Chimerism, graft survival, and withdrawal of immunosuppressive drugs in HLA matched and mismatched patients after living donor kidney and hematopoietic cell transplantation

Thirty-eight HLA matched and mismatched patients given combined living donor kidney and enriched CD34(+) hematopoietic cell transplants were enrolled in tolerance protocols using posttransplant conditioning with total lymphoid irradiation and anti-thymocyte globulin. Persistent chimerism for at least 6 months was associated with successful complete withdrawal of immunosuppressive drugs in 16 of 22 matched patients without rejection episodes or kidney disease recurrence with up to 5 years follow up thereafter. One patient is in the midst of withdrawal and five are on maintenance drugs. Persistent mixed chimerism was achieved in some haplotype matched patients for at least 12 months by increasing the dose of T cells and CD34(+) cells infused as compared to matched recipients in a dose escalation study. Success of drug withdrawal in chimeric mismatched patients remains to be determined. None of the 38 patients had kidney graft loss or graft versus host disease with up to 14 years of observation. In conclusion, complete immunosuppressive drug withdrawal could be achieved thus far with the tolerance induction regimen in HLA matched patients with uniform long-term graft survival in all patients.

Statin-AE: a novel angiostatin-endostatin fusion protein with enhanced antiangiogenic and antitumor activity

The combination of angiostatin and endostatin has been shown to have synergistic antiangiogenic and antitumor effects when the genes for these proteins are delivered to tumor cells by retroviral gene transfer. Here we report the construction of a murine angiostatin-endostatin fusion gene (Statin-AE) which shows enhanced antiangiogenic activity on human umbilical vein endothelial cell (HUVEC) tube formation in vitro compared with angiostatin or endostatin alone. Similarly, the fusion gene demonstrates antiangiogenic effects in vivo and antitumor activity in a B16F10 melanoma model when co-delivered by retroviral packaging cell inoculation in mice. The fusion gene demonstrates significantly greater inhibition of tumor growth compared with angiostatin, endostatin or the combination of genes.

Idiotype vaccination following ABMT can stimulate specific anti-idiotype immune responses in patients with B-cell lymphoma

Vaccination with the idiotype (Id) protein derived from B-cell malignancies can produce Id-specific immune responses that correlate with improved remission duration and survival rates in patients with follicular non-Hodgkin's lymphoma (NHL). A state of minimal or no residual disease correlates strongly with the laboratory detection of a cellular or humoral immune response. High-dose cytotoxic therapy (HDCT) with autologous stem cell support (autologous bone marrow transplantation [ABMT]) can provide profound cytoreduction of B-cell NHL, but the potential immune suppression associated with myeloablative therapy may compromise a patient's ability to mount a specific immune response. To determine whether patients with NHL could mount detectable immuneresponses following ABMT, Id vaccines were administered at 2 to 12 months following myeloablative therapy to a series of patients with relapsed or resistant B-cell NHL. Two different vaccination strategies produced robust immune responses against KLH in all patients, supporting the capacity of the reconstituted immune system following HDCT to react against a strong antigen. Combining the results from both vaccination strategies, 10 of 12 patients mounted Id-specific humoral or cellular responses. Vaccinations were consistently well tolerated. Of the 12 patients, 7 have experienced prolonged remissions with a follow-up from HDCT ranging from 3 to more than 11 years. Our experience serves to document the ability of the recovering immune system to react against both self and xenotypic antigens and supports the feasibility and safety of antigen-specific vaccination following myeloablative therapy in patients with B-cell NHL.

Dendritic cell-based xenoantigen vaccination for prostate cancer immunotherapy

Many tumor-associated Ags represent tissue differentiation Ags that are poorly immunogenic. Their weak immunogenicity may be due to immune tolerance to self-Ags. Prostatic acid phosphatase (PAP) is just such an Ag that is expressed by both normal and malignant prostate tissue. We have previously demonstrated that PAP can be immunogenic in a rodent model. However, generation of prostate-specific autoimmunity was seen only when a xenogeneic homolog of PAP was used as the immunogen. To explore the potential role of xenoantigen immunization in cancer patients, we performed a phase I clinical trial using dendritic cells pulsed with recombinant mouse PAP as a tumor vaccine. Twenty-one patients with metastatic prostate cancer received two monthly vaccinations of xenoantigen-loaded dendritic cells with minimal treatment-associated side effects. All patients developed T cell immunity to mouse PAP following immunization. Eleven of the 21 patients also developed T cell proliferative responses to the homologous self-Ag. These responses were associated with Ag-specific IFN-gamma and/or TNF-alpha secretion, but not IL-4, consistent with induction of Th1 immunity. Finally, 6 of 21 patients had clinical stabilization of their previously progressing prostate cancer. All six of these patients developed T cell immunity to human PAP following vaccination. These results demonstrate that xenoantigen immunization can break tolerance to a self-Ag in humans, resulting in a clinically significant antitumor effect.

Altered peptide ligand vaccination with Flt3 ligand expanded dendritic cells for tumor immunotherapy

Most tumor-associated antigens represent self-proteins and as a result are poorly immunogenic due to immune tolerance. Here we show that tolerance to carcinoembryonic antigen (CEA), which is overexpressed by the majority of lethal malignancies, can be reversed by immunization with a CEA-derived peptide. This peptide was altered to make it a more potent T cell antigen and loaded onto dendritic cells (DCs) for delivery as a cellular vaccine. Although DCs are rare in the blood, we found that treatment of advanced cancer patients with Flt3 ligand, a hematopoietic growth factor, expanded DCs 20-fold in vivo. Immunization with these antigen-loaded DCs induced CD8 cytotoxic T lymphocytes that recognized tumor cells expressing endogenous CEA. Staining with peptide-MHC tetramers demonstrated the expansion of CD8 T cells that recognize both the native and altered epitopes and possess an effector cytotoxic T lymphocyte phenotype (CD45RA(+)CD27(-)CCR7(-)). After vaccination, two of 12 patients experienced dramatic tumor regression, one patient had a mixed response, and two had stable disease. Clinical response correlated with the expansion of CD8 tetramer(+) T cells, confirming the role of CD8 T cells in this treatment strategy.

Dendritic cell development from common myeloid progenitors

Dendritic cells (DCs) are professional antigen-presenting cells which both initiate adaptive immune responses and control tolerance to self-antigens. It has been suggested that these different effects on responder cells depend on subsets of DCs arising from either myeloid or lymphoid hematopoietic origins. In this model, CD8 alpha+ Mac-1- DCs are supposed to be of lymphoid while CD8 alpha- Mac-1+ DCs are supposed to be of myeloid origin. Here we summarize our findings that both CD8 alpha+ and CD8 alpha- DCs can arise from clonogenic common myeloid progenitors (CMPs) in both thymus and spleen. Therefore CD8 alpha expression DCs does not indicate a lymphoid origin and differences among CD8 alpha+ and CD8 alpha- DCs might rather reflect maturation status than ontogeny. On the basis of transplantation studies, it seems likely that most of the DCs in secondary lymphoid organs and a substantial fraction of thymic DCs are myeloid-derived.

