Selective capture of anti‐N‐glucosylated NTHi adhesin peptide antibodies by a multivalent dextran conjugate

Tentacle-like polymers decorated with several copies of peptide antigens can be interesting tools to increase the ability to capture circulating antibodies in patient sera, using cooperative effects for stronger avidity. We previously showed that antibodies from multiple sclerosis (MS) patient sera preferentially recognize hyperglucosylated adhesin protein HMW1 of non-typeable Haemophilus influenzae (NTHi). We selected the C-terminal HMW1(1347-1354) minimal epitope and prepared the diglucosylated analogue Ac-KAN(Glc)VTLN(Glc)TTG-K(N3)-NH2 to graft a 40 kDa dextran scaffold modified with glycidyl-propargyl moieties to perform a copper catalysed alkyne-azide coupling reaction (CuAAC). Quantitative NMR measurements allowed to characterize the peptide loading (19.5%) on the multivalent dextran conjugate. This novel polymeric structure displayed optimal capturing properties of both IgG and, more interestingly, IgM antibodies in MS sera. Specific antibodies from a representative MS serum, were successfully depleted using a sepharose resin bearing the new glucosylated multivalent conjugate, as confirmed by ELISA. These results may offer a promising proof-of-concept for the selective purification of high affinity autoantibodies from sera of autoimmune patients, in general, and of specific high affinity antibodies against a minimally glycosylated epitope Asn(Glc) from sera of multiple sclerosis (MS) patients, in particular.