title: Characterization and specificity of the linear epitope of the enterovirus 71 VP2 protein.
abstract: BACKGROUND
  Enterovirus 71 (EV71) has emerged as a major causative agent of hand, foot and mouth disease in the Asia-Pacific region over the last decade. Hand, foot and mouth disease can be caused by different etiological agents from the enterovirus family, mainly EV71 and coxsackieviruses, which are genetically closely related. Nevertheless, infection with EV71 may occasionally lead to high fever, neurologic complications and the emergence of a rapidly fatal syndrome of pulmonary edema associated with brainstem encephalitis. The rapid progression and high mortality of severe EV71 infection has highlighted the need for EV71-specific diagnostic and therapeutic tools. Monoclonal antibodies are urgently needed to specifically detect EV71 antigens from patient specimens early in the infection process. Furthermore, the elucidation of viral epitopes will contribute to the development of targeted therapeutics and vaccines.
  
  
  RESULTS
  We have identified the monoclonal antibody 7C7 from a screen of hybridoma cells derived from mice immunized with the EV71-B5 strain. The linear epitope of 7C7 was mapped to amino acids 142-146 (EDSHP) of the VP2 capsid protein and was characterized in detail. Mutational analysis of the epitope showed that the aspartic acid to asparagine mutation of the EV71 subgenogroup A (BrCr strain) did not interfere with antibody recognition. In contrast, the serine to threonine mutation at position 144 of VP2, present in recently emerged EV71-C4 China strains, abolished antigenicity. Mice injected with this virus strain did not produce any antibodies against the VP2 protein. Immunofluorescence and Western blotting confirmed that 7C7 specifically recognized EV71 subgenogroups and did not cross-react to Coxsackieviruses 4, 6, 10, and 16. 7C7 was successfully used as a detection antibody in an antigen-capture ELISA assay.
  
  
  CONCLUSIONS
  Detailed mapping showed that the VP2 protein of Enterovirus 71 contains a single, linear, non-neutralizing epitope, spanning amino acids 142-146 which are located in the VP2 protein's E-F loop. The S/T(144) mutation in this epitope confers a loss of VP2 antigenicity to some newly emerged EV71-C4 strains from China. The corresponding monoclonal antibody 7C7 was used successfully in an AC-ELISA and did not cross-react to coxsackieviruses 4, 6, 10, and 16 in immunofluorescence assay and Western blots. 7C7 is the first monoclonal antibody described, that can differentiate Coxsackievirus 16 from Enterovirus 71.
authors.affiliation: Animal Health Biotechnology, Temasek Life Sciences Laboratory, National University of Singapore, 117604 Singapore, Singapore.
authors.forename: Tanja K
authors.initials: TK
authors.lastname: Kiener
authors.forename: Qiang
authors.initials: Q
authors.lastname: Jia
authors.forename: Xiao Fang
authors.initials: XF
authors.lastname: Lim
authors.forename: Fang
authors.initials: F
authors.lastname: He
authors.forename: Tao
authors.initials: T
authors.lastname: Meng
authors.forename: Vincent Tak Kwong
authors.initials: VT
authors.lastname: Chow
authors.forename: Jimmy
authors.initials: J
authors.lastname: Kwang
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000276:immunology; D000914:Antibodies, Viral / Q000096:biosynthesis / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology*; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D003429:Cross Reactions / Q000276:immunology; D029821:Enterovirus A, Human / Q000737:chemistry* / Q000276:immunology*; D004769:Enterovirus Infections / Q000175:diagnosis; D018604:Epitope Mapping; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D006801:Humans; D051379:Mice; D009154:Mutation
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D036022:Capsid Proteins; D000939:Epitopes