Acquired cancer resistance to combination immunotherapy from transcriptional loss of class I HLA

Understanding mechanisms of late/acquired cancer immunotherapy resistance is critical to improve outcomes; cellular immunotherapy trials offer a means to probe complex tumor-immune interfaces through defined T cell/antigen interactions. We treated two patients with metastatic Merkel cell carcinoma with autologous Merkel cell polyomavirus specific CD8+ T cells and immune-checkpoint inhibitors. In both cases, dramatic remissions were associated with dense infiltration of activated CD8+s into the regressing tumors. However, late relapses developed at 22 and 18 months, respectively. Here we report single cell RNA sequencing identified dynamic transcriptional suppression of the specific HLA genes presenting the targeted viral epitope in the resistant tumor as a consequence of intense CD8-mediated immunologic pressure; this is distinguished from genetic HLA-loss by its reversibility with drugs. Transcriptional suppression of Class I loci may underlie resistance to other immunotherapies, including checkpoint inhibitors, and have implications for the design of improved immunotherapy treatments.

Transferred WT1-reactive CD8+ T cells can mediate antileukemic activity and persist in post-transplant patients

Relapse remains a leading cause of death after allogeneic hematopoietic cell transplantation (HCT) for patients with high-risk leukemias. The potentially beneficial donor T cell-mediated graft-versus-leukemia (GVL) effect is often mitigated by concurrent graft-versus-host disease (GVHD). Providing T cells that can selectively target Wilms tumor antigen 1 (WT1), a transcription factor overexpressed in leukemias that contributes to the malignant phenotype, represents an opportunity to promote antileukemic activity without inducing GVHD. HLA-A*0201-restricted WT1-specific donor-derived CD8 cytotoxic T cell (CTL) clones were administered after HCT to 11 relapsed or high-risk leukemia patients without evidence of on-target toxicity. The last four treated patients received CTL clones generated with exposure to interleukin-21 (IL-21) to prolong in vivo CTL survival, because IL-21 can limit terminal differentiation of antigen-specific T cells generated in vitro. Transferred cells exhibited direct evidence of antileukemic activity in two patients: a transient response in one patient with advanced progressive disease and the induction of a prolonged remission in a patient with minimal residual disease (MRD). Additionally, three treated patients at high risk for relapse after HCT survive without leukemia relapse, GVHD, or additional antileukemic treatment. CTLs generated in the presence of IL-21, which were transferred in these latter three patients and the patient with MRD, all remained detectable long-term and maintained or acquired in vivo phenotypic and functional characteristics associated with long-lived memory CD8 T cells. This study supports expanding efforts to immunologically target WT1 and provides insights into the requirements necessary to establish potent persistent T cell responses.

Genetic modification of T cell clones to improve the safety and efficacy of adoptive T cell therapy

Our laboratory has developed methods to isolate human antigen-specific cytolytic CD8+ T cell clones and to expand such clones in vitro to numbers sufficient for T cell therapy of human diseases. Studies in immunocompromised bone marrow transplant patients at high risk for disease associated with cytomegalovirus have demonstrated that administration of more than 10(9) CD8+ T cell clones is safe and can effectively reconstitute a deficient human immune response. Our laboratory is applying this strategy of adoptive therapy to the treatment of human cancer, starting with the subset of patients with Hodgkin's disease who show expression of proteins encoded by the Epstein-Barr virus in their malignant Reed-Sternberg cells. The development of efficient systems such as retroviral vectors for the introduction of genes into primary cells has made it possible to consider overcoming some of the limitations of the effector T cells that normally mediate response to an antigen. Our laboratory is attempting to modify T cell clones by the introduction of genes before transfer as a means to improve the safety and/or efficacy of T cell therapy.

Engineering T cell receptors for potential therapeutic applications (48.28)

Using T cell receptors (TCRs) for potential therapeutic applications provides an opportunity to target an expanded array of antigens, compared to those now targeted with monoclonal antibodies. Relative to antibodies, TCRs typically exhibit reduced solubility and lower affinity, properties that hamper their production and efficacy. To improve these parameters, we have developed strategies using yeast display engineering. Several different TCRs were cloned as single chain (sc) TCRs and VαCα/VβCβ heterodimers, as each of these display scaffolds has unique advantages for engineering and potential applications. Display of scTCRs, unlike that of scFv fragments, required mutagenesis and selection. Analysis of a collection of mutants revealed distinct regions of the scTCR that require mutations to allow yeast surface display, as well as solubility of purified protein. Although the sc format has several potential advantages such as increased tissue penetration, mutagenesis and selection of displayed mutants can present a technical challenge. To overcome this obstacle, we have recently explored the role of the C domains in driving heterodimer association. In addition, we have developed mutagenic strategies to improve the association of engineered, full λετ γη α and β chains.

Supported by grants from NIH.

Decline in haemoglobin A1c values in diabetic patients receiving interferon-alpha and ribavirin for chronic hepatitis C

Haemoglobin A1c (A1c) levels are lower during haemolysis because of the shorter exposure of haemoglobin (Hb) to plasma glucose. Ribavirin (RBV) used in combination with interferon-alpha (IFN) for chronic hepatitis C causes reversible haemolytic anaemia. This study examined the extent to which RBV treatment influences A1c levels in diabetic patients. A retrospective analysis identified 32 diabetic patients who underwent hepatitis C treatment with IFN and RBV. Each subject had at least three measures of A1c, Hb and glucose: before, during and after therapy. A1c values decreased from a mean pretreatment level of 7.2% to an on-treatment A1c level of 5.2% [mean paired difference -2.01%; 95% confidence interval (CI) -1.59% to -2.43%; P < 0.001]. During therapy, mean Hb levels decreased from 15.1 g/dL at baseline to a nadir of 11.7 g/dL (P < 0.001) with a rise in lactose dehydrogenase levels and reticulocyte counts, and unchanged mean corpuscular volume values confirming haemolysis. At the same time, glucose levels declined by a mean of 38.4 mg/dL (95% CI 13.4-63.5 mg/dL; P = 0.002) as did body weights by a mean of 3.15 kg (P < 0.001). According to published glucose-A1c correlation tables, this decline of glucose concentration by 38.4 mg/dL correlates to a decline in A1c level of 1.08%. In conclusion, reductions of A1c levels by a mean of 2.01% during hepatitis C therapy with IFN + RBV are due to a combination of decreased glucose levels (1.08%) and RBV-induced haemolysis (0.93%). A1c levels should not be measured during hepatitis C treatment with IFN + RBV because they do not adequately reflect glycaemic control.

Development of a novel strategy for engineering high-affinity proteins by yeast display

Yeast display provides a system for engineering high-affinity proteins using a fluorescent-labeled ligand and fluorescence-activated cell sorting (FACS). In cases where it is difficult to obtain purified ligands, or to access FACS instrumentation, an alternative selection strategy would be useful. Here we show that yeast expressing high-affinity proteins against a mammalian cell surface ligand could be rapidly selected by density centrifugation. Yeast cell-mammalian cell conjugates were retained at the density interface, separated from unbound yeast. High-affinity T cell receptors (TCRs) displayed on yeast were isolated using antigen presenting cells that expressed TCR ligands, peptides bound to products of the major histocompatibility complex (MHC). The procedure yielded 1000-fold enrichments, in a single centrifugation, of yeast displaying high-affinity TCRs. We defined the affinity limits of the method and isolated high-affinity TCR mutants against peptide variants that differed by only a single residue. The approach was applied to TCRs specific for class I or class II MHC, an important finding since peptide-class II MHC ligands have been particularly difficult to purify. As yeast display has also been used previously to identify antigen-specific antibodies, the method should be applicable to the selection of antibodies, as well as TCRs, with high-affinity for tumor cell-surface antigens.

