Infectious entry of equine herpesvirus-1 into host cells through different endocytic pathways

Abstract

We investigated the mechanism by which equine herpesvirus-1 (EHV-1) enters primary cultured equine brain microvascular endothelial cells (EBMECs) and equine dermis (E. Derm) cells. EHV-1 colocalized with caveolin in EBMECs and the infection was greatly reduced by the expression of a dominant negative form of equine caveolin-1 (ecavY14F), suggesting that EHV-1 enters EBMECs via caveolar endocytosis. EHV-1 entry into E. Derm cells was significantly reduced by ATP depletion and treatments with lysosomotropic agents. Enveloped virions were detected from E. Derm cells by infectious virus recovery assay after viral internalization, suggesting that EHV-1 enters E. Derm cells via energy- and pH-dependent endocytosis. These results suggest that EHV-1 utilizes multiple endocytic pathways in different cell types to establish productive infection.

Glycoprotein H and α4β1 Integrins Determine the Entry Pathway of Alphaherpesviruses

“…Our results are consistent with data of Frampton and coworkers, who showed that EHV-1 enters ED cells through direct fusion at the plasma membrane, and also with earlier results showing that EHV-1 can enter RK-13 cells through direct fusion at the plasma membrane and through low-pH-dependent endocytosis in CHO-K1 cells (26). However, our data contradict results claiming that yet another EHV-1 strain, Ab4p, can enter ED cells via energy-and pH-dependent endocytosis (27). It is important to note that the authors failed to find any colocalization of the virus with either caveolin or clathrin.…”

“…Previous reports have suggested that cellular tyrosine kinases play a role in alphaherpesvirus infection (10,26,27). Here, we tested the effect of a tyrosine kinase inhibitor, genistein, on virus infection.…”

“…Previous reports had suggested that EHV-1 entry into CHO-K1 cells requires acidic pH, whereas low-pH requirements for EHV-1 infection of ED cells are discussed controversially (26,27). To further elucidate equine herpesvirus entry, cells were incubated with BFLA, an inhibitor of vacuolar ATPase, for 1 h before infection.…”

“…The decision of which of the two pathways will be taken is dependent mainly on viral gH and its ability to interact with ␣4␤1 integrins expressed on the surface of target cells (Table 2). EHV-1 entry into different cells has been studied previously (26)(27)(28). However, no data are available on the details of EHV-4 entry.…”

“…As is the case with HSV-1, EHV-1 can enter some cells, such as rabbit kidney (RK13) and equine dermal (ED) cells, through direct fusion with the plasma membrane at neutral pH, a process that is mediated by gC, gD, gB, and the gH/gL complex (23)(24)(25). In addition, EHV-1 can enter CHO-K1 cells, peripheral blood mononuclear cells, and equine brain microvascular endothelial cells through pH-dependent or -independent endocytic pathways (26)(27)(28). However, the viral and cellular factors that govern the entry process and route viruses to various compartments are still unknown.…”