661 Neoantigen-specific CD4+ T cells in human melanoma have diverse differentiation states and correlate with CD8+ T cell, macrophage, and B cell function

Background

Tumor-antigen specific CD4+ T cells are crucial for the efficacy of antibodies that block immune checkpoint proteins in mouse tumor models, but their activities in human tumor immunity are less clear. CD8+ T cells infiltrating human tumors, including those specific for tumor antigens, have been studied using single cell profiling techniques and exist in a variety of dysfunctional states. The transcriptional states of tumor-specific CD4+ T cells present in tumors and their potential contributions to the tumor microenvironment are less well understood.

Methods

We used targeted single cell RNA sequencing and matching of T cell receptor (TCR) sequences to identify phenotypic signatures that discriminated tumor antigen- and viral antigen-specific CD4+ T cells infiltrating human melanoma tumors in four patients. The presence of CD4+ T cells with these signatures was correlated with the number and phenotype of other immune cells in the tumor microenvironment in an extended cohort of 20 patients.

Results

We identified 259 CD4+ T cells representing 40 different TCR clonotypes specific for 13 neoantigens and 108 cells representing 14 TCR clonotypes specific for self-antigens in four melanoma patients. High expression of CXCL13 defined conventional CD4+ T cells that recognize tumor associated neoantigens and self-antigens from bystander and viral antigen-specific CD4+ T cells. Tumor-reactive CD4+ T cells could be subdivided into clusters expressing memory and T follicular helper markers, and those expressing cytolytic markers and IFN-g. In an extended cohort of 20 patients with melanoma, the frequency of CXCL13+ CD4+ T cells in the tumor microenvironment correlated with the presence and proliferation of CD8+ T cells, the presence and maturation of B cells, the activation of interferon responsive genes in tumor associated macrophages, and patient survival. CD4+ T cells with similar transcriptional signatures were identified in data sets from breast and non-small cell lung cancer, suggesting these markers may enrich for tumor-reactive CD4+ T cells in many cancers.

Conclusions

These results identify a subset of tumor infiltrating conventional CD4+ T cells in melanoma that are enriched for reactivity to tumor antigens and exist in multiple phenotypic states. Correlations of the presence of these cells with the frequency and phenotype of other immune cells suggest roles for these tumor antigen-specific CD4+ T cells in providing CD8+ T cell help, driving recruitment and maturation of B cells, and activating macrophages. Isolating such cells based on their unique phenotype and utilizing them for adoptive therapy could alter the tumor microenvironment for therapeutic benefit.

Ethics Approval

All Patient samples in this study were obtained from patients who signed informed consent in a study approved by the institutional review board of the Fred Hutchinson Cancer Research Center (protocol #2643).

Therapeutic Targeting of Mesothelin with Chimeric Antigen Receptor T Cells in Acute Myeloid Leukemia

PURPOSE

We previously identified mesothelin (MSLN) as highly expressed in a significant fraction of acute myeloid leukemia (AML) but entirely silent in normal hematopoiesis, providing a promising antigen for immunotherapeutic targeting that avoids hematopoietic toxicity. Given that T cells genetically modified to express chimeric antigen receptors (CAR) are effective at eradicating relapsed/refractory acute lymphocytic leukemia, we developed MSLN-directed CAR T cells for preclinical evaluation in AML.

EXPERIMENTAL DESIGN

The variable light (VL) and heavy (VH) sequences from the MSLN-targeting SS1P immunotoxin were used to construct the single-chain variable fragment of the standard CAR containing 41-BB costimulatory and CD3Zeta stimulatory domains. The preclinical efficacy of MSLN CAR T cells was evaluated against AML cell lines and patient samples expressing various levels of MSLN in vitro and in vivo.

RESULTS

We demonstrate that MSLN is expressed on the cell surface of AML blasts and leukemic stem cell-enriched CD34⁺CD38^- subset, but not on normal hematopoietic stem and progenitor cells (HSPC). We further establish that MSLN CAR T cells are highly effective in eliminating MSLN-positive AML cells in cell line- and patient-derived xenograft models. Importantly, MSLN CAR T cells can target and eradicate CD34⁺CD38^- cells without impacting the viability of normal HSPCs. Finally, we show that CAR T-cell functionality can be improved by inhibition of the ADAM17 metalloprotease that promotes shedding of MSLN.

CONCLUSIONS

These findings demonstrate that MSLN is a viable target for CAR T-cell therapy in AML and that inhibiting MSLN shedding is a promising approach to improve CAR T-cell efficacy.

Metabolic regulation by PD-1 signaling promotes long-lived quiescent CD8 T cell memory in mice

[Figure: see text].

Abstract 2222: Engineered variants of Neo-2/15 potently expand CAR-T cells and promote antitumor activity in lymphoma and solid tumor mouse models