Idiotype vaccination using dendritic cells after autologous peripheral blood progenitor cell transplantation for multiple myeloma

The idiotype (Id) determinants on the multiple myeloma immunoglobulin can serve as tumor-specific antigens. An anti-Id immune response may stem the growth of the malignant clone. We report on 26 patients treated at our institution with high-dose chemotherapy and peripheral blood progenitor cell transplantation (PBPCT) and vaccinated with the Id protein. The patients received chemotherapy and PBPCT to establish a minimal residual disease state. After high-dose therapy, the patients received a series of monthly immunizations consisting of 2 intravenous infusions of dendritic cells (DCs) pulsed with either Id protein or Id coupled with keyhole limpet hemocyanin (KLH) as an immunogenic carrier protein, followed by subcutaneous boosts of Id-KLH conjugates. DCs were obtained in all patients from a leukapheresis product 3 to 9 months after PBPCT. Patients were observed for toxicity, immune responses, and tumor status. The DC infusions and the administration of Id-KLH boosts were well tolerated, with patients experiencing only minor and transient side effects. Of the patients, 24 of 26 generated a KLH-specific cellular proliferative immune response. Only 4 patients developed an Id-specific proliferative immune response. Three of these immune responders were in complete remission at the time of vaccination. A total of 17 patients are alive at a median follow-up of 30 months after transplantation. Id vaccination with autologous DCs is feasible for myeloma patients after transplantation. Id-specific cellular responses can be induced in patients who are in complete remission. Further studies are needed to increase the rate of anti-Id immune responses in patients who do not achieve complete remission.

Dendritic cells injected via different routes induce immunity in cancer patients

Dendritic cells (DC) represent potent APCs that are capable of generating tumor-specific immunity. We performed a pilot clinical trial using Ag-pulsed DC as a tumor vaccine. Twenty-one patients with metastatic prostate cancer received two monthly injections of DC enriched and activated from their PBMC. DC were cocultured ex vivo with recombinant mouse prostatic acid phosphatase as the target neoantigen. Following enrichment, DC developed an activated phenotype with up-regulation of CD80, CD86, and CD83 expression. During culture, the DC maintained their levels of various adhesion molecules, including CD44, LFA-1, cutaneous lymphocyte-associated Ag, and CD49d, up-regulated CCR7, but lost CD62 ligand and CCR5. In the absence of CD62 ligand, such cells would not be expected to prime T cells efficiently if administered i.v. due to their inability to access lymphoid tissue via high endothelial venules. To assess this possibility, three patient cohorts were immunized with Ag-pulsed DC by i.v., intradermal (i.d.), or intralymphatic (i.l.) injection. All patients developed Ag-specific T cell immune responses following immunization, regardless of route. Induction of IFN-gamma production, however, was seen only with i.d. and i.l. routes of administration, and no IL-4 responses were seen regardless of route, consistent with the induction of Th1-type immunity. Five of nine patients who were immunized by the i.v. route developed Ag-specific Abs compared with one of six for i.d. and two of six for i.l. routes. These results suggest that while activated DC can prime T cell immunity regardless of route, the quality of this response and induction of Ag-specific Abs may be affected by the route of administration.

Combination angiostatin and endostatin gene transfer induces synergistic antiangiogenic activity in vitro and antitumor efficacy in leukemia and solid tumors in mice

Angiostatin and endostatin are potent endothelial cell growth inhibitors that have been shown to inhibit angiogenesis in vivo and tumor growth in mice. However, tumor shrinkage requires chronic delivery of large doses of these proteins. Here we report synergistic antitumor activity and survival of animals when these factors are delivered in combination to tumors by retroviral gene transfer. We have demonstrated this efficacy in both murine leukemia and melanoma models. Complete loss of tumorigenicity was seen in 40% of the animals receiving tumors transduced by the combination of angiostatin and endostatin in the leukemia model. The synergy was also demonstrated in vitro on human umbilical vein endothelial cell differentiation and this antiangiogenic activity may suggest a mechanism for the antitumor activity in vivo. These findings imply separate pathways by which angiostatin and endostatin mediate their antiangiogenic effects. Together, these data suggest that a combination of antiangiogenic factors delivered by retroviral gene transfer may produce synergistic antitumor effects in both leukemia and solid tumors, thus avoiding long-term administration of recombinant proteins. The data also suggest that novel combinations of antiangiogenic factors delivered into tumors require further investigation as therapeutic modalities.

Development of CD8alpha-positive dendritic cells from a common myeloid progenitor

Dendritic cells (DCs) are critical in both initiating adaptive immune responses and maintaining tolerance to self antigens. These apparently contradictory roles have been suggested to depend on different subsets of DCs that arise from either myeloid or lymphoid hematopoietic origins, respectively. Although DC expression of CD8alpha is attributed to a lymphoid origin, here we show that both CD8alpha+ and CD8alpha- DCs can arise from clonogenic common myeloid progenitors in both thymus and spleen. Thus, expression of CD8alpha is not indicative of a lymphoid origin, and phenotypic and functional differences among DC subsets are likely to reflect maturation status rather than ontogeny.

Differentiation of myeloid dendritic cells into CD8alpha-positive dendritic cells in vivo

Bone marrow-derived dendritic cells (DC) represent a family of antigen-presenting cells (APC) with varying phenotypes. For example, in mice, CD8alpha(+) and CD8alpha(-) DC are thought to represent cells of lymphoid and myeloid origin, respectively. Langerhans cells (LC) of the epidermis are typical myeloid DC; they do not express CD8alpha, but they do express high levels of myeloid antigens such as CD11b and FcgammaR. By contrast, thymic DC, which derive from a lymphoid-related progenitor, express CD8alpha but only low levels of myeloid antigens. CD8alpha(+) DC are also found in the spleen and lymph nodes (LN), but the origin of these cells has not been determined. By activating and labeling CD8alpha(-) epidermal LC in vivo, it was found that these cells expressed CD8alpha on migration to the draining LN. Similarly, CD8alpha(-) LC generated in vitro from a CD8 wild-type mouse and injected into the skin of a CD8alphaKO mouse expressed CD8alpha when they reached the draining LN. The results also show that CD8alpha(+) LC are potent APC. After migration from skin, they localized in the T-cell areas of LN, secreted high levels of interleukin-12, interferon-gamma, and chemokine-attracting T cells, and they induced antigen-specific T-cell activation. These results demonstrate that myeloid DC in the periphery can express CD8alpha when they migrate to the draining LN. CD8alpha expression on these DC appears to reflect a state of activation, mobilization, or both, rather than lineage. (Blood. 2000;96:1865-1872)

Dendritic cells in cancer immunotherapy

The potential to harness the potency and specificity of the immune system underlies the growing interest in cancer immunotherapy. One such approach uses bone marrow-derived dendritic cells, phenotypically distinct and extremely potent antigen-presenting cells, to present tumor-associated antigens and thereby generate tumor-specific immunity. Support for this strategy comes from animal studies that have demonstrated that dendritic cells, when loaded ex vivo with tumor antigens and administered to tumor-bearing hosts, can elicit T cell-mediated tumor destruction. These observations have led to clinical trials designed to investigate the immunologic and clinical effects of antigen-loaded dendritic cells administered as a therapeutic vaccine to patients with cancer. In the design and conduct of such trials, important considerations include antigen selection, methods for introducing the antigen into MHC class I and II processing pathways, methods for isolating and activating dendritic cells, and route of administration. Although current dendritic cell-based vaccination methods are cumbersome, promising results from clinical trials in patients with malignant lymphoma, melanoma, and prostate cancer suggest that immunotherapeutic strategies that take advantage of the antigen presenting properties of dendritic cells may ultimately prove both efficacious and widely applicable to human tumors.

Clinical transplantation tolerance twelve years after prospective withdrawal of immunosuppressive drugs: studies of chimerism and anti-donor reactivity

BACKGROUND

Previous studies showed the feasibility of inducing transplantation tolerance to cadaveric renal allografts in patients given pretransplant total lymphoid irradiation (TLI). Microchimerism has been theorized to be an important or necessary factor in long-term graft acceptance and tolerance in humans.

METHODS

A cadaveric renal transplant recipient given pretransplant total lymphoid irradiation and withdrawn from immunosuppressive drugs more than 12 years ago was tested for microchimerism using a sensitive nested polymerase chain reaction technique, and for anti-donor reactivity using the mixed leukocyte reaction and an ELISA screen for anti-HLA antibodies. Donor and recipient were mismatched for all HLA-A, B, and DR antigens.

