CT109-SN-38, a Novel Antibody-drug Conjugate with Dual Specificity for CEACAM5 and 6, Elicits Potent Killing of Pancreatic Cancer Cells

BACKGROUND

CEACAM5 and CEACAM6 are glycosylphosphatidylinositol (GPI)- linked members of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family, which are frequently upregulated in epithelial cancers where they contribute to invasion, metastasis, immune evasion, and resistance to anoikis. CT109 is a novel antibody with dual specificity to both CEACAM5 and 6.

OBJECTIVE

In this study, we aimed to perform the preclinical characterization of CT109 and antibody- drug conjugate (ADCs) derivatives of CT109, focusing on CT109-SN-38.

METHODS

CT109's cognate epitope was characterized by scanning mutagenesis. CT109 specificity and internalization kinetics were assessed by immunoblot and flow cytometry, respectively. Cognate antigen expression prevalence in colorectal cancer and normal tissue arrays was determined by immunohistochemistry. CT109 conjugations were generated by the reaction of reduced CT109 cysteines with maleimide-functionalized payload linkers. In vitro cytotoxic activity of CT109 ADCs was characterized on antigen-positive and negative pancreatic ductal adenocarcinoma cell (PDAC) lines using a luminometric viability assay. In vivo efficacy of CT109-SN-38 was assessed on a PDAC tumor xenograft model at 10 and 25 mg/kg concentrations.

RESULTS

CT109 showed to bind a glycoepitope centered on N309. CT109 is internalized in the CEACAM5+/CEACAM6+ double-positive PDAC line, BxPC-3, with a t1/2 of 2.3 hours. CT109 ADCs elicit a dose and antigen-dependent cytotoxic effect, with CT109-SN-38 exhibiting an IC50 value of 21 nM in BxPC-3 cells. In a BxPC-3 tumor xenograft model, CT109-SN-38 reduced tumor growth and induced regression in 3/10 mice at 25 mg/kg concentration.

CONCLUSIONS

These data suggest that further preclinical and clinical development of CT109-SN-38 is warranted.

SERPIN-Derived Small Peptide (SP16) as a Potential Therapeutic Agent against HIV-Induced Inflammatory Molecules and Viral Replication in Cells of the Central Nervous System

Despite the success of combined antiretroviral therapy (cART) increasing the survival rate in human immunodeficiency virus (HIV) patients, low levels of viremia persist in the brain of patients leading to glia (microglia and astrocytes)-induced neuroinflammation and consequently, the reactivation of HIV and neuronal injury. Here, we tested the therapeutic efficacy of a Low-Density Lipoprotein Receptor-Related Protein 1 (LRP-1) agonistic small peptide drug (SP16) in attenuating HIV replication and the secretion of inflammatory molecules in brain reservoirs. SP16 was developed by Serpin Pharma and is derived from the pentapeptide sequence of the serine protease inhibitor alpha-1-antitrypsin (A1AT). The SP16 peptide sequence was subsequently modified to improve the stability, bioavailability, efficacy, and binding to LRP-1; a scavenger regulatory receptor that internalizes ligands to induce anti-viral, anti-inflammatory, and pro-survival signals. Using glial cells infected with HIV, we showed that: (i) SP16 attenuated viral-induced secretion of pro-inflammatory molecules; and (ii) SP16 attenuated viral replication. Using an artificial 3D blood-brain barrier (BBB) system, we showed that: (i) SP16 was transported across the BBB; and (ii) restored the permeability of the BBB compromised by HIV. Mechanistically, we showed that SP16 interaction with LRP-1 and binding lead to: (i) down-regulation in the expression levels of nuclear factor-kappa beta (NF-κB); and (ii) up-regulation in the expression levels of Akt. Using an in vivo mouse model, we showed that SP16 was transported across the BBB after intranasal delivery, while animals infected with EcoHIV undergo a reduction in (i) viral replication and (ii) viral secreted inflammatory molecules, after exposure to SP16 and antiretrovirals. Overall, these studies confirm a therapeutic response of SP16 against HIV-associated inflammatory effects in the brain.