Multigene DNA priming-boosting vaccines protect macaques from acute CD4+-T-cell depletion after simian-human immunodeficiency virus SHIV89.6P mucosal challenge

We evaluated four priming-boosting vaccine regimens for the highly pathogenic simian human immunodeficiency virus SHIV89.6P in Macaca nemestrina. Each regimen included gene gun delivery of a DNA vaccine expressing all SHIV89.6 genes plus Env gp160 of SHIV89.6P. Additional components were two recombinant vaccinia viruses, expressing SHIV89.6 Gag-Pol or Env gp160, and inactivated SHIV89.6 virus. We compared (i) DNA priming/DNA boosting, (ii) DNA priming/inactivated virus boosting, (iii) DNA priming/vaccinia virus boosting, and (iv) vaccinia virus priming/DNA boosting versus sham vaccines in groups of 6 macaques. Prechallenge antibody responses to Env and Gag were strongest in the groups that received vaccinia virus priming or boosting. Cellular immunity to SHIV89.6 peptides was measured by enzyme-linked immunospot assay; strong responses to Gag and Env were found in 9 of 12 vaccinia virus vaccinees and 1 of 6 DNA-primed/inactivated-virus-boosted animals. Vaccinated macaques were challenged intrarectally with 50 50% animal infectious doses of SHIV89.6P 3 weeks after the last immunization. All animals became infected. Five of six DNA-vaccinated and 5 of 6 DNA-primed/particle-boosted animals, as well as all 6 controls, experienced severe CD4(+)-T-cell loss in the first 3 weeks after infection. In contrast, DNA priming/vaccinia virus boosting and vaccinia virus priming/DNA boosting vaccines both protected animals from disease: 11 of 12 macaques had no loss of CD4(+) T cells or moderate declines. Virus loads in plasma at the set point were significantly lower in vaccinia virus-primed/DNA-boosted animals versus controls (P = 0.03). We conclude that multigene vaccines delivered by a combination of vaccinia virus and gene gun-delivered DNA were effective against SHIV89.6P viral challenge in M. nemestrina.

Adoptive T cell therapy using antigen-specific CD8+ T cell clones for the treatment of patients with metastatic melanoma: in vivo persistence, migration, and antitumor effect of transferred T cells

Adoptive T cell therapy, involving the ex vivo selection and expansion of antigen-specific T cell clones, provides a means of augmenting antigen-specific immunity without the in vivo constraints that can accompany vaccine-based strategies. A phase I study was performed to evaluate the safety, in vivo persistence, and efficacy of adoptively transferred CD8+ T cell clones targeting the tumor-associated antigens, MART1MelanA and gp100 for the treatment of patients with metastatic melanoma. Four infusions of autologous T cell clones were administered, the first without IL-2 and subsequent infusions with low-dose IL-2 (at 0.25, 0.50, and 1.0 x 10(6) unitsm(2) twice daily for the second, third, and fourth infusions, respectively). Forty-three infusions of MART1MelanA-specific or gp100-specific CD8+ T cell clones were administered to 10 patients. No serious toxicity was observed. We demonstrate that the adoptively transferred T cell clones persist in vivo in response to low-dose IL-2, preferentially localize to tumor sites and mediate an antigen-specific immune response characterized by the elimination of antigen-positive tumor cells, regression of individual metastases, and minor, mixed or stable responses in 8 of 10 patients with refractory, metastatic disease for up to 21 mo.

Viral dynamics of early HIV infection in neonatal macaques after oral exposure to HIV-2287: an animal model with implications for maternal-neonatal HIV transmission

A model of vertical HIV transmission was developed using oral HIV-2(287) exposure of newborn Macaca nemestrina. The minimal Animal Infectious Dose for this oral route was found to be 10-fold higher than that for atraumatic viral transmission across other mucosal membranes (vaginal/rectal) of juvenile macaques. However, once infection was established, viral replication was rapid and plasma viremia could be detected by reverse-transcriptase polymerase chain reaction and viral co-culture within 1 week following exposure. No animal was resistant to infection and all macaques initially exposed to a subinfectious viral inoculum were subsequently infected by re-exposure of mucosal membranes. Higher viral load during primary infection correlated with a more rapid CD4 depletion; however, all HIV-2(287)-infected animals developed CD4 depletion during the observation period. This animal model can now be used to study early viral replication in the presence and absence of anti-retroviral agents to help identify conditions to reduce vertical HIV transmission in human newborns.

Induction of potent human immunodeficiency virus type 1-specific T-cell-restricted immunity by genetically modified dendritic cells

A novel technology combining replication- and integration-defective human immunodeficiency virus type 1 (HIV-1) vectors with genetically modified dendritic cells was developed in order to induce T-cell immunity. We introduced the vector into dendritic cells as a plasmid DNA using polyethylenimine as the gene delivery system, thereby circumventing the problem of obtaining viral vector expression in the absence of integration. Genetically modified dendritic cells (GMDC) presented viral epitopes efficiently, secreted interleukin 12, and primed both CD4(+) and CD8(+) HIV-specific T cells capable of producing gamma interferon and exerting potent HIV-1-specific cytotoxicity in vitro. In nonhuman primates, subcutaneously injected GMDC migrated into the draining lymph node at an unprecedentedly high rate and expressed the plasmid DNA. The animals presented a vigorous HIV-specific effector cytotoxic-T-lymphocyte (CTL) response as early as 3 weeks after a single immunization, which later developed into a memory CTL response. Interestingly, antibodies did not accompany these CTL responses, indicating that GMDC can induce a pure Th1 type of immune response. Successful induction of a broad and long-lasting HIV-specific cellular immunity is expected to control virus replication in infected individuals.

A Transcriptional Block in the IL-2 Promoter at the −150 AP-1 Site in Effector CD8+T Cells

Both CD4+ and CD8+ T cells that produce IL-2 in response to Ag recognition have been isolated. However, most effector CD8+ T cells recovered after exposure to Ag do not produce sufficient IL-2 to sustain growth, and depend on CD4+ T helper cells for this obligate growth factor. IL-2 expression in CD4+ T cells is primarily controlled at the level of transcription, but mechanisms restricting IL-2 production in CD8+ T cells have not been elucidated. To evaluate transcriptional regulation of the IL-2 gene in CD8+ T cells, we stably transfected reporter genes into Ag-specific CD8+ T cell clones. CD28+ CD8(+) T cells unable to transcribe the IL-2 gene in response to antigenic stimulation had a block in transactivation of the -150 CD28 response element (CD28RE)/AP-1 site of the IL-2 promoter, but did transactivate the composite NFAT/AP-1 and OCT/AP-1 sites, and a consensus AP-1 motif. Mutation of the nonconsensus -150 AP-1 site to a consensus AP-1 site, or insertion of a CD28RE/AP-1 consensus site upstream of the native -150 CD28RE/AP-1 site restored transactivation of the altered promoter. These results suggest that the defect at the -150 site may reflect the absence or inactivity of a required factor rather than repression of the IL-2 promoter.

