Molecular mechanism of antibody neutralization of coxsackievirus A16

Completely conserved VP2 residue K140 of KREMEN1-dependent enteroviruses is critical for virus-receptor interactions and viral infection

The KREMEN1 (KRM1) protein is a cellular receptor for multiple enteroviruses that cause hand, foot, and mouth disease (HFMD), including coxsackievirus CVA2, CVA3, CVA4, CVA5, CVA6, CVA10, and CVA12. The molecular basis for the broad recognition of these viruses by the KRM1 receptor remains unclear. Here, we report the indispensable role of the completely conserved VP2 capsid protein residue K140 (designated K2140) in mediating receptor recognition and infection by CVA10 and other KRM1-dependent enteroviruses. Residue K2140 not only facilitates receptor recognition, cell attachment, and infection of CVA10 but also contributes to CVA10 pathogenicity in vivo. Notably, residue K2140 is completely conserved in all strains of the KRM1-dependent enteroviruses. Mutational analysis confirms the importance of K2140 for infection by CVA2-CVA6, and CVA12. Moreover, CVA8, an enterovirus for which the cellular receptor has not yet been identified, also possesses the conserved K2140 residue. We experimentally demonstrate that CVA8 utilizes KRM1 as its receptor, with K2140 being essential for viral infection. Additionally, residue D90 of KRM1 engages with residue K2140 and plays a crucial role in KRM1-mediated enterovirus infections. Collectively, our findings underscore the significance of the absolutely conserved K2140 residue in receptor interactions and infection of all KRM1-binding enteroviruses, providing novel insights into the molecular basis of enterovirus infection and informing the development of broad-spectrum therapies against HFMD.

IMPORTANCE

Hand, foot, and mouth disease (HFMD) annually affects millions of children worldwide. HFMD is caused by various enteroviruses, such as coxsackieviruses CVA6, CVA16, CVA10, and enterovirus 71 (EV-A71). Licensed inactivated EV-A71 vaccines do not provide cross-protection against other enteroviruses. There are no drugs specifically for HFMD. KREMEN1 (KRM1) serves as the cellular receptor for many HFMD-related enteroviruses, including CVA2-CVA6, CVA10, and CVA12. However, the molecular basis for broad recognition of these enteroviruses by the KRM1 receptor remains elusive. Here, we report that VP2 residue K140 (K2140) is completely conserved among all KRM1-dependent enteroviruses and is essential for virus-receptor binding and viral infection by interacting with residue D90 of KRM1. Overall, our findings provide a deeper understanding of the molecular basis of KRM1-dependent enterovirus infection in vitro and in vivo and may contribute to the development of broad-spectrum anti-enterovirus vaccines and treatments.

Broadly therapeutic antibody provides cross-serotype protection against enteroviruses via Fc effector functions and by mimicking SCARB2

Enteroviruses contain multiple serotypes and can cause severe neurological complications. The intricate life cycle of enteroviruses involving dynamic virus-receptor interaction hampers the development of broad therapeutics and vaccines. Here, using function-based screening, we identify a broadly therapeutic antibody h1A6.2 that potently protects mice in lethal models of infection with both enterovirus A71 and coxsackievirus A16 through multiple mechanisms, including inhibition of the virion-SCARB2 interactions and monocyte/macrophage-dependent Fc effector functions. h1A6.2 mitigates inflammation and improves intramuscular mechanics, which are associated with diminished innate immune signalling and preserved tissue repair. Moreover, cryogenic electron microscopy structures delineate an adaptive binding of h1A6.2 to the flexible and dynamic nature of the VP2 EF loop with a binding angle mimicking the SCARB2 receptor. The coordinated binding mode results in efficient binding of h1A6.2 to all viral particle types and facilitates broad neutralization of enterovirus, therefore informing a promising target for the structure-guided design of pan-enterovirus vaccine.

Identification of four neutralizing antigenic sites on the enterovirus D68 capsid

IMPORTANCE

Enterovirus D68 (EV-D68) is an emerging respiratory pathogen associated with acute flaccid myelitis. Currently, no approved vaccines or antiviral drugs are available. Here, we report four functionally independent neutralizing antigenic sites (I to IV) by analyses of neutralizing monoclonal antibody (MAb)-resistant mutants. Site I is located in the VP1 BC loop near the fivefold axis. Site II resides in the VP2 EF loop, and site III is situated in VP1 C-terminus; both sites are located at the south rim of the canyon. Site IV is composed of residue in VP2 βB strand and residues in the VP3 BC loop and resides around the threefold axis. The developed MAbs targeting the antigenic sites can inhibit viral binding to cells. These findings advance the understanding of the recognition of EV-D68 by neutralizing antibodies and viral evolution and immune escape and also have important implications for the development of novel EV-D68 vaccines.

VP2 residue N142 of coxsackievirus A10 is critical for the interaction with KREMEN1 receptor and neutralizing antibodies and the pathogenicity in mice

Coxsackievirus A10 (CVA10) has recently emerged as one of the major causative agents of hand, foot, and mouth disease. CVA10 may also cause a variety of complications. No approved vaccine or drug is currently available for CVA10. The residues of CVA10 critical for viral attachment, infectivity and in vivo pathogenicity have not been identified by experiment. Here, we report the identification of CVA10 residues important for binding to cellular receptor KREMEN1. We identified VP2 N142 as a key receptor-binding residue by screening of CVA10 mutants resistant to neutralization by soluble KREMEN1 protein. The receptor-binding residue N142 is exposed on the canyon rim but highly conserved in all naturally occurring CVA10 strains, which provides a counterexample to the canyon hypothesis. Residue N142 when mutated drastically reduced receptor-binding activity, resulting in decreased viral attachment and infection in cell culture. More importantly, residue N142 when mutated reduced viral replication in limb muscle and spinal cord of infected mice, leading to lower mortality and less severe clinical symptoms. Additionally, residue N142 when mutated could decrease viral binding affinity to anti-CVA10 polyclonal antibodies and a neutralizing monoclonal antibody and render CVA10 resistant to neutralization by the anti-CVA10 antibodies. Overall, our study highlights the essential role of VP2 residue N142 of CVA10 in the interactions with KREMEN1 receptor and neutralizing antibodies and viral virulence in mice, facilitating the understanding of the molecular mechanisms of CVA10 infection and immunity. Our study also provides important information for rational development of antibody-based treatment and vaccines against CVA10 infection.