RESULTS

The "tolerant" recipient had good graft function, no detectable donor-type cells in the blood by polymerase chain reaction analysis, vigorous reactivity to donor stimulator cells in the mixed leukocyte reaction, and no detectable serum anti-HLA antibodies.

CONCLUSIONS

Operational tolerance to HLA-A, B, and DR mismatched organ allografts can be induced prospectively in humans for at least 12 years after withdrawal of immunosuppressive drugs. The allograft can be maintained in the absence of detectable donor microchimerism and in the presence of anti-donor reactivity in the mixed leukocyte reaction, suggesting that neither chimerism nor clonal deletion or anergy of recipient T cells to alloantigens presented by donor Class II HLA molecules is required for persistence of the tolerant state using this total lymphoid irradiation protocol.

Adhesion defects of antibody-mediated target cell binding of neonatal natural killer cells

Neonates are unusually susceptible to herpes simplex virus infection, which may be explained in part by defects in killing of herpes simplex virus-infected cells by natural killer (NK) cell cytotoxicity and antibody-dependent cellular cytotoxicity. The mechanism for these defects remains poorly defined. We have for the first time used immunomagnetically enriched NK cells to explore neonatal NK cell phenotype and target cell adhesion. CD56-positive neonatal NK cells had markedly lower CD57 expression, but adult level expression of adhesive glycoproteins (CD18, CD44) and Fc receptor for IgG (CD16). Although the cells conjugated normally with target cells in the absence of antibody, antibody-mediated conjugation was significantly lower than that of NK cells from adults (p < 0.002). These results demonstrate intact adhesion in neonatal NK cell cytotoxicity. In contrast, defective neonatal antibody-dependent cellular cytotoxicity is caused, in part, by an adhesion defect in the presence of antibody.

Induction of immunity to antigens expressed by recombinant adeno-associated virus depends on the route of administration

Recombinant adeno-associated virus (rAAV) is a replication-defective parvovirus which is being explored as a vector for gene therapy because of its broad host range, excellent safety profile, and durable transgene expression in infected hosts. rAAV has also been reported by several groups to induce little or no immune response to its encoded transgene products. In this study we examined the immunogenicity of rAAV by studying the immune response of C57BL/6 mice to a single dose of rAAV-encoding ovalbumin (AAV-Ova) administered by a variety of routes. Mice injected with AAV-Ova intraperitoneally (ip), intravenously, or subcutaneously developed potent ovalbumin-specific cytotoxic T lymphocytes (CTL) as well as anti-ovalbumin antibodies and antibodies to AAV. In contrast, mice injected with AAV-Ova intramuscularly developed a humoral response to the virus and the transgene but minimal ovalbumin-specific CTLs. The induced CTL response after ip administration of AAV-Ova protected mice against a subsequent tumor challenge with an ovalbumin-transfected B16 melanoma cell line. Studies of the mechanism by which AAV-Ova induces CTL confirmed that the virus delivers the transgene product into the classical MHC class I pathway of antigen processing. Mice that previously had been exposed to rAAV vectors failed to develop ovalbumin-specific CTL following administration of AAV-Ova. Analysis of these mice revealed the presence of circulating anti-AAV antibodies that blocked rAAV transduction in vitro and inhibited CTL induction in vivo. These results suggest a possible role for rAAV in the immunotherapy of malignancies and viral infections, although induced antibody responses to AAV may limit its ability to be administered for repeated vaccinations.

Idiotype vaccination using dendritic cells after autologous peripheral blood stem cell transplantation for multiple myeloma--a feasibility study

The idiotype (Id) determinant on the multiple myeloma (MM) protein can be regarded as a tumor-specific marker. Immunotherapy directed at the MM Id may stem the progression of this disease. We report here on the first 12 MM patients treated at our institution with high-dose therapy and peripheral blood stem cell transplantation (PBSCT) followed by Id immunizations. MM patients received PBSCT to eradicate the majority of the disease. PBSCT produced a complete response in 2 patients, a partial response in 9 patients and stable disease in 1 patient. Three to 7 months after high-dose therapy, patients received a series of monthly immunizations that consisted of two intravenous infusions of Id-pulsed autologous dendritic cells (DC) followed by five subcutaneous boosts of Id/keyhole limpet hemocyanin (KLH) administered with adjuvant. Between 1 and 11 x 10(6) DC were obtained by leukapheresis in all patients even after PBSCT. The administration of Id-pulsed DC and Id/KLH vaccines were well tolerated with patients experiencing only minor and transient side effects. Two of 12 patients developed an Id-specific, cellular proliferative immune response and one of three patients studied developed a transient but Id-specific cytotoxic T-cell (CTL) response. Eleven of the 12 patients generated strong KLH-specific cellular proliferative immune responses showing the patients' immunocompetence at the time of vaccination. The two patients who developed a cellular Id-specific immune response remain in complete remission. Of the 12 treated patients, 9 are currently alive after autologous transplantation with a minimum follow-up of 16 months, 2 patients died because of recurrent MM and 1 patient succumbed to acute leukemia. These studies show that patients make strong anti-KLH responses despite recent high-dose therapy and that DC-based Id vaccination is feasible after PBSCT and can induce Id-specific T-cell responses. Further vaccine development is necessary to increase the proportion of patients that make Id-specific immune responses. The clinical benefits of Id vaccination in MM remain to be determined.

Comparison of primary sensitization of naive human T cells to varicella-zoster virus peptides by dendritic cells in vitro with responses elicited in vivo by varicella vaccination

Dendritic cells (DC) are potent APC during primary and secondary immune responses. The first objective of this study was to determine whether human DC mediate in vitro sensitization of naive CD4+ T cells to epitopes of the immediate early 62 (IE62) protein of varicella zoster virus (VZV). The induction of CD4+ T cell proliferative responses to eight synthetic peptides representing amino acid sequences of the VZV IE62 protein was assessed using T cells and DC from VZV-susceptible donors. The second objective was to compare in vitro responses of naive T cells with responses to VZV peptides induced in vivo after immunization with varicella vaccine. T cell proliferation was induced by three peptides, P1, P4, and P7, in 71-100% of the donors tested before and after vaccination using DC as APC. Monocytes were effective APC for VZV peptides only after immunization. Two peptides, P2 and P8, induced naive T cell proliferation less effectively and were also less immunogenic for T cells from vaccinated or naturally immune donors. T cell recognition of specific peptides was concordant between naive, DC-mediated responses, and postvaccine responses using monocytes as APC in 69% of comparisons (p = 0.05; chi2); the predictive value of a positive response to an IE62 peptide before immunization for T cell sensitization in vivo was 82%. These observations indicate that primary T cell responses detected in vitro using DC as APC may be useful to characterize the potential immunogenicity of viral protein epitopes in vivo.

Isolation and utilization of human dendritic cells from peripheral blood to assay an in vitro primary immune response to varicella-zoster virus peptides

A human dendritic cell-based assay used to monitor a T cell proliferation response to viral peptides in vitro is described. Dendritic cells and autologous CD4+ T cells were isolated from peripheral blood by a series of density-gradient centrifugations or magnetic bead separations (or both). Peptides corresponding to residues of the immediate early protein, IE62, of varicella-zoster virus (VZV) were used as stimulating antigens, and persons with no history of varicella and no humoral or cellular immunity to VZV served as naive donors for the assays. Three VZV-susceptible donors were tested, and all demonstrated an in vitro response to multiple VZV peptides. This assay has potential as a screen to establish the immunogenicity of viral antigens in vitro using T cells from naive donors.