Severe babesiosis in Long Island: review of 34 cases and their complications

Thirty-four consecutive patients were hospitalized with diagnosis of severe Babesia infection over the course of 13 years. The average time from onset of symptoms to diagnosis was 15 days. When compared with uninfected febrile control patients, affected patients complained significantly more often of malaise, arthralgias and myalgias, and shortness of breath (P<.05), and they more often had thrombocytopenia and abnormal liver function (P<.05). Forty-one percent of patients with Babesia developed complications such as acute respiratory failure, disseminated intravascular coagulation, congestive heart failure, and renal failure. Analysis of data revealed that complicated babesiosis was more commonly associated with the presence of severe anemia (hemoglobin level <10 g/dL; P=.01) and higher parasitemia levels (>10%; P=.08). Patients were treated with a combination of drugs that included clindamycin, quinine, atovaquone, or azithromycin. Despite treatment, parasitemia persisted for an average of 8.5 days (range, 3--21 days). Exchange transfusion was performed for 7 patients, and it effectively reduced the high levels of parasitemia. Three patients died. Improved outcomes may result with prompt recognition and treatment of babesiosis.

Targeting antigen in mature dendritic cells for simultaneous stimulation of CD4+ and CD8+ T cells

Due to their potent immunostimulatory capacity, dendritic cells (DC) have become the centerpiece of many vaccine regimens. Immature DC (DCimm) capture, process, and present Ags to CD4(+) lymphocytes, which reciprocally activate DCimm through CD40, and the resulting mature DC (DCmat) loose phagocytic capacity, but acquire the ability to efficiently stimulate CD8(+) lymphocytes. Recombinant vaccinia viruses (rVV) provide a rapid, easy, and efficient method to introduce Ags into DC, but we observed that rVV infection of DCimm results in blockade of DC maturation in response to all activation signals, including CD40L, monocyte-conditioned medium, LPS, TNF-alpha, and poly(I:C), and failure to induce a CD8(+) response. By contrast, DCmat can be infected with rVV and induce a CD8(+) response, but, having lost phagocytic activity, fail to process the Ag via the exogenous class II pathway. To overcome these limitations, we used the CMV protein pp65 as a model Ag and designed a gene containing the lysosomal-associated membrane protein 1 targeting sequence (Sig-pp65-LAMP1) to target pp65 to the class II compartment. DCmat infected with rVV-Sig-pp65-LAMP1 induced proliferation of pp65-specific CD4(+) clones and efficiently induced a pp65-specific CD4(+) response, suggesting that after DC maturation the intracellular processing machinery for class II remains intact for at least 16 h. Moreover, infection of DCmat with rVV-Sig-pp65-LAMP1 resulted in at least equivalent presentation to CD8(+) cells as infection with rVV-pp65. These results demonstrate that despite rVV interference with DCimm maturation, a single targeting vector can deliver Ags to DCmat for the effective simultaneous stimulation of both CD4(+) and CD8(+) cells.

In vivo tracking of tumor-specific T cells

Novel immunologic assays now enable visualization of the antigen-specific response to an extent not previously possible. Assessment of not only the numeric frequency but also the functional properties of individual tumor-specific T cells in the endogenous and manipulated immune response has provided insights that will facilitate the development of immunotherapeutic strategies.

Expression of a tolerizing tumor antigen in peripheral tissue does not preclude recovery of high-affinity CD8+ T cells or CTL immunotherapy of tumors expressing the antigen

Transgenic (TG) mice were generated selectively expressing the gag protein of Friend murine leukemia virus (FMuLV) in the liver. FMuLV(gag) is also expressed by the FBL leukemia, and is the immunodominant tumor Ag of the CD8(+) T cell response in C57BL/6 mice. gag-TG mice expressing FMuLV(gag) in the liver were tolerant to the protein and failed to generate a CTL response to either FBL or FMuLV(gag). This tolerance reflected anergy rather than deletion, as CTL responsiveness could be recovered after four cycles of in vitro stimulation. Adoptively transferred gag-specific T cells were not anergized in gag-TG recipients, as revealed by antitumor activity in vivo. Also, such T cells did not induce detectable autoimmune injury in gag-TG liver cells. These results suggest that the requirements for a tissue Ag to provide a tolerizing stimulus are distinct from those for being the target of a T cell-mediated autoimmune response and that the requirements for induction and maintenance of peripheral tolerance are distinct for naive and primed T cells. That anergic T cells reactive with tumor-associated Ags can be recovered by repetitive in vitro stimulation and can mediate tumor therapy suggests strategies that use such Ags to generate CTL for adoptive immunotherapy should be further developed.

Nonmyeloablative immunosuppressive regimen prolongs In vivo persistence of gene-modified autologous T cells in a nonhuman primate model

The in vivo persistence of gene-modified cells can be limited by host immune responses to transgene-encoded proteins. In this study we evaluated in a nonhuman primate model whether the administration of a nonmyeloablative regimen consisting of low-dose total-body irradiation with 200 cGy followed by immunosuppression with mycophenolate mofetil and cyclosporin A for 28 and 35 days, respectively, could be used to facilitate persistence of autologous gene-modified T cells when a transgene-specific immune response had already been established or to induce long-lasting tolerance in unprimed recipients. Two macaques (Macaca nemestrina) received infusions of T cells transduced to express either the enhanced green fluorescent protein and neomycin phosphotransferase genes or the hygromycin phosphotransferase and herpes simplex virus thymidine kinase genes. In the absence of immunosuppression, both macaques developed potent class I major histocompatibility complex-restricted CD8(+) cytotoxic T-lymphocyte (CTL) responses that rapidly eliminated the gene-modified T cells and that persisted long term as memory CTL. Treatment with the nonmyeloablative regimen failed to abrogate preexisting memory CTL responses but interfered with the induction of transgene-specific CTL and facilitated in vivo persistence of gene-modified cells in an unprimed host. However, sustained tolerance to gene-modified T cells was not achieved with this regimen, indicating that further modifications will be required to permit sustained persistence of gene-modified T cells.

Transfer of specificity for human immunodeficiency virus type 1 into primary human T lymphocytes by introduction of T-cell receptor genes

The introduction of genes encoding T-cell receptor (TCR) chains specific for human immunodeficiency virus into T cells of infected patients represents a means to quantitatively and qualitatively improve immunity to the virus. Our results demonstrate that the high level of TCR expression required for physiologic functioning can be reproducibly achieved with retroviral vectors encoding full-length unmodified TCR chains under the control of a strong internal constitutive phosphoglycerate kinase promoter.

Expression of herpes simplex virus ICP47 and human cytomegalovirus US11 prevents recognition of transgene products by CD8(+) cytotoxic T lymphocytes

The in vivo persistence of gene-modified cells may be limited by the development of a host immune response to vector-encoded proteins. Herpesviruses evade cytotoxic T-lymphocyte (CTL) recognition by expressing genes which interfere selectively with presentation of viral antigens by class I major histocompatibility complex (MHC) molecules. Here, we studied the use of retroviral vectors encoding herpes simplex virus ICP47, human cytomegalovirus (HCMV) US3, or HCMV US11 to decrease presentation of viral proteins and transgene products to CD8(+) CTL. Human fibroblasts and T cells transduced to express the ICP47, US3, or US11 genes alone exhibited a decrease in cell surface class I MHC expression. The combination of ICP47 and US11 rendered fibroblasts negative for surface class I MHC and allowed a class I MHC-low population of T cells to be sorted by flow cytometry. Fibroblasts and T cells expressing both ICP47 and US11 were protected from CTL-mediated lysis and failed to stimulate specific memory T-cell responses to transgene products in vitro. Our findings suggest that expression of immunoregulatory viral gene products could be a potential strategy to prolong transgene expression in vivo.

