技术资料

The mutagenic enzyme activation-induced cytidine deaminase (AID) is required for immunoglobulin class switch recombination (CSR) and somatic hypermutation (SHM) in germinal center (GC) B cells. Deregulated expression of AID is associated with various B-cell malignancies and,currently,it remains unclear how AID activity is extinguished to avoid illegitimate mutations. AID has also been shown to be alternatively spliced in malignant B cells,and there is limited evidence that this also occurs in normal blood B cells. The functional significance of these splice variants remains unknown. Here we show that normal GC human B cells and blood memory B cells similarly express AID splice variants and show for the first time that AID splicing variants are singly expressed in individual normal B cells as well as malignant B cells from chronic lymphocytic leukemia patients. We further demonstrate that the alternative AID splice variants display different activities ranging from inactivation of CSR to inactivation or heightened SHM activity. Our data therefore suggest that CSR and SHM are differentially switched off by varying the expression of splicing products of AID at the individual cell level. Most importantly,our findings suggest a novel tumor suppression mechanism by which unnecessary AID mutagenic activities are promptly contained for GC B cells. View Publication

B lymphocyte stimulator (BLyS) is a well-known direct costimulator of adaptive immune cells,particularly B lineage cells. However,we have reported recently that BLyS is also able to activate monocytes. Other innate immune cells,such as dendritic cells (DCs),play a key role in the initiation of adaptive immune responses and the purpose of the current study was to assess whether there is a direct role for BLyS in modulating human DC functions. In this study,we show that BLyS induces DC activation and maturation. Thus,BLyS strongly induced up-regulation of surface costimulatory molecule expression and secretion of specific cytokines and chemokines in DCs. BLyS-stimulated DCs (BLyS-DCs) were also able to augment allogeneic CD4 T cell proliferation to a greater extent than control DCs. BLyS-DCs secreted elevated levels of the major Th1-polarizing cytokine,IL-12p70,and they promoted naive CD4 T cell differentiation into Th1 T cells. Regarding BLyS receptor expression,DCs primarily express cytoplasmic transmembrane activator and CAML interactor; however,low levels of cell surface transmembrane activator and CAML interactor are expressed as well. Collectively,our data suggest that BLyS may modulate adaptive immune cells indirectly by inducing DC maturation. View Publication

Chaetocin,a thiodioxopiperazine natural product previously unreported to have anticancer effects,was found to have potent antimyeloma activity in IL-6-dependent and -independent myeloma cell lines in freshly collected sorted and unsorted patient CD138(+) myeloma cells and in vivo. Chaetocin largely spares matched normal CD138(-) patient bone marrow leukocytes,normal B cells,and neoplastic B-CLL (chronic lymphocytic leukemia) cells,indicating a high degree of selectivity even in closely lineage-related B cells. Furthermore,chaetocin displays superior ex vivo antimyeloma activity and selectivity than doxorubicin and dexamethasone,and dexamethasone- or doxorubicin-resistant myeloma cell lines are largely non-cross-resistant to chaetocin. Mechanistically,chaetocin is dramatically accumulated in cancer cells via a process inhibited by glutathione and requiring intact/unreduced disulfides for uptake. Once inside the cell,its anticancer activity appears mediated primarily through the imposition of oxidative stress and consequent apoptosis induction. Moreover,the selective antimyeloma effects of chaetocin appear not to reflect differential intracellular accumulation of chaetocin but,instead,heightened sensitivity of myeloma cells to the cytotoxic effects of imposed oxidative stress. Considered collectively,chaetocin appears to represent a promising agent for further study as a potential antimyeloma therapeutic. View Publication

