A Sialic Acid Binding Site in a Human Picornavirus

Abstract

The picornaviruses coxsackievirus A24 variant (CVA24v) and enterovirus 70 (EV70) cause continued outbreaks and pandemics of acute hemorrhagic conjunctivitis (AHC), a highly contagious eye disease against which neither vaccines nor antiviral drugs are currently available. Moreover, these viruses can cause symptoms in the cornea, upper respiratory tract, and neurological impairments such as acute flaccid paralysis. EV70 and CVA24v are both known to use 5-N-acetylneuraminic acid (Neu5Ac) for cell attachment, thus providing a putative link between the glycan receptor specificity and cell tropism and disease. We report the structures of an intact human picornavirus in complex with a range of glycans terminating in Neu5Ac. We determined the structure of the CVA24v to 1.40 Å resolution, screened different glycans bearing Neu5Ac for CVA24v binding, and structurally characterized interactions with candidate glycan receptors. Biochemical studies verified the relevance of the binding site and demonstrated a preference of CVA24v for α2,6-linked glycans. This preference can be rationalized by molecular dynamics simulations that show that α2,6-linked glycans can establish more contacts with the viral capsid. Our results form an excellent platform for the design of antiviral compounds to prevent AHC.

High-speed fixed-target serial virus crystallography

“…For non-enveloped viruses, numerous X-ray crystallographic structures have been solved, at resolutions of up to 1.4 Å 1 . Due to the large unit cell dimensions and limited size of the crystals, Bragg reflections from virus crystals are typically weak 2,3 .…”

Structural features of glycan recognition among viral pathogens

“…In most EV structures, a hydrophobic pocket in VP1 is located underneath the canyon which holds a branched elongated fatty acid-like ‘pocket factor’ that stabilizes the virion. Recent structural studies on EV members including EV-D68 that causes childhood respiratory diseases [6] and coxsackievirus A24 variant (CVA24v) that causes acute hemorrhagic conjunctivitis (AHC) [7] show that they utilize SA receptors with a preference for α 2, 6-linked Neu5Ac glycans. Interestingly, the SA-binding sites in EV-D68 and CVA24v capsid structures are distinct and lie 40 Å apart with respect to each other.…”

“…These conformational changes disrupt the hydrophobic pocket resulting in the release of the ‘pocket factor’ to potentially facilitate destabilization and uncoating of the virion. In contrast to EV-D68, the SA binding site in CVA24v lies at a solvent-exposed protruding region on VP1 close to the fivefold axis [7] (Figure 3d). The residues binding the Neu5Ac of the sialoglycan are contributed by loop regions from a VPI monomer and a clockwise (cw) rotated VP1 protomer (Figure 3f).…”

“…Glycan-binding can dictate virus–host specificity, tissue tropism, pathogenesis and interspecies transmission. Viruses predominantly recognize three distinct families of host glycans including: histo-blood group antigens (HBGAs) recognized by noroviruses (NoVs) [2] and human rotaviruses (HRVs) [3]; sialoglycans recognized by influenza viruses [4], orthoreoviruses [5] and specific picornaviruses [6,7]; and glycosaminoglycans (GAGs) recognized by papillomaviruses [8] and parvoviruses [9] among others. Understanding virus–glycan interactions is critical, as blocking this interaction using glycomimetics or antibodies can lead to reduced virus infectivity and targeting these interactions can lead to the development of antivirals and vaccines.…”

Inhibition of Coxsackievirus A24 in permissive Hep2 cells by small interfering RNA (siRNA)

“…Therefore, nucleic acid based therapeutics may be very useful to destroy transcription and translation of CA24 i.e., complete destruction of virus [13,14].Successful inhibition of CA24 by siRNA was done earlier targeting 3D and Cre regions [15,16]. In this study, instead of these regions, both of the untranslated regions (5'UTR and 3' UTR) of CA24 was also targeted.…”