Enhancement of antibody dependent cellular cytotoxicity (ADCC) by combination of cytokines

A Noncanonical CD56dimCD16dim/- NK Cell Subset Indicative of Prior Cytotoxic Activity Is Elevated in Patients with Autoantibody-Mediated Neurologic Diseases

Neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein Ab disease, and autoimmune myasthenia gravis (MG) are autoantibody-mediated neurologic conditions where autoantibodies can induce Ab-dependent cellular cytotoxicity (ADCC), a NK cell-mediated effector function. However, whether ADCC is a pathogenic mechanism in patients with these conditions has not been confirmed. We sought to characterize circulatory NK cells using functional assays, phenotyping, and transcriptomics to elucidate their role in pathology. NK cells from NMOSD patients and MG patients with elevated disease burden exhibited reduced ADCC and CD56dimCD16hi NK cells, along with an elevated frequency of CD56dimCD16dim/- NK cells. We determined that ADCC induces a similar phenotypic shift in vitro. Bulk RNA sequencing distinguished the CD56dimCD16dim/- population from the canonical CD56dimCD16hi cytotoxic and CD56hiCD16- immunomodulatory subsets, as well as CD56hiCD16+ NK cells. Multiparameter immunophenotyping of NK cell markers, functional proteins, and receptors similarly showed that the CD56dimCD16dim/- subset exhibits a unique profile while still maintaining expression of characteristic NK markers CD56, CD94, and NKp44. Notably, expression of perforin and granzyme is reduced in comparison with CD56dimCD16hi NK cells. Moreover, they exhibit elevated trogocytosis capability, HLA-DR expression, and many chemokine receptors, including CCR7. In contrast with NMOSD and MG, myelin oligodendrocyte glycoprotein Ab disease NK cells did not exhibit functional, phenotypic, or transcriptomic perturbations. In summary, CD56dimCD16dim/- NK cells are a distinct peripheral blood immune cell population in humans elevated upon prior cytotoxic activity by the CD56dimCD16hi NK cell subset. The elevation of this subset in NMOSD and MG patients suggests prior ADCC activity.

Possible Roles of Interleukin-4 and -13 and Their Receptors in Gastric and Colon Cancer

Interleukin (IL)-4 and -13 are structurally and functionally related cytokines sharing common receptor subunits. They regulate immune responses and, moreover, are involved in the pathogenesis of a variety of human neoplasms. Three different receptors have been described for IL-4, but only IL-4 receptor type II (IL-4Rα/IL-13Rα1) is expressed in solid tumors. While IL-13 can also bind to three different receptors, IL-13 receptor type I (IL-4Rα/IL-13Rα1/IL-13Rα2) and type II (IL-4Rα/IL-13Rα1) are expressed in solid tumors. After receptor binding, IL-4 and IL-13 can mediate tumor cell proliferation, survival, and metastasis in gastric or colon cancer. This review summarizes the results about the role of IL-4/IL-13 and their receptors in gastric and colon cancer.

Order of administration of combination cytokine therapies can decouple toxicity from efficacy in syngeneic mouse tumor models

In combination cancer immunotherapies, consideration should be given to designing treatment schedules that harmonize with the immune system's natural timing. An efficacious temporally programmed combination therapy of extended half-life interleukin 2 (eIL2), tumor targeting antibody, and interferon (IFN) α was recently reported; however, tumor-ablative efficacy was associated with significant toxicity. In the current work, altering the order and timing of the three agents is shown to decouple toxicity from efficacy. Delaying the administration of eIL2 to be concurrent with or after IFNα eliminates toxicity without affecting efficacy in multiple syngeneic tumor models and mouse strains. The toxicity resulting from eIL2 administration before IFNα is dependent on multiple systemic inflammatory cytokines including IL6, IL10, IFNγ, and tumor necrosis factor α. Natural killer (NK) cells are the main cellular contributor to toxicity, but are not essential for tumor control in this system. When pre-conditioned with eIL2, splenic NK cells became hyper-activated and upregulate IFNα signaling proteins that cause an excessive, toxic response to subsequent IFNα exposure. This work illustrates an example where accounting for the temporal dynamics of the immune system in combination therapy treatment schedule can favorably decouple efficacy and toxicity.