Cannabinoids Reduce Extracellular Vesicle Release from HIV-1 Infected Myeloid Cells and Inhibit Viral Transcription

Of the 37.9 million individuals infected with human immunodeficiency virus type 1 (HIV-1), approximately 50% exhibit HIV-associated neurocognitive disorders (HAND). We and others previously showed that HIV-1 viral RNAs, such as trans-activating response (TAR) RNA, are incorporated into extracellular vesicles (EVs) and elicit an inflammatory response in recipient naïve cells. Cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC), the primary cannabinoids present in cannabis, are effective in reducing inflammation. Studies show that cannabis use in people living with HIV-1 is associated with lower viral load, lower circulating CD16+ monocytes and high CD4+ T-cell counts, suggesting a potentially therapeutic application. Here, HIV-1 infected U1 monocytes and primary macrophages were used to assess the effects of CBD. Post-CBD treatment, EV concentrations were analyzed using nanoparticle tracking analysis. Changes in intracellular and EV-associated viral RNA were quantified using RT-qPCR, and changes in viral proteins, EV markers, and autophagy proteins were assessed by Western blot. Our data suggest that CBD significantly reduces the number of EVs released from infected cells and that this may be mediated by reducing viral transcription and autophagy activation. Therefore, CBD may exert a protective effect by alleviating the pathogenic effects of EVs in HIV-1 and CNS-related infections.

α1-Antitrypsin derived SP16 peptide demonstrates efficacy in rodent models of acute and neuropathic pain

SP16 is an innovative peptide derived from the carboxyl-terminus of α1-Antitrypsin (AAT), corresponding to residues 364-380, and contains recognition sequences for the low-density lipoprotein receptor-related protein-1 (LRP1). LRP1 is an endocytic and cell-signaling receptor that regulates inflammation. Deletion of Lrp1 in Schwann cells increases neuropathic pain; however, the role of LRP1 activation in nociceptive and neuropathic pain regulation remains unknown. Herein, we show that SP16 is bioactive in sensory neurons in vitro. Neurite length and regenerative gene expression were increased by SP16. In PC12 cells, SP16 activated Akt and ERK1/2 cell-signaling in an LRP1-dependent manner. When formalin was injected into mouse hind paws, to model inflammatory pain, SP16 dose-dependently attenuated nociceptive pain behaviors in the early and late phases. In a second model of acute pain using capsaicin, SP16 significantly reduced paw licking in both male and female mice (p < .01) similarly to enzymatically inactive tissue plasminogen activator, a known LRP1 interactor. SP16 also prevented development of tactile allodynia after partial nerve ligation and this response was sustained for nine days (p < .01). Immunoblot analysis of the injured nerve revealed decreased CD11b (p < .01) and Toll-like receptor-4 (p < .005). In injured dorsal root ganglia SP16 reduced CD11b⁺ cells (p < .05) and GFAP (p < .005), indicating that inflammatory cell recruitment and satellite cell activation were inhibited. In conclusion, administration of SP16 blocked pain-related responses in three distinct pain models, suggesting efficacy against acute nociceptive, inflammatory, and neuropathic pain. SP16 also attenuated innate immunity in the PNS. These studies identify SP16 as a potentially effective treatment for pain.

A phase 1 clinical trial of SP16, a first-in-class anti-inflammatory LRP1 agonist, in healthy volunteers

BACKGROUND

Endogenous serine protease inhibitors are associated with anti-inflammatory and pro-survival signaling mediated via Low-density lipoprotein receptor-related protein 1 (LRP1) signaling. SP16 is a short polypeptide that mimics the LRP1 binding portion of alpha-1 antitrypsin.

METHODS

A pilot phase I, first-in-man, randomized, double blind, placebo-controlled safety study was conducted to evaluate a subcutaneous injection at three dose levels of SP16 (0.0125, 0.05, and 0.2 mg/kg [up to 12 mg]) or matching placebo in 3:1 ratio in healthy individuals. Safety monitoring included vital signs, laboratory examinations (including hematology, coagulation, platelet function, chemistry, myocardial toxicity) and electrocardiography (to measure effect on PR, QRS, and QTc).

RESULTS

Treatment with SP16 was not associated with treatment related serious adverse events. SP16 was associated with mild-moderate pain at the time of injection that was significantly higher than placebo on a 0-10 pain scale (6.0+/-1.4 [0.2 mg/kg] versus 1.5+/-2.1 [placebo], P = 0.0088). No differences in vital signs, laboratory examinations and electrocardiography were found in those treated with SP16 versus placebo.

