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=24 antibodies). Patterns of cross-reactivity were reproducible between individuals, and B-cells binding multiple BKPyV genotypes were present in all patients. However, the specific subset of B-cells enriched for expression of broadly neutralizing antibodies made up only 1.2% of the BKPyV-specific repertoire, and was not detected in all patient samples. The proportions of broadly-specific and isotype switched antibodies, and rates of somatic hypermutation increased with time following peak DNAemia, and 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 intact virus capsids 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/26345220v2_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@b3b898org.highwire.dtl.DTLVardef@11c0dc6org.highwire.dtl.DTLVardef@cc542corg.highwire.dtl.DTLVardef@aa1830_HPS_FORMAT_FIGEXP M_FIG C_FIG