A prospective multicenter evaluation of new fecal occult blood tests in patients undergoing colonoscopy

OBJECTIVE

Guaiac-based fecal occult blood (FOB) tests, in particular, Hemoccult II (HO), are commonly used to detect colorectal neoplasia. Because the sensitivity and specificity of these tests are critical to cost-effective screening programs, we aimed to investigate the improved performance characteristics of new FOB tests for known colonic lesions.

METHODS

Nine centers worldwide performed FOB testing with guaiac-based tests (Hemoccult II [HO] and Hemoccult II SENSA [SENSA]) and immunochemical tests (HemeSelect [HS] and FlexSure OBT [FS]) on 554 patients referred for colonoscopy for predetermined indications. A combination testing strategy consisting of SENSA followed by HS or FS (which was considered positive only when both tests were positive) was also evaluated. Results of FOB tests were compared to findings on colonoscopy.

RESULTS

Cancers were identified in 2.9% of subjects, whereas adenomas > or =10 mm were found in 39 patients. Small adenomas, colitis, and other lesions were identified in 141 patients. The positivity rate of HO for adenomas > or =10 mm was less than for SENSA (20.5% vs 35.9%, p < 0.05), whereas the positivity rate of HO, SENSA, FS, HS, or the combination tests for cancers was not statistically different. The overall positivity rates were significantly greater for FS (15.9%, p = 0.0002) and significantly lower using the combination tests (SENSA/FS 6.0%, p = 0.01; SENSA/HS 6.2%, p = 0.02) compared to HO (9.4%). In this study population, the relative specificity (i.e., true-negative tests/true-negatives + false-positives in patients without adenomas > or =10 mm or cancers) of HO (93.9%; 95% CI, 91.7-96.1) was similar to that of SENSA (92.8%; 95% CI, 90.4-95.2) and HS (90.1%; 95% CI, 87.4-92.8), and greater than FS (88.0%; 95% CI, 85.1-90.9, p < 0.001). When considering adenomas > or =10 mm, cancers alone or cancers and adenomas combined, the combination test using SENSA/FS was associated with significantly fewer false-positive tests than any of the individual tests.

CONCLUSIONS

Compared to single tests, the combination test with the highly sensitive SENSA and an immunochemical test had slightly reduced sensitivity but significantly fewer false-positive tests than any single test. These data raise the possibility that a combination test (i.e., highly sensitive guaiac plus immunochemical) could reduce the costs of screening for colon cancer, and suggest that further study of combination test strategies is warranted.

HIV-specific cytotoxic T lymphocytes traffic to lymph nodes and localize at sites of HIV replication and cell death

We have tracked the in vivo migration and have identified in vivo correlates of cytotoxic T-lymphocyte (CTL) activity in HIV-seropositive subjects infused with autologous gene-marked CD8(+) HIV-specific CTL. The number of circulating gene-marked CTL ranged from 1.6 to 3.5% shortly after infusion to less than 0.5% 2 weeks later. Gene-marked CTL were present in the lymph node at 4.5- to 11-fold excess and colocalized within parafollicular regions of the lymph node adjacent to cells expressing HIV tat fusion transcripts, a correlate of virus replication. The CTL clones expressed the CCR5 receptor and localized among HIV-infected cells expressing the ligands MIP-1alpha and MIP-1beta, CC-chemokines produced at sites of virus replication. Aggregates of apoptotic cells and cells expressing granzyme-B localized within these same sites. In contrast, lymph node sections from untreated HIV-seropositive subjects, all with significant viral burden (> 50,000 HIV RNA copies/mL plasma), showed no CC-chemokine expression and exhibited only sporadic and randomly distributed cells expressing granzymes and/or apoptotic cells. These studies show that the infused CTL specifically migrate to sites of HIV replication and retain their antigen-specific cytolytic potential. Moreover, these studies provide a methodology that will facilitate studies of both the magnitude and functional phenotype of Ag-specific CD8(+) T cells in vivo.

T-cell therapy of cytomegalovirus and human immunodeficiency virus infection

Acute and persistent virus infections are limited by the development and maintenance of host T-cell responses to viral antigens. Individuals with congenital or acquired immunodeficiencies are at risk of progressive and often life-threatening infection. Recent studies have provided insight into the nature of protective T-cell responses to viruses and advances in T-cell culture technology have made it possible to evaluate the adoptive transfer of T-cell clones of defined antigen specificity and function to restore deficient responses in immunocompromised hosts. The progress of these studies in cytomegalovirus and human immunodeficiency virus infection is the subject of this review.

The IL-2 receptor promotes lymphocyte proliferation and induction of the c-myc, bcl-2, and bcl-x genes through the trans-activation domain of Stat5

Studies assessing the role of Stat5 in the IL-2 proliferative signal have produced contradictory, and thus inconclusive, results. One factor confounding many of these studies is the ability of IL-2R to deliver redundant mitogenic signals from different cytoplasmic tyrosines on the IL-2R beta-chain (IL-2Rbeta). Therefore, to assess the role of Stat5 in mitogenic signaling independent of any redundant signals, all cytoplasmic tyrosines were deleted from IL-2Rbeta except for Tyr510, the most potent Stat5-activating site. This deletion mutant retained the ability to induce Stat5 activation and proliferation in the T cell line CTLL-2 and the pro-B cell line BA/F3. A set of point mutations at or near Tyr510 that variably compromised Stat5 activation also compromised the proliferative signal and revealed a quantitative correlation between the magnitude of Stat5 activation and proliferation. Proliferative signaling by a receptor mutant with a weak Stat5 activating site could be rescued by overexpression of wt Stat5a or b. Additionally, the ability of this receptor mutant to induce c-myc, bcl-x, and bcl-2 was enhanced by overexpression of wt Stat5. By contrast, overexpression of a version of Stat5a lacking the C-terminal trans-activation domain inhibited the induction of these genes and cell proliferation. Thus, Stat5 is a critical component of the proliferative signal from Tyr510 of the IL-2R and regulates expression of both mitogenic and survival genes through its trans-activation domain.

The human UTY gene encodes a novel HLA-B8-restricted H-Y antigen

The mammalian Y chromosome encodes male-specific minor histocompatibility (H-Y) Ags that are recognized by female T cells in an MHC-restricted manner. Two human H-Y epitopes presented by HLA-A2 and HLA-B7, respectively, have been identified previously and both are derived from the SMCY gene. We previously isolated CD8+ CTL clones that recognized a male-specific minor histocompatibility Ag presented by HLA-B8. In contrast to the SMCY-encoded H-Y epitopes, the B8/H-Y Ag was not presented by fibroblasts from male donors, suggesting that it was encoded by a novel gene. We now report that the HLA-B8-restricted H-Y epitope is defined by the octameric peptide LPHNHTDL corresponding to aa residues 566-573 of the human UTY protein. Transcription of the UTY gene is detected in a wide range of human tissues, but presentation of the UTY-derived H-Y epitope to CTL by cultured human cells shows significant cell-type specificity. Identification of this CTL-defined H-Y epitope should facilitate analysis of its contribution to graft/host interactions following sex-mismatched organ and bone marrow transplantation.

