The prognosis of chronic lymphocytic leukemia (CLL) depends on different markers, including cytogenetic aberrations, oncogenic mutations, and mutational status of the immunoglobulin (Ig) heavy-chain variable (IGHV) gene. The number of IGHV mutations distinguishes mutated (M) CLL with a markedly superior prognosis from unmutated (UM) CLL cases. In addition, B cell antigen receptor (BCR) stereotypes as defined by IGHV usage and complementarity-determining regions (CDRs) classify ∼30% of CLL cases into prognostically important subsets. Subset 2 expresses a BCR with the combination of IGHV3-21–derived heavy chains (HCs) with IGLV3-21–derived light chains (LCs), and is associated with an unfavorable prognosis. Importantly, the subset 2 LC carries a single-point mutation, termed R110, at the junction between the variable and constant LC regions. By analyzing 4 independent clinical cohorts through BCR sequencing and by immunophenotyping with antibodies specifically recognizing wild-type IGLV3-21 and R110-mutated IGLV3-21 (IGLV3-21R110), we show that IGLV3-21R110–expressing CLL represents a distinct subset with poor prognosis independent of IGHV mutations. Compared with other alleles, only IGLV3-21*01 facilitates effective homotypic BCR–BCR interaction that results in autonomous, oncogenic BCR signaling after acquiring R110 as a single-point mutation. Presumably, this mutation acts as a standalone driver that transforms IGLV3-21*01–expressing B cells to develop CLL. Thus, we propose to expand the conventional definition of CLL subset 2 to subset 2L by including all IGLV3-21R110–expressing CLL cases regardless of IGHV mutational status. Moreover, the generation of monoclonal antibodies recognizing IGLV3-21 or mutated IGLV3-21R110 facilitates the recognition of B cells carrying this mutation in CLL patients or healthy donors.

Aberrant CXCR4/CXCL12 signaling is involved in many pathophysiological processes such as cancer and inflammatory diseases. A natural fragment of serum albumin, named EPI-X4, has previously been identified as endogenous peptide antagonist and inverse agonist of CXCR4 and is a promising compound for the development of improved analogues for the therapy of CXCR4-associated diseases. To generate optimized EPI-X4 derivatives we here performed molecular docking analysis to identify key interaction motifs of EPI-X4/CXCR4. Subsequent rational drug design allowed to increase the anti-CXCR4 activity of EPI-X4. The EPI-X4 derivative JM#21 bound CXCR4 and suppressed CXCR4-tropic HIV-1 infection more efficiently than the clinically approved small molecule CXCR4 antagonist AMD3100. EPI-X4 JM#21 did not exert toxic effects in zebrafish embryos and suppressed allergen-induced infiltration of eosinophils and other immune cells into the airways of animals in an asthma mouse model. Moreover, topical administration of the optimized EPI-X4 derivative efficiently prevented inflammation of the skin in a mouse model of atopic dermatitis. Thus, rationally designed EPI-X4 JM#21 is a novel potent antagonist of CXCR4 and the first CXCR4 inhibitor with therapeutic efficacy in atopic dermatitis. Further clinical development of this new class of CXCR4 antagonists for the therapy of atopic dermatitis, asthma and other CXCR4-associated diseases is highly warranted.

In chronic lymphocytic leukemia (CLL), the B cell receptor (BCR) plays a critical role in disease development and progression, as indicated by the therapeutic efficacy of drugs blocking BCR signaling. However, the mechanism(s) underlying BCR responsiveness are not completely defined. Selective engagement of membrane IgM or IgD on CLL cells, each coexpressed by more than 90% of cases, leads to distinct signaling events. Since both IgM and IgD carry the same antigen-binding domains, the divergent actions of the receptors are attributed to differences in immunoglobulin (Ig) structure or the outcome of signal transduction. We showed that IgM, not IgD, level and organization associated with CLL-cell birth rate and the type and consequences of BCR signaling in humans and mice. The latter IgM-driven effects were abrogated when BCR signaling was inhibited. Collectively, these studies demonstrated a critical, selective role for IgM in BCR signaling and B cell fate decisions, possibly opening new avenues for CLL therapy.

BackgroundAberrant CXCR4/CXCL12 signaling is involved in many pathophysiological processes including chronic inflammatory diseases. Thus, the chemokine receptor CXCR4 is a promising target for the therapy of inflammatory disorders, such as atopic dermatitis or allergic asthma. A natural fragment of serum albumin, named EPI-X4, has previous been identified as endogenous peptide antagonist and inverse agonist of CXCR4. The endogenous CXCR4 antagonist provides a promising basis for the development of improved analogues for the therapy of inflammatory diseases.ObjectiveTo increase the anti-CXCR4 activity of EPI-X4 and to evaluate the therapeutic potential of optimized analogs in mouse models of atopic dermatitis and asthma.MethodsMolecular docking analysis of the interaction of EPI-X4 with CXCR4 was performed to define critical interaction motifs and to rationally design analogs with increased activity. EPI-X4 derivatives were synthesized and CXCR4 binding and antagonizing activity determined in assays for antibody competition, inhibition of CXCR4-mediated HIV-1 infection, CXCL12-dependent Ca2+ mobilization, ERK and AKT phosphorylation and cell migration. Toxicity of peptides was evaluated in zebrafish embryos. The therapeutic efficacy of the lead peptide EPI-X4 JM#21 was determined in mouse models of atopic dermatitis and asthma.ResultsDocking analysis identified key interaction motifs of EPI-X4/CXCR4. Rational drug design allowed to increase the anti-CXCR4 activity of EPI-X4 and resulted in the generation of the lead analog JM#21, which bound CXCR4 and suppressed CXCR4-tropic HIV-1 infection more efficiently than the clinically approved small molecule CXCR4 antagonist AMD3100. JM#21 did not exert toxic effects in zebrafish embryos and efficiently prevented inflammation of the skin in a mouse model of atopic dermatitis. Moreover, EPI-X4 and its improved derivative suppressed allergen-induced infiltration of eosinophils and other immune cells into the airways of animals in an asthma mouse model.ConclusionThe rationally designed EPI-X4 derivative JM#21 is a potent antagonist of CXCR4 and the first CXCR4 inhibitor with therapeutic efficacy in atopic dermatitis. Further clinical development of this new class of CXCR4 antagonists for the therapy of atopic dermatitis, asthma and other CXCR4-associated diseases is highly warranted.Graphical Abstract

The random gene segment rearrangement during B cell development ensures Ab repertoire diversity. Because this process might generate autoreactive specificities, it has been proposed that stringent selection mechanisms prevent the development of autoreactive B cells. However, conventional assays to identify autoreactive B cells usually employ in vitro-generated Abs, which differ from membrane-bound BCRs. In this study, we used a cell-based assay to investigate the autoreactivity of membrane-bound BCRs derived from different B cell developmental stages of human peripheral blood. Contrasted to soluble Ab counterparts, only a few of the tested BCRs were autoreactive, although the cell-based assay sensitively detects feeble Ag recognition of a germline-reverted murine BCR that was selected after OVA immunization of mice, whereas conventional assays failed to do so. Together, these data suggest that proper identification of autoreactive B cells requires the membrane-bound BCR, as the soluble Ab may largely differ from its BCR counterpart in Ag binding.