CONCLUSION

A one-time treatment with SP16 for doses up to 0.2 mg/kg or 12 mg was safe in healthy volunteers.

Proteome changes in muscles, ganglia, and gills in Corbicula fluminea clams exposed to crude oil: Relationship with behavioural disturbances

The use of online remote control for 24/7 behavioural monitoring can play a key role in estimating the environmental status of aquatic ecosystems. Recording the valve activity of bivalve molluscs is a relevant approach in this context. However, a clear understanding of the underlying disturbances associated with behaviour is a key step. In this work, we studied freshwater Asian clams after exposure to crude oil (measured concentration, 167 ± 28 μg·L^-1) for three days in a semi-natural environment using outdoor artificial streams. Three complementary approaches to assess and explore disturbances were used: behaviour by high frequency non-invasive (HFNI) valvometry, tissue contamination with polycyclic aromatic hydrocarbons (PAH), and proteomic analysis. Two tissues were targeted: the pool adductor muscles - retractor pedal muscle - cerebral and visceral ganglia, which is the effector of any valve movement and the gills, which are on the frontline during contamination. The behavioural response was marked by an increase in valve closure-duration, a decrease in valve opening-amplitude and an increase in valve agitation index during opening periods. There was no significant PAH accumulation in the muscle plus nervous ganglia pool, contrary to the situation in the gills, although the latter remained in the low range of data available in literature. Major proteomic changes included (i) a slowdown in metabolic and/or cellular processes in muscles plus ganglia pool associated with minor toxicological effect and (ii) an increase of metabolic and/or cellular processes in gills associated with a greater toxicological effect. The nature of the proteomic changes is discussed in terms of unequal PAH distribution and allows to propose a set of explanatory mechanisms to associate behaviour to underlying physiological changes following oil exposure. First, the first tissues facing contaminated water are the inhalant siphon, the mantle edge and the gills. The routine nervous activity in the visceral ganglia should be modified by nervous information originating from these tissues. Second, the nervous activity in the visceral ganglia could be modified by its own specific contamination. Third, a decrease in nervous activity of the cerebral ganglia close to the mouth, including some kind of narcosis, could contribute to a decrease in visceral ganglia activity via a decrease or blockage of the downward neuromodulation by the cerebro-visceral connective. This whole set of events can explain the decrease of metabolic activity in the adductor muscles, contribute to initiate the catch mechanism and then deeply modify the valve behaviour.

Asiatic clam Corbicula fluminea exhibits distinguishable behavioural responses to crude oil under semi-natural multiple stress conditions

Aquatic ecosystems are subject to many anthropogenic disturbances, and understanding their possible impacts is a real challenge. Developing approaches based on the behaviour of bivalve mollusks, an integrating marker of the state of the organisms, and therefore of their environment, is relevant, whether within a natural ecosystem or an ecosystem subject to industrial activities. The main objective of this study was to identify by HFNI Valvometry a reliable and reproducible clam behavioural response in the presence of crude oil in a multistress context. To closely replicate actual field conditions, Corbicula fluminea was exposed in outdoor artificial streams that were subject to natural variations and were continuously fed by fresh water from the Gave de Pau (S.W. France). After a period of 26 days in these artificial streams, the clams (n = 14-16 per condition) were separately exposed for 10 days to crude oil alone, crude oil and barium, crude oil and noise pollution, crude oil and turbidity pulses, barium alone, noise pollution alone, turbidity pulses alone or natural changes alone. The secondary objective was to characterize the accumulation of polycyclic aromatic hydrocarbons (PAH) in 3 tissues (gills, adductor muscles and foot) in clams exposed for 10 days to crude oil alone or under multistress conditions (n = 5 clams per condition) and then to compare the accumulation and behaviour of clams under these conditions. The response of clams to crude oil alone or under multistress conditions was visually and statistically significant and not confounded by the other disturbances tested, despite large variations in water temperature. In the presence of crude oil, the behaviour of clams was characterized by an increase in valve-closure duration, a decrease in valve-opening amplitude and an increase in valve agitation index. In the presence of crude oil, the clam behaviour showed no direct relationship with PAH accumulation in the gills, adductor muscles or foot, although hypothetical mechanisms are discussed. This work supports the growing interest in studying the behaviour of bivalve mollusks in the context of biomonitoring of the aquatic environment surrounding oil facilities.

