FEMS Microbiology Letters 100 (1992) 483-488 © 1992 Federation of European Microbiological Societies 0378-1097/92/$05.00 Published by Elsevier 483 FEMSLE 80012 The conformational specificity of viral epitopes Marc H.V. Van Regenmortel Institut de Biologic Mol~culaire et Cellulaire, CNRS, Strasbourg, France Received 12 June 1992 Accepted 29 June 1992 Key words: Virus; Virus antigenicity; Epitope; Tobacco mosaic virus; Influenza virus; Antigen conformation 1. SUMMARY Four types of antigenic sites found in viruses are discussed: cryptotopes, neotopes, metatopes and neutralization epitopes. The role played by conformation on the specificity of viral epitopes is illustrated in the case of tobacco mosaic virus and influenza virus. It appears that mechanisms remi- niscent of induced fit contribute to the recogni- tion of viral epitopes by antibodies. 2. INTRODUCTION The antigenic sites or epitopes of a virus parti- cle correspond to those parts of the capsid or envelope proteins that are recognized by the combining sites or paratopes of antibody molecules. In the absence of further qualification, the term epitope refers to a B cell epitope, i.e. recognized by a B cell receptor and by an anti- body. In the present review, only B cell epitopes Correspondence to: M.H.V. Van Regenmortel, Institut de Biologic Mol6culaire et Cellulaire, CNRS, 15 rue Ren6 Descartes, 67084 Strasbourg Cedex, France. will be considered. A second type of epitope known as T cell epitope corresponds to peptide fragments of viral proteins that have undergone processing within an antigen-presenting cell. These T cell epitopes are recognized by T cell receptors in association with proteins of the major histocompatibility complex [1]. During the development of an immune re- sponse to a virus, B cell receptors recognize the intact tertiary and quaternary structures of the capsid and envelope proteins of the virus. Like- wise the antibody molecules that are subse- quently produced by plasmocytes are also specific for the intact three-dimensional structure of virus particles. In addition, however, antibodies may also be produced against the dissociated or dena- tured viral subunits (the so-called soluble anti- gens) that often accompany the intact virions used for immunization. Furthermore, some viruses such as enteroviruses may have their cap- sid proteins selectively cleaved by proteases dur- ing replication in the gut and this may lead to an alteration of the viral epitopes [2]. This is proba- bly the reason why the distribution of epitopes recognized by neutralizing type 3 poliovirus anti- bodies in children immunized with chemically inactivated poliovirus vaccine (containing un- Downloaded from https://academic.oup.com/femsle/article-abstract/100/1-3/483/569197 by guest on 17 June 2020