Structural basis for HCMV Pentamer receptor recognition and antibody neutralization

Abstract

Human cytomegalovirus (HCMV) represents the viral leading cause of congenital birth defects and uses the gH/gL/UL128-130-131A complex (Pentamer) to enter different cell types, including epithelial and endothelial cells. Upon infection, Pentamer elicits the most potent neutralizing response against HCMV, representing a key vaccine candidate. Despite its relevance, the structural basis for Pentamer receptor recognition and antibody neutralization is largely unknown. Here, we determine the structures of Pentamer bound to neuropilin 2 (NRP2) and a set of potent neutralizing antibodies against HCMV. Moreover, we identify thrombomodulin (THBD) as a functional HCMV receptor and determine the structures of the Pentamer-THBD complex. Unexpectedly, both NRP2 and THBD also promote dimerization of Pentamer. Our results provide a framework for understanding HCMV receptor engagement, cell entry, antibody neutralization, and outline strategies for antiviral therapies against HCMV.

Viral and Cellular Factors Contributing to the Hematogenous Dissemination of Human Cytomegalovirus via Polymorphonuclear Leukocytes

“…The trimer binds its cellular receptor PDGFRα on fibroblasts and also appears to be required for infection of other cell types [ 32 , 33 , 34 , 67 ]. Recently, Nrp2 was identified as a cellular receptor of the pentamer on endothelial and epithelial cells [ 29 , 31 ]. Although hematogenous spread is assumed to contribute markedly to the pathogenesis of HCMV, molecular mechanisms underlying this type of spread are not as well understood as for entry of cell-free virus.…”

“…While neuropilin-2 (Nrp2) has been identified as a cellular receptor of the pentameric complex on endothelial and epithelial cells [ 29 ], it is unclear whether it also contributes to pentamer-mediated uptake into leukocytes. The soluble decoy receptor Nrp2-Fc inhibits infection of endothelial and epithelial cells by binding to pUL128, pUL130, and pUL131A [ 29 , 30 , 31 ]. It is tempting to speculate whether this soluble receptor would also be effective during PMN-mediated transfer of HCMV to endothelial cells.…”

Overview of how HCMV manipulation of host cell intracellular trafficking networks can promote productive infection

“…Other HCMV-encoded proteins such as UL79 and UL84 contain a non-conventional NLS site (PY-NLS) that allow direct interaction with nuclear import machinery components such as Imp-b (100, 101). HCMV-encoded UL94 contains both a putative NLS an NES to manage efficient bidirectional nuclear import and export (100). HCMV proteins such as UL83 has been shown to interact directly with nuclear export machinery (such as Crm1) to manage its export from the nucleus (100,102).…”

“…HCMV-encoded UL94 contains both a putative NLS an NES to manage efficient bidirectional nuclear import and export (100). HCMV proteins such as UL83 has been shown to interact directly with nuclear export machinery (such as Crm1) to manage its export from the nucleus (100,102). HCMV IE and E gene expression has been shown to induce the formation of F-actin within the nucleus (103).…”

Intermittent bulk release of human cytomegalovirus

“…In general, the pentameric complex guides tropism for specific cell types such as endothelial, epithelial and myeloid cells [4][5][6][7][8]10]. It has been shown to interact with cellular receptors such as neuropilin 2 (NRP2), the olfactory receptor family member OR14l1 and thrombomodulin (THBD) [15][16][17]. Extended culturing on fibroblasts such as done for the strains AD169 and Towne leads to the selection of mutations in the UL/b' region, which also codes for the pentameric complex, resulting in the loss of tropism for specific cell types in comparison to clinical strains [18][19][20][21][22].…”