Low-Density Lipoprotein Receptor-Related Protein-1 Is a Therapeutic Target in Acute Myocardial Infarction

Low-density lipoprotein receptor-related protein-1 (LRP1) is a ubiquitous membrane receptor functioning as a scavenger and regulatory receptor, inducing anti-inflammatory and prosurvival signals. Based on the known structure-activity of the LRP1 receptor binding site, the authors synthesized a small peptide (SP16). SP16 induced a >50% reduction in infarct size (p < 0.001) and preservation of left ventricular systolic function (p < 0.001), and treatment with an LRP1 blocking antibody eliminated the protective effects of SP16. In conclusion, LRP1 activation with SP16 given within 30 min of reperfusion during experimental acute myocardial infarction leads to a cardioprotective signal reducing infarct size and preservation of cardiac systolic function.

Abstract 2485: Novel monoclonal antibody targeting cancer stem cells

Caerus Therapeutics (Caerus) is developing a monoclonal antibody directed to a cancer specific epitope on CD66c (CEACAM6) designated 109.12. CD66c has been shown in preclinical studies to be expressed on the colorectal cancer stem cell population but not on normal intestinal stem cells, making this a potential target for a therapeutic antibody. Previous attempts by other companies to develop anti-CD66c antibodies were unsuccessful due to cross-reactivity with CD66c on normal tissues. Caerus has developed a monoclonal antibody to a cancer-specific, glycan epitope that is only expressed in the adult during malignant transformation, enabling the targeting of CD66c on both cancer stem cells (CSCs) as well as bulk tumor without cross-reactivity with CD66c on normal cells. The glycan epitope recognized by the antibody has a novel structure not previously described that is highly protein-specific and site-specific. The specificity is due to a unique dual-recognition determinant for the site-specific glycosylation.

In addition to its expression on colorectal tumorspheres, the epitope recognized by the 109.12 antibody is expressed by a wide variety of cancers including colon, pancreatic, lung stomach and a subtype of breast cancer. The biological role of CD66c in malignancy and tumor dissemination is well documented; the specificity of the antibody for a CD66c epitope only expressed in malignant cells offers multiple opportunities for immunotherapy and diagnosis of a diverse spectrum of cancers.

Citation Format: Jeff Holderness, Amy Turner, Sam dolezal, Steve Wolpe, Michael Pierce, Cohava Gelber. Novel monoclonal antibody targeting cancer stem cells. [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 2485. doi:10.1158/1538-7445.AM2015-2485

Establishment of the first international repository for transfusion-relevant bacteria reference strains: ISBT working party transfusion-transmitted infectious diseases (WP-TTID), subgroup on bacteria

BACKGROUND

Bacterial contamination of platelet concentrates (PCs) still remains a significant problem in transfusion with potential important clinical consequences, including death. The International Society of Blood Transfusion Working Party on Transfusion-Transmitted Infectious Diseases, Subgroup on Bacteria, organised an international study on Transfusion-Relevant Bacteria References to be used as a tool for development, validation and comparison of both bacterial screening and pathogen reduction methods.

MATERIAL AND METHODS

Four Bacteria References (Staphylococcus epidermidis PEI-B-06, Streptococcus pyogenes PEI-B-20, Klebsiella pneumoniae PEI-B-08 and Escherichia coli PEI-B-19) were selected regarding their ability to proliferate to high counts in PCs and distributed anonymised to 14 laboratories in 10 countries for identification, enumeration and bacterial proliferation in PCs after low spiking (0·3 and 0·03 CFU/ml), to simulate contamination occurring during blood donation.

RESULTS

Bacteria References were correctly identified in 98% of all 52 identifications. S. pyogenes and E. coli grew in PCs in 11 out of 12 laboratories, and K. pneumoniae and S. epidermidis replicated in all participating laboratories. The results of bacterial counts were very consistent between laboratories: the 95% confidence intervals were for S. epidermidis: 1·19-1·32 × 10(7) CFU/ml, S. pyogenes: 0·58-0·69 × 10(7) CFU/ml, K. pneumoniae: 18·71-20·26 × 10(7) CFU/ml and E. coli: 1·78-2·10 × 10(7) CFU/ml.

