Using LIBRA-seq to map the BK-polyomavirus specific B-cell response in kidney transplant recipients

BK polyomavirus (BKPyV) is a major complication in kidney transplant recipients (KTR), for whom no specific antiviral therapy is available. Modulation of immunosuppressive therapy results in virus clearance in most KTR with BKPyV DNAemia (controllers), but a significant minority fail to clear the virus (non-controllers). Here, we adapt LIBRA-seq, which links antibody sequence data to antigen specificity, to intact viral capsids of the four BKPyV genotypes to study and compare BKPyV-specific B-cell repertoires in controllers (n=8) versus non-controllers (n=3). Sequences were obtained for 5197 BKPyV-specific antibodies, and predicted antigen specificities were validated by ELISA and neutralizing assays (n=21 antibodies). We show that cross-genotype reactivity results from the recruitment of numerous broadly cross-reactive B-cell clones with preferential binding to the infecting genotype, making up 4,3% to 44,6% of the BKPyV-specific repertoire, while true broadly neutralizing antibodies are rare. The proportions of broadly-specific and isotype switched antibodies, rates of somatic hypermutation and repertoire diversity were comparable in both patient groups, indicating that there is no identifiable deficit in the humoral response mounted by BKPyV non-controllers, and supporting the notion that humoral immunity alone is insufficient to control established BKPyV replication. This work shows that LIBRA-seq can be successfully applied to a non-enveloped virus and provides a framework for analyzing antiviral B-cell repertoires and antibody specificity in clinically relevant settings. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=180 SRC="FIGDIR/small/26345220v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@18ef2b6org.highwire.dtl.DTLVardef@1e0b7a2org.highwire.dtl.DTLVardef@3822fcorg.highwire.dtl.DTLVardef@180deea_HPS_FORMAT_FIGEXP M_FIG C_FIG