TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: POI is an enzyme, in particular a protease. The transgenic animals are Human Leukocyte Antigen (HLA) DR3/DQ2 and have been backcrossed with mice lacking the expression of endogenous I-A class II molecules. The T-cell epitope is altered with amino acid substitutions by having a terminal portion of the POI which includes the T-cell epitope replaced with a corresponding terminal portion of a homolog of the POI, where the homolog does not comprise a T-cell epitope identical to the replaced T-cell epitope. The antigen specific immunoglobulin is IgG. The immunogenic response produced by the variant is less or more than the immunogenic response produced by POI. (III) further comprises comparing the proliferation of the T-cells to the proliferation of a second protein. POI and the second protein are protease and are homologs of one another, or are each different peptides of the same protein. WIDER DISCLOSURE - Disclosed are nucleic acids encoding polypeptides producing the desired immunogenic response and expression vectors and host cells comprising the nucleic acids.    ACTIVITY - Antiallergic.    MECHANISM OF ACTION - Reduces allergenicity.    Substitutions in the amino acid sequence of FNA (B.amyloliquefaciens protease) led to reduced T cell proliferation. To demonstrate this effect, both FNA and the FNA variant (with Y217L substitution) containing amino acid changes in the epitopes 70-84 and 109-123 were used to immunize HLA DR3/DQ2 transgenic mice that had been backcrossed onto I-Ab knockout mice (lacking the expression of endogenous I-A class II molecules, referred to as C2D). Adult male HLA-DR3/DQ2/C2D mice were immunized with 50mug of FNA or FNA variant emulsified in Complete Freund's Adjuvant. The immunization was administered intraperitoneally. Two weeks later, the mice received another intraperitoneal immunization of 50 mug of FNA or FNA variant emulsified in Incomplete Freund's Adjuvant. One week later, the mice were bled by retro-orbital route, and the serum collected. Serum was assessed for antigen-specific IgG antibodies in a direct enzyme linked immunosorbent assay (ELISA) protocol. The results indicated that the changes introduced into regions 70-84 and 109-123 significantly reduced the ability of DQ2 transgenic mice to mount a humoral response to the variant.    EXAMPLE - T-cell epitopes were identified in protease from Bacillus lentus and human subtilisin. Peptides for use in the assay were prepared based on the B.lentus and human subtilisin amino acid sequences. From the full length amino acid sequence of either human subtilisin or B.lentus protease, 15 mers were synthetically prepared, each 15 mer overlapping with the previous and the subsequent 15 mer except for three residues. Individuals were sensitized with the peptide. T-cell proliferation was measured. The immunogenic response of the naive blood samples from unsensitized individuals showed a marked allergenic response at the peptide fragment from B.lentus corresponding to the residues 170-173 of B.amyloliquefaciens protease. The corresponding fragment in human subtilisin evoked merely baseline response. Peptide E05 represented the region corresponding to 170-173 in protease from B.amyloliquefaciens. The hypersensitive individual was highly responsive to the T-cell epitope represented by the peptide E05. This result confirmed that it was possible to predict the major epitopes identified by the T-cells of a hypersensitive individual. T-cells response to various substitutions in the E05 peptide derived from B.lentus protease in a sample taken from an individual known to be hypersensitive to B.lentus protease was evaluated. Alanine substitutions were used as substitutions for the purpose of determining the role of any specific residue within the epitope. Substitution of either of the residues of R170A, Y171A and/or N173A in protease from B.lentus resulted in dramatically reduced response in the hypersensitive individuals blood sample. From these results, it was apparent that the residues 170, 171 and 173 were largely responsible for the initiation of allergic reaction within the protease from B.lentus.