(454d) Serum Antibody Profiling of Nivolumab/Azacytidine-Treated Acute Myeloid Leukemia Patients Via High-Throughput Sequencing of Peptide Phage-Display Library

Phage panning combined with high-throughput sequencing permits profiling of humoral responses elicited by the immune system against foreign entities like pathogens, or the host’s tissues in the context of autoimmune disease and cancer. Part of this response involves the production of antibodies — the detection of which forms the basis of many diagnostic tests. Conventional antibody-based diagnostic tests rely on an antigen or antigens to be known. However, for this approach to work, it implies that suitable antigenic targets are available and, more importantly, it is possible to deduce the disease or to shortlist diseases considered suspect for testing. Phage panning provides an attractive way of multiplexing a person’s entire antibody repertoire by recovering the antigen-mimicking fraction of the phage display library. High-throughput sequencing allows the peptide sequence space to be deduced, establishing biomarker patterns correlated to the individual’s disease state. In this study, a combinatorial library of phage-displayed linear dodecapeptides was offered to sera from an acute myeloid leukemia cohort before and after the first cycle of combination therapy (nivolumab + azacytidine). Our strategy involves incorporating two sets of samples as controls: (1) comparison of the sequence space in the naïve library before and after phage amplification to identify propagation-biased subsets and, (2) screening AML sequences against motifs derived from a flu-vaccinated cohort. Candidate peptides are matched to a custom reference database of human proteins and other human-associated microorganisms. Findings on sequence motifs and implications of custom database matches will be discussed.