Relationship of low-dose aspirin to GI injury and occult bleeding: a pilot study

BACKGROUND

Low-dose aspirin is commonly used in patients with cardiovascular disease. However, little is known about the effect of aspirin on occult blood loss caused by gastrointestinal injury. Therefore, we studied endoscopic injury and fecal occult blood loss in patients ingesting different quantities of low-dose aspirin.

METHODS

Forty healthy volunteers were enrolled in a randomized, double-blind, prospective, pilot endoscopic study. Each volunteer underwent 30 days of treatment with daily aspirin 30 mg, 81 mg, 325 mg, or placebo. Subjects completed fecal occult blood test cards before and at the end of treatment of two types: guaiac impregnated (Hemoccult and Hemoccult SENSA) and immunochemical (HemeSelect and FlexSure OBT). Each volunteer underwent upper endoscopy at baseline and after completing 30 days of study medication.

RESULTS

Aspirin did not induce significant injury as determined by endoscopy when compared with placebo. Six of 30 volunteers taking aspirin developed erosions, whereas 1 of 10 subjects on placebo developed a new erosion (p = 0.66). Aspirin (325 mg) was associated with a higher mean symptom score than the lower aspirin dosages and the placebo group (p = 0.12). Only one subject taking aspirin (325 mg) had fecal occult blood on a single HemeSelect card. No subject had a positive fecal occult blood test with Hemoccult II, Hemoccult II SENSA, or FlexSure OBT cards.

CONCLUSIONS

Aspirin in dosages commonly used for cardiovascular prophylaxis does not generally cause significant gastric or duodenal mucosal endoscopic lesions. In the absence of frank ulceration, low-dose aspirin does not result in positive fecal occult blood tests. Low-dose aspirin should not interfere with fecal occult blood testing and probably should not be stopped during stool collection.

Lack of effect of treatment for Helicobacter pylori on symptoms of nonulcer dyspepsia

BACKGROUND

Prior studies have yielded conflicting results on whether or not Helicobacter pylori causes nonulcer dyspepsia.

PATIENTS AND METHODS

We enrolled 100 consecutive patients with nonulcer dyspepsia into a randomized, double-blind, placebo-controlled trial. Patients with peptic ulcer disease, esophagitis, hepatobiliary disease, irritable bowel disease, or predominantly reflux-related symptoms were excluded by history and upper endoscopy. Helicobacter pylori infection was determined by biopsy and histologic examination. Serum H. pylori IgG antibodies and CagA status were determined by Western blot. Enrolled patients were randomized to a 14-day regimen of omeprazole (20 mg twice daily) and clarithromycin (500 mg three times daily) or placebo. Dyspeptic symptoms were assessed by use of a visual analog scale at baseline and at 1, 3, 6, and 12 months after treatment. Follow-up upper endoscopy with biopsy was performed 4 weeks after treatment. Compliance was measured by tablet counts.

RESULTS

At 1 year, the change in dyspeptic symptoms was -24.0 (95% confidence interval, -69.0 to 21.0) in the omeprazole and clarithromycin group and -24.2 in the placebo group (95% confidence interval, -70.0 to 21.6). Furthermore, patients with persistent H. pylori infection demonstrated a greater, but not significant, improvement in symptoms (-40 +/- 144 [mean +/- SD], -65 +/- 142, -45 +/- 138, and -39 +/- 163) than those with successful eradication (-26 +/- 126, -26 +/- 148, -12 +/- 126, and -25 +/- 151) at months 1, 3, 6, and 12, respectively.

CONCLUSION

Patients with nonulcer dyspepsia should not routinely be treated for H. pylori, since it is not a cause of this condition in most patients.

Expression of chimeric granulocyte-macrophage colony-stimulating factor/interleukin 2 receptors in human cytotoxic T lymphocyte clones results in granulocyte-macrophage colony-stimulating factor-dependent growth

Adoptive immunotherapy with ex vivo-expanded antigen-specific cytotoxic T lymphocytes (CTLs) has been shown to clear viral infections and eliminate tumors in murine models. Clinical trials have also reported promising data for the use of adoptive immunotherapy to treat cytomegalovirus (CMV) and Epstein-Barr viral (EBV) infections in bone marrow transplant recipients. For these indications, the need for ex vivo-expanded CTLs is often short lived, until the immune system is reconstituted by the donor transplant. In chronic disease settings, increased longevity of adoptively transferred CTLs and generation of memory will be necessary. The additional administration of helper functions normally supplied by antigen-specific T helper (Th) cells will probably be essential for long-term survival of adoptively transferred CTLs. Toward this goal of supplying helper functions, we transduced human CTLs with chimeric GM-CSFR/IL-2R receptors that deliver an IL-2 signal on binding GM-CSF. Clones expressing the chimeric receptors proliferated in response to GM-CSF. Stimulation with antigen induced GM-CSF production and resulted in an autocrine growth loop such that the CTL clones proliferated in the absence of exogenous cytokines. This type of genetic modification has potential for increasing the circulating half-life and, by extension, the efficacy of ex vivo-expanded CTLs.

Antigen-specific cytokine responses in vaccinated Macaca nemestrina

We describe a new surrogate assay for CD8 + T lymphocyte activity that has the capability of discriminating between cytotoxic T lymphocyte (CTL) activity and cytokine-mediated suppressive activity. We applied this approach to two groups of Macaca nemestrina vaccinated with a minimally pathogenic strain of human immunodeficiency virus type 2 [HIV-2 (HIV-2(KR))] as a model of an attenuated virus vaccine. Group 1 was then inoculated with a non-infectious stock of a pathogenic strain, HIV-2287. Both groups 1 and 2 were subsequently challenged with an infectious stock of HIV-2287. Five out of six group 1 animals were protected against CD4 decline, whereas three out of six animals in group 2 were protected. Analysis of CTL responses demonstrated strong activity against HIV-2(KR)-Gag in group 1. It was determined that strong CTL responses correlate with antigen-specific T-helper (Th) type 1 responses. This antigen-specific cytokine assay has the potential to better elucidate the functional mechanisms of CD8 + T-cell-mediated protection than traditional methods to date.

Deficient cellular immunity--finding and fixing the defects

The critical role of cellular immunity in resistance to infectious diseases is glaringly revealed by life-threatening infections if T cell function is disrupted by an inherited or acquired immunodeficiency. Although treatment has historically focused on infectious complications, understanding of the cellular and molecular basis of immunodeficiency and technologies useful for enhancing cellular immunity have both been rapidly evolving. A new era of molecular and cellular therapy is emerging as approaches to correct abnormal genes, the loss of T cell subpopulations, and aberrant T cell homeostasis make the transition from bench to bedside.

CD8(+) minor histocompatibility antigen-specific cytotoxic T lymphocyte clones eliminate human acute myeloid leukemia stem cells

Effective immunotherapy for human leukemia based on infusions of T lymphocytes requires the identification of effector T cells that target the leukemic stem cell. The transplantation of human acute myeloid leukemia into nonobese diabetic/severe combined immune deficient (SCID) mice has identified a rare leukemic progenitor termed the SCID leukemia-initiating cell, which is present in low frequency in the leukemic population and is essential for establishing leukemic hematopoiesis. Thus, this transplant model may be ideally suited to identify effector T cells with antileukemic activity. We report that CD8(+) cytotoxic T lymphocyte (CTL) clones specific for minor histocompatibility antigens inhibit the engraftment of human acute myeloid leukemia cells in nonobese diabetic/SCID mice and demonstrate that this inhibition is mediated by direct CTL recognition of SCID leukemia-initiating cells. These results indicate that CD8(+) minor histocompatibility antigen-specific CTL may be mediators of the graft-versus-leukemia effect associated with allogeneic hematopoietic cell transplantation and provide an experimental model to identify and select T cell clones for immunotherapy to prevent or treat relapse after allogeneic hematopoietic cell transplantation.