Chimeric antigen receptor (CAR) T cells have achieved remarkable success as therapies for B cell malignancies, but failure might occur due to insufficient CAR-T cell expansion. Furthermore, CAR-T cells have been less effective in treating epithelial cancers, which is believed to be due to poor CAR-T cell accumulation at the tumor site. Interleukin-2 (IL-2) is a potent signaling molecule that induces T cell proliferation and survival. Therefore, it has been suggested that IL-2 co-administration might be effective in promoting CAR-T expansion, persistence, and tumor infiltration. Natural IL-2 acts by binding to the trimeric IL-2 receptor complex consisting of the IL-2Rα, IL-2Rβ and common-γ subunits. Although the IL-2Rα subunit is not directly involved in the signaling cascade, when present, it greatly increases the binding (and signaling) potency of IL-2. An obstacle to applying IL-2 to CAR-T therapy is the expression of IL-2Rα on many target-cells, such as immunosuppressive regulatory T cells (Treg) and endothelial cells. Consequently, high doses of IL-2 cause severe toxicities, including vascular leak syndrome, while low doses are therapeutically suboptimal due to preferential expansion of Treg cells. In addition, as a therapeutic, IL-2 has poor pharmacokinetics, necessitating frequent dosing or continuous infusion. Neoleukin-2/15 (Neo-2/15), a recently reported de novo IL-2 and IL-15 mimetic, effectively agonizes the IL-2 receptor IL-2Rβγ and has no dependency (or interaction) with IL-2Rα. Therefore, Neo-2/15 can activate T cells with high potency regardless of IL-2Rα expression. Here, we studied the combination of CAR-T cells with two reengineered versions of Neo-2/15. In the first strategy, NL-201, a half-life-extended version of Neo-2/15, was dosed weekly (300μg/kg) in a B cell lymphoma xenograft model. NL-201 induced potent CD19 CAR-T cell expansion and prolonged mice survival. NL-201 also induced potent ROR1 CAR-T cell expansion in a solid tumor syngeneic model of mice engrafted with the mutant K-ras/p53-/- tumor line overexpressing hROR1. NL-201 significantly increased the frequency of CAR-T cells at the tumor site compared to IL-2 and also dramatically increased the CD8:Treg ratio in the tumor. In the second approach, Neo-2/15 was targeted to engineered CAR-T cells by fusing the molecule to a DARPin domain specific for a transduction marker co-expressed with the CAR. In a B cell tumor xenograft model, targeted Neo-2/15 effectively increased CAR-T cell expansion and prolonged survival compared to treatment with CAR-T cells and non-targeted Neo-2/15. Together, these results show that engineered versions of Neo-2/15 induce robust expansion of CAR-T cells and can enhance their antitumor activity.

Citation Format: Isabel Leung, Megan Templeton, Alfredo Rubio, Carl Walkey, Daniel-Adriano Silva, Stanley Riddell. Engineered variants of Neo-2/15 potently expand CAR-T cells and promote antitumor activity in lymphoma and solid tumor mouse models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2222.

PD-1 Signals are Critical for Homeostatic Maintenance of Memory CD8 T Cells

Inhibitory signaling in dysfunctional CD8 T cells through the PD-1 axis is well established in chronic viral infections and cancers. PD-1 is also transiently induced to high levels during priming of acute infections and immunizations, yet its impact on the development of long-lived antigen-independent T cell memory remains unclear. Here we show that in addition to its expected role in restraining clonal expansion, PD-1 expression on antigen-specific CD8 T cells during priming and activation is critically required for the development of a durable CD8 T cell memory pool after antigen clearance. Loss of T cell-specific PD-1 signaling led to increased contraction and a striking defect in antigen-independent renewal of memory CD8 T cells in response to homeostatic cytokine signals, thus resulting in attrition and near ablation of the memory pool over time. Notably, in the setting of PD-1 checkpoint blockade immunotherapy of chronic viral infection, while the exhausted CTLs expectedly regained function, the pre-existing pool of resting functional memory cells established in response to a previously administered vaccine underwent attrition. Metabolically, PD-1 signals were necessary for regulating the critical balance of anabolic glycolysis and fatty acid oxidation programs through mTOR to meet the bioenergetics needs of quiescent memory. These studies define PD-1 as a key metabolic regulator of protective T cell immunity, and have potential clinical implications for pre-existing T cell memory to prior infections and vaccinations during PD-1 checkpoint-blockade immunotherapy in cancer.

Experimental Hendra virus infection of dogs: virus replication, shedding and potential for transmission

OBJECTIVE

Characterisation of experimental Hendra virus (HeV) infection in dogs and assessment of associated transmission risk.

METHODS

Beagle dogs were exposed oronasally to Hendra virus/Australia/Horse/2008/Redlands or to blood collected from HeV-infected ferrets. Ferrets were exposed to oral fluids collected from dogs after canine exposure to HeV. Observations made and samples tested post-exposure were used to assess the clinical course and replication sites of HeV in dogs, the infectivity for ferrets of canine oral fluids and features of HeV infection in dogs following contact with infective blood.

RESULTS

Dogs were reliably infected with HeV and were generally asymptomatic. HeV was re-isolated from the oral cavity and virus clearance was associated with development of virus neutralising antibody. Major sites of HeV replication in dogs were the tonsils, lower respiratory tract and associated lymph nodes. Virus replication was documented in canine kidney and spleen, confirming a viraemic phase for canine HeV infection and suggesting that urine may be a source of infectious virus. Infection was transmitted to ferrets via canine oral secretions, with copy numbers for the HeV N gene in canine oral swabs comparable to those reported for nasal swabs of experimentally infected horses.

CONCLUSION

HeV is not highly pathogenic for dogs, but their oral secretions pose a potential transmission risk to people. The time-window for transmission risk is circumscribed and corresponds to the period of acute infection before establishment of an adaptive immune response. The likelihood of central nervous system involvement in canine HeV infection is unclear, as is any long-term consequence.