Current antiretroviral therapy (ART) for HIV/AIDS slows disease progression by reducing viral loads and increasing CD4 counts. Yet ART is not curative due to the persistence of CD4+ T-cell proviral reservoirs that chronically resupply active virus. Elimination of these reservoirs through the administration of synergistic combinations of latency reversing agents (LRAs),such as histone deacetylase (HDAC) inhibitors and protein kinase C (PKC) modulators,provides a promising strategy to reduce if not eradicate the viral reservoir. Here,we demonstrate that largazole and its analogues are isoform-targeted histone deacetylase inhibitors and potent LRAs. Significantly,these isoform-targeted HDAC inhibitors synergize with PKC modulators,namely bryostatin-1 analogues (bryologs). Implementation of this unprecedented LRA combination induces HIV-1 reactivation to unparalleled levels and avoids global T-cell activation within resting CD4+ T-cells. View Publication

HIV-1 infected cells are eliminated in infected individuals by a variety of cellular mechanisms,the best characterized of which are cytotoxic T cell and NK cell-mediated killing. An additional antiviral mechanism is antibody-dependent cellular cytotoxicity. Here we use primary CD4(+) T cells infected with the BaL clone of HIV-1 as target cells and autologous NK cells,monocytes,and neutrophils as effector cells,to quantify the cytotoxicity mediated by the different effectors. This was carried out in the presence or absence of HIV-1-specific antiserum to assess antibody-dependent cellular cytotoxicity. We show that at the same effector to target ratio,NK cells and monocytes mediate similar levels of both antibody-dependent and antibody-independent killing of HIV-1-infected T cells. Neutrophils mediated significant antibody-dependent killing of targets,but were less effective than monocytes or NK cells. These data have implications for acquisition and control of HIV-1 in natural infection and in the context of vaccination. View Publication

Cytoplasmic APOBEC3G has been reported to block wild-type human immunodeficiency virus type 1 (HIV-1) infection in some primary cells. It is not known whether cytoplasmic APOBEC3G has residual activity in activated T cells,even though virion-packaged APOBEC3G does restrict HIV-1 in activated T cells. Because we found that APOBEC3G expression is greater in activated CD4(+) T-helper type 1 (Th1) lymphocytes than in T-helper type 2 (Th2) lymphocytes,we hypothesized that residual target cell restriction of incoming Vif-positive virions that lack APOBEC3G,if present,would be greater in Th1 than Th2 lymphocytes. Infection of activated Th1 cells with APOBEC3-negative virions did result in decreased amounts of early and late reverse transcription products and integrated virus relative to infection of activated Th2 cells. Two-long terminal repeat (2-LTR) circles,which are formed in the nucleus when reverse transcripts do not integrate,were increased after APOBEC3-negative virus infection of activated Th1 cells relative to infection of activated Th2 cells. In contrast,2-LTR circle forms were decreased after infection of APOBEC3G-negative cells with APOBEC3G-containing virions relative to APOBEC3G-negative virions and with Th1 cell-produced virions relative to Th2 cell-produced virions. Increasing APOBEC3G in Th2 cells and decreasing APOBEC3G in Th1 cells modulated the target cell phenotypes,indicating causation by APOBEC3G. The comparison between activated Th1 and Th2 cells indicates that cytoplasmic APOBEC3G in activated Th1 cells partially restricts reverse transcription and integration of incoming Vif-positive,APOBEC3G-negative HIV-1. The differing effects of cytoplasmic and virion-packaged APOBEC3G on 2-LTR circle formation indicate a difference in their antiviral mechanisms. View Publication

Treatment of HIV-infected patients with IFN-α results in significant,but clinically insufficient,reductions of viremia. IFN induces the expression of several antiviral proteins including BST-2,which inhibits HIV by multiple mechanisms. The viral protein Vpu counteracts different effects of BST-2. We thus asked if Vpu proteins from IFN-treated patients displayed improved anti-BST-2 activities as compared to Vpu from baseline. Deep-sequencing analyses revealed that in five of seven patients treated by IFN-α for a concomitant HCV infection in the absence of antiretroviral drugs,the dominant Vpu sequences differed before and during treatment. In three patients,vpu alleles that emerged during treatment improved virus replication in the presence of IFN-α,and two of them conferred improved virus budding from cells expressing BST-2. Differences were observed for the ability to down-regulate CD4,while all Vpu variants potently down-modulated BST-2 from the cell surface. This report discloses relevant consequences of IFN-treatment on HIV properties. View Publication