The antiviral activity of HIV-specific CD8+ CTL clones is limited by elimination due to encounter with HIV-infected targets

Adoptive immunotherapy of virus infection with viral-specific CTL has shown promise in animal models and human virus infections and is being evaluated as a therapy for established HIV-1 infection. Defining the individual obstacles for success is difficult in human trials. We have therefore examined the localization, persistence, and antiviral activity of HIV-1 gag-specific CTL clones in both HIV-1-infected and uninfected haplotype-matched human (hu)-PBL-SCID mice. Injection of gag-specific clones but not control CTL into HIV-1-infected hosts reduced plasma viremia by >10-fold but failed to eliminate the virus infection from most treated animals. The failure to eradicate virus did not reflect selection of escape variants because the gag epitope remained unmutated in virus isolates obtained after CTL therapy. Injection of carboxyfluorescein diacetate succinimide ester-labeled CTL demonstrated markedly different fates for gag-specific CTL in the presence or absence of HIV-1 infection. HIV-1-specific CTL rapidly disappeared in infected recipients, whereas they were maintained at high numbers in uninfected mice. By contrast, control CTL were long lived in both infected and uninfected recipients. Thus, interaction of CTL with virus-infected target cells in vivo leads not only to target destruction but also to the rapid disappearance of the infused CTL, and it limits the capacity of CTL therapy to eliminate HIV-1 infection.

Characterization of circulating T cells specific for tumor-associated antigens in melanoma patients

We identified circulating CD8+ T-cell populations specific for the tumor-associated antigens (TAAs) MART-1 (27-35) or tyrosinase (368-376) in six of eleven patients with metastatic melanoma using peptide/HLA-A*0201 tetramers. These TAA-specific populations were of two phenotypically distinct types: one, typical for memory/effector T cells; the other, a previously undescribed phenotype expressing both naive and effector cell markers. This latter type represented more than 2% of the total CD8+ T cells in one patient, permitting detailed phenotypic and functional analysis. Although these cells have many of the hallmarks of effector T cells, they were functionally unresponsive, unable to directly lyse melanoma target cells or produce cytokines in response to mitogens. In contrast, CD8+ T cells from the same patient were able to lyse EBV-pulsed target cells and showed robust allogeneic responses. Thus, the clonally expanded TAA-specific population seems to have been selectively rendered anergic in vivo. Peptide stimulation of the TAA-specific T-cell populations in other patients failed to induce substantial upregulation of CD69 expression, indicating that these cells may also have functional defects, leading to blunted activation responses. These data demonstrate that systemic TAA-specific T-cell responses can develop de novo in cancer patients, but that antigen-specific unresponsiveness may explain why such cells are unable to control tumor growth.

Isolation of high avidity melanoma-reactive CTL from heterogeneous populations using peptide-MHC tetramers

Immunogenic peptides of human tumor Ag have been used to generate antigen-specific CTL. However, the vast majority of these peptide-specific CTL clones are of low avidity and are peptide, but not tumor, reactive. Peptide-MHC tetramers have been shown to bind specific TCRs with sufficient affinity to be useful reagents for flow cytometry. In this paper we demonstrate that peptide-MHC tetramers can also be used to selectively identify high avidity tumor-reactive CTL and enrich, from a heterogeneous population, the subpopulation of peptide-reactive T cells that can lyse tumor targets. The melanoma proteins, MART-1 and gp100, were used to induce potentially tumor-reactive T cells, and the intensity of T cell staining by TCR binding of specific peptide-MHC tetramers was assessed. A range of fluorescence intensity was detected, and the magnitude of tetramer binding was correlated with T cell avidity. The population of peptide-reactive T cells was phenotypically similar with regard to expression of TCR and adhesion molecules, suggesting that this differential avidity for tumor cells reflected differential affinity of the TCR for its peptide-MHC ligand. Sorting, cloning, and expansion of tetramerhigh CTL from a heterogeneous population of peptide-stimulated PBMCs enabled rapid selection of high avidity tumor-reactive CTL clones, which retained their functional and tetramerhigh phenotype on re-expansion. These results demonstrate that the avidity of a T cell for its tumor target is due to the specific affinity of the TCR for its peptide-MHC ligand, that this interaction can be described using peptide-MHC tetramers and used to isolate high avidity tumor-reactive CTL.

Detection of upper gastrointestinal blood with fecal occult blood tests

OBJECTIVE

Although fecal occult blood (FOB) tests have most often been used to detect occult bleeding from the lower gastrointestinal (GI) tract, their utility in detecting occult blood loss from the upper GI tract is less well understood. The aims of this study were to determine whether small amounts of blood from the upper GI tract can be detected by currently available FOB tests and, if so, to correlate FOB tests with semiquantitative GI blood.

METHODS

Groups of 10 healthy volunteers without a history of GI disease drank 5, 10, or 20 ml of their own blood mixed with tomato juice for 5 or 3 consecutive days. Standard dietary and medication restrictions were observed. Consecutive stools were tested for 2 days before, as well as 4 days after, blood ingestion. Each stool was simultaneously tested for FOB with HemoQuant (HQ), Hemoccult II (HO II), Hemoccult II SENSA (SENSA), HemeSelect (HS), and FlexSure OBT (FS).

RESULTS

The mean age and hemoglobin concentration of the study population were 29.3+/-0.5 yr and 14.3+/-0.3 g/dl, respectively. No subject noted GI symptoms during blood ingestion. Fecal blood levels (measured by HQ) were elevated within 2 days after initiation of blood ingestion and remained elevated until 2-3 days after cessation of blood ingestion. Mean fecal blood levels peaked at 2.1, 7.9, 8.0, and 13.5 (mg hemoglobin/g stool) in groups ingesting 5 ml/5 days, 10 ml/3 days, 10 ml/5 days, and 20 ml/3 days, respectively. The proportion of positive tests during and immediately after the period of blood ingestion was greatest in the 20 ml/3 day group; 16% of HO II samples were positive as were 64% of SENSA and 67% of HQ samples. SENSA was more sensitive than HO II in all blood ingestion groups. At least one positive SENSA test was present in 50% of subjects ingesting 10 ml of blood (each 3 and 5 day groups) and in all subjects ingesting 20 ml/day. Immunochemical tests did not detect upper GI blood in any blood ingestion group.

CONCLUSION

Inasmuch as many upper GI tract lesions have been reported to bleed small quantities of blood such as that studied here, and this amount of blood is readily detected with widely used guaiac-based FOB tests including Hemoccult II SENSA, the data emphasize that caution is warranted before attributing positive guaiac tests only to sites in the lower GI tract. The data raise the possibility that a combination of a highly sensitive guaiac-based FOB test plus an immunochemical could help differentiate occult upper from lower GI bleeding.

