Serum glycan-binding IgG antibodies in HIV-1 infection and during the development of broadly neutralizing responses.

CAPRISA, 2017.Abstract available in pdf

Anti-glycan IgM repertoires in newborn human cord blood.

Natural antibodies are an innate-like subset of serum antibodies involved in host defense, tumor surveillance, homeostasis, and autoimmunity. Defining the natural antibody repertoire is critical for identifying biomarkers, developing vaccines, controlling and preventing autoimmunity, and understanding the development and organization of the immune system. While natural antibodies to protein antigens have been studied in depth, little is known about natural antibodies to carbohydrate antigens. To address this, we profiled IgM from umbilical cord blood and matched maternal sera on a glycan microarray. Since standard methods to detect maternal contamination in cord serum did not have sufficient sensitivity for our study, we developed a highly sensitive microarray-based assay. Using this method, we found that over 50% of the cord samples had unacceptable levels of maternal contamination. For the cord samples with high purity, anti-glycan IgM antibodies were prevalent and recognized a broad range of non-human and human glycans. Using principal component analysis and hierarchical clustering, cord IgM repertoires showed a high degree of similarity with each other but were distinct from maternal IgM repertoires. Our results demonstrate that many anti-glycan antibodies in human serum are natural antibodies and provide new insights into the development of anti-glycan antibody repertoires

Therapeutic Antibodies to Ganglioside GD2 Evolved from Highly Selective Germline Antibodies

Antibodies play a crucial role in host defense and are indispensable research tools, diagnostics, and therapeutics. Antibody generation involves binding of genomically encoded germline antibodies followed by somatic hypermutation and in vivo selection to obtain antibodies with high affinity and selectivity. Understanding this process is critical for developing monoclonal antibodies, designing effective vaccines, and understanding autoantibody formation. Prior studies have found that antibodies to haptens, peptides, and proteins evolve from polyspecific germline antibodies. The immunological evolution of antibodies to mammalian glycans has not been studied. Using glycan microarrays, protein microarrays, cell binding studies, and molecular modeling, we demonstrate that therapeutic antibodies to the tumor-associated ganglioside GD2 evolved from highly specific germline precursors. The results have important implications for developing vaccines and monoclonal antibodies that target carbohydrate antigens. In addition, they demonstrate an alternative pathway for antibody evolution within the immune system that is distinct from the polyspecific germline pathway

Divergent Behavior of Glycosylated Threonine and Serine Derivatives in Solid Phase Peptide Synthesis

Solid phase peptide coupling of glycosylated threonine derivatives was systematically evaluated. In contrast to glycosylated serine derivatives which are highly prone to epimerization, glycosylated threonine derivatives produce only negligible amounts of epimerization. Under forcing conditions, glycosylated threonine analogs undergo β-elimination, rather than epimerization. Mechanistic studies and molecular modeling were used to understand the origin of the differences in reactivity