Donor blood monocytes but not T or B cells facilitate long-term allograft survival after total lymphoid irradiation

BACKGROUND

Previous studies showed that a combination of posttransplant total lymphoid irradiation (TLI), rabbit antithymocyte globulin (ATG), and a single donor blood transfusion induced tolerance to ACI heart allografts in Lewis rats. All three modalities were required to achieve tolerance. The objective of the current study was to determine the subset(s) of cells in the donor blood that facilitated long-term allograft survival.

METHODS

Lewis hosts received TLI, ATG, and donor cell infusion after heart transplantation. Graft survival, mixed leukocyte reaction (MLR), and intragraft cytokine mRNA were studied.

RESULTS

The intravenous injection of 25 x 10(6) ACI peripheral blood mononuclear cells (PBMC) significantly prolonged graft survival as compared with that of Lewis hosts given TLI and ATG alone. Injection of highly enriched blood T cells or splenic B cells adjusted for the number contained in 25 x 10(6) PBMC failed to induce significant graft prolongation. Unexpectedly, depletion of monocytes (CD11b+ cells) from PBMC resulted in the loss of graft prolongation activity. Enriched populations of monocytes obtained by plastic adherence were more efficient in prolonging graft survival than PBMC on a per cell basis. Hosts with long-term grafts (>100-day survival) showed evidence of immune deviation, because the MLR to ACI stimulator cells was vigorous, but secretion of interferon-gamma in the MLR was markedly reduced. In situ hybridization studies of long-term grafts showed markedly reduced levels of interferon-gamma mRNA as compared with rejecting grafts.

CONCLUSION

Infusion of donor monocytes facilitated graft prolongation via immune deviation.

CTL response to Mycobacterium tuberculosis: identification of an immunogenic epitope in the 19-kDa lipoprotein

The successful resolution of infection with Mycobacterium tuberculosis (M.tb) is believed to involve the induction of CTLs that are capable of killing cells harboring this pathogen, although little information is known about the MHC restriction or fine specificity of such CTLs. In this study, we used knowledge of the HLA-A*0201-binding motif and an immunofluorescence-based peptide-binding assay to screen for potential HLA-A*0201-binding epitopes contained in the 19-kDa lipoprotein of M.tb (M.tb19). CD8+ T cells derived from HLA-A*0201+ patients with active tuberculosis (TB) as well as tuberculin skin test-positive individuals who had no history of TB were used as effector cells to determine whether these epitopes are recognized by in vivo-primed CTLs. An in vitro vaccination system using HLA-A*0201+ dendritic cells (DCs) as APCs was used to determine whether these epitopes can sensitize naive CD8+ T cells in vitro, leading to the generation of Ag-specific CTLs. The results show that an HLA-A*0201-binding peptide comprised of residues 88 to 97 of M.tb19 (P88-97) is recognized by circulating CD8+ CTLs from both healthy tuberculin skin test-positive individuals and patients with active TB but not by tuberculin skin test-negative subjects. Moreover, dendritic cells pulsed with this peptide induced class I MHC-restricted CTLs from the T cells of healthy unsensitized persons. Finally, CTL lines that were specific for P88-97 were shown to lyse autologous monocytes that had been infected acutely with the H37Ra strain of M.tb. These results demonstrate that M.tb19 elicits HLA class I-restricted CTLs in vitro and in vivo that recognize endogenously processed Ag. Epitopes of the type identified here may prove useful in the design of an M.tb vaccine.

V7 (CD101) ligation inhibits TCR/CD3-induced IL-2 production by blocking Ca2+ flux and nuclear factor of activated T cell nuclear translocation

Ligation of the V7 (CD101) molecule on T cells with anti-V7 mAb blocks TCR/CD3-induced proliferation by inhibiting IL-2 transcription. To explore the basis for this observation, we analyzed the effects of V7 ligation on CD3/TCR-induced changes in intracellular free Ca2+ and Ca2+-dependent nuclear factor of activated T cells (NF-AT) translocation to the nucleus, which is required for IL-2 transcription. T cells exposed to anti-V7 mAb fluxed Ca2+ transiently, but did not flux Ca2+ in response to subsequent treatment with anti-CD3; however, they recovered the capacity to flux Ca2+ after treatment with pervanadate, indicating that tyrosine dephosphorylation of a critical V7-related substrate is required in the desensitization process. One such substrate, phospholipase C (PLC)-gamma1, becomes tyrosine phosphorylated on CD3/TCR activation and mediates inositol triphosphate-dependent Ca2+ flux. Co-cross-linking of T cells with anti-CD3 and anti-V7 resulted in selective inhibition of PLC-gamma1 tyrosine phosphorylation, which may explain V7-mediated blockade of anti-CD3-induced Ca2+ flux. Moreover, anti-CD3-induced binding of transcription factors to a consensus NF-AT-binding oligonucleotide, which is dependent on Ca2+, was blocked completely by treatment of the cells with anti-V7, whereas binding to a consensus-activating protein-1 oligonucleotide was unaffected. Western blot analysis of cytoplasmic and nuclear extracts confirmed that anti-V7 prevented nuclear translocation of NF-ATc induced by anti-CD3. We conclude that V7 ligation interferes with T cell activation and IL-2 secretion through a Ca2+ and tyrosine kinase-dependent pathway that inhibits PLC-gamma1 phosphorylation and prevents NF-AT translocation to the nucleus.

Treatment of systemic lupus erythematosus with dehydroepiandrosterone: 50 patients treated up to 12 months

OBJECTIVE

To determine whether longterm therapy (up to 1 year) with the weakly androgenic adrenal steroid dehydroepiandrosterone (DHEA) is feasible and beneficial in patients with mild to moderate systemic lupus erythematosus (SLE).

METHODS

In a prospective, open label, uncontrolled longitudinal study 50 female patients (37 premenopausal, 13 postmenopausal) with mild to moderate SLE were treated with oral DHEA 50-200 mg/day.

RESULTS

DHEA therapy was associated with increases in the serum levels of DHEA, DHEA sulfate, and testosterone and, for those patients who continued DHEA, with decreasing disease activity measured by SLE Disease Activity Index score (p < 0.01), patient global assessment (p < 0.01), and physician global assessment (p < 0.05), compared to baseline. Concurrent prednisone doses were reduced (p < 0.05). These improvements were sustained over the entire treatment period. Thirty-four patients (68%) completed 6 months of treatment and 21 patients (42%) completed 12 months. Mild acneiform dermatitis was the most common adverse event (54%). Pre and postmenopausal women experienced similar efficacy and adverse effects from DHEA.

CONCLUSION

DHEA was well tolerated and appeared clinically beneficial, with the benefits sustained for at least one year in those patients who maintained therapy.

Generation of Primary Peptide-Specific Cd8+ Cytotoxic T-lymphocytes in Vitro using allogeneic dendritic cells

Dendritic ceils (DC) are potent antigen-presenting cells (APC) capable of inducing strong T-cell–mediated immunity. Infusion of lymphoma-specific antigen-loaded autologous DC has been demonstrated to result in the generation of antigen-specific immunity and reduction in tumor burden in B-cell lymphoma patients. Cellular immunotherapy employing antigen-loaded DC could have a potential therapeutic impact in tumors and viral infections, including HIV infection. However, DC in HIV-infected individuals and breast cancer patients are believed to be functionally defective. Therefore, the potential of using allogeneic DC offers significant implications for DC immunotherapy in AIDS and immunocompromised cancer patients. To explore the potential of allogeneic DC therapy in vivo, we tested the ability of allogeneic DC to generate primary peptide-specific CD8+ cytotoxic T-lymphocyte (CTL) responses in vitro. Our results indicate that DC from HLA class I-matched individuals elicit primary immune responses in vitro using viral peptides as naive antigens. A primary peptide-specific immune response could also be detected even when only one HLA allele (HLA-A*0201) was matched between the allogeneic DC and T-lymphocytes. The ability to generate primary peptide-specific responses in vitro is strongly indicative of the in vivo therapeutic potential of allogeneic DC.

