Repetitive versus monomeric antigen presentation: direct visualization of antibody affinity and specificity.
The concept of presenting antigens in a repetitive array to obtain high titers of specific antibodies is increasingly applied by using surface-engineered viruses or bacterial envelopes as novel vaccines. A case for this concept was made 25 years ago, when producing high-titer antisera against ordered arrays of gp23, the major capsid protein of bacteriophage T4 (Aebi et al., Proc. Natl. Acad. Sci. USA, 74 (1977) 5514-5518). In view of the current interest in this concept we thought it useful to employ this system to directly visualize the dependence of antibody affinity and specificity on antigen presentation. We compared antibodies raised against T4 polyheads, a tubular variant of the bacteriophage T4 capsid, which have gp23 hexamers arranged in a crystalline lattice (gp23(repetitive)), with those raised against the hexameric gp23 subunits (gp23(monomeric)). The labeling patterns of Fab-fragments prepared from these antibodies when bound to polyheads were determined by electron microscopy and image enhancement. Anti-gp23(repetitive) bound in a monospecific, stoichiometric fashion to the gp23 units constituting the polyhead surface. In contrast, anti-gp23(monomeric) decorated the polyhead surface randomly and with a 40-fold lower occupancy. These results concur with the difference in titers established by ELISA for the antisera against the repetitively displayed form of antigen (anti-gp23(repetitive)) and the randomly presented antigen (gp23(monomeric)), and they constitute a compelling visual documentation of the concept of repetitive antigen presentation to elicite a serotype-like immune response.
Baschong
Werner
W
Biozentrum, M. E. Mueller Institute for Structural Biology, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
Hasler
Lorenz
L
Häner
Markus
M
Kistler
Joerg
J
Aebi
Ueli
U
D000818:Animals; D000914:Antibodies, Viral / Q000378:metabolism / Q000648:ultrastructure; D000915:Antibody Affinity; D000918:Antibody Specificity; D017951:Antigen Presentation; D000956:Antigens, Viral / Q000737:chemistry / Q000648:ultrastructure; D017122:Bacteriophage T4 / Q000737:chemistry / Q000276:immunology; D036022:Capsid Proteins / Q000737:chemistry / Q000276:immunology / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D015202:Protein Engineering; D011817:Rabbits
D000914:Antibodies, Viral; D000956:Antigens, Viral; D036022:Capsid Proteins; D007140:Immunoglobulin Fab Fragments; C064517:gp23 protein, Bacteriophage T4