Effect of intratumoral (IT) injection of the toll-like receptor 4 (TLR4) agonist G100 on a clinical response and CD4 T-cell response locally and systemically

71

Background: Soft tissue sarcomas (STS) are heterogeneous tumors which are morbid and lethal. G100 is under investigation in multiple clinical trials and contains a potent TLR4 agonist (oil-in-water emulsion of glucopyranosyl lipid A) that has been tested as vaccine adjuvant. We hypothesized IT G100 would induce robust local and potentially systemic anti-tumor immune response, leading to improved outcomes. Methods: 15 metastatic STS patients with superficial lesions were treated with weekly IT G100 for 8-12 wks; 12 patients received radiation (RT) for 2 wks to start, while 3 received IT G100 for 6 wks prior to RT. Biopsies and PBMC were collected pre and post treatment, and flow cytometry was performed on biopsies. TIL and PBMC were analyzed with TCR deep sequencing. PBMC were analyzed by single cell multiplex cytokine profiling. Results: No grade ≥ 3 toxicity was observed, and local tumor control was achieved in all evaluable tumors (14/14). Treated tumors tracked post-trial (mean 156 days) had persistent local control with 1 CR (7%), 1 PR (7%), and 11 SD (79%). In 3 patients with long term follow up, treated lesions remained controlled vs index lesions (-53% vs +31% at mean 235 days, p = 0.002). In all tumors after G100 alone, T cell infiltration increased. In P14, CD3 live cells in tumor rose from < 1% to 62%. PBMC clonality increased in 8/14 tested including P06, who had 4× increase in clonality and CR in the injected lesion; PBMC and TIL TCR overlap increased from 13.4% to 21.5%. P13 had a 2.3× rise in TIL clonality; the top clone (a CD4 T cell) expanded from 0.1% to 38% and expressed more TNFα than the rest (p < 0.0001). Single cell cytokine analysis of PBMC showed 7/13 (54%) increased in polyfunctionality (producing > 2 cytokines) in CD4 T cells; no consistent increase was seen in CD8 T cells. TNFα levels in pre-treatment monocytes correlated with PFS (R2= 0.5, p = 0.02). Conclusions: IT G100 is a viable agent for local control of metastatic STS lesions. With or without RT, G100 appears to cause CD4 T cell mediated local and systemic response. Combination of G100 with other immunomodulators could induce clinically significant systemic responses, as seen in follicular NHL treated with G100. Clinical trial information: NCT02180698.

Phase I study of immunotherapy for advanced ROR1+ malignancies with autologous ROR1-specific chimeric antigen receptor-modified (CAR)-T cells

TPS79

Background: CAR-T cells have demonstrated marked tumor regression in patients (pts) with hematologic malignancies. ROR1, a tyrosine kinase orphan receptor, is expressed in triple negative breast cancers (TNBC) and non-small cell lung cancers (NSCLC) and is a novel candidate for CAR-T cell therapy. ROR1-specific CAR-T cells are engineered with lentiviral vector encoding ROR1 scFv/4-1BB/CD3ζ and a truncated EGFR molecule to permit elimination of ROR1 CAR-T cells in case of toxicity. Methods: NCT02706362 is a phase I study evaluating the safety and anti-tumor activity of adoptively transferred autologous ROR1 CAR-T cells in pts with advanced ROR1+ TNBC and NSCLC. Eligibility criteria include: metastatic TNBC or NSCLC; measurable disease; prior standard therapy with no maximum on number of prior regimens; tumor ROR1 expression > 20% by IHC; KPS > 70%; age ≥18; negative pregnancy test for women of childbearing potential; informed consent; adequate organ function. Exclusions are: active autoimmune disease or uncontrolled infection, HIV seropositive status, contraindication to cyclophosphamide, anticipated survival < 3 months, and/or untreated CNS metastases. After screening, leukapheresis is performed, CD8+ and CD4+ T cells are selected, then transduced with the ROR1+ CAR lentivirus and expanded. Lymphodepletion with cyclophosphamide and fludarabine is followed 36-96 hours later by infusion of ROR1 CAR-T cells in escalating doses (3.3 x 105/kg - 1 x 107/kg cells with defined CD8+ and CD4+ composition). Pts are treated in cohorts of 2 to determine cell dose associated with an estimated toxicity rate of < 25%. Primary aim is to determine the maximum tolerated dose (MTD) and safety of ex vivo expanded ROR1 CAR-T cells. Secondary aims include persistence and phenotype of transferred T cells, trafficking of T cells to tumor site, in vivo function, and preliminary antitumor activity of ROR1 CAR-T cells by RECIST 1.1. Dose escalation is determined by CRM algorithm with minimum of 21-day interval following infusion between pts. Preliminary estimates of efficacy will be obtained among all pts and those treated at estimated MTD. Six of 30 pts have been enrolled with no DLTs observed. Clinical trial information: NCT02706392.

Cytomegalovirus-Specific T Cells Restricted by HLA-Cw*0702 Increase Markedly with Age and Dominate the CD8+ T-Cell Repertoire in Older People

Cytomegalovirus (CMV) infection elicits a strong T-cell immune response, which increases further during aging in a process termed "memory inflation." CMV downregulates the expression of HLA-A and HLA-B on the surface of infected cells to limit presentation of viral peptides to T-cells although HLA-C is relatively spared as it also engages with inhibitory killer immunoglobulin receptor receptors and therefore reduces lysis by natural killer cells. We investigated the magnitude and functional properties of CMV-specific CD8+ T-cells specific for 10 peptides restricted by HLA-C in a cohort of 53 donors between the age of 23 and 91 years. This was achieved via peptide stimulation of PBMCs followed by multicolor flow cytometry. Three peptides, derived from proteins generated in the immediate-early period of viral replication and restricted by HLA-Cw*0702, elicited strong immune responses, which increased substantially with age such that the average aggregate response represented 37% of the CD8+ T-cell pool within donors above 70 years of age. Remarkably, a single response represented 70% of the total CD8+ T-cell pool within a 91-year-old donor. HLA-Cw*0702-restricted CD8+ T-cell responses were immunodominant over HLA-A and HLA-B-restricted CMV-specific responses and did not show features of exhaustion such as PD-1 or CD39 expression. Indeed, such CTL exhibit a polyfunctional cytokine profile with co-expression of IFN-γ and TNF-α and a strong cytotoxic phenotype with intracellular expression of perforin and granzymeB. Functionally, HLA-Cw*0702-restricted CTL show exceptionally high avidity for cognate peptide-HLA and demonstrate very early and efficient recognition of virally infected cells. These observations indicate that CD8+ T-cells restricted by HLA-C play an important role in the control of persistent CMV infection and could represent a novel opportunity for CD8+ T-cell therapy of viral infection within immunosuppressed patients. In addition, the findings provide further evidence for the importance of HLA-C-restricted T-cells in the control of chronic viral infection.