Generation of primary peptide-specific CD8+ cytotoxic T-lymphocytes in vitro using allogeneic dendritic cells

Dendritic cells (DC) are potent antigen-presenting cells (APC) capable of inducing strong T-cell-mediated immunity. Infusion of lymphoma-specific antigen-loaded autologous DC has been demonstrated to result in the generation of antigen-specific immunity and reduction in tumor burden in B-cell lymphoma patients. Cellular immunotherapy employing antigen-loaded DC could have a potential therapeutic impact in tumors and viral infections, including HIV infection. However, DC in HIV-infected individuals and breast cancer patients are believed to be functionally defective. Therefore, the potential of using allogeneic DC offers significant implications for DC immunotherapy in AIDS and immunocompromised cancer patients. To explore the potential of allogeneic DC therapy in vivo, we tested the ability of allogeneic DC to generate primary peptide-specific CD8+ cytotoxic T-lymphocyte (CTL) responses in vitro. Our results indicate that DC from HLA class I-matched individuals elicit primary immune responses in vitro using viral peptides as naive antigens. A primary peptide-specific immune response could also be detected even when only one HLA allele (HLA-A*0201) was matched between the allogeneic DC and T-lymphocytes. The ability to generate primary peptide-specific responses in vitro is strongly indicative of the in vivo therapeutic potential of allogeneic DC.

Induction of tissue-specific autoimmune prostatitis with prostatic acid phosphatase immunization: implications for immunotherapy of prostate cancer

Prostatic acid phosphatase (PAP) is uniquely expressed in prostatic tissue and prostate cancer. In this study, the immunogenicity of PAP was investigated in a male rat model. We show that immunization with recombinant rat or human PAP in CFA leads to a significant Ab response, but does not generate CTL or result in autoimmune prostatitis. In contrast, immunization with recombinant vaccinia expressing human PAP, but not rat PAP, generates a CTL response and tissue-specific prostatitis in the absence of detectable PAP-specific Abs. These findings suggest that a cellular immune response to PAP, rather than Abs, mediates destructive autoimmune prostatitis. Thus, xenogeneic forms of PAP are a new tool for the induction of prostate-specific immunity and may prove useful for the immunotherapy of prostate cancer.

Induction of tissue-specific autoimmune prostatitis with prostatic acid phosphatase immunization: implications for immunotherapy of prostate cancer

Prostatic acid phosphatase (PAP) is uniquely expressed in prostatic tissue and prostate cancer. In this study, the immunogenicity of PAP was investigated in a male rat model. We show that immunization with recombinant rat or human PAP in CFA leads to a significant Ab response, but does not generate CTL or result in autoimmune prostatitis. In contrast, immunization with recombinant vaccinia expressing human PAP, but not rat PAP, generates a CTL response and tissue-specific prostatitis in the absence of detectable PAP-specific Abs. These findings suggest that a cellular immune response to PAP, rather than Abs, mediates destructive autoimmune prostatitis. Thus, xenogeneic forms of PAP are a new tool for the induction of prostate-specific immunity and may prove useful for the immunotherapy of prostate cancer.

Introduction of soluble proteins into the MHC class I pathway by conjugation to an HIV tat peptide

Protection against most intracellular pathogens requires T cells that recognize pathogen-derived peptides in association with MHC class I molecules on the surface of infected cells. However, because exogenous proteins do not ordinarily enter the cytosol and access the MHC class I-processing pathway, protein-based vaccines that induce class I-restricted CTL responses have proved difficult to design. We have addressed this problem by conjugating proteins, such as OVA, to a short cationic peptide derived from HIV-1 tat (residues 49-57). When APC were exposed in vitro to such protein conjugates, they processed and presented the peptides in association with MHC class I molecules and stimulated CD8+ Ag-specific T cells. Moreover, Ag-specific CTLs were generated in vivo by immunizing mice with histocompatible dendritic cells that had been exposed to protein-tat conjugates.

Introduction of soluble proteins into the MHC class I pathway by conjugation to an HIV tat peptide

Protection against most intracellular pathogens requires T cells that recognize pathogen-derived peptides in association with MHC class I molecules on the surface of infected cells. However, because exogenous proteins do not ordinarily enter the cytosol and access the MHC class I-processing pathway, protein-based vaccines that induce class I-restricted CTL responses have proved difficult to design. We have addressed this problem by conjugating proteins, such as OVA, to a short cationic peptide derived from HIV-1 tat (residues 49-57). When APC were exposed in vitro to such protein conjugates, they processed and presented the peptides in association with MHC class I molecules and stimulated CD8+ Ag-specific T cells. Moreover, Ag-specific CTLs were generated in vivo by immunizing mice with histocompatible dendritic cells that had been exposed to protein-tat conjugates.

Ligation of the V7 molecule on T cells blocks anergy induction through a CD28-independent mechanism

Previous studies have demonstrated that a mAb that recognizes the leukocyte surface Ag V7 inhibits TCR/CD3-dependent T cell activation. In the current study, we demonstrate that in addition to inhibiting T cell proliferation and IL-2 production, anti-V7 blocks tyrosine phosphorylation of TCR/CD3-associated substrates. PMA overcomes this effect, and both PMA and exogenous IL-2 overcome anti-V7-mediated inhibition of T cell proliferation and IL-2 production. T cells stimulated with anti-CD3 in the absence of CD28 or V7 ligation become unresponsive (anergic) to restimulation with anti-CD3; T cells primed in the presence of either anti-V7 or anti-CD28 retain their ability to respond to restimulation with anti-CD3. When T cells are primed in the presence of optimal concentrations of anti-V7 and anti-CD28 Abs, they proliferate normally, indicating that the costimulatory signals generated through CD28 dominate the inhibitory signals generated through V7. However, as the anti-CD28 stimulus is diluted, the V7 effect becomes dominant and proliferation is inhibited. Thus, although both anti-V7 and anti-CD28 Abs prevent anergy, they induce distinct, competing intracellular signals. Wortmannin, which blocks phosphoinositol 3-kinase-dependent signaling, has little effect on V7-mediated inhibition, while herbimycin, an inhibitor of tyrosine kinase, synergizes with anti-V7 to inhibit T cell activation. On the basis of these findings, V7-mediated signals appear to inhibit TCR-dependent tyrosine kinases that are required for IL-2 production and cellular proliferation.

Ligation of the V7 molecule on T cells blocks anergy induction through a CD28-independent mechanism

Previous studies have demonstrated that a mAb that recognizes the leukocyte surface Ag V7 inhibits TCR/CD3-dependent T cell activation. In the current study, we demonstrate that in addition to inhibiting T cell proliferation and IL-2 production, anti-V7 blocks tyrosine phosphorylation of TCR/CD3-associated substrates. PMA overcomes this effect, and both PMA and exogenous IL-2 overcome anti-V7-mediated inhibition of T cell proliferation and IL-2 production. T cells stimulated with anti-CD3 in the absence of CD28 or V7 ligation become unresponsive (anergic) to restimulation with anti-CD3; T cells primed in the presence of either anti-V7 or anti-CD28 retain their ability to respond to restimulation with anti-CD3. When T cells are primed in the presence of optimal concentrations of anti-V7 and anti-CD28 Abs, they proliferate normally, indicating that the costimulatory signals generated through CD28 dominate the inhibitory signals generated through V7. However, as the anti-CD28 stimulus is diluted, the V7 effect becomes dominant and proliferation is inhibited. Thus, although both anti-V7 and anti-CD28 Abs prevent anergy, they induce distinct, competing intracellular signals. Wortmannin, which blocks phosphoinositol 3-kinase-dependent signaling, has little effect on V7-mediated inhibition, while herbimycin, an inhibitor of tyrosine kinase, synergizes with anti-V7 to inhibit T cell activation. On the basis of these findings, V7-mediated signals appear to inhibit TCR-dependent tyrosine kinases that are required for IL-2 production and cellular proliferation.

