Immunological Response from an Entirely Carbohydrate Antigen: Design of Synthetic Vaccines Based on Tn−PS A1 Conjugates

Abstract

An entirely carbohydrate-based immunogen consisting of a zwitterionic polysaccharide (ZPS) PS A1 and the well-known tumor antigen Tn has been designed, synthesized, and studied for immunological effects. The PS A1 motif was included to act as an MHCII elicitor for a T-cell-dependent immune response with increased immunogenicity against tumor-associated carbohydrate antigens, providing an alternative to carrier proteins. Through the use of C57BL/6 mice, it has been shown that chemical modification of PS A1 does not alter the recognition sequence responsible for an MHCII-mediated, T-cell-dependent immune response. The Tn-PS A1 conjugate construct confers specificity toward the Tn antigen alone, and specific carbohydrate immunoglobulins, namely, IgG3, are generated from intraperitoneal immunizations with or without adjuvant. The properties of the vaccine candidate are attributed to a site-specific linking strategy that incurs significant incorporation of Tn antigen.

Elucidating structural features of an entirely carbohydrate cancer vaccine construct employing circular dichroism and fluorescent labeling

“…9,26 These fragments are able to facilitate binding to MHCII proteins in a reduced pH environment that allows presentation to the T-cell. 9 However, the positive MHCII mediated immune responses against our Tn-PS A1 suggests that the construct retains the ability to induce production of IgG antibodies 16,17 even when there is depletion of helical character due to changes in conformation induced by reduced pH and oxidative depolymerisation. Based on the data found within, we now believe that it is most critical to retain the alternating charge character of Tn-PS A1.…”

“…In previous work, we conjugated the Thomsen-nouveau (Tn) 16,17 and Thomas-Friedenreich (TF) 18 tumor associated carbohydrate antigens (TACAs) to 1 and discovered an antigen specific immune response. 16,17 The Tn TACA was chosen for two main reasons: 1) it represents the simplest structure of all the known TACAs 19 rendering it readily accessible through synthetic strategies and 2) a number of reports exist detailing Tn as a glycoprotein conjugate that provides data points for comparison purposes in our own studies. Our approach involved conjugating the Tn aminooxy sugar ( 2 ) to PS A1 ( 1 ) via selective oxidative cleavage of the vicinal diol (1° 6-OH, 2° 5-OH) found on the bacterial-exclusive D-galactofuranose using 0.01 M NaIO 4 (Scheme 1).…”

“…The Tn-PS A1 ( 3 ) immunogen has been characterized using NMR showing distinct oxime doublets of the Z and E isomers at 6.3 and 7.21 ppm respectively in ~ 1:1 ratio. 16 …”

Kinetic Products Under Thermal Conditions: Rapid Entry into α/β-D-Galactofuranosides Using Microwave Irradiation and Selective Lewis Acids

“…As our current research program focuses on chemical modifications of D-Galf in ZPS PS A1 (1) for immunogen development, [27] having a reliable means to obtain D-galactofuranoside in very good yield and high purity is of great importance.…”

Carbohydrate antigen delivery by water soluble copolymers as potential anti-cancer vaccines

“…The most common type of carrier is immunogenic proteins such as keyhole limpet haemocyanin, 14–17 tetanus toxoid, 18,19 and Bacillus Calmette–Guerin. 20 Other antigen presenting platforms include dendrimers, 21,22 regioselectively addressable functionalized templates, 23 nanomaterials, 24,25 liposomes and proteoliposomes 26,27 polysaccharides 28 and virus-like particles. 29,30 …”