Therapeutic T cell engineering

Genetically engineered T cells are powerful new medicines, offering hope for curative responses in patients with cancer. Chimaeric antigen receptors (CARs) are a class of synthetic receptors that reprogram lymphocyte specificity and function. CARs targeting CD19 have demonstrated remarkable potency in B cell malignancies. Engineered T cells are applicable in principle to many cancers, pending further progress to identify suitable target antigens, overcome immunosuppressive tumour microenvironments, reduce toxicities, and prevent antigen escape. Advances in the selection of optimal T cells, genetic engineering, and cell manufacturing are poised to broaden T-cell-based therapies and foster new applications in infectious diseases and autoimmunity.

Abstract 3155: Neuroblastoma (NB), Medulloblastoma (MB), and Ewing's sarcoma (ES) express ROR1 and can be effectively targeted with NK cells modified to express an anti ROR1 chimeric antigen receptor (CAR)

Background:

Metastatic pediatric neuroectodermal solid tumors especially NB, MB, and ES have a dismal prognosis (Perkins et al, PLoS One, 2014; Smoll, Cancer, 2012). Targeted cellular therapy with T or NK cells modified with CARs is a novel approach to chemo-resistant childhood solid tumors (Grupp SA, Clin Cancer Res, 2012; Mackall C,Front Oncol, 2012). NK cells can be significantly expanded by co-culture with genetically engineered K562 cells overexpressing mb-IL21 (Lee D, PLOS, 2012). ROR1 has been identified as a novel target on B cell tumors in which CARs can be developed and utilized for targeted cellular therapy (Hudecek et al., Blood, 2010).

Objective:

To evaluate the in-vitro cytotoxic activity and function of PBNK expanded ex-vivo with K562 mb-IL21 and nucleofected with mRNA encoding an anti ROR1-CAR against NB, MB, and ES.

Material and Methods:

PBNK were expanded with irradiated K562 Clone 9.mb-IL21 (generously provided by Lee D, MD, PhD, MD Anderson, TX). Ex-vivo expanded PBNK (ExPBNK) cells were electroporated with anti ROR1-CD28-41BBl-CD3ζ-tEGFR-mRNA. The cell surface expression of the ROR1-CAR on NK cells was detected using anti-mouse IgG, F(ab’)2. Cytotoxicity of ROR1 CAR-NK cells was investigated against NB (SKNBE2, SKNFI & SHSY5Y), MB (DAOY) and ES (TC71, EWS 502 & A673) cell lines by DELFIA cytotoxicity assay at an E:T ratio of 10:1. Intracellular staining of CD107a, interferon gamma, perforin and granzyme B was performed using a 10:1 E:T ratio of ROR1-CAR-NK cells against tumor targets and analyzed on the MACSQuant flow cytometer.

Results:

NB, MB, and ES cell lines expressed ROR1 (50.2±15.6%), (55.5±5.1%), and (31.5±12%), respectively. Expansion of NK cells was significantly increased 3988 ± 435 fold (p = 0.00001) at day 14 vs day 0. CAR expression after nucleofection was measured by F(ab’)2 staining and showed a significant increase in anti-ROR1-CAR- (88.3±1.7%) vs mock-electroporated NK cell populations (8.1± 6.9%) p = 0.0001 at 36-48 hours. Anti-ROR1-CAR-NK cells exhibited significantly increased lysis of ROR1 expressing tumor cell lines compared to mock NK cells (93±4.6% vs 63.6±7.4%) p = 0.00001 at an E:T of 10:1. Similarly, expression of CD107a (46.1±9.1 vs 27.6±2.4%) p = 0.001, interferon gamma (34.1±11.6 vs 16.7±6.7%) p = 0.003, granzyme B (68.5±8.9 vs 46±7.2%) p = 0.002, and perforin (51.3±7.7 vs 30.3±11.9%) p = 0.002 were significantly increased in anti-ROR1-CAR-NK cells vs Mock-NK cells at 10:1 E:T ratio against the ROR1 expressing targets.

Conclusion:

Anti-ROR1-CAR-ex-PBNK cells had significant enhanced cytotoxicity and significantly increased CD107a, interferon gamma, perforin, and granzyme B activity against ROR1 expressing tumors. Future directions include investigating the ex-PBNK anti ROR1-CAR cells in-vivo against ROR1 expressing pediatric solid tumors.

Citation Format: Mona Elmacken, Aradhana Awasthi, Janet Ayello, Carmella VanDeVen,, Wen Luo, Yanling Liao, Stanley Riddell, Mitchell S. Cairo. Neuroblastoma (NB), Medulloblastoma (MB), and Ewing's sarcoma (ES) express ROR1 and can be effectively targeted with NK cells modified to express an anti ROR1 chimeric antigen receptor (CAR). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3155. doi:10.1158/1538-7445.AM2015-3155

Adoptive therapy of ROR1+ murine solid tumors with chimeric antigen receptor-modified T cells (VAC7P.1045)

Adoptive therapy with T cells modified to express chimeric antigen receptors (CARs) holds promise for treating epithelial cancers if target molecules can be identified and strategies developed to overcome the immunosuppressive mechanisms of solid tumors. Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is expressed in many blood and solid tumors but is absent from vital adult tissues, making it a potential tumor-specific target for therapy. We developed ROR1-specific CARs comprised of an extracellular single chain antibody linked to various intracellular signaling modules. T cells modified to express ROR1-CARs exerted potent anti-tumor effects against ROR1+ leukemia and lymphoma in vivo, but their effectiveness against solid tumors is not known. To test this, we used the orthotopic 4T1 mouse mammary tumor model that recapitulates the immunosuppressive microenvironment and metastatic pattern of human breast cancer. We transduced 4T1 cells with firefly luciferase (ffluc) to allow in vivo imaging of tumor growth, along with mouse or human ROR1. Murine CD8+ T cells modified to express ROR1-CARs lysed ROR1+ but not ROR1- 4T1 cells in vitro, while unmodified T cells were unable to lyse either ROR1+ or ROR1- 4T1 cells. We are currently evaluating the anti-tumor activity of ROR1-CAR T cells against 4T1-ffluc/ROR1 cells in vivo to define optimal CAR constructs and cell compositions and identify what immunosuppressive pathways to target to improve anti-tumor activity.

