技术资料

Acute myeloid leukemia (AML) is the most common type of acute leukemia affecting older individuals at a median age of 67 years. Resistance to intensive induction chemotherapy is the major cause of death in elderly AML; hence novel treatment strategies are warranted. CD33-directed antibody-drug conjugates (Gemtuzumab ozogamicin) have been shown to improve overall survival,validating CD33 as a target for antibody-based therapy of AML. Here we report the in vitro efficacy of BI 836858,a fully human,Fc-engineered,anti-CD33 antibody using AML cell lines and primary AML blasts as targets. BI 836858-opsonized AML cells significantly induced both autologous and allogeneic natural killer (NK)-cell degranulation and NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC). In vitro treatment of AML blasts with decitabine (DAC) or 5-azacytidine,two hypomethylating agents that show efficacy in older patients,did not compromise BI 836858-induced NK cell-mediated ADCC. Evaluation of BI 836858-mediated ADCC in serial marrow AML aspirates in patients who received a ten-day course of DAC (pre-DAC,days 4,11 and 28 post-DAC) revealed significantly higher ADCC in samples at day 28 post-DAC when compared to pre-DAC treatment. Analysis of ligands (L) to activating receptors (NKG2D showed significantly increased NKG2DL expression in day 28 post-DAC samples compared to pre-DAC samples; when NKG2DL receptor was blocked using antibodies,BI 836858-mediated ADCC was significantly decreased,suggesting that DAC enhances AML blast susceptibility to BI 836858 by upregulating NKG2DL. These data provide a rationale for combination therapy of Fc-engineered antibodies such as BI 836858 with azanucleosides in elderly patients with AML. View Publication

We investigated the contribution of host immune cells to bacterial killing in a whole-blood bactericidal activity (WBA) assay,an ex vivo model used to test efficacy of drugs against mycobacterium tuberculosis (Mtb). We performed WBA assays with immuno-magnetic depletion of specific cell types,in the presence or absence of rifampicin. Innate immune cells decreased Mtb growth in absence of drug,but appeared to diminish the cidal activity of rifampicin,possibly attributable to intracellular bacterial sequestration. Adaptive immune cells had no effect with or without drug. The WBA assay may have potential for testing adjunctive host-directed therapies acting on phagocytic cells. View Publication

B cell activation and Ab production in response to protein Ags requires presentation of peptides for recruitment of T cell help. We and others have recently demonstrated that B cells can also acquire innate help by presenting lipid Ags via CD1d to NKT cells. Given the newfound contribution of NKT cells to humoral immunity,we sought to identify the pathways that regulate CD1 molecule expression in human B cells. We show that ex vivo,activated and memory B cells expressed lower levels of CD1d compared with resting,naive,and marginal zone-like B cells. In vitro,CD1d was downregulated by all forms of B cell activation,leaving a narrow temporal window in which B cells could activate NKT cells. CD1c expression and function also decreased following activation by CD40L alone,whereas activation via the BCR significantly upregulated CD1c,particularly on marginal zone-like B cells. We found that the CD40L-induced downregulation of CD1d and CD1c correlated with diminished expression of retinoic acid receptor α (RARα) response genes,an effect that was reversed by RARα agonists. However,BCR-induced upregulation of CD1c was independent of the RAR pathway. Our findings that both CD1d and CD1c are upregulated by RARα signaling in human B cells is distinct from effects reported in dendritic cells,in which CD1c is inversely downregulated. One functional consequence of CD1d upregulation by retinoic acid was NKT cell cytotoxicity toward B cells. These results are central to our understanding of how CD1-restricted T cells may control humoral immunity. View Publication