CONCLUSION

The study was undertaken as a proof of principle with the aim to demonstrate (i) the quality, stability and suitability of the bacterial strains for low-titre spiking of blood components, (ii) the property of donor-independent proliferation in PCs, and (iii) their suitability for worldwide shipping of deep frozen, blinded pathogenic bacteria. These aims were successfully fulfilled. The WHO Expert Committee Biological Standardisation has approved the adoption of these four bacteria strains as the first Repository for Transfusion-Relevant Bacteria Reference Strains and, additionally, endorsed as a project the addition of six further bacteria strain preparations suitable for control of platelet contamination as the next step of enlargement of the repository.

The costs of using unauthenticated, over-passaged cell lines: how much more data do we need?

Increasing data demonstrate that cellular cross-contamination, misidentified cell lines, and the use of cultures at high-passage levels contribute to the generation of erroneous and misleading results as well as wasted research funds. Contamination of cell lines by other lines has been recognized and documented back to the 1950s. Based on submissions to major cell repositories in the last decade, it is estimated that between 18% and 36% of cell lines may be contaminated or misidentified. More recently, problems surrounding practices of over-subculturing cells are being identified. As a result of selective pressures and genetic drift, cell lines, when kept in culture too long, exhibit reduced or altered key functions and often no longer represent reliable models of their original source material. A review of papers showing significant experimental variances between low- and high-passage cell culture numbers, as well as contaminated lines, makes a strong case for using verified, tested cell lines at low- or defined passage numbers. In the absence of cell culture guidelines, mandates from the National Institutes of Health (NIH) and other funding agencies or journal requirements, it becomes the responsibility of the scientific community to perform due diligence to ensure the integrity of cell cultures used in research.

A new small cell lung cancer (SCLC)-specific marker discovered through antigenic subtraction of neuroblastoma cells

Small cell lung cancer (SCLC) is an aggressive form of lung cancer associated with cigarette smoking and presently accounts for approximately 20% of all lung cancer cases. SCLC cells derive from a neuroendocrine origin and therefore their antigenic profile coincides, to a great extent, with that of neuroendocrine cells. Multiple attempts to generate SCLC-specific MoAbs during the past decade have failed because all SCLC-specific MoAbs isolated also react against neuroendocrine tissues or normal immune cells. Cross-reactivity with normal antigens raises safety concerns due to the inevitable toxicity of such interactions and the dreaded effects. The concept of DIAAD trade mark ( Differential Immunization for Antigen and Antibody Discovery) provides for an immune response that can be effectively focused on cancer antigens. The object is to overcome obstacles resulting from an antigenic hierarchical pattern biased towards a response to dominant antigens in order to induce a robust immune response to cancer antigens. Cancer antigens are weak or nonimmunogenic molecules. Due to the fact that the immune system responds more strongly to immunodominant antigens than to weak immunogenic antigens, cancer cell proliferation is unencumbered. DIAAD employs protocols of induction of tolerance and immunity, conducted in sequential order to "biologically subtract" the immune response of dominant antigens expressed by normal cells. This biological subtraction is achieved in a laboratory animal by first eliminating the immune response to the normal cells or closely related cancer cells, followed by immunization of the same laboratory animal with diseased cells. This procedure directs the immune response exclusively towards antigens expressed by the diseased and not the normal cells. Our objective was to use DIAAD to generate monoclonal antibodies specific to SCLC antigens that are not shared by neuroendocrine cells by contrasting a pool of human SCLC cell lines with a pool of human neuroendocrine cancer cell lines. Four monoclonal antibodies reacted strongly and exclusively with SCLC cells and identified a membrane molecule comprising a single chain glycoprotein. Two of four antibodies were selected for a detailed analysis that revealed a narrow tissue specificity of antigen expressed by colon, lung, and pancreatic cancers (less than 20% staining was found on breast, ovarian and prostate cancer). These antibodies did not bind to various other cancers such as kidney, carcinoid, lymphoma, sarcoma, adrenal, liver, melanoma, seminoma, leiomyoma, basal cell cancer, or undifferentiated cancer. The epitope recognized by the selected MoAbs was destroyed with the removal of carbohydrates from SCLC cells. This result does not exclude the possibility of protein-carbohydrate cooperation in epitope recognition. However, it strongly suggests the pivotal role of carbohydrates in antibody binding to this molecule. Upon binding to the extracellular molecule on SCLC cells, the antibodies were shown to internalize. A low or insignificant level of internalization was recorded following incubation of the antibodies with neuroendocrine-derived tumors. The capacity of these antibodies to internalize upon binding the extracellular receptors renders them potential candidates for prodrug or immunotoxin-targeted therapeutics. In a qualitative experiment involving immunoaffinity purification, the SCLC antigen was shown to be differentially detected in sera of SCLC patients. Plans are being generated to explore the possible utility of this novel SCLC-specific antigen recognized by the above MoAbs as a new biomarker for early diagnosis of the disease, as well as for therapeutic intervention for SCLC.