Differential response of CD4+ V7+ and CD4+ V7- T cells to T cell receptor-dependent signals: CD4+ V7+ T cells are co-stimulation independent and anti-V7 antibody blocks the induction of anergy by bacterial superantigen

V7 is a novel cell surface glycoprotein that is expressed on 25% of circulating T lymphocytes. This molecule appears to play a critical role in T cell activation based on the observation that a monoclonal anti-V7 antibody inhibits T cell receptor (TCR)-dependent interleukin-2 (IL-2) production and proliferation of T cells. In the current study, CD4+ V7+ and CD4+ V7- T cells were separated from one another and their response to various stimuli analyzed. Although there were only minor differences between the two subsets in the expression of activation/differentiation markers, including CD45RA and R0 isotypes, when exposed to immobilized anti-CD3 or anti-TCR antibodies in the absence of APC, CD4+ V7+ T cells alone produced IL-2 and proliferated vigorously. By contrast, CD4+ V7- cells responded poorly to such stimuli, but they recovered their capacity to respond if antigen-presenting cells (APC) or anti-CD28-antibody were added to the cultures. The enhancement of the V7- T cell response by APC appears to be related to augmentation of TCR signals because the effect could be blocked by antibodies against molecules on APC [major histocompatibility (MHC) class II, CD86] that are known to up-regulate such signals through their interaction with counter-receptors on T cells. To assess the role of V7 in a system independent of co-stimulation, CD4+ T cells were stimulated with the bacterial superantigens, staphylococcal enterotoxins A and B. The cells responded by proliferating and then becoming anergic. Addition of anti-V7 antibody at the initiation of culture with superantigen did not inhibit cellular proliferation but prevented T cells from becoming anergic, while addition of anti-CD28 antibody had no effect on either proliferation or anergy induction. These results indicate that V7 and CD28 mediate distinct intracellular signals and suggest that V7 functions to preserve T cell reactivity whether the stimulus is mitogenic or anergizing.

Dendritic cells that process and present nominal antigens to naive T lymphocytes are derived from CD2+ precursors

Dendritic cells (DC) are potent APC that, in mature form, can be distinguished from other mononuclear cells on the basis of their distinct morphology, absence of lineage markers, and dense expression of MHC and costimulatory molecules. While comparing different DC preparation methods, we observed that DC derived from cultured PBMC that had been depleted of CD2+ cells before culture were functionally distinct from DC derived from PBMC that had not been depleted of CD2+ cells. Thus, both types of DC stimulated allogeneic T cells to proliferate in the MLR, but only DC derived from CD2+ precursors could sensitize naive T cells to soluble Ags such as keyhole limpet hemocyanin and HIV gp160 glycoprotein. Subsequent studies confirmed the existence of CD2+ and CD2- DC precursor populations among HLA-DRbright, lineage-negative PBMC. Immediately after their isolation, these populations were morphologically similar to one another by light and electron microscopy, and neither had substantial Ag-presenting activity. After culture for 24 to 48 h with supernatant from PHA-activated PBMC, both populations developed dendrites, formed clusters with T cells, and stimulated allogeneic T cell responses in the MLR as well as autologous T cell responses to tetanus toxoid, a recall Ag. However, CD2+ DC precursors alone gave rise to APC that presented soluble Ags to naive CD4+ T cells, a property that could be inhibited by Abs to CD4, CD11a, and CD28 on T cells or CD86 on DC. The expression of CD54 and CD86 on CD2+ DC precursors was increased markedly after their culture and differentiation, while the expression of these molecules on CD2- DC precursors was not remarkably changed. These findings reveal the existence of two functionally distinct populations of DC, each derived from a phenotypically distinct precursor present in monocyte-depleted peripheral blood.

Dendritic cells that process and present nominal antigens to naive T lymphocytes are derived from CD2+ precursors

Dendritic cells (DC) are potent APC that, in mature form, can be distinguished from other mononuclear cells on the basis of their distinct morphology, absence of lineage markers, and dense expression of MHC and costimulatory molecules. While comparing different DC preparation methods, we observed that DC derived from cultured PBMC that had been depleted of CD2+ cells before culture were functionally distinct from DC derived from PBMC that had not been depleted of CD2+ cells. Thus, both types of DC stimulated allogeneic T cells to proliferate in the MLR, but only DC derived from CD2+ precursors could sensitize naive T cells to soluble Ags such as keyhole limpet hemocyanin and HIV gp160 glycoprotein. Subsequent studies confirmed the existence of CD2+ and CD2- DC precursor populations among HLA-DRbright, lineage-negative PBMC. Immediately after their isolation, these populations were morphologically similar to one another by light and electron microscopy, and neither had substantial Ag-presenting activity. After culture for 24 to 48 h with supernatant from PHA-activated PBMC, both populations developed dendrites, formed clusters with T cells, and stimulated allogeneic T cell responses in the MLR as well as autologous T cell responses to tetanus toxoid, a recall Ag. However, CD2+ DC precursors alone gave rise to APC that presented soluble Ags to naive CD4+ T cells, a property that could be inhibited by Abs to CD4, CD11a, and CD28 on T cells or CD86 on DC. The expression of CD54 and CD86 on CD2+ DC precursors was increased markedly after their culture and differentiation, while the expression of these molecules on CD2- DC precursors was not remarkably changed. These findings reveal the existence of two functionally distinct populations of DC, each derived from a phenotypically distinct precursor present in monocyte-depleted peripheral blood.

Dendritic cells: potential role in cancer therapy

Dendritic cells (DC) are extremely potent antigen presenting cells, uniquely capable of sensitizing naive T cells to protein antigens and eliciting antigen specific immune responses. Studies of human DC isolated from peripheral blood indicate that these cells can be used to stimulate and expand antigen specific CD4+ and CD8+ T cells, in vitro. On the basis of these findings we have initiated pilot clinical studies to investigate the ability of DC pulsed ex vivo with tumor associated proteins to stimulate host anti-tumor immunity when re-infused as a vaccine. In the first such study DC pulsed with tumor derived idiotype protein were infused into patients with low grade malignant B cell lymphoma who had failed conventional chemotherapy. The majority of treated patients developed T cell mediated anti-idiotype immune responses and some of the patients experienced tumor regression. These results suggest that DC based immunotherapy is a potentially useful approach to B cell lymphoma and raises the possibility that the approach may prove useful in the treatment of other tumors as well.

Allogeneic dendritic cell induction of HIV-specific cytotoxic T lymphocyte responses from T cells of HIV type 1-infected and uninfected individuals

The potential benefit of T cell-based vaccination for HIV-1 infection remains to be determined. Cytotoxic T lymphocytes (CTLs) appear to clear substantial populations of HIV-1 virus in vivo, although CTL activity may contribute to the decline in CD4+ T cell count observed in the course of the disease. To investigate further the role of specific CTL responses in the control of HIV-1 replication, we raised primary CTL lines against a panel of conserved HIV-1 epitopes using blood-derived dendritic cells as antigen-presenting cells (APCs). Specific primary human CTL responses were induced against HLA-A*0201-restricted peptides with dendritic cells from HIV-1-seronegative donors. This method of immunization elicited cytotoxic activities capable of recognizing endogenously processed antigen. The CTL induction protocol was extended in order to explore the capacity of HLA-matched allogeneic dendritic cells to evoke novel CTL responses in T cells from an HIV-seropositive asymptomatic individual. Allogeneic peptide-pulsed dendritic cells from a healthy sibling were capable of eliciting a CTL response directed against an HIV epitope (env814: SLLNATDIAV) that was initially not detected in the CTL effector population of the HIV-1-infected patient. The possibility of manipulating CTL specificity directed against multiple conserved HIV-1 epitopes represents a significant step in the evaluation of T cell-based vaccination for treatment of disease.

