Local and systemic antibody responses to dextran-cholera toxin B subunit conjugates

Abstract

This study was designed to test local and systemic immunity following mucosal immunization with a polysaccharide-protein conjugate. After preparing and characterizing dextran-cholera toxin B subunit (CTB) conjugates, we studied their immunogenicity in mice following systemic or mucosal immunizations. Dextran was chosen as a model polysaccharide antigen and conjugated via adipic acid dihydrazide and N-succinimidyl-3-(2-pyridyldithio)propionate to CTB. Mice were immunized either subcutaneously, intranasally, or perorally three times, and cholera toxin was used as an adjuvant for the mucosal immunizations. Three conjugates with different molecular weights for dextran (40,000 and 76,000) or varying dextran/CTB molar ratios were tested. Peroral immunizations with all conjugates evoked local immunoglobulin A (IgA) antibody responses against dextran in the small intestine, and intranasal immunizations did the same in the lung. Intranasal immunizations also elicited serum antibody titers that were significantly higher than or equal to those after subcutaneous immunizations. Intranasal immunizations evoked serum IgG antidextran titers which were dependent on the dextran/CTB molar ratio and inversely related to the local IgA response, which was not the case for subcutaneous immunizations. This is the first study of local and systemic immunity following mucosal immunization with a polysaccharide-protein conjugate. The results show that it is possible to evoke a local as well as a systemic antibody response against a polysaccharide by conjugating it to CTB and using an appropriate route of immunization.

Refocusing of B‐cell responses following a single amino acid substitution in an antigen

“…We and others have previously shown that mice intranasally immunized with proteins mixed with LT or cholera toxin B not only produce a systemic IgG response but also antibody responses at different mucosal sites 7,9–12,16–19 . As has been shown for model immunogens such as ovalbumin, the C‐fragment of TT 11,12 and herpes simplex virus type 2 glycoprotein, 19 mice immunized intranasally with hCG mixed with LT will produce antigen‐specific IgG in the serum as well as sIgA in both the respiratory and genital tracts.…”

Mucosal and systemic antibody responses after peroral or intranasal immunization: Effects of conjugation to enterotoxin B subunits and/or of co‐administration with free toxin as adjuvant

“…It is therefore important to define the optimal routes, and to identify suitable delivery systems and adjuvants for inducing local immunity. We have used CT and its B subunit, CTB, since these molecules have been proved to be good mucosal immunogens and carriers for other antigens (4,23,(29)(30)(31)33). The toxicity of CT precludes its exploitation in human vaccines, whereas CTB is non-toxic as tested by different routes in humans (1 1, 18, 34).…”

“…This may partly be due to their lack of uptake by mucosal tissues (16). Cholera toxin (CT) and the heatlabile enterotoxin from Escherichia coli (LT) are exceptionally potent mucosa-binding molecules and have been shown to induce strong immune responses after mucosal immunization (4,17,(18)(19)(20)(21). These molecules bind with high affinity to mucosal (and other) cells (18) and they have been used as mucosal adjuvants and carriers for non-binding protein, peptide and polysaccharide antigens (4,(19)(20)(21).…”

The immunostimulating complex (ISCOM) is an efficient mucosal delivery system for respiratory syncytial virus (RSV) envelope antigens inducing high local and systemic antibody responses

“…Two to five mice from each group were killed, and the lungs or upper respiratory tracts were removed. Secretory antibodies were extracted as described by Bergquist et al [16]. Briefly, the mice were injected intraperitoneally with 0·1 ml 1% heparin-PBS under anaesthesia.…”