Downregulation of neuropilin-1 on macrophages modulates antibody-mediated tumoricidal activity

Neuropilin-1 (NRP-1)-expressing macrophages are engaged in antitumor immune functions via various mechanisms. In this study, we investigated the role of NRP-1 on macrophages in antibody-mediated tumoricidal activity. Treatment of macrophages with NRP-1 knockdown or an anti-NRP-1-neutralizing antibody significantly suppressed antibody-dependent cellular cytotoxicity and modulated cytokine secretion from macrophages in vitro. Furthermore, in vivo studies using a humanized mouse model bearing human epidermal growth factor receptor-2 (HER2)-positive breast cancer xenografts showed that antibody-mediated antitumor activity and tumor infiltration of CD4+ T lymphocytes were significantly downregulated when peripheral blood mononuclear cells in which NRP-1 was knocked down were co-administered with an anti-HER2 antibody. These results revealed that NRP-1 expressed on macrophages plays an important role in antibody-mediated antitumor immunity. Taken together, the induction of NRP-1 on macrophages may be a therapeutic indicator for antibody treatments that exert antibody-dependent cellular cytotoxicity activity, although further studies are needed in order to support this hypothesis.

Interferon-alpha-based immunotherapies in the treatment of B cell-derived hematologic neoplasms in today's treat-to-target era

B cell lymphoma and multiple myeloma (MM) are the most common hematological malignancies which benefit from therapeutic monoclonal antibodies (mAbs)-based immunotherapies. Despite significant improvement on patient outcome following the use of novel therapies for the past decades, curative treatment is unavailable for the majority of patients. For example, the 5-year survival of MM is currently less than 50%. In the 1980s, interferon-α was used as monotherapy in newly diagnosed or previously treated MM with an overall response rate of 15-20%. Noticeably, a small subset of patients who responded to long-term interferon-α further achieved sustained complete remission. Since 1990, interferon-α-containing regimens have been used as a central maintenance strategy for patients with MM. However, the systemic administration of interferon-α was ultimately limited by its pronounced toxicity. To address this, the selective mAb-mediated delivery of interferon-α has been developed to enhance specific killing of MM and B-cell malignant cells. As such, targeted interferon-α therapy may improve therapeutic window and sustain responses, while further overcoming suppressive microenvironment. This review aims to reinforce the role of interferon-α by consolidating our current understanding of targeting interferon-α with tumor-specific mAbs for B cell lymphoma and myeloma.

Selective Delivery of PEGylated Compounds to Tumor Cells by Anti-PEG Hybrid Antibodies

Polyethylene glycol (PEG) is attached to many peptides, proteins, liposomes, and nanoparticles to reduce their immunogenicity and improve their pharmacokinetic and therapeutic properties. Here, we describe hybrid antibodies that can selectively deliver PEGylated medicines, imaging agents, or nanomedicines to target cells. Human IgG1 hybrid antibodies αPEG:αHER2 and αPEG:αCD19 were shown by ELISA, FACS, and plasmon resonance to bind to both PEG and HER2 receptors on SK-BR-3 breast adenocarcinoma and BT-474 breast ductal carcinoma cells or CD19 receptors on Ramos and Raji Burkitt's lymphoma cells. In addition, αPEG:αHER2 specifically targeted PEGylated proteins, liposomes, and nanoparticles to SK-BR-3 cells that overexpressed HER2, but not to HER2-negative MCF-7 breast adenocarcinoma cells. Endocytosis of PEGylated nanoparticles into SK-BR-3 cells was induced specifically by the αPEG:αHER2 hybrid antibody, as observed by confocal imaging of the accumulation of Qdots inside SK-BR-3 cells. Treatment of HER2(+) SK-BR-3 and BT-474 cancer cells with αPEG:αHER2 and the clinically used chemotherapeutic agent PEGylated liposomal doxorubicin for 3 hours enhanced the in vitro effectiveness of PEGylated liposomal doxorubicin by over two orders of magnitude. Hybrid anti-PEG antibodies offer a versatile and simple method to deliver PEGylated compounds to cellular locations and can potentially enhance the therapeutic efficacy of PEGylated medicines.

A new flow cytometric assay for the simultaneous analysis of antigen-specific elimination of T cells in heterogeneous T cell populations

Novel immunosuppressive strategies are targeting for an antigen-specific deletion of T cells responsible for organ damage in autoimmunity and allograft rejection. Here, we present a new flow cytometry-based assay that allows the reliable and efficient detection of T cells that were eliminated in an antigen-specific fashion. A stable cell-labelling technique utilizing the two membrane dyes PKH26 and PKH67 has been combined with annexin V and 7-aminoactinomycin (7-AAD) staining to detect apoptotic cells. A differential gating strategy enabled us to determine the viability/apoptosis for each PKH-stained T cell subpopulation independently. The capability to simultaneously analyze apoptosis within T cell mixtures of different antigen specificities establishes this assay as a superior tool for the further development of novel antigen-specific immunosuppressive approaches.

Complement-induced cell death by rituximab depends on CD20 expression level and acts complementary to antibody-dependent cellular cytotoxicity

PURPOSE

The use of the CD20-specific antibody rituximab has greatly improved the response to treatment of CD20+ follicular lymphoma. Despite the success of rituximab, resistance has been reported and prognostic markers to predict individual response are lacking. The level of CD20 expression on tumors has been related to response, but results of several studies are contradictory and no clear relationship could be established. Complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) are thought to be important effector mechanisms, but the exact mechanism of rituximab-mediated cell kill is still unknown. Importantly, no data have been reported on the combined contribution of CDC and ADCC.

