How well can a T-cell epitope replace its parent carrier protein? A dose-response study.
OBJECTIVE
This work examines the effectiveness of synthetic peptide immunogens derived from immunodominant T-cell epitopes as replacements for their intact parent protein in vaccines.


METHODS
Fluorescein was conjugated to hen egg lysozyme (FL-HEL, positive control) and three synthetic peptide immunogens: (a) murine B10.A (H-2a) immunodominant T-cell epitope of HEL [FL-(T-cell epitope)]; (b) multiple antigenic peptide (MAP) multimer of this epitope ([FL-(T epitope)]n-MAP, n = 2-4); and (c) negative control MAP with T-cell epitope residues replaced with glycine [(FL-Gly18)4-MAP]. The dose response of each immunogen was examined over a 300-fold range in B10.A mice. The immune response was monitored using antifluorescein ELISA assays.


RESULTS
FL-(T epitope)'s immune response correlated positively with dose, with maximum response comparable to that of [FL-(T epitope)]n-MAP, or FL-HEL. This trend was consistent across 1 degrees, 2 degrees, and 3 degrees responses, although interanimal variability was higher in the latter two because of an all-or-none response in mice immunized with this peptide. [FL-(T epitope)]n-MAP's immune response was consistently high and nearly dose independent, a trend observed across 1 degrees, 2 degrees, and 3 degrees responses. FL-HEL's immune response correlated negatively to dose in the 1 degrees response but was nearly dose independent in the 2 degrees and 3 degrees responses. The magnitude of these latter responses was comparable to that observed for [FL-(T epitope)]n-MAP. (FL-Gly18)4-MAP did not elicit an immune response except at the highest dose. This trend was consistent across 1 degrees, 2 degrees, and 3 degrees responses.


CONCLUSIONS
The monomeric epitope was 300-fold less potent than its parent carrier protein, but increasing immunogen valency using MAP technology compensated totally for reduced potency. (FL-Gly18)4-MAP's lack of response at all but the highest dose strongly suggests that a specific immunodominant T-cell epitope sequence for HEL is necessary for successful peptide mimicry of HEL. This work also demonstrates the importance of quality assessment of commercial MAP core resins.
Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah 84112, USA.
James S
JS
Cavenaugh
Hsu-Kun
HK
Wang
Cory
C
Hansen
Richard S
RS
Smith
James N
JN
Herron
D000818:Animals; D000941:Antigens / Q000008:administration & dosage / Q000276:immunology; D002352:Carrier Proteins / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D004797:Enzyme-Linked Immunosorbent Assay; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D019793:Fluorescein / Q000008:administration & dosage; D016056:Immunodominant Epitopes / Q000276:immunology*; D008297:Male; D051379:Mice; D009113:Muramidase / Q000008:administration & dosage; D010455:Peptides / Q000008:administration & dosage / Q000276:immunology
D000941:Antigens; D002352:Carrier Proteins; D018984:Epitopes, T-Lymphocyte; D016056:Immunodominant Epitopes; D010455:Peptides; C421864:hen egg lysozyme; D009113:Muramidase; D019793:Fluorescein