Heteroclitic CD33 Peptide With Enhanced Anti-Acute Myeloid Leukemic Immunogenicity

Abstract

The goal of these studies was to engineer a synthetic CD33 peptide with enhanced immunogenicity for the induction of acute myeloid leukemia (AML)-specific CTLs. Eight modified CD33 peptides YLISGDSPV, YIGSGDSPV, YII-IGDSPV, YIILGDSPV, YIISGISPV, YIISGDLPV, YIIS-GDSWV and YIISGDSPL were designed for increased HLA-A2.1 or T cell receptor affinity and compared with the native CD33 65-73 peptide, AIISGDSPV, for enhanced immunogenicity. The YLISGDSPV peptide was found to be the most immunogenic epitope producing highly cytolytic CTLs against AML target cells. The CTLs generated with YLIS-GDSPV peptide showed CD33 peptide-specificity through targeting of both native (AIISGDSPV) and modified (YLIS-GDSPV) peptide presenting EBV-BLCL. The CTL cultures displayed a distinct phenotype consisting of a high percentage of activated memory (CD69 ؉ /CD45RO ؉ )-CD8 ؉ and a low percentage of naïve (CD45RA ؉ /CCR7 ؉ )-CD8 ؉ cells. In addition, T-cell clones specific to the YLISGDSPV peptide were isolated and characterized to target AML cells. The clones exhibited both HLA-A2.1-restricted and AML cellspecific cytotoxicity that was mediated through a granuledependent pathway. More importantly, the CTL clones did not lyse or inhibit the proliferation of normal CD34 ؉ progenitor cells. In conclusion, we report on the identification of a highly immunogenic heteroclitic YLISGDSPV CD33 epitope that is a promising candidate for immunotherapy targeting AML.

Cytotoxic activity of gemtuzumab ozogamicin (Mylotarg) in acute myeloid leukemia correlates with the expression of protein kinase Syk

“…Recent studies showed that ligation of CD33 molecules mediated AML cell growth inhibition, [7][8][9][10] activation of protein tyrosine phosphatases SHP-1 and SHP-2, 3-5 and a recruitment of the Syk protein tyrosine kinase. 28,29 These events led to apoptosis and inhibition of cell growth.…”

“…As GO is widely used in the treatment of AML, 10 but effective only in one-third of patients, understanding the mechanisms of its cytotoxicity is important. We hypothesize that determining Syk expression before treatment can serve as a biomarker and, therefore, increase the efficacy of GO or unconjugated anti-CD33 mAb.…”

“…[4][5][6] Engagement of CD33 induced apoptosis and inhibition of proliferation in leukemia cells from AML and chronic myeloid leukemia patients. [7][8][9][10] However, little is known about the molecular mechanisms of the CD33 signaling events leading to inhibition of cell growth and apoptosis.…”

Analogue peptides for the immunotherapy of human acute myeloid leukemia

“…Bae et al predicted a number of modified CD33 peptides with potentially enhanced immunogenicity [63,64]. Their modifications, in the form of single amino acid replacement, were designed to increase HLA-A*0201 or TCR affinity when compared to the native CD33…”

Does our Current Understanding of Immune Tolerance, Autoimmunity, and Immunosuppressive Mechanisms Facilitate the Design of Efficient Cancer Vaccines?

“…In this respect, modification of native peptides in solid tumours, leukaemia, or lymphomas led to peptides with increased immunogenicity against tumour cells [41][42][43][44][45]. On the basis of these findings, one would think that our immune system has failed to eliminate tumours not because tumour antigens were absent, but rather because appropriate lymphocytes were not activated to a threshold required for tumour rejection.…”