of the porcine alphaherpesvirus pseudorabies virus (PRV) was inhibited by sphingomyelin-depletion of cells. Treatment of BoHV-1 particles with sphingomyelinase inhibited viral entry activity, suggesting that viral SM plays a role in BoHV-1 entry, while cellular SM does not. Treatment of cells with noncytotoxic concentrations of the functional inhibitors of host acid sphingomyelinase, imipramine and amitriptyline, which induce degradation of the cellular enzyme, did not significantly inhibit BoHV-1 entry. In contrast, inhibition of cellular acid sphingomyelinase inhibited PRV entry. Entry of the human alphaherpesvirus herpes simplex virus 1 (HSV-1) was independent of both host SM and acid sphingomyelinase, in a manner similar to BoHV-1. Together, the results suggest that among the alphaherpesviruses, there is variability in entry requirements for cellular sphingomyelin and acid sphingomyelinase activity. IMPORTANCE Bovine herpesvirus 1 (BoHV-1) is an ubiquitous pathogen affecting cattle populations worldwide. Infection can result in complicated, polymicrobial infections due to the immunosuppressive properties of the virus. Available vaccines limit disease severity and spread but do not prevent infection. The financial and animal welfare ramifications of BoHV-1 are significant. In order to develop more effective prevention and treatment regimens, a more complete understanding of the initial steps in viral infection is necessary. We recently identified a low pH endocytosis pathway for BoHV-1. Here, we examine the role of cellular factors responsible for membrane integrity and repair in alphaherpesviral entry. This study allows comparisons of the BoHV-1 entry pathway with those of other alphaherpesviruses (pseudorabies virus [PRV] and herpes simplex virus 1 [HSV-1]). Lastly, this is the first report of sphingomyelin and lysosomal sphingomyelinase playing a role in the entry of a herpesvirus. The results may lead to the development of more effective prevention and treatment regimens.