Monoclonal antibody identifies a distinctive epitope expressed by human multiple myeloma cells

Employing a technology called differential immunization for antigen and antibody discovery (DIAAD), we aimed to generate monoclonal antibodies (mAbs) specific to human multiple myeloma (MM) cells. The fundamental principles of DIAAD rely on the induction of high zone tolerance to the "wild type" (normal) antigen. followed by immunization with the modified (diseased) antigen. Because chronic myelogenic leukemia (CML) cells are derived from a lineage closely related to MM, we immunized mice by contrasting a pool of MM cells with CML cells. Monoclonal antibody VAC69 reacted exclusively with MM cells, identifying a membrane molecule composed of a single-chain glycoprotein with a molecular weight of 78-120 kd. This antigen exhibited narrow tissue specificity and was not found on human cancers such as prostate, breast, or cervical carcinoma; leukemia; or lymphoma, nor was it seen on normal human peripheral lymphocytes or on Epstein-Barr virus-transformed B-cell lines. By immunohistochemistry, mAb VAC69 showed no binding to antigens expressed on normal human ovary, breast, prostate, lung or colon tissue, nor did it bind to human breast or prostate cancer. Conversely, mAb VAC69 bound strongly to human MM, although showing only slight binding to histiocytes or inflamed cells in human lymph nodes and human tumors of the colon, lung, and ovary. Monoclonal antibody VAC69 also triggered cancer-specific cytotoxicity in vitro (in the presence of complement) as well as in vivo using a sever combined immunodeficiency model transplanted with human MM. Further studies showed the ability of mAb VAC69 to be specifically internalized by human MM cells, indicating its potential use for therapeutic intervention in MM by delivering drugs into cancer cells.

Dendritic cells improve the generation of Epstein-Barr virus-specific cytotoxic T lymphocytes for the treatment of posttransplantation lymphoma

BACKGROUND

The use of immunosuppressive therapies after solid organ transplantation has been shown to increase a patient's risk for Epstein-Barr virus (EBV)-associated lymphoma. A potential therapy for this disorder is the adoptive transfer of EBV-specific cytotoxic T lymphocytes (CTLs). We proposed that dendritic cells (DCs) could be loaded with EBV antigens and be used to improve the in vitro generation of EBV-specific CTLs.

METHODS

Autologous EBV-transformed B-lymphoblastoid cell lines (BLCLs) were generated from normal donors, and CTLs were initiated by culturing peripheral blood mononuclear cells with DCs alone, disrupted BLCLs alone, intact, irradiated BLCLs alone, and DCs loaded with disrupted BLCLs. Lytic activities were determined with a 4-hour chromium-release assay against autologous BLCLs, and statistical calculations were performed by a Student t test assuming equal variance.

RESULTS

The lytic activity of CTLs generated with DCs loaded with disrupted BLCLs reached 78% and was statistically significant (P < .01) at all effector/target ratios compared with CTLs generated with DCs alone, disrupted BLCLs alone, or intact BLCLs alone. Total numbers of CTLs were also greater than those of control groups for DCs loaded with disrupted BLCLs.

CONCLUSIONS

DCs improved the in vitro generation of EBV-specific CTLs as evidenced by this group's significantly increased lytic activity over that of the control group. The improved lytic activity of DC-generated EBV-CTLs suggests that adoptive transfer of these cells could lead to a more effective immunotherapeutic response against posttransplantation EBV-associated lymphoma.