Despite large clonal expansions of cytotoxic T cells with age and chronic CMV exposure, the underlying repertoire appears completely normal, suggesting that holes in the T cell repertoire are not responsible for immunosenesence (VIR4P.1012)

Age is thought to restrict the cytotoxic immune repertoire, both in terms of number and diversity of naïve T cells available for responding to novel pathogens and vaccinogens. Studies have shown that CMV-induced chronic stimulation exacerbates this immune restriction. CMV infection leads to CD8 T cell clonal expansions (TCEs), bearing classical memory as well as late-differentiated memory phenotypes. Such TCEs become huge in the elderly, where they have been held responsible for constriction of the remainder of the repertoire. In turn, this has been linked with the CMV-associated immune risk profile and increased mortality in the elderly, although it is not known how TCEs affect immune competence. Here we address the premise that immune competence with age could be compromised because of repertoire restriction. We do so by describing the structure of the elderly repertoire at an unprecedented resolution in terms of both clonal origin and broad CD8 T cell phenotypes. We then proceed to exhaustively identify CMV-specific clones. This presents us with a close look at the rest of the repertoire, which does not respond to CMV. We compare this with the full repertoire in CMV- individuals. Our observations suggest that CMV-specific TCEs are restricted to components of the repertoire that expand without affecting the absolute size or diversity elsewhere in the repertoire, so “holes” are unlikely to develop in the T cell repertoire.

Henipavirus microsphere immuno-assays for detection of antibodies against Hendra virus

Hendra and Nipah viruses (HeV and NiV) are closely related zoonotic pathogens of the Paramyxoviridae family. Both viruses belong to the Henipavirus genus and cause fatal disease in animals and humans, though only HeV is endemic in Australia. In general and due to the acute nature of the disease, agent detection by PCR and virus isolation are the primary tools for diagnostic investigations. Assays for the detection of antibodies against HeV are fit more readily for the purpose of surveillance testing in disease epidemiology and to meet certification requirements in the international movement of horses. The first generation indirect ELISA has been affected by non-specific reactions which must be resolved using virus neutralisation serology conducted at laboratory bio-safety level 4 containment (PC4). Recent developments have enabled improvements in the available serology assays. The production of an expressed recombinant truncated HeV G protein has been utilised in ELISA and in Luminex-based multiplexed microsphere assays. In the latter format, two Luminex assays have been developed for use in henipavirus serology: a binding assay (designed for antibody detection and differentiation) and a blocking assay (designed as a surrogate for virus neutralisation). Equine and canine field sera were used to evaluate the two Luminex assays relative to ELISA and virus neutralisation serology. Results showed that Luminex assays can be effective as rapid, sensitive and specific tests for the detection of HeV antibody in horse and dog sera. The tests do not require PC4 containment and are appropriate for high throughput applications as might be required for disease investigations and other epidemiological surveillance. Also, the results show that the Luminex assays detect effectively HeV vaccine-induced antibodies.

HLA-F and MHC-I open conformers cooperate in an MHC-I antigen cross presentation pathway. (P5015)

Peptides that are presented by MHC class I (MHC-I) are processed from two potential sources - newly synthesized endogenous proteins for direct presentation on the surface of most nucleated cells and exogenous proteins for cross-presentation typically by professional antigen presenting cells. Here we present data that implicates the non-classical HLA-F and open conformers of MHC-I expressed on activated cells in a pathway for the presentation of exogenous proteins by MHC-I. This pathway is distinguished from the conventional endogenous pathway by its independence from TAP and Tapasin and its sensitivity to inhibitors of lysosomal enzymes, and further distinguished by its dependence on MHC-I allotype-specific epitope recognition for antigen uptake. Thus, our data from in vitro experiments collectively support a previously unrecognized model of antigen cross-presentation mediated by HLA-F and MHC-I open conformers on activated lymphocytes and monocytes, which may significantly contribute to the regulation of immune system functions and the immune defense.

Induction of transgene-specific cytotoxic T lymphocyte responses after transplantation of gene-modified CD34+ cells despite nonablative immunosuppressive conditioning

In previous studies we showed that low-dose irradiation and immunosuppression with cyclosporine and mycophenolate mofetil prolonged in vivo persistence of gene-modified T cells but was unable to induce tolerance. We hypothesized that the lack of sustained antigen presentation because of the limited life span of the infused T cells might be responsible for the lack of tolerance induction. Thus, we examined whether tolerance could be induced by infusion of long-lived stem cells. Two baboons were transplanted with YFP/neo-transduced CD34+ cells. The transgene-marked cells disappeared completely within 5 weeks and CD8+ transgene-specific cytotoxic T lymphocytes were detected in both animals. Thus, this nonablative conditioning regimen did not provide sufficient immunosuppression for the induction of tolerance after infusion of gene-modified CD34+ cells.