Immune recognition by T cells relies on the presentation of pathogen-derived peptides by infected cells,but the persistence of chronic infections calls for new approaches to modulate immune recognition. Ag cross-presentation,the process by which pathogen Ags are internalized,degraded,and presented by MHC class I,is crucial to prime CD8 T cell responses. The original degradation of Ags is performed by pH-dependent endolysosomal cathepsins. In this article,we show that HIV protease inhibitors (PIs) prescribed to HIV-infected persons variably modulate cathepsin activities in human APCs,dendritic cells and macrophages,and CD4 T cells,three cell subsets infected by HIV. Two HIV PIs acted in two complementary ways on cathepsin hydrolytic activities: directly on cathepsins and indirectly on their regulators by inhibiting Akt kinase activities,reducing NADPH oxidase 2 activation,and lowering phagolysosomal reactive oxygen species production and pH,which led to enhanced cathepsin activities. HIV PIs modified endolysosomal degradation and epitope production of proteins from HIV and other pathogens in a sequence-dependent manner. They altered cross-presentation of Ags by dendritic cells to epitope-specific T cells and T cell-mediated killing. HIV PI-induced modulation of Ag processing partly changed the MHC self-peptidome displayed by primary human cells. This first identification,to our knowledge,of prescription drugs modifying the regulation of cathepsin activities and the MHC-peptidome may provide an alternate therapeutic approach to modulate immune recognition in immune disease beyond HIV. View Publication

We previously reported on a panel of HIV-1 clade B envelope (Env) proteins isolated from a patient treated with the CCR5 antagonist aplaviroc (APL) that were drug resistant. These Envs used the APL-bound conformation of CCR5,were cross resistant to other small-molecule CCR5 antagonists,and were isolated from the patient's pretreatment viral quasispecies as well as after therapy. We analyzed viral and host determinants of resistance and their effects on viral tropism on primary CD4(+) T cells. The V3 loop contained residues essential for viral resistance to APL,while additional mutations in gp120 and gp41 modulated the magnitude of drug resistance. However,these mutations were context dependent,being unable to confer resistance when introduced into a heterologous virus. The resistant virus displayed altered binding between gp120 and CCR5 such that the virus became critically dependent on the N' terminus of CCR5 in the presence of APL. In addition,the drug-resistant Envs studied here utilized CCR5 very efficiently: robust virus infection occurred even when very low levels of CCR5 were expressed. However,recognition of drug-bound CCR5 was less efficient,resulting in a tropism shift toward effector memory cells upon infection of primary CD4(+) T cells in the presence of APL,with relative sparing of the central memory CD4(+) T cell subset. If such a tropism shift proves to be a common feature of CCR5-antagonist-resistant viruses,then continued use of CCR5 antagonists even in the face of virologic failure could provide a relative degree of protection to the T(CM) subset of CD4(+) T cells and result in improved T cell homeostasis and immune function. View Publication

Many pathogens evade cytotoxic T lymphocytes (CTLs) by downregulating HLA molecules on infected cells,but the loss of HLA can trigger NK cell-mediated lysis. HIV-1 is thought to subvert CTLs while preserving NK cell inhibition by Nef-mediated downregulation of HLA-A and -B but not HLA-C molecules. We find that HLA-C is downregulated by most primary HIV-1 clones,including transmitted founder viruses,in contrast to the laboratory-adapted NL4-3 virus. HLA-C reduction is mediated by viral Vpu and reduces the ability of HLA-C restricted CTLs to suppress viral replication in CD4+ cells in vitro. HLA-A/B are unaffected by Vpu,and primary HIV-1 clones vary in their ability to downregulate HLA-C,possibly in response to whether CTLs or NK cells dominate immune pressure through HLA-C. HIV-2 also suppresses HLA-C expression through distinct mechanisms,underscoring the immune pressure HLA-C exerts on HIV. This viral immune evasion casts new light on the roles of CTLs and NK cells in immune responses against HIV. View Publication