Down-regulation of poison ivy/oak-induced contact sensitivity by treatment with a class II MHC binding peptide:hapten conjugate

Immune regulation of contact sensitivity to the poison ivy/oak catechol was studied at the level of class II MHC-restricted T cell recognition of hapten:peptide conjugates. In this study we have shown that 1) T cells from C3H/HeN (H-2k) mice, immunized with a synthetic I-Ak binding peptide coupled to 3-pentadecyl-catechol (PDC; a representative catechol in urushiol), recognized peptides derived from syngeneic cells linked to the same catechol; 2) T cells from draining lymph nodes of C3H/HeN mice skin-painted with PDC proliferated in response to a peptide carrier:PDC conjugate only when it was linked at the 7th, but not the 4th or the 10th, position on the peptide carrier; and 3) tolerization studies confirmed down-regulation of PDC-induced delayed-type hypersensitivity following treatment with a single I-Ak binding peptide carrying PDC covalently bound to a lysine residue at the middle (7th) TCR contact position. Tolerization with peptide:PDC conjugate resulted in abrogation of hapten-specific T cell proliferative responses that correlated with diminished IL-2 secretion. On the basis of these data we propose that it may be sufficient to couple the hapten at a single, well-chosen position on a carrier peptide to target a relevant population of T cells involved in contact sensitivity.

Down-regulation of poison ivy/oak-induced contact sensitivity by treatment with a class II MHC binding peptide:hapten conjugate

Immune regulation of contact sensitivity to the poison ivy/oak catechol was studied at the level of class II MHC-restricted T cell recognition of hapten:peptide conjugates. In this study we have shown that 1) T cells from C3H/HeN (H-2k) mice, immunized with a synthetic I-Ak binding peptide coupled to 3-pentadecyl-catechol (PDC; a representative catechol in urushiol), recognized peptides derived from syngeneic cells linked to the same catechol; 2) T cells from draining lymph nodes of C3H/HeN mice skin-painted with PDC proliferated in response to a peptide carrier:PDC conjugate only when it was linked at the 7th, but not the 4th or the 10th, position on the peptide carrier; and 3) tolerization studies confirmed down-regulation of PDC-induced delayed-type hypersensitivity following treatment with a single I-Ak binding peptide carrying PDC covalently bound to a lysine residue at the middle (7th) TCR contact position. Tolerization with peptide:PDC conjugate resulted in abrogation of hapten-specific T cell proliferative responses that correlated with diminished IL-2 secretion. On the basis of these data we propose that it may be sufficient to couple the hapten at a single, well-chosen position on a carrier peptide to target a relevant population of T cells involved in contact sensitivity.

Isolation of nonobese diabetic mouse T-cells that recognize novel autoantigens involved in the early events of diabetes

Insulin-dependent diabetes mellitus (IDDM) is thought to result from chronic, cell-mediated, autoimmune islet damage. Our aim was to identify the earliest T-cell autoantigen in IDDM, reasoning that this antigen could be causally involved in the initiation of the disease. Identification of the earliest beta-cell-specific autoantigen is extremely important in allowing advances in prevention and treatment of initial events in the development of inflammatory insulitis that precedes beta-cell destruction and overt diabetes. Therefore, we analyzed the proliferative responses of peripheral T-cells from young, female nonobese diabetic (NOD) mice to extracts of pancreatic beta-cell lines. We were able to demonstrate that T-cells responsive to beta-cell antigens exist in the peripheral lymphoid tissue of these mice in the absence of deliberate priming before the manifestation of histologically detectable insulitis. T-cell lines and clones isolated from the peripheral lymphatic tissues of young, unimmunized, female NOD mice were also shown to react with extracts of beta-cells. Fractionation of the beta-cell extracts showed that these T-cell clones recognized multiple beta-cell-specific autoantigens but none of the previously reported putative autoantigens (glutamic acid decarboxylase [GAD]65, GAD67, Hsp65, insulin, ICA 69, carboxypeptidase-H, and peripherin). Thus, we can conclude that these responses are specific for novel beta-cell autoantigens. Finally, NOD T-cell proliferative responses were also seen to an extract of human islets suggesting potential shared antigenic determinants between human and mouse beta-cells.(ABSTRACT TRUNCATED AT 250 WORDS)

T-cell subset analysis of Lewis lung carcinoma tumor rejection: heterogeneity of effectors and evidence for negative regulatory lymphocytes correlating with metastasis