Role of natural killer cells in the generation of influenza virus-specific cytotoxic T cells

Recently we reported that natural killer (NK) cells are critical accessory cells required for the differentiation of alloantigen-stimulated CD8+ T cells into effector cytotoxic T lymphocytes (CTL) in vitro. In this study we provide evidence that NK cells are also required for the generation of influenza virus-specific CTL. Depletion of NK cells from responder human peripheral blood mononuclear cells or mouse splenocytes abolished the induction of influenza A virus-specific CTL under culture conditions. Treatment of C57BL/6 mice with the NK cell-depleting NK1.1 monoclonal antibody (mAb) before primary or secondary immunization with influenza A virus abrogated the capacity of CTL precursors to differentiate into influenza virus-specific CTL effectors in vivo. These results extend our previous findings and demonstrate that NK cells critically influence the induction of antigen-specific CTL, both in vitro and in vivo.

B4B, a novel growth-arrest gene, is expressed by a subset of progenitor/pre-B lymphocytes negative for cytoplasmic mu-chain

We subjected PBMC of normal adults to density fractionation to enrich for an immunoblast fraction that would include early immune lineage precursors. Differential display PCR experiments identified one transcript that is expressed specifically in this immunoblast fraction. This cDNA, designated B4B, encodes a novel gene product containing four putative transmembrane-spanning domains. B4B+ cells, detected with anti-B4B Ig, were found at very low frequency in PBMC (0.01%) and were enriched significantly in intermediate density fractions (0.1-1.0%). B4B+ cells were shown to be CD19+CD45+HLA-DR+ and negative for CD20, cytoplasmic mu-chain, CD3, CD16, CD56, CD34, and CD68 (monocyte), consistent with a progenitor/pre-B lymphocyte subset that does not express cytoplasmic mu-chain and thus may lack productive Ig rearrangement. This phenotypic description of the B4B+ subset agrees with our finding that the frequency of B4B+ cells was greatly increased in bone marrow (3-10%) as compared with PBMC (0.01%). The B4B polypeptide sequence exhibits significant homology to only one known protein, PMP-22/gas-3, a Schwann cell-specific protein that induces cell growth arrest. Transient expression of B4B specifically inhibited cellular proliferation by more than 50%. Based on its antiproliferative effect and pattern of expression restricted to a subpopulation of immature B cells, the B4B gene product may be involved in the elimination of B cells before productive VDJC rearrangement of Ig loci or, alternatively, in the growth arrest of transformed progenitor B cells.

B4B, a novel growth-arrest gene, is expressed by a subset of progenitor/pre-B lymphocytes negative for cytoplasmic mu-chain

We subjected PBMC of normal adults to density fractionation to enrich for an immunoblast fraction that would include early immune lineage precursors. Differential display PCR experiments identified one transcript that is expressed specifically in this immunoblast fraction. This cDNA, designated B4B, encodes a novel gene product containing four putative transmembrane-spanning domains. B4B+ cells, detected with anti-B4B Ig, were found at very low frequency in PBMC (0.01%) and were enriched significantly in intermediate density fractions (0.1-1.0%). B4B+ cells were shown to be CD19+CD45+HLA-DR+ and negative for CD20, cytoplasmic mu-chain, CD3, CD16, CD56, CD34, and CD68 (monocyte), consistent with a progenitor/pre-B lymphocyte subset that does not express cytoplasmic mu-chain and thus may lack productive Ig rearrangement. This phenotypic description of the B4B+ subset agrees with our finding that the frequency of B4B+ cells was greatly increased in bone marrow (3-10%) as compared with PBMC (0.01%). The B4B polypeptide sequence exhibits significant homology to only one known protein, PMP-22/gas-3, a Schwann cell-specific protein that induces cell growth arrest. Transient expression of B4B specifically inhibited cellular proliferation by more than 50%. Based on its antiproliferative effect and pattern of expression restricted to a subpopulation of immature B cells, the B4B gene product may be involved in the elimination of B cells before productive VDJC rearrangement of Ig loci or, alternatively, in the growth arrest of transformed progenitor B cells.

Vaccination of patients with B-cell lymphoma using autologous antigen-pulsed dendritic cells

In this pilot study, we investigated the ability of autologous dendritic cells pulsed ex vivo with tumor-specific idiotype protein to stimulate host antitumor immunity when infused as a vaccine. Four patients with follicular B-cell lymphoma received a series of three or four infusions of antigen-pulsed dendritic cells followed, in each instance, by subcutaneous injections of soluble antigen two weeks later. All patients developed measurable antitumor cellular immune responses. In addition, clinical responses have been measured with one patient experiencing complete tumor regression, a second patient having partial tumor regression, and a third patient resolving all evidence of disease as detected by a sensitive tumor-specific molecular analysis.

Dehydroepiandrosterone in systemic lupus erythematosus. Results of a double-blind, placebo-controlled, randomized clinical trial

OBJECTIVE

To determine if dehydroepiandrosterone (DHEA) is beneficial in the treatment of systemic lupus erythematosus (SLE).

METHODS

In a double-blind, placebo-controlled, randomized trial, 28 female patients with mild to moderate SLE were given DHEA 200 mg/day or placebo for 3 months. Outcomes included the SLE Disease Activity Index (SLEDAI) score, patient's and physician's overall assessments of disease activity, and concurrent corticosteroid dosages (which were adjusted as clinically indicated).

RESULTS

In the patients who were receiving DHEA, the SLEDAI score, patient's and physician's overall assessment of disease activity, and concurrent prednisone dosage decreased, while in the patients taking placebo, small increases were seen. The difference in patient's assessment between the groups was statistically significant (P = 0.022, adjusted). Lupus flares occurred more frequently in the placebo group (P = 0.053). Mild acne was a frequent side effect of DHEA.

CONCLUSION

DHEA may be useful as a therapeutic agent for the treatment of mild to moderate SLE. Further studies of DHEA in the treatment of SLE are warranted.

Inhibition of antigen-presenting cell function by alendronate in vitro

Bisphosphonates are potent inhibitors of bone resorption in vivo and are emerging as important and widely used drugs for the treatment of a variety of abnormal bone resorptive processes. In the current study we investigated the in vitro effects of 4-amino-1-hydroxybutylidene-1,1-bisphosphonate (alendronate), a recently developed, extremely potent bisphosphonate, on the immune functions of human peripheral blood mononuclear cells (PBMCs). PBMC proliferation induced by lectins, alloantigens, and a nominal antigen (tetanus toxoid) was inhibited in a dose-dependent manner by alendronate. Pretreatment of monocytes, but not T cells, with the compound at concentrations ranging from 10(-4) to 10(-8) M was inhibitory, indicating that alendronate acts selectively on antigen-presenting cells (APCs). Alendronate did not affect the viability of monocytes or T cells or the expression of cell surface molecules known to play critical roles in antigen presentation. Alendronate exhibited dose-dependent inhibition of the production of interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) by activated monocytes. The inhibitory effect of 10(-6) M alendronate on PBMC proliferation was reversed by 10 U/ml recombinant rIL-1 beta, whereas other cytokines such as IL-6, TNF-alpha, and granulocyte-macrophage colony-stimulating factor (GM-CSF) had no effect. Thus, alendronate acts on monocytes to inhibit their antigen-presenting/accessory cell functions through a mechanism that can be overcome by exogenous IL-1. The inhibitory effect of this agent on cytokine production may contribute to its inhibitory effect on bone resorption.

