Impact of quaternary organization on the antigenic structure of the tick-borne encephalitis virus envelope glycoprotein E.
The envelope protein E of flaviviruses mediates both receptor-binding and membrane fusion. At the virion surface, 180 copies of E are tightly packed and organized in a herringbone-like icosahedral structure, whereas in noninfectious subviral particles, 60 copies are arranged in a T=1 icosahedral symmetry. In both cases, the basic building block is an E dimer which exposes the binding sites for neutralizing antibodies at its surface. It was the objective of our study to assess the dependence of the antigenic structure of E on its quaternary arrangement, i.e., as part of virions, recombinant subviral particles, or soluble dimers. For this purpose, we used a panel of 11 E protein-specific neutralizing monoclonal antibodies, mapped to distinct epitopes in each of the three E protein domains, and studied their reactivity with the different soluble and particulate forms of tick-borne encephalitis virus E protein under nondenaturing immunoassay conditions. Significant differences in the reactivities with these forms were observed that could be related to (i) limited access of certain epitopes at the virion surface; (ii) limited occupancy of epitopes in virions due to steric hindrance between antibodies; (iii) differences in the avidity to soluble forms compared to the virion, presumably related to the flexibility of E at its domain junctions; and (iv) modulations of the external E protein surface through interactions with its stem-anchor structure. We have thus identified several important factors that influence the antigenicity of the flavivirus E protein and have an impact on the interaction with neutralizing antibodies.
Kiermayr
Stefan
S
Institute of Virology, Medical University of Vienna, Kinderspitalgasse 15, A-1095 Vienna, Austria.
Stiasny
Karin
K
Heinz
Franz X
FX
D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology; D000915:Antibody Affinity; D000956:Antigens, Viral / Q000737:chemistry* / Q000276:immunology*; D004669:Encephalitis Viruses, Tick-Borne / Q000737:chemistry* / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D008954:Models, Biological; D008958:Models, Molecular; D009500:Neutralization Tests / Q000379:methods; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D014759:Viral Envelope Proteins; C065696:glycoprotein E, Flavivirus