Synthetic MUC1 Antitumor Vaccine with Incorporated 2,3‐Sialyl‐T Carbohydrate Antigen Inducing Strong Immune Responses with Isotype Specificity

Abstract

The endothelial glycoprotein MUC1 is known to underlie alterations in cancer by means of aberrant glycosylation accompanied by changes in morphology. The heavily shortened glycans induce a collapse of the peptide backbone and enable accessibility of the latter to immune cells, rendering it a tumor-associated antigen. Synthetic vaccines based on MUC1 tandem repeat motifs, comprising tumor-associated 2,3-sialyl-T antigen, conjugated to the immunostimulating tetanus toxoid, are reported herein. Immunization with these vaccines in a simple water/oil emulsion produced a strong immune response in mice to which stimulation with complete Freund's adjuvant (CFA) was not superior. In both cases, high levels of IgG1 and IgG2a/b were induced in C57BL/6 mice. Additional glycosylation in the immunodominant PDTRP domain led to improved binding of the induced antisera to MCF-7 breast tumor cells, compared with that of the monoglycosylated peptide vaccine.

Liposomal Antitumor Vaccines Targeting Mucin 1 Elicit a Lipid‐Dependent Immunodominant Response

“…Next, blood samples were collected from each mouse on days 14, 28 and 42 after the first immunization, and the anti‐MUC1 antibody titers in the antisera were assessed by enzyme‐linked immunosorbent assay (ELISA) using a MUC1‐binding protein conjugate (Figure S47) as the coating antigen . As shown in Figure c, for the liposomal vaccines with the NKT agonist αGalCer as the adjuvant, the final anti‐MUC1 IgG antibody titers induced by the lipid‐conjugated Pam 2 ‐MUC1 antigen were 34‐ and 190‐fold higher than those induced by the Pam‐MUC1 antigen and the MUC1 antigen without lipid tails, respectively.…”

The Development of Vaccines from Synthetic Tumor‐Associated Mucin Glycopeptides and their Glycosylation‐Dependent Immune Response

“…[175] In addition, a 2,3-ST was synthesized and conjugated to the threonine at position 18 in the amino acid sequence and formed the MUC1 (22) T 18 2,3-ST-TTox vaccine (Figure 5). [176] Another MUC1 (22) T 11 T N -T 18 2,3-ST-TTox vaccine [176] was intended to evaluate whether the additional glycosylation with T N on threonine at position 11 in the immunodominant PDTRP motif changes the immune response. Furthermore, the humoral immune response after immunization with a MUC1 ( 22) -TTox vaccine without glycosylation [182] was tested.…”

“…The lowest binding to the TA MUC1 was shown by the antisera, which were induced by the 22) T 6 T N -T 18 T N -TTox vaccine, [175] MUC1 (22) S 17 ST N -TTox vaccine [72] and MUC1 (22) T 11 T N -T 18 2,3-ST-TTox vaccine. [176] T 6 T N -T 18 T N glycopeptide and by the peptide only glycosylated with 2,3-ST. The binding analyses show that in the case of additional glycosylation outside the STAPPA sequence, great attention must be paid to the positioning of the second glycan.…”

Glycans in drug discovery

“…These insights were essential, since the use of glycopeptides able to imitate the conformational behaviour of cancer-associated MUC1 glycopeptides must be advantageous for the design of potent vaccines 96. The enhanced potency of 2,3-sialyl-T antigen based vaccines was also attributed to the improved turn-type conformation of the glycopeptide bearing this specific carbohydrate epitope 97. Interestingly, the O/S or O/Se substitution at the glycosidic linkage of MUC1 glycopeptides increases the affinity of the corresponding mimetic antigens 98.…”