Optimizing adoptive polyclonal T cell immunotherapy of lymphomas, using a chimeric T cell receptor possessing CD28 and CD137 costimulatory domains

We previously demonstrated the feasibility of generating therapeutic numbers of cytotoxic T lymphocyte (CTL) clones expressing a CD20-specific scFvFc:CD3zeta chimeric T cell receptor (cTCR), making them specifically cytotoxic for CD20+ B lymphoma cells. However, the process of generating and expanding he CTL clones was laborious, the CTL clones expressed the cTCR at low surface density, and they exhibited suboptimal proliferation and cytotoxicity. To improve the performance of the CTLs in vitro and in vivo, we engineered "second-generation'' plasmid constructs containing a translational enhancer (SP163) and CD28 and CD137 costimulatory domains in cis with the CD3zeta intracellular signaling domain of the cTCR gene. Furthermore, we verified the superiority of generating genetically modified polyclonal T cells expressing the second-generation cTCR rather than T cell clones. Our results demonstrate that SP163 enhances the surface expression of the cTCR; that the second-generation cTCR improves CTL activation, proliferation, and cytotoxicity; and that polyclonal T cells proliferate rapidly in vitro and mediate potent CD20-specific cytotoxicity. This study provides the preclinical basis for a clinical trial of adoptive T cell immunotherapy for patients with relapsed CD20+ mantle cell lymphoma and indolent lymphomas.

Impact of HLA A2 and cytomegalovirus serostatus on outcomes in patients with leukemia following matched-sibling myeloablative allogeneic hematopoietic cell transplantation

BACKGROUND AND OBJECTIVES

Donor cytomegalovirus seropositivity was reported to improve leukemia outcomes in HLA-A2 identical hematopoietic cell transplant (HCT) recipients, due to a possible cross-reactivity of donor HLA-A2-restricted CMV-specific T cells with minor histocompatibility (H) antigen of recipient cells. This study analyzed the role of donor CMV serostatus and HLA-A2 status on leukemia outcomes in a large population of HLA-identical HCT recipients.

DESIGN AND METHODS

Leukemia patients transplanted between 1992 and 2003 at the Fred Hutchinson Cancer Research Center were categorized as standard risk [leukemia first remission, chronic myeloid leukemia in chronic phase (CML-CP)] and high risk (advanced disease) patients. Time-to-event analysis was used to evaluate the risk of relapse and death associated with HLA-A2 status and donor CMV serostatus.

RESULTS

In standard risk patients, acute leukemia (p<0.001) and sex mismatch (female to male, p=0.004)) independently increased the risk of death, while acute leukemia increased the risk of relapse (p<0.001). In high risk patients acute leukemia (p=0.01), recipient age > or = 40 (p=0.005) and herpes simplex virus (HSV) seropositivity (p<0.001) significantly increased the risk death; HSV seropositivity (p=0.006) increased the risk of relapse. Donor CMV serostatus had no significant effect on mortality or relapse in any HLA group.

INTERPRETATION AND CONCLUSION

This epidemiological study did not confirm the previously reported effect of donor CMV serostatus on the outcomes of leukemia in HLA-A2-identical HCT recipients. Addressing the question of cross-reactivity of HLA-A2-restricted CMV-specific T cells with minor H antigens in a clinical study would require knowledge of the patient's minor H antigen genotype. However, because of the unbalanced distribution of HLA-A2-restricted minor H antigens in the population and their incomplete identification, this question might be more appropriately evaluated in in vitro experiments than in a clinical study.

Chicken functional genomics: an overview

Chickens have undergone intensive selection to produce highly productive strains with excellent growth rates and feed conversion ratios. There does not appear to be any reduction in the rate of strain improvement. The recently completed chicken genome sequencing project and adjunct projects cataloging single nucleotide polymorphisms demonstrate that there is still a high level of genetic variation present in modern breeds. The information provided by genome and transcriptome studies furnishes the chicken biologist with powerful tools for the functional analysis of gene networks. Gene microarrays have been constructed and used to investigate gene expression patterns associated with certain production traits and changes in expression induced by pathogen challenge. Such studies have the potential to identify important genes involved in biological processes influencing animal productivity and health. Fundamental regulatory mechanisms controlled by non-coding RNAs, such as microRNAs, can now be studied following the identification of many potential genes by homology with previously identified genes from other organisms. We demonstrate here that microarrays and northern blotting can be used to detect expression of microRNAs in chicken tissue. Other tools are being used for functional genomic analysis including the production of transgenic birds, still a difficult process, and the use of gene silencing. Gene silencing via RNA interference is having a large impact in many areas of functional genomics and we and others have shown that the mechanisms needed for its action are functional in chickens. The chicken genome sequence has revealed a large number of immune related genes that had not previously been identified in chickens. Functional analysis of these genes is likely to lead to applications aimed at improving chicken health and productivity.

Cellular immunotherapy for follicular lymphoma using genetically modified CD20-specific CD8+ cytotoxic T lymphocytes

Humoral immunotherapy using the monoclonal anti-CD20 antibody rituximab induces remissions in approximately 60% of patients with relapsed follicular lymphoma; however, most patients eventually relapse despite continued expression of CD20 on lymphoma cells. We have hypothesized that cellular immunotherapy targeting CD20(+) cells might provide a more effective mechanism for eliminating lymphoma cells than anti-CD20 antibodies and are therefore investigating the utility of cytotoxic T lymphocytes (CTL) genetically modified to target the CD20 antigen. Peripheral blood mononuclear cells were activated with anti-CD3 antibody (OKT3) and recombinant human interleukin-2 and electroporated with a plasmid containing a CD20-specific scFvFc:zeta chimeric T cell receptor gene and a neomycin phosphotransferase gene (neo(R)). Transfected cells were selected using the antibiotic G418 and cloned by limiting dilution. Using this approach, we have generated CD8(+) CTL clones with CD20-specific cytotoxicity, which specifically lysed CD20(+) target cells, including actual tumor cells from patients with follicular lymphoma, small lymphocytic lymphoma, splenic marginal zone lymphoma, diffuse large B cell lymphoma, and chronic lymphocytic leukemia. The CTL clones have been expanded to numbers sufficient for therapy ( approximately 10(9) cells). Our data indicate the feasibility of generating and expanding CD20-specific CTL and, for the first time, demonstrate that such CTL exhibit specific cytotoxicity against actual tumor cells isolated from patients with a variety of B lymphoid malignancies. In view of these promising findings, a Phase I clinical trial for relapsed follicular lymphoma is being initiated.

