Melan-A (26-35) A27L peptide (ELAGIGILTV) – Immunology – Antigens/Epitotes/Pools/Librairies

Native Melan-A (26-35) decapeptide derives from the melanocyte lineage-specific protein Melan-A/MART-1 (UniProtKB - Q16655),which is expressed in almost 75-100% of primary and metastatic melanomas. Melan-A,also known as melanoma antigen,recognized by T-cells 1 (Th1) or MART-1 cells,is a 118 amino acids (AA) type III transmembrane protein,consisting in a 26 AA extracellular region (AA 1-26) and a 71 AA cytoplasmic domain. The latter is only expressed on the surface of melanocytes,melanoma,and retinal pigment epithelium cells,but not in other normal tissues. This unique feature is used in anatomic pathology for melanocytic differentiation that is useful to diagnose melanomas. The latter is found in the Golgi apparatus but the inversion of its membrane topology leads to its retention in the endoplasmic reticulum (ER). Human Melan-A is involved in melanosome biogenesis by maintaining the stability of GPR143 and its vital role in the functioning of glycoprotein-100 (gp100),also known as the melanocyte protein (PMEL),which is a critical player in the formation of stage II melanosomes. The region 26-35 of Melan-A protein acts as an antigenic peptide that is recognized by CD8+ tumor-reactive cytolytic T lymphocytes (CTLs) for designing antigen-specific cancer vaccines. It has been shown that CD8+ Melan-A-specific CTLs isolated from melanoma patients efficiently lyse the Melan-A-expressing HLA-A*0201 melanoma cell line. However,CTLs preferentially recognize the Melan-A (26-35) peptide as compared with the Melan-A (27-35) peptide. Later,Melan-A (26-35) A27L analog (ELAGIGILTV) emerged as an even more promising lead to target melanomas. The latter has a higher binding affinity to HLA-A*0201 than the native Melan-A (26-35) peptide (EAAGIGILTV) and consequently displays more potent antigenicity and immunogenicity. It has been reported that the concentration of Melan-A (26-35) A27L analog required to obtain 50% of maximal antigenic activity is EC50 = 0.01 nM,whereas that of the native Melan-A (26-35) peptide is 0.25 nM. Therefore,the relative activity of Melan-A (26-35) A27L analog is 25 times higher than that of the native Melan-A (26-35) peptide. Furthermore,functional competition assay has shown that the concentration of Melan-A (26-35) A27L analog required to achieve 50% inhibition of tumor lysis is IC50 = 2 nM,which is 10 times lower than that of the native Melan-A (26-35) peptide. Regarding peptide stability in human serum,the half-lives (t1/2) of the native Melan-A (26-35) peptide and the A27L analog are quite similar (45 and 40 min,respectively),as measured by HPLC-ESI-MS,but much higher than that of the Melan-A (27-35) nonapeptide (5 min). IC-PEPTIDE also offers the native version of Melan-A (26-35) peptide,as well as its scrambled version (see sections "Melan-A (26-35) peptide" & "Melan-A (26-35) scrambled").

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