Scientific Resources

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

Following activation through the TCR,CD4+ T cells can differentiate into three major subsets: Th1,Th2,and Th17 cells. IL-17-secreting Th17 cells play an important role in the pathogenesis of several autoimmune diseases and in immune responses to pathogens,but little is known about the regulation of apoptosis in Th17 cells. In this study,the sensitivity of in vitro-polarized Th1,Th2,and Th17 cells to Fas-mediated apoptosis was compared directly by different methods. The order of sensitivity of T cell subsets to Fas-mediated apoptosis is: Th1 textgreater Th17 textgreater Th2. The greater sensitivity of Th17 cells to Fas-mediated apoptosis compared with Th2 cells correlated with their higher expression of FasL and comparable expression of the antiapoptotic molecule FLIP. The decreased sensitivity of Th17 compared with Th1 cells correlated with the higher expression of FLIP by Th17 cells. Transgenic overexpression of FLIP in T cells protected all three subsets from Fas-mediated apoptosis. These findings provide new knowledge for understanding how survival of different subsets of T cells is regulated. View Publication

Clonal analysis is important for many areas of hematopoietic stem cell research,including in vitro cell expansion,gene therapy,and cancer progression and treatment. A common approach to measure clonality of retrovirally transduced cells is to perform integration site analysis using Southern blotting or polymerase chain reaction-based methods. Although these methods are useful in principle,they generally provide a low-resolution,biased,and incomplete assessment of clonality. To overcome those limitations,we labeled retroviral vectors with random sequence tags or barcodes." On integration� View Publication

Small intestinal CD103(+) dendritic cells (DCs) have the selective ability to promote de novo generation of regulatory T cells via the production of retinoic acid (RA). Considering that aldehyde dehydrogenase (ALDH) activity controls the production of RA,we used a flow cytometry-based assay to measure ALDH activity at the single-cell level and to perform a comprehensive analysis of the RA-producing DC populations present in lymphoid and nonlymphoid mouse tissues. RA-producing DCs were primarily of the tissue-derived,migratory DC subtype and can be readily found in the skin and in the lungs as well as in their corresponding draining lymph nodes. The RA-producing skin-derived DCs were capable of triggering the generation of regulatory T cells,a finding demonstrating that the presence of RA-producing,tolerogenic DCs is not restricted to the intestinal tract as previously thought. Unexpectedly,the production of RA by skin DCs was restricted to CD103(-) DCs,indicating that CD103 expression does not constitute a universal" marker for RA-producing mouse DCs. Finally� View Publication

Although Th17 cells play critical roles in the pathogenesis of many inflammatory and autoimmune diseases,their prevalence among tumor-infiltrating lymphocytes (TILs) and function in human tumor immunity remains largely unknown. We have recently demonstrated high percentages of Th17 cells in TILs from ovarian cancer patients,but the mechanisms of accumulation of these Th17 cells in the tumor microenvironment are still unclear. In this study,we further showed elevated Th17 cell populations in the TILs obtained from melanoma and breast and colon cancers,suggesting that development of tumor-infiltrating CD4(+) Th17 cells may be a general feature in cancer patients. We then demonstrated that tumor microenvironmental RANTES and MCP-1 secreted by tumor cells and tumor-derived fibroblasts mediate the recruitment of Th17 cells. In addition to their recruitment,we found that tumor cells and tumor-derived fibroblasts produce a proinflammatory cytokine milieu as well as provide cell-cell contact engagement that facilitates the generation and expansion of Th17 cells. We also showed that inflammatory TLR and nucleotide oligomerization binding domain 2 signaling promote the attraction and generation of Th17 cells induced by tumor cells and tumor-derived fibroblasts. These results identify Th17 cells as an important component of human TILs,demonstrate mechanisms involved in the recruitment and regulation of Th17 cells in tumor microenvironments,and provide new insights relevant for the development of novel cancer immunotherapeutic approaches. View Publication