In vivo migration and function of transferred HIV-1-specific cytotoxic T cells

The persistence of HIV replication in infected individuals may reflect an inadequate host HIV-specific CD8+ cytotoxic T lymphocyte (CTL) response. The functional activity of HIV-specific CTLs and the ability of these effector cells to migrate in vivo to sites of infection was directly assessed by expanding autologous HIV-1 Gag-specific CD8+ CTL clones in vitro and adoptively transferring these CTLs to HIV-infected individuals. The transferred CTLs retained lytic function in vivo, accumulated adjacent to HIV-infected cells in lymph nodes and transiently reduced the levels of circulating productively infected CD4+ T cells. These results provide direct evidence that HIV-specific CTLs target sites of HIV replication and mediate antiviral activity, and indicate that the development of immunotherapeutic approaches to sustain a strong CTL response to HIV may be a useful adjunct to treatment of HIV infection.

The IL-2 receptor promotes proliferation, bcl-2 and bcl-x induction, but not cell viability through the adapter molecule Shc

IL-2, the principal mitogenic factor for activated T cells, delivers a proliferative signal through ligation of the heterotrimeric IL-2R. This proliferative signal is critically dependent upon cytoplasmic tyrosines on the beta-chain of this receptor (IL-2Rbeta) becoming phosphorylated in response to ligand. We found that at least one of these tyrosines (Y338) also mediates cell survival and induction of bcl-2, bcl-x, and c-myc in the murine T cell line CTLL-2. Since the adapter molecule Shc binds to phosphorylated Y338, the specific contribution of Shc to these events was evaluated. An IL-2Rbeta/Shc fusion protein, in which Shc was covalently tethered to a truncated version of IL-2Rbeta lacking all cytoplasmic tyrosines, revealed a robust proliferative signal mediated through Shc. This Shc-mediated signal induced expression of c-myc as well as the antiapoptotic genes bcl-2 and bcl-x with normal magnitude and kinetics. Nonetheless, signals from this fusion protein failed to sustain the long-term viability of CTLL-2 cells. Thus, induction of bcl family genes and delivery of a competent proliferative signal are not sufficient to promote cell survival and mediate the antiapoptotic effects associated with a complete IL-2 signal.

Androgens induce the expression of vascular endothelial growth factor in human fetal prostatic fibroblasts

Androgens are known to directly stimulate prostate cancer cell growth. We have previously reported that LNCaP prostate cancer cells were dependent upon stromal coinoculation for growth in nude mice and that the stromal cells secreted a potent angiogenic factor, vascular endothelial growth factor (VEGF), which stimulated tumor angiogenesis. Immunohistochemical staining localized VEGF expression primarily to the stromal cells of human fetal and adult hyperplastic prostates, with both stromal and epithelial cell VEGF expression in prostate cancer. In the present studies, we test the hypothesis that androgens, in addition to their direct effects on prostate epithelial cells, have indirect effects on these cells via up-regulation of stromal VEGF production and angiogenesis. Primary cultures of human prostate fetal fibroblasts were treated with dihydrotestosterone (DHT), and the effects on VEGF messenger RNA (mRNA) expression were determined by Northern blotting. DHT (10 nM) increased VEGF mRNA levels maximally after 2 h. Nuclear run-on transcription assays demonstrated a 2-fold increase in the VEGF transcription rate 2 h after the addition of DHT. VEGF mRNA stability was unaffected by DHT addition. VEGF protein levels were determined by enzyme-linked immunosorbent assay and were increased 2-fold 4 h after DHT addition. These data indicate that androgens increase VEGF transcription and secretion of biologically active VEGF from human prostatic stroma. Androgens, therefore, may indirectly enhance prostate growth via up-regulation of VEGF from the surrounding stroma.

Minor histocompatibility antigens as targets for T-cell therapy after bone marrow transplantation

In allogeneic bone marrow transplantation, differences between donor and recipient at minor histocompatibility loci, which encode allelic proteins containing variant peptide sequences, may result in adverse immune reactions such as graft-versus-host disease (GVHD), or graft rejection, but also a beneficial graft versus leukemia (GVL) response. Some minor H antigens are restricted in their expression to hematopoietic cells, including leukemic progenitors, suggesting it may be possible to separate GVHD and GVL responses. The antigenic peptides for a few human minor H antigens have been identified, and efforts to identify the genes encoding minor H antigens are being pursued. These advances promise to provide a more detailed understanding of the immunobiology and pathogenesis of GVHD and GVL responses and opportunities to selectively augment T-cell responses that promote a GVL effect by adoptive immunotherapy with T-cell clones specific for defined minor H determinants.

Cytotoxic T-lymphocyte-defined human minor histocompatibility antigens with a restricted tissue distribution

Cytotoxic T lymphocytes (CTL) specific for human minor histocompatibility (H) antigens can be isolated from the blood of major histocompatibility complex (MHC)-matched allogeneic bone marrow transplant (BMT) recipients and may play a prominent role in the graft-versus-host (GVH) and graft-versus-leukemia (GVL) reactions (Tsoi et al, J Immunol 125:2258, 1980; Tsoi et al, Transplant Proc 15:1484, 1983; Goulmy et al, Nature 302:159, 1983; Irle et al, Transplantation 40:329, 1985; and Niederwieser et al, Blood 81:2200, 1993). The identification of minor H antigens that are expressed in hematopoietic cells, including leukemic cells, but not in fibroblasts and other tissue types has suggested that such tissue-restricted antigens could potentially serve as targets for T-cell immunotherapy to enhance GVL activity without inducing GVH disease (de Bueger et al, J Immunol 149:1788, 1992; van der Harst et al, Blood 83:1060, 1994; and Dolstra et al, J Immunol 158:560, 1997). To explore the feasibility of this strategy, donor CD3+CD8+ CTL clones specific for recipient minor H antigens were isolated and characterized from allogeneic BMT recipients. CTL clones were obtained from the majority of donor/recipient pairs. Seventeen distinct minor H antigens distinguishable by their MHC-restricting allele, population frequency, and/or distribution of tissue expression were defined by 56 CD3+CD8+ CTL clones isolated from these patients. The MHC-restricting alleles for these CTL clones included HLA-A2 and HLA-B7, which had previously been shown to present minor H antigens to CTL, as well as HLA-A3, -A11, -B8, -B53, and -Cw7, which had not previously been described to present minor H antigens to CTL. Estimated phenotype frequencies for these 17 distinct minor H antigens range from 0.17 to 0.92. In vitro cytotoxicity assays using hematopoietic cells and fibroblasts as target cells showed that 5 of the 17 minor H antigens were expressed in both hematopoietic cells and fibroblasts. However, 12 were presented for CTL recognition only by hematopoietic cells and not by dermal fibroblasts derived from the same donors. These results significantly extend the spectrum of CTL-defined human minor H antigens that could potentially serve as target antigens for cellular immunotherapy to promote GVL activity after allogeneic BMT.

The outpatient evaluation of hematochezia

OBJECTIVE

The objective of this study was to determine whether specific clinical symptoms associated with hematochezia are predictive of important GI pathology and whether full colonoscopic examination is necessary.

METHODS

A total of 103 outpatients (> or = 45 yr) with hematochezia, defined as the passage of bright red blood per rectum, underwent anoscopy and colonoscopy. Before endoscopy, patients completed a detailed interview, quantitating the amount and frequency of bleeding, weight loss, use of aspirin/NSAIDs, change in bowel habits, family history, and prior GI illnesses. Based on this information, physicians were asked to predict whether the bleeding was from a perianal or more proximal site. At colonoscopy, pathology was stratified as either proximal or distal to the sigmoid/descending junction. Substantial pathology was defined as one or more adenomas > 8 mm, carcinoma, or colitis.

