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STRUCTURAL BASIS OF HUMAN PARECHOVIRUS NEUTRALIZATION BY HUMAN MONOCLONAL ANTIBODIESSTRUCTURAL BASIS OF HUMAN PARECHOVIRUS NEUTRALIZATION BY HUMAN MONOCLONAL ANTIBODIES
Structural highlights
FunctionPOLG_HPE1H Capsid proteins VP0, VP2, VP3 form a closed capsid enclosing the viral positive strand RNA genome. Capsid proteins interact with host alpha-V/beta-3 integrin heterodimer to provide virion attachment target cell. This attachment induces virion internalization predominantly through clathrin-mediated endocytosis.[1] Protein 2A: Is not a protease. Protein 2B: Affects membrane integrity and cause an increase in membrane permeability. Protein 2C: Associates with and induces structural rearrangements of intracellular membranes. It displays RNA-binding, nucleotide binding and NTPase activities (By similarity). Protein 3A, via its hydrophobic domain, serves as membrane anchor. Protease 3C: cysteine protease that generates mature viral proteins from the precursor polyprotein. In addition to its proteolytic activity, it binds to viral RNA, and thus influences viral genome replication. RNA and substrate bind cooperatively to the protease (By similarity). RNA-directed RNA polymerase 3D-POL replicates genomic and antigenomic RNA by recognizing replications specific signals.[PROSITE-ProRule:PRU00539] Publication Abstract from PubMedSince it was first recognized in 2004 that human parechoviruses (HPeV) are a significant cause of central nervous system and neonatal sepsis, their clinical importance, primarily in children, has started to emerge. Intravenous immunoglobulin treatment is the only treatment available in such life-threatening cases and has given moderate success. Direct inhibition of parechovirus infection using monoclonal antibodies is a potential treatment. We have developed two neutralising monoclonal antibodies against HPeV1 and HPeV2, namely AM18 and AM28 that also cross-neutralise other viruses. Here we present the mapping of their epitopes using peptide scanning, surface plasmon resonance, fluorescence-based thermal shift assays, electron cryo-microscopy and image reconstruction. We determined by peptide scanning and surface plasmon resonance that AM18 recognizes a linear epitope motif including the 'arginine-glycine-aspartic acid' on the C-terminus of capsid protein VP1. This epitope is normally used by the virus to attach to host cell-surface integrins during entry and is found in 3 other viruses that AM18 neutralises. Therefore, AM18 is likely to cause virus neutralization by aggregation and by blocking integrin binding to the capsid. Further, we show by electron cryo-microscopy, three-dimensional reconstruction and pseudo-atomic model fitting that ordered RNA interacts with HPeV1 VP1 and VP3. AM28 recognizes quaternary epitopes on the capsid composed of VP0 and VP3 loops from neighbouring pentamers, thereby increasing the RNA accessibility temperature for the virus-AM28 complex compared to the virus alone. Thus, inhibition of RNA uncoating probably contributes to neutralisation by AM28. IMPORTANCE: Human parechoviruses can cause mild infections to severe diseases in young children such as neonatal sepsis, encephalitis and cardiomyopathy. Intravenous immunoglobulin treatment is the only treatment available in such life-threatening cases. In order to develop more targeted treatment we have searched for human monoclonal antibodies that would neutralize human parechovirus 1 and 2, associated with mild infections such as gastroenteritis and severe infections of the central nervous system and thus to allow safe treatment. In the current study we show how two such promising antibodies interact with the virus, modelling the atomic interactions between the virus and the antibody to propose how neutralization occurs. Both antibodies can cause aggregation, in addition, one antibody interferes with the virus recognising its target cell, the other, recognising only the whole virus, inhibits the genome uncoating and replicating in the cell. Structural Basis of Human Parechovirus Neutralization by Human Monoclonal Antibodies.,Shakeel S, Westerhuis BM, Ora A, Koen G, Bakker AQ, Claassen Y, Wagner K, Beaumont T, Wolthers KC, Butcher SJ J Virol. 2015 Jul 8. pii: JVI.01429-15. PMID:26157123[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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