Leucocyte function-associated antigen-1 (LFA-1) is known to be involved in immune reactions leading to allograft rejection. The role of deactivating LFA-1 in this context has not been investigated yet,although it is accepted that regulating LFA-1 activity is essential for T-cell function. Expressing LFA-1 locked in an active state in mice (LFA-1(d/d)) allowed us to investigate the in vivo function of LFA-1 deactivation for allograft rejection in a model of heterotopic cardiac transplantation. We provide in vivo evidence that regulating LFA-1 activity from an active to an inactive state controls antigen-specific priming and proliferation of T cells in response to allogeneic stimuli. Consequently,defective LFA-1 deactivation significantly prolonged cardiac allograft survival. Furthermore,reduced numbers of alloantigen-specific T cells and non-allo-specific innate immune cells within allografts of LFA-1(d/d) recipients indicate that expression of active LFA-1 impairs inflammatory responses involving all major leucocyte subpopulations. Taken together,our in vivo data suggest that LFA-1 deactivation is important for the formation of inflammatory lesions and rejection of cardiac allografts. Thus,the dynamic regulation of LFA-1 activity,rather than the mere presence of LFA-1,appears to contribute to the control of immune reactions inducing allogeneic transplant rejection. View Publication

Frequent hallmarks of T-cell acute lymphoblastic leukemia (T-ALL) include aberrant NOTCH signaling and deletion of the CDKN2A locus,which contains 2 closely linked tumor suppressor genes (INK4A and ARF). When bone marrow cells or thymocytes transduced with a vector encoding the constitutively activated intracellular domain of Notch1 (ICN1) are expanded ex vivo under conditions that support T-cell development,cultured progenitors rapidly induce CD4+/CD8+ T-ALLs after infusion into healthy syngeneic mice. Under these conditions,enforced ICN1 expression also drives formation of T-ALLs in unconditioned CD-1 nude mice,bypassing any requirements for thymic maturation. Retention of Arf had relatively modest activity in suppressing the formation of T-ALLs arising from bone marrow-derived ICN1+ progenitors in which the locus is epigenetically silenced,and all resulting Arf (+/+) tumors failed to express the p19(Arf) protein. In striking contrast,retention of Arf in thymocyte-derived ICN1+ donor cells significantly delayed disease onset and suppressed the penetrance of T-ALL. Use of cultured thymocyte-derived donor cells expressing a functionally null Arf-GFP knock-in allele confirmed that ICN1 signaling can induce Arf expression in vivo. Arf activation by ICN1 in T cells thereby provides stage-specific tumor suppression but also a strong selective pressure for deletion of the locus in T-ALL. View Publication

Interleukin 17 (IL-17)-producing CD4(+) helper T cells (T(H)-17 cells) share a developmental relationship with Foxp3(+) regulatory T cells (T(reg) cells). Here we show that a T(H)-17 population differentiates in the thymus in a manner influenced by recognition of self antigen and by the cytokines IL-6 and transforming growth factor-beta (TGF-beta). Like previously described T(H)-17 cells,the T(H)-17 cells that developed in the thymus expressed the transcription factor RORgamma t and the IL-23 receptor. These cells also expressed alpha(4)beta(1) integrins and the chemokine receptor CCR6 and were recruited to the lung,gut and liver. In the liver,these cells secreted IL-22 in response to self antigen and mediated host protection during inflammation. Thus,T(H)-17 cells,like T(reg) cells,can be selected by self antigens in the thymus. View Publication

Because IL-1beta plays an important role in inflammation in human and murine arthritis,we investigated the contribution of the inflammasome components ASC,NALP-3,IPAF,and caspase-1 to inflammatory arthritis. We first studied the phenotype of ASC-deficient and wild-type mice during Ag-induced arthritis (AIA). ASC(-/-) mice showed reduced severity of AIA,decreased levels of synovial IL-1beta,and diminished serum amyloid A levels. In contrast,mice deficient in NALP-3,IPAF,or caspase-1 did not show any alteration of joint inflammation,thus indicating that ASC associated effects on AIA are independent of the classical NALP-3 or IPAF inflammasomes. Because ASC is a ubiquitous cytoplasmic protein that has been implicated in multiple cellular processes,we explored other pathways through which ASC may modulate inflammation. Ag-specific proliferation of lymph node and spleen cells from ASC-deficient mice was significantly decreased in vitro,as was the production of IFN-gamma,whereas IL-10 production was enhanced. TCR ligation by anti-CD3 Abs in the presence or absence of anti-CD28 Abs induced a reduction in T cell proliferation in ASC(-/-) T cells compared with wild-type ones. In vivo lymph node cell proliferation was also significantly decreased in ASC(-/-) mice,but no effects on apoptosis were observed either in vitro or in vivo in these mice. In conclusion,these results strongly suggest that ASC modulates joint inflammation in AIA through its effects on cell-mediated immune responses but not via its implication in inflammasome formation. View Publication

