Annexin II Binds to Capsid Protein VP1 of Enterovirus 71 and Enhances Viral Infectivity

Abstract

Enterovirus type 71 (EV71) causes hand, foot, and mouth disease (HFMD), which is mostly self-limited but may be complicated with a severe to fatal neurological syndrome in some children. Understanding the molecular basis of virus-host interactions might help clarify the largely unknown neuropathogenic mechanisms of EV71. In this study, we showed that human annexin II (Anx2) protein could bind to the EV71 virion via the capsid protein VP1. Either pretreatment of EV71 with soluble recombinant Anx2 or pretreatment of host cells with an anti-Anx2 antibody could result in reduced viral attachment to the cell surface and a reduction of the subsequent virus yield in vitro. HepG2 cells, which do not express Anx2, remained permissive to EV71 infection, though the virus yield was lower than that for a cognate lineage expressing Anx2. Stable transfection of plasmids expressing Anx2 protein into HepG2 cells (HepG2-Anx2 cells) could enhance EV71 infectivity, with an increased virus yield, especially at a low infective dose, and the enhanced infectivity could be reversed by pretreating HepG2-Anx2 cells with an anti-Anx2 antibody. The Anx2-interacting domain was mapped by yeast two-hybrid analysis to VP1 amino acids 40 to 100, a region different from the known receptor binding domain on the surface of the picornavirus virion. Our data suggest that binding of EV71 to Anx2 on the cell surface can enhance viral entry and infectivity, especially at a low infective dose.Enterovirus type 71 (EV71) is a member of the Enterovirus genus of the family Picornaviridae and is one of the causative viral agents of hand, foot, and mouth disease (HFMD) (6,7,14,16,41). HFMD is largely a common self-limited childhood illness but may have complications of severe to fatal neurological symptoms in some children (1,5,6,16,21). In the past decade, the frequency of EV71 outbreaks associated with severe neurological illness appeared to have increased in the Pacific region, most notably in China, where large outbreaks have been occurring annually since 2007 (24, 53). While the epidemiological or virological mechanism underlying this regional focus of severe EV71 infection remains largely unknown, the impact of EV71 infection is a global concern, as evidenced by the increase in virological surveillance and studies of EV71 infection in many regions of the world (29,46,53).EV71 is composed of a single-stranded, positive-polarity RNA molecule surrounded by a nonenveloped, pentameric icosahedral capsid (3, 35), which consists of 60 copies of the four structural proteins VP1 to VP4. While there is no animal model for EV71 infection in humans, intraperitoneal injection of EV71 is lethal to suckling mice. Suckling mice born to mothers previously immunized with VP1 subunit vaccines acquire resistance to lethal EV71 challenge (8, 50), and administration of a VP1-based antigen, either protein or DNA, to mice could elicit a neutralizing antibody against EV71 infection in vitro (8,42,44). The serum collected from EV71-infected individuals during the convalescent pha...

Cell Surface Nucleolin Facilitates Enterovirus 71 Binding and Infection

“…VP1, an outer surface capsid protein of EV71, is reportedly involved in virus infectivity (68) and immunogenicity (69,70). VP1 has been shown to interact with the cell surface receptors SCARB2 and PSGL-1 (71,72) and with the binding molecules lactoferrin and annexin IIA (10,73). Treatment with peptides derived from VP1 also inhibits the infection of host cells by EV71 (74).…”

“…In addition, PSGL-1 participates in EV71 virus binding but not virus entry and viral RNA release (16). Although EV71 uses multiple receptors (18), none of the antireceptor or antiattachment molecule antibodies can completely abolish the infection of host cells by EV71 (7)(8)(9)(10)(11)(12)18). Undiscovered receptors or cofactors that are involved in the binding and infection of EV71 urgently need to be identified.…”

“…Because virus receptors determine the host range, tissue tropism, and pathogenesis (4-6), the identification of factors that mediate the recognition and/or entry of EV71 to host cells is essential to decipher infection mechanisms. Several receptors or attachment molecules for EV71 have been identified, including scavenger receptor B2 (SCARB2), P-selectin glycoprotein ligand-1 (PSGL-1), sialylated glycoprotein, dendritic cell-specific ICAM 3-grabbing nonintegrin, annexin II, vimentin, and polysaccharide (heparin sulfate) (7)(8)(9)(10)(11)(12)(13). EV71 strains can be divided into different subgenotypes based on sequence homology (14).…”

Identification of Positively Charged Residues in Enterovirus 71 Capsid Protein VP1 Essential for Production of Infectious Particles

“…In the mature capsid, VP1 to -3 together form the icosahedral shell of the virion (pseudo-T ϭ 3), while VP4 is distributed on the inner surface of the particle (14,15). Upon binding to a cellular receptor(s), such as P-selectin glycoprotein ligand 1 (PSGL-1) (16), scavenger receptor B2 (SCARB2) (17), sialylated glycans (18,19), annexin II (20), heparin sulfate (21), or vimentin (22), the EV71 virions undergo an important conformational change to convert into an expanded, altered "A-particle." The A-particle lacks the internal capsid protein VP4 and exposes N-terminal amphipathic sequences of VP1, allowing for its direct interaction with a lipid bilayer.…”

Emerging functions as host cell factors – an encyclopedia of annexin-pathogen interactions

“…However, this was not confirmed in another study (Pietropaolo and Compton, 1999). AnxA2 on the host cell surface was also implicated in the entry of enterovirus type 71 (EV71), the causative agent of the hand, foot, and mouth disease, to the host cell surface, possibly by binding the viral capsid protein VP1 on the cell surface (Yang et al, 2011). Rabbit vesivirus (RaV) virions might also depend on interaction with AnxA2 for their attachment and internalization (González-Reyes et al, 2009).…”