RESULTS

Anoscopy demonstrated internal and external hemorrhoids in 78 and 29 patients, respectively. On colonoscopy, 36 patients had 43 substantial lesions. Thirty-seven of these lesions were distal to the junction of the descending and sigmoid colons and six were proximal lesions. Four patients had cancer; all were distal lesions. Patients with substantial lesions were more likely to give a history of blood mixed within their stool (p = 0.03), to have more episodes of hematochezia per month (p = 0.008), and to have a significantly shorter duration of bleeding before medical evaluation (p = 0.02) than did patients without such lesions. However, the physician's clinical assessment did not predict reliably which patients were likely to have substantial pathology.

CONCLUSIONS

In patients with hematochezia, clinicians were unable to distinguish between those patients with and those without significant colonic lesions by history alone. Flexible sigmoidoscopy would have demonstrated most (95%) substantial lesions. The lesions that flexible sigmoidoscopy missed were an unlikely cause of bleeding in this small group of patients.

Prospects for adoptive T cell therapy

Since the establishment of methods to isolate genes encoding cytotoxic T lymphocyte defined tumor antigens, several antigens have been identified and characterized for suitability as target antigens for immunotherapy. The development of innovative strategies to generate T cells targeting these antigens and lessons learned from clinical trials of adoptive immunotherapy of viral diseases should facilitate the design of clinical trials for specific adoptive immunotherapy of cancer.

T cell therapy of human CMV and EBV infection in immunocompromised hosts

Acute virus infections in normal hosts are typically controlled by the development of a host immune response that includes MHC-restricted virus-specific T cells. Many viruses have developed methods to evade T cell recognition to facilitate initial infection and the establishment of a persistent infection in the host. Human cytomegalovirus (CMV) and Epstein-Barr virus (EBV) are ubiquitous human pathogens that utilise novel strategies to evade immune elimination. Despite these evasion methods, CD4(+) and CD8(+) T cells expressing alphabeta T cell receptors have been shown to play a pivotal role in controlling initial infection and in maintaining CMV and EBV in a latent state. However, in settings of iatrogenic or acquired T cell deficiency, primary infection or reactivation of CMV and EBV frequently progresses to cause life threatening disease. In this article the role of MHC-restricted CD8(+) and CD4(+) T cell responses in controlling CMV and EBV infections in healthy individuals and the development of novel strategies to restore protective T cell immunity to deficient hosts by the adoptive transfer of virus-specific T cells is reviewed. Copyright 1997 John Wiley & Sons, Ltd.

The IL-4 receptor alpha-chain cytoplasmic domain is sufficient for activation of JAK-1 and STAT6 and the induction of IL-4-specific gene expression

The common gamma-chain (gamma(c)) is a functional component of the IL-4R, yet cells lacking gamma(c) are able to respond to IL-4. This has led to the suggestion that a surrogate gamma'-chain, which can interact with the IL-4R alpha chain to mediate signaling, is expressed on cells lacking gamma(c). An alternative possibility is that in the absence of gamma(c), the IL-4R alpha chain is able to transduce signals by homodimerization. To test this latter possibility, a chimeric receptor containing the extracellular domain of c-kit (the stem cell factor (SCF) receptor) and the cytoplasmic and transmembrane domains of the IL-4R alpha chain was generated. Treatment of cells expressing the chimeric receptor kit/IL-4R alpha with SCF induces activation of the IL-4R alpha-associated kinase JAK-1 and the transcription factor STAT6. However, tyrosine phosphorylation of JAK-3, which associates with gamma(c), is not induced by SCF in these cells. SCF-mediated ligation of kit/IL-4R alpha is sufficient to elicit IL-4-specific gene expression, including up-regulation of CD23 and synthesis of germ-line epsilon transcripts. In the T cell line CTLL2, ligation of kit/IL-4R alpha induces cellular proliferation. Finally, in JAK-1-deficient HeLa cells, STAT6 activation by IL-4 is completely abolished. Together, these data demonstrate that the IL-4R alpha cytoplasmic domain is sufficient to activate JAK-1 and STAT6 and to induce expression of IL-4 target genes, thus identifying a mechanism by which IL-4 signaling can proceed in the absence of JAK-3 and gamma(c).

The IL-4 receptor alpha-chain cytoplasmic domain is sufficient for activation of JAK-1 and STAT6 and the induction of IL-4-specific gene expression

The common gamma-chain (gamma(c)) is a functional component of the IL-4R, yet cells lacking gamma(c) are able to respond to IL-4. This has led to the suggestion that a surrogate gamma'-chain, which can interact with the IL-4R alpha chain to mediate signaling, is expressed on cells lacking gamma(c). An alternative possibility is that in the absence of gamma(c), the IL-4R alpha chain is able to transduce signals by homodimerization. To test this latter possibility, a chimeric receptor containing the extracellular domain of c-kit (the stem cell factor (SCF) receptor) and the cytoplasmic and transmembrane domains of the IL-4R alpha chain was generated. Treatment of cells expressing the chimeric receptor kit/IL-4R alpha with SCF induces activation of the IL-4R alpha-associated kinase JAK-1 and the transcription factor STAT6. However, tyrosine phosphorylation of JAK-3, which associates with gamma(c), is not induced by SCF in these cells. SCF-mediated ligation of kit/IL-4R alpha is sufficient to elicit IL-4-specific gene expression, including up-regulation of CD23 and synthesis of germ-line epsilon transcripts. In the T cell line CTLL2, ligation of kit/IL-4R alpha induces cellular proliferation. Finally, in JAK-1-deficient HeLa cells, STAT6 activation by IL-4 is completely abolished. Together, these data demonstrate that the IL-4R alpha cytoplasmic domain is sufficient to activate JAK-1 and STAT6 and to induce expression of IL-4 target genes, thus identifying a mechanism by which IL-4 signaling can proceed in the absence of JAK-3 and gamma(c).

Isolation of Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes that lyse Reed-Sternberg cells: implications for immune-mediated therapy of EBV+ Hodgkin's disease

A subset of Hodgkin's disease (HD) patients have detectable Epstein-Barr virus (EBV) genomes in the malignant Reed-Sternberg (R-S) cells. R-S cells express only a limited set of latent EBV proteins, but only LMP1 and LMP2 can potentially elicit a CD8+ cytotoxic T-lymphocyte (CTL) response. We have evaluated if either of these proteins could be used as targets for specific adoptive T-cell therapy for EBV-positive (EBV+) HD. The success of this strategy requires that R-S cells are susceptible to lysis by CD8+ CTL, and that CTL specific for LMP1 and LMP2 can be detected and potentially amplified in HD patients. Antigen presentation and CTL sensitivity was evaluated with an in vitro maintained, phenotypically representative R-S cell line, HDLM-2. The R-S cells were able to process and present viral proteins, and to be efficiently lysed by specific CTL in a Class I-restricted manner. Since CTL responses to LMP1 and LMP2 do not represent the dominant responses to EBV, we examined if CTL clones specific for these proteins could be isolated despite the presence of weak or nondetectable responses in polyclonal T-cell lines. LMP-specific clones were generated from individuals either by cloning from the polyclonal EBV-reactive T-cell lines or by direct stimulation of peripheral blood mononuclear cells (PBMC) with cells expressing LMP1 or LMP2 as the only EBV protein. Our ability to isolate CTL specific for LMP proteins from individuals with HD and the sensitivity of R-S cells for CTL-mediated lysis suggest that the pursuit of specific adoptive immunotherapy represents a viable strategy for the subset of HD patients with EBV+ tumors.