Status of Cytomegalovirus Prevention and Treatment in 2000

Cytomegalovirus (CMV) infection continues to be a problem in selected populations following hematopoietic stem cell transplantation (SCT). Although there have been no new antiviral agents for management of this infection in recent years, the methods for using the existing agents have improved with newer assays for detection of virus. In addition, our understanding of immunity to CMV has undergone considerable expansion. This paper will address these new aspects relating to CMV infection in the setting of SCT. In Section I Dr. Zaia reviews the pathogenesis of CMV and the current epidemiology of CMV disease following marrow or blood allo-SCT with emphasis on late-onset disease. The current lab tests available for preemptive management are summarized including the role for conventional shell vial cultures, and a comparison of the CMV antigenemia assay with the new nucleic acid-based assays, including the hybrid capture assay, the NASBA assay, and "real-time" PCR assays. Use of antiviral agents with these tests in the preemptive management of CMV infection is discussed. Ultimately, what is necessary is restoration of adequate CMV immunity, and that requires understanding the basics of the CMV-specific immune response. In Section II, Dr. Sissons traces the evolution of the CTL response from primary infection into memory and reviews recent advances in the understanding of cytotoxic T cell based immunity to CMV, based on the use of T cell clonotypic analysis and markers of T cell memory and activation, with conventional CTL functional assays. In Section III Dr. Riddell presents approaches to correction of the problem of CMV pathogenesis, namely direct restoration of the CMV-specific cellular immune deficiency. Attempts at passive therapies will be reviewed with the focus on current problems and approaches to these problems. In Section IV, Dr. Diamond presents work on the identification of multiple HLA-allele specific cytotoxic T cell epitopes specific for CMV-pp65 and - pp150. Specific epitopes are recognized by CMV-seropositive individuals including healthy donors, SCT recipients, and AIDS patients, indicating their potential usefulness as vaccines. One of these epitopes is recognized by most individuals who express the HLA A(*)0201 Class I allele. Pre-clinical evaluation in HLA2.1 transgenic mice of vaccine structures utilizing this epitope, and alternative delivery systems are described. Possible methods for vaccination of donor and/or recipient of a SCT as well as their limitations, utilizing synthetic or viral vaccines, are discusseed.

Granulocyte colony-stimulating factor given to donors before apheresis does not prevent aplasia in patients treated with donor leukocyte infusion for recurrent chronic myeloid leukemia after bone marrow transplantation

We conducted 2 sequential studies of donor leukocyte infusion (DLI) in 26 patients with chronic myeloid leukemia in hematologic relapse after unmodified allogeneic bone marrow transplantation. In the first study, cells for DLI were collected from 13 donors who were not treated with granulocyte colony-stimulating factor (G-CSF) (group 1). In the second study, cells were collected from 13 donors who received G-CSF before apheresis (group 2) in an attempt to avoid aplasia after DLI. Patients in group 2 received 550-fold more CD34+ cells than those in group 1. We found no significant difference in the incidence (31% versus 22%), onset time (41 vs. 48 days), or duration (15 vs. 14 days) of cytopenia after DLI in the 2 groups. G-CSF given to donors before collection of cells did not prevent aplasia. These findings support the hypothesis that the pathogenesis of aplasia after DLI is not restricted to the destruction of recipient hematopoietic cells but also involves failure of donor hematopoiesis by undefined mechanisms.

Safety and immunogenicity of the Towne strain cytomegalovirus vaccine

BACKGROUND

Women with naturally acquired serum antibodies to cytomegalovirus (CMV) are usually protected against both frequent secondary infection and giving birth to infants severely affected by intrauterine CMV infection.

OBJECTIVE

To determine the feasibility of using a live attenuated strain of CMV (Towne) to achieve immunity similar to that provided by wild-type infection, we evaluated a new lot of the Towne strain of CMV in 3 open label trials involving 68 men, 63 women of childbearing age and 13 children, respectively.

RESULTS

Mild local reactions occurred among approximately one-third of subjects. There were no systemic reactions. All 45 subjects tested developed lymphoproliferative responses to CMV. CD8+ class I-restricted cytotoxic T cell responses specific for CMV antigens were detected in three of four subjects and persisted for 6 months. Neutralizing titers were maximal at 2 to 4 months postimmunization, were dose-dependent and were comparable to those induced by natural infection.

CONCLUSION

These results support further evaluation of the Towne strain of CMV in women at risk for acquiring CMV infection during pregnancy or among children transmitting CMV to pregnant women.

