The present invention provides compositions and methods of use of therapeutic and/or prophylactic treatment of pathogen infection and/or disease states. The compositions may comprise variable eptidope libraries (VELs), containing antigenic epitopes with one or more amino acid substitutions in the native epitope sequence. In preferred embodiments, the substituted amino acid may be replaced with each of the 19 other naturally occurring amino acids. In more preferred embodiments, multiple amino acid residues may be substituted. Such compositions and methods may be of use for production of vaccines against pathogens or diseases that show a high degree of genetic variability.