Murine CMV (MCMV) establishes a systemic,low-level persistent infection resulting in the accumulation of CD8(+) T cells specific for a subset of viral epitopes,a process called memory inflation. Although replicating virus is rarely detected in chronically infected C57BL/6 mice,these inflationary cells display a phenotype suggestive of repeated Ag stimulation,and they remain functional. CD4(+) T cells have been implicated in maintaining the function and/or number of CD8(+) T cells in other chronic infections. Moreover,CD4(+) T cells are essential for complete control of MCMV. Thus,we wondered whether CD4(+) T cell deficiency would result in impaired MCMV-specific CD8(+) T cell responses. Here we show that CD4(+) T cell deficiency had an epitope-specific impact on CD8(+) T cell memory inflation. Of the three codominant T cell responses during chronic infection,only accumulation of the late-appearing IE3-specific CD8(+) T cells was substantially impaired in CD4(+) T cell-deficient mice. Moreover,the increased viral activity did not drive increased CD8(+) T cell division or substantial dysfunction in any MCMV-specific population that we studied. These data show that CD4(+) T cell help is needed for inflation of a response that develops only during chronic infection but is otherwise dispensable for the steady state maintenance and function of MCMV-specific CD8(+) T cells. View Publication

To date,studies on T cells in acute myeloid leukemia (AML) have been limited to flow cytometric analysis of whole peripheral blood mononuclear cell (PBMC) specimens or functional work looking at the impact of AML myeloblasts on normal or remission T cells. This lack of information on T cells at the time of presentation with disease is due in part to the difficulty in isolating sufficiently pure T cells from these specimens for further study. Negative immunomagnetic selection has been the method of choice for isolating immune cells for functional studies due to concerns that binding antibodies to the cell surface may induce cellular activation,block ligand-receptor interactions or result in immune clearance. In order specifically to study T cells in presentation AML specimens,we set out to develop a method of isolating highly pure CD4 and CD8 T cells by negative selection from the peripheral blood (PB) of newly diagnosed AML patients. This technique,unlike T cell selection from PB from normal individuals or from patients with chronic lymphocytic leukaemia,was extremely problematic due to properties of the leukaemic myeloblasts. A successful method was eventually optimized requiring the use of a custom antibody cocktail consisting of CD33,CD34,CD123,CD11c and CD36,to deplete myeloblasts. View Publication

The presence of interleukin-2 (IL-2)-producing human immunodeficiency virus type 1 (HIV-1)-specific CD4(+) T-cell responses has been associated with the immunological control of HIV-1 replication; however,the causal relationship between these factors remains unclear. Here we show that IL-2-producing HIV-1-specific CD4(+) T cells can be cloned from acutely HIV-1-infected individuals. Despite the early presence of these cells,each of the individuals in the present study exhibited progressive disease,with one individual showing rapid progression. In this rapid progressor,three IL-2-producing HIV-1 Gag-specific CD4(+) T-cell responses were identified and mapped to the following optimal epitopes: HIVWASRELER,REPRGSDIAGT,and FRDYVDRFYKT. Responses to these epitopes in peripheral blood mononuclear cells were monitored longitudinally to textgreater1 year postinfection,and contemporaneous circulating plasma viruses were sequenced. A variant of the FRDYVDRFYKT epitope sequence,FRDYVDQFYKT,was observed in 1/21 plasma viruses sequenced at 5 months postinfection and 1/10 viruses at 7 months postinfection. This variant failed to stimulate the corresponding CD4(+) T-cell clone and thus constitutes an escape mutant. Responses to each of the three Gag epitopes were rapidly lost,and this loss was accompanied by a loss of antigen-specific cells in the periphery as measured by using an FRDYVDRFYKT-presenting major histocompatibility complex class II tetramer. Highly active antiretroviral therapy was associated with the reemergence of FRDYVDRFYKT-specific cells by tetramer. Thus,our data support that IL-2-producing HIV-1-specific CD4(+) T-cell responses can exert immune pressure during early HIV-1 infection but that the inability of these responses to enforce enduring control of viral replication is related to the deletion and/or dysfunction of HIV-1-specific CD4(+) T cells rather than to the fixation of escape mutations at high frequencies. View Publication