Intrapatient sequence variation of the gag gene of human immunodeficiency virus type 1 plasma virions

Because certain regions of the gag gene, such as p24, are highly conserved among human immunodeficiency virus (HIV) isolates, many therapeutic strategies have been directed at gag gene targets. Although intrapatient variation of segments of gag have been determined, little is known about the variability of the full-length gag gene for HIV isolated from a single individual. To evaluate intrapatient full-length gag variability, we derived the nucleotide sequences of at least 10 cDNA gag clones of virion RNA isolated from plasma for each of four asymptomatic HIV type 1-infected patients with relatively high CD4+ T-cell counts (300 to 450 cells per mm3). Mean values of intrapatient gag nucleotide variation obtained by pairwise comparisons ranged from 0.55 to 2.86%. For three subjects, this value was equivalent to that reported for intrapatient full-length env variation. The greatest range of intrapatient mean nucleotide variation for individual protein-coding regions was observed for p7. We did not detect any G-to-A hypermutation, as A-to-G and G-to-A transitions occurred at similar frequencies, accounting for 29 and 25%, respectively, of the changes. Mean variation values and phylogenetic analysis suggested that the extent of nucleotide variation correlated with the length of viral infection. Furthermore, no distinct subpopulations of quasispecies were detectable within an individual. The predicted amino acid sequences indicated that there were no regions within a gag protein that were comprised of clustered changes.

High-dose cytarabine and total body irradiation with or without cyclophosphamide as a preparative regimen for marrow transplantation for acute leukemia

Twenty-nine patients were conditioned for allogeneic marrow transplant with cytarabine (ara-C) (3 g/m2 every 12 hours for 12 doses) and total body irradiation (TBI) (200 cGy daily for six days) with or without cyclophosphamide (CY) (60 mg/kg) to determine toxicity and efficacy. Four patients had chronic myelogenous leukemia (CML) in accelerated phase or blast crisis, and 25 patients had acute leukemia, 24 at stages later than first remission. Three patients (10%) had fatal regimen-related toxicity and another 10% experienced severe toxicity in at least one organ system. The addition of CY to the ara-C and TBI regimen was not associated with an increase in the frequency of severe toxicity. Twenty-five of 29 patients engrafted eight to 33 days posttransplant: three died early before engraftment, and one patient failed to engraft. Ten of 29 patients are alive without disease, and the actuarial probability of disease-free survival for the entire group at 3 years is 33%. Three of ten patients with acute nonlymphocytic leukemia (ANL), six of 15 with acute lymphocytic leukemia (ALL), and one of four with CML are alive and disease free 25 to 42 months (median, 30 months) after transplant. High-dose ara-C (HDara-C) and TBI with or without CY can be administered with approximately the same toxicity as CY plus TBI. Phase III studies appear warranted to determine if these newer regimens provide improved results compared with currently used regimens.

Colonization with slime-positive coagulase-negative staphylococci as a risk factor for invasive coagulase-negative staphylococci infections in neonates

Mucocutaneous cultures obtained at admission and subsequent weekly nasopharyngeal cultures were obtained on 182 infants in the neonatal intensive care unit (NICU) over 3 months to assess whether a relationship existed between colonization with coagulase-negative staphylococci and invasive infection, particularly with respect to slime production. Nasopharyngeal colonization by coagulase-negative staphylococci occurred in a mean of 58% of infants weekly, with an equal prevalence of slime-positive and slime-negative isolates over time. Colonization of the nasopharynx on admission increased from 8.9% of those admitted within the first day of life to 33% of those admitted thereafter (p less than 0.005). The presence of slime-positive coagulase-negative staphylococci on admission was not predictive of later patterns of colonization with respect to slime. Of infants not colonized on admission who had subsequent cultures, 72% became colonized with coagulase-negative staphylococci that were equally likely to be slime-positive or slime-negative. The incidence of invasive infections was 4.4%. Infants with slime-positive mucocutaneous colonization were more likely to develop invasive coagulase-negative staphylococci disease than infants with slime-negative or no colonization (8.4% versus 1.1%; p less than 0.025). The incidence of slime-positive coagulase-negative staphylococci isolates from blood cultures was 6/7 (86%) whereas those from mucocutaneous cultures was 131/260 (50%) (p = 0.06). Colonization with slime-positive coagulase-negative staphylococci is a significant risk factor for developing invasive coagulase-negative staphylococci disease and these organisms are responsible for the majority of coagulase-negative staphylococci invasive infections.

The double gammopathies. Clinical and immunological studies

A retrospective review of 1135 patients with paraproteinemias recorded 28 (2.5%) as having two M components. This group included 11 patients with myeloma, 6 with lymphoproliferative disease, 5 with a nonlymphoproliferative malignancy, and 6 with a double gammopathy of undetermined significance. In 13 cases in which the M components were measured over a period of time, three distinct patterns were observed, which may reflect the cellular and subcellular origin of the two proteins: 1) In 2 cases the minor component remained relatively stable while the dominant protein changed with time and treatment, suggesting the origin to be two cell lines--the minor arising from a quiescent clone of the monoclonal gammopathy of undetermined significance, and the major M component arising from a more rapidly proliferating plasma cell line; 2) a discordant pattern was seen in 4 patients, suggesting that the two M components arose from two separate plasma cell clones; 3) seven cases in which the proteins behaved in a concordant manner probably arose from a single plasma cell clone with incomplete class switching, producing two M components with different heavy chains.

The treatment resistance of lymphocyte depleted Hodgkin's disease

Lymphocyte-depleted Hodgkin's Disease (LDHD) is a very aggressive form of cancer that presents at an advanced stage and for which no increase in overall survival has been demonstrated with the advent of multiple agent chemotherapy. All cases of Hodgkin's disease diagnosed in the Province of Manitoba between 1971 and 1977 were reviewed. Those cases identified as LDHD were reviewed by a single pathologist, and data was abstracted to obtain a clinical profile. Survival curves were constructed comparing the LDHD group to those with other types of Hodgkin's disease. The LDHD group was also compared with an earlier LDHD group treated with single agent chemotherapy in the 1960s. The LDHD group had a significantly shortened survival compared with the other histologies. This was just as significant when mixed cellularity Hodgkin's was compared with LDHD and matched for Stage B symptomatology. Furthermore, there was no difference in survival between the earlier LDHD groups treated with single agent chemotherapy and the later group treated with multiple agent chemotherapy.