We have analyzed the phenotypes of the T-cell subsets generated in response to Lewis lung carcinoma clones in C57BL/6J recipients. The metastatic derivative, which expresses low levels of H-2Kb gene, predominantly elicited CD8, V beta 8, and V beta 9+ T-cells. The nonmetastatic clone expressing high levels of H-Kb gene triggered a more heterogeneous response of V beta-5, -6, -8, -9, and -11 CD8+ T-cells. Comparison of the T-cell receptor (TCR) expression of the T-cells infiltrating the tumor site with the lymphocytes in the periphery of tumor-bearing animals revealed a pattern of homing of CD4+ T-cells bearing V beta-5, -6, and -11 TCR chains and CD8+ T-cells bearing V beta-5, -6, -9, and -11. Depletion of V beta 5 or V beta 6+ T-cells correlated with accelerated tumor growth, implying their protective role as tumor-specific effectors and consistent with the cytotoxicity of T-cells with this TCR phenotype. V beta 11 TCR expression in the tumor-infiltrating lymphocytes increased with the tumor size. Depletion of V beta 11+ T-cells enhanced resistance to primary tumor growth and conferred protection from metastasis in recipients cleared of V beta 5 and V beta 6 T-cell subsets. Those results suggest that tumor-specific effectors as well as negative regulator T-cells home, infiltrate, and coexist in the tumor site.

H-2Db gene transfer into highly metastatic D122 cells results in tumor rejection in allogeneic recipients, but does not affect metastasis in syngeneic recipients. Implications for mechanisms of allorejection

Highly metastatic, weakly immunogenic Lewis lung carcinoma clones express very low levels of H-2Kb and moderate levels of H-2Db class-I major histocompatibility complex antigens. These cells metastasize spontaneously in mice with C57BL/6 genetic background possessing the H-2Db locus, and grow as local tumors across allogeneic barriers. Transfection of the H-2Db genes into the highly metastatic clone D122 did not alter the growth or metastatic capacity of these cells in syngeneic mice. However, these cells were rejected in allogeneic mice. Transfection of the H-2Kd or H-2Kk genes into D122 elicited a CTL population that cross-reacted with cells bearing native H-2Db antigens. These data suggest that overlapping allo-CTL populations are induced by a native alloantigen and by alloantigen peptides presented through self class-I molecules.

T-cell subset analysis of 3LL tumor growth

We have partially characterized the T-cell subsets that control the growth of the C57BL/6 Lewis lung carcinoma 3LL transplanted into syngeneic mice. By analyzing the phenotypes of anti-tumor lymphocytes generated in vitro and in vivo, we have characterized a CD8 T-cell receptor (TcR) V beta 5,6 positive subpopulation of cytotoxic effectors important in retarding the growth of the transplanted tumor. In contrast, the rejection of 3LL appears to be hindered by the presence of a CD4 V beta II-positive subset since depletion of these lymphocytes in vivo with the appropriate monoclonal antibodies (MAbs) results in significant retardation of tumor growth. These results suggest that the cumulative positive and negative effects of distinct T-cell sub-populations determine the outcome of tumor progression and metastasis.

Abolishment of metastasis formation by murine tumor cells transfected with "foreign" H-2K genes

High metastatic, low immunogenic Lewis lung carcinoma clones express low levels of H-2Kb major histocompatibility complex antigens. These cells metastasize spontaneously in mice with C57BL/6 genetic background possessing the H-2Db locus. Transfection of different H-2K genes abrogates metastasis in H-2K, H-2D compatible mice and in C57BL/6 recipients. The transfected cells are potent inducers of H-2K-restricted and alloreactive cytotoxic lymphocytes that kill H-2K-positive cells and cross-react with parental nontransfected cells.

Reversal of the metastatic phenotype in Lewis lung carcinoma cells after transfection with syngeneic H-2Kb gene

High metastatic clones of the murine 3LL carcinoma express greatly reduced levels of H-2Kb major histocompatibility complex class I antigens, while low metastatic clones of the same tumor express high levels of H-2Kb. Induced expression of this antigen after transfection with the H-2Kb gene resulted in conversion of a metastatic to a non- or low-metastatic phenotype. Unlike the parental cells, transfected cells are potent inducers of H-2Kb-restricted syngeneic cytotoxic lymphocytes that kill the Kb-positive clones and cross-react with parental nontransfected cells. Preimmunization of mice with Kb-positive transfectants conferred protection against metastatic spread of malignant cells. Moreover, immunotherapy of metastasis was achieved by immunization with the H-2Kb-transfected cells of animals already carrying a growing local tumor of the parental cells.