Internal images: human anti-idiotypic Fab antibodies mimic the IgE epitopes of grass pollen allergen Phl p 5a.
BACKGROUND
The role of anti-idiotypic antibodies in allergic disease is still poorly understood. According to Jerne, anti-idiotypic antibodies to IgE should represent internal images of an allergen. Our aim was to ultimately prove whether this hypothesis holds true in allergy. Here, we describe the selection of anti-idiotypic antibodies against Phl p 5a-specific IgE directly from the B-cell repertoire of a grass pollen allergic individual.


METHODS
Taking Phleum pratense grass pollen allergen Phl p 5 as a model, we selected anti-idiotypic antibodies against allergen-specific IgE directly from the B-cell repertoire of an allergic individual. We screened a combinatorial phage display library of human monovalent antibody heavy and light chain fragments (Fabs) with anti-Phl p 5a-IgE to identify and characterize Fabs with anti-idiotypic specificity.


RESULTS
Five different Fab clones with anti-idiotypic specificity for anti-Phl p 5a-IgE were identified. Their hypervariable regions revealed partial sequence homology with solvent accessible antigenic sites of Phl p 5a, which have been identified by our previous mimotope approach. Phagemid DNA derived from the phage clones was used to produce two soluble recombinant anti-idiotypic Fab clones in E. coli. As a proof of molecular mimicry, both Fabs induced anti-Phl p 5a-specific antibodies in immunized BALB/c mice. Molecular modeling of the heavy and light chain hypervariable loops of the anti-idiotypic Fabs illustrated structural similarity with dominant IgE epitopes of Phl p 5a.


CONCLUSIONS
In this straightforward phage technology approach, antibodies with anti-idiotypic specificities could be isolated from a human allergic's repertoire. As predicted by the immune network hypothesis, their hypervariable domains mimic IgE epitopes like internal images and, more importantly, induce allergen-specific immune responses in the absence of the allergen.
Hantusch
Brigitte
B
Center of Physiology and Pathophysiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
Knittelfelder
Regina
R
Wallmann
Julia
J
Krieger
Sigurd
S
Szalai
Krisztina
K
Untersmayr
Eva
E
Vogel
Monique
M
Stadler
Beda M
BM
Scheiner
Otto
O
Boltz-Nitulescu
George
G
Jensen-Jarolim
Erika
E
D000595:Amino Acid Sequence; D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000737:chemistry / Q000276:immunology*; D052179:Antigens, Plant / Q000276:immunology; D022801:Complementarity Determining Regions / Q000737:chemistry / Q000276:immunology; D000939:Epitopes / Q000276:immunology*; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology*; D007073:Immunoglobulin E / Q000276:immunology; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D018716:Molecular Mimicry / Q000276:immunology*; D008969:Molecular Sequence Data; D019151:Peptide Library; D010940:Plant Proteins / Q000276:immunology*; D011994:Recombinant Proteins; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
D000888:Antibodies, Anti-Idiotypic; D052179:Antigens, Plant; D022801:Complementarity Determining Regions; D000939:Epitopes; D007140:Immunoglobulin Fab Fragments; D019151:Peptide Library; C076049:Phl p V protein, Phleum pratense; D010940:Plant Proteins; D011994:Recombinant Proteins; D007073:Immunoglobulin E