Requirement for natural killer cells in the induction of cytotoxic T cells

Cell-mediated immunity involves the participation of both regulatory and cytotoxic cells. The conversion of precursors to effector CD8+ cytotoxic T (Tc) cells requires cell-cell collaboration in which CD4+ T cells are traditionally viewed as helper cells. An in vitro system was used here to demonstrate that the generation of human alloantigen-specific CD8+ Tc cells requires the participation of CD3-CD16+CD56+ NK cells but not CD4+ T helper cells. Depletion of NK cells from responders abolished the induction of alloantigen-specific Tc cells in mixed lymphocyte cultures (MLC). Purified CD5+CD8+ T cells stimulated with alloantigen proliferated but did not differentiate into fully functional effector Tc cells. Coculture of responder CD5+CD8+ T cells with NK cells promoted the conversion of CD8+ Tc cell precursors (pTc) into effector Tc cells. Anti-CD56 mAbs blocked Tc cell induction in MLC, suggesting a role for CD56 molecules expressed on NK cells in either alloantigen recognition or delivery of accessory signals to pTc cells. These findings suggest a novel critical link between the natural and specific immune responses.

Requirement for natural killer cells in the induction of cytotoxic T cells

Cell-mediated immunity involves the participation of both regulatory and cytotoxic cells. The conversion of precursors to effector CD8+ cytotoxic T (Tc) cells requires cell-cell collaboration in which CD4+ T cells are traditionally viewed as helper cells. An in vitro system was used here to demonstrate that the generation of human alloantigen-specific CD8+ Tc cells requires the participation of CD3-CD16+CD56+ NK cells but not CD4+ T helper cells. Depletion of NK cells from responders abolished the induction of alloantigen-specific Tc cells in mixed lymphocyte cultures (MLC). Purified CD5+CD8+ T cells stimulated with alloantigen proliferated but did not differentiate into fully functional effector Tc cells. Coculture of responder CD5+CD8+ T cells with NK cells promoted the conversion of CD8+ Tc cell precursors (pTc) into effector Tc cells. Anti-CD56 mAbs blocked Tc cell induction in MLC, suggesting a role for CD56 molecules expressed on NK cells in either alloantigen recognition or delivery of accessory signals to pTc cells. These findings suggest a novel critical link between the natural and specific immune responses.

Role of B70/B7-2 in CD4+ T-cell immune responses induced by dendritic cells

Dendritic cells (DC) are potent antigen-presenting cells (APC). However, the molecular basis underlying this activity remains incompletely understood. To address this question, we generated murine monoclonal antibodies (mAb) against human peripheral blood-derived DC. One such antibody, designated IT209, stained differentiated DC and adherent monocytes, but failed to stain freshly isolated peripheral blood mononuclear cells (PBMC). The antigen recognized by IT209 was identified as B70 (B7-2; also recently identified as CD86). Using this mAb we studied the role of B70 in CD4+ T-cell activation by DC in vitro. IT209 partly inhibited the proliferative response of CD4+ T cells to allogeneic DC and to recall antigens, such as tetanus toxoid (TT) and purified protein derivative (PPD) of tuberculin, presented by autologous DC. More importantly, the mAb had a potent inhibitory effect on the primary response of CD4+ T cells to autologous DC pulsed with human immunodeficiency virus (HIV) gp160 or keyhole limpet haemocyanin (KLH). Adherent monocytes, despite their expression of B70, failed to induce T-cell responses to these antigens. IT209-mediated inhibition of CD4+ T-cell responses was equivalent to that produced by anti-CD25 mAb, whereas an anti-CD80 mAb was only marginally inhibitory and did not augment the effect of IT209. These findings indicate that the B70 antigen plays an important role in DC-dependent CD4+ T-cell activation, particularly in the induction of primary CD4+ T-cell responses to soluble antigens. However, since activated monocytes, despite their expression of B70, failed to prime naive T cells to these antigens, our results suggest that additional molecules contribute to the functions of DC in CD4+ T-cell activation.

V7, a novel leukocyte surface protein that participates in T cell activation. I. Tissue distribution and functional studies

Among a panel of mouse mAbs generated to a human T cell clone, one mAb, V7.1, inhibited T cell activation in the mixed lymphocyte reaction and was studied further. V7.1 reacted strongly with Ag-specific T cell clones, in addition to freshly isolated monocytes and granulocytes. However, the mAb reacted weakly with freshly isolated PBLs (T cells, B cells, and NK cells), T cells stimulated with phytohemagglutinin, or Con A, and did not stain the vast majority of transformed cell lines of hemopoietic origin. Stimulation of T cells with anti-CD3, or the combination of anti-CD3 and PMA, or anti-CD3, PMA and ionomycin, markedly increased V7.1 surface staining. The mAb precipitated a single polypeptide chain of approximately 135 kDa from alloactivated T cells or monocytes, which was reduced to approximately 110 kDa after treatment with N-glycanase. The proliferative response of T cells to allogeneic monocytes or B lymphoblastoid cells was inhibited by V7.1, and inhibition was maximal when the mAb was present at the initiation of culture. V7.1 also exhibited dose-dependent inhibition of the T cell response to immobilized anti-CD3 Ab in the absence of APCs, indicating that the inhibitory effect of this Ab occurs at the T cell level. Expression of CD25 (IL-2R) on anti-CD3-activated T cells and secretion of IL-2 induced with anti-CD3 and PMA were inhibited by V7.1, whereas the Ab had no effect on T cell proliferation induced by PHA or Con A or on T cell-mediated cytotoxicity. These results indicate that V7.1 recognizes a novel leukocyte surface glycoprotein, designated V7, that is up-regulated on Ag but not lectin-activated T cells, and appears to play a role in TCR/CD3-dependent T cell activation. In an accompanying study, the gene encoding the V7 Ag is described and the molecule is shown to be a novel member of the Ig superfamily.

Generation of antigen-specific CD4+ T cell lines from naive precursors

The conditions required for sensitizing naive T cells to nominal antigen are poorly understood. In this report we describe an in vitro system for generating antigen-specific CD4+ T cells from previously unprimed individuals. Freshly isolated CD4+ T cells were cultured with keyhole limpet hemocyanin (KLH), sperm whale myoglobin (SWM), or human immunodeficiency virus (HIV) gp160, antigens to which most persons have not been sensitized, in the presence of either dendritic cells (DC) or macrophages (M phi). In short-term (< 8 days) cultures, CD4+ T cells or their CD4+, CD45RA (naive) subpopulation mounted significant proliferative responses to KLH, SWM, and HIV gp160, but only if the antigens were presented by DC. In contrast, CD4+, CD45RO (memory) T cells responded poorly to these antigens, although they responded vigorously to tetanus toxoid, a recall antigen, presented by either DC or M phi. KLH- and SWM-specific CD4+ T cell lines were established from the starting population that had been sensitized in vitro, following repeated stimulation with antigen and M phi in medium supplemented with interleukin-2 and interleukin-4. Despite the continued presence of these cytokines during T cell expansion, the expanded lines retained their ability to respond to the priming antigen in the absence of exogenous cytokines. When the CD45RA and CD45RO subpopulations were sensitized and expanded separately, the CD45RA cells alone gave rise to antigen-specific T cell lines, while the CD45RO cells proliferated nonspecifically. These results demonstrate that human naive CD4+ T cells can be sensitized in vitro to nominal antigens presented by DC and that the sensitized cells can be expanded into long-term lines that retain their antigen specificity.