EXPERIMENTAL DESIGN

We have developed a system of clonally related CEM-CD20 cells by retroviral transfer of the human CD20 cDNA (n = 90). This set of cells, with the CD20 molecule as the only variable, was used to study the importance of CD20 expression level on rituximab-mediated CDC, ADCC, and the combination.

RESULTS

We show a sigmoidal correlation of CD20 expression level and rituximab-mediated killing via CDC but not ADCC. On both high and low CD20-expressing cells, all CD20 molecules were translocated into lipid rafts after rituximab binding. Furthermore, CDC and ADCC act simultaneously and CDC-resistant cells are sensitive to ADCC and vice versa.

CONCLUSIONS

These findings suggest that CDC depends on CD20 expression level and that both CDC and ADCC act complementary. These data give new insights into novel strategies to improve the efficacy of CD20-specific antibodies for the treatment of CD20+ tumors.

Recombinant interleukin-2 significantly augments activity of rituximab in human tumor xenograft models of B-cell non-Hodgkin lymphoma

Recombinant interleukin-2 (rIL-2) is a pleiotropic cytokine that activates select immune effector cell responses associated with antitumor activity, including antibody-dependent cellular cytotoxicity (ADCC). Rituximab is an anti-CD20 monoclonal antibody that activates ADCC in non-Hodgkin lymphoma (NHL). The ability of rIL-2 to augment rituximab-dependent tumor responses was investigated. The efficacy of rIL-2 in combination with rituximab was evaluated in 2 NHL tumor xenograft models: the CD20hi, rituximab-sensitive, low-grade Daudi model and the CD20lo, aggressive, rituximab-resistant Namalwa model. Combination of rIL-2 plus rituximab was synergistic in a rituximab-sensitive Daudi tumor model, as evidenced by significant tumor regressions and increased time to tumor progression, compared with rIL-2 and rituximab single agents. In contrast, rituximab-resistant Namalwa tumors were responsive to single-agent rIL-2 and showed an increased response when combined with rituximab. Using in vitro killing assays, rIL-2 was shown to enhance activity of rituximab by activating ADCC and lymphokine-activated killer activity. Additionally, the activity of rIL-2 plus rituximab F(ab')2 was similar to that of rIL-2 alone, indicating a critical role for immunoglobulin G1 Fc-FcgammaR-effector responses in mediating ADCC. Antiproliferative and apoptotic tumor responses, along with an influx of immune effector cells, were observed by immunohistochemistry. Collectively, the data suggest that rIL-2 mediates potent tumoricidal activity against NHL tumors, in part, through activation and trafficking of monocytes and natural killer cells to tumors. These data support the mechanistic and therapeutic rationale for combination of rIL-2 with rituximab in NHL clinical trials and for single-agent rIL-2 in rituximab-resistant NHL patients.

Influence of immunomodulatory drugs on the cytotoxicity induced by monoclonal antibody 17-1A and interleukin-2

Patients treated with monoclonal antibodies and cytokines for cancer receive often co-medication, which may influence treatment efficacy. Therefore, we investigated with a flowcytometric cytotoxicity assay the effect of several immunomodulatory drugs on antibody dependent cellular cytotoxicity (ADCC), interleukin-2 (IL-2) induced cytotoxicity and IL-2-induced-ADCC. We found that dexamethasone markedly inhibited the IL-2 induced cytotoxicity and the IL-2-induced-ADCC. Ondansetron, a 5-HT-3 serotonin receptor antagonist augmented significantly ADCC. Clemastine, a histamine type-2 receptor antagonist augmented the IL-2-induced-ADCC. The TNF antagonist thalidomide suppressed ADCC whereas pentoxifylline proved to be ineffective. Other tested drugs namely ibuprofen and indomethacin, both prostaglandin E2 antagonists, cimetidine a histamine type-2 receptor antagonist, the opioid pethidine, prostaglandin E2 and histamine exerted minor effects or had no influence on the tested parameters. We conclude that glucocorticosteroids should be avoided with monoclonal antibody and cytokine treatment. According to our in vitro data the other drugs tested did not have a negative impact on cellular cytotoxicity and ADCC.

Antibodies from patients with dengue viral infection mediate cellular cytotoxicity

Acute and late convalescent sera (collected at day 5 of disease onset and 1 year later) from dengue fever (DF) and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) laboratory confirmed cases, were tested for antibody-dependent cell-mediated cytotoxicity (ADCC) activity using dengue 1 (DENV-1) or dengue 2 (DENV-2) infected cells as target. All patients experienced their first dengue virus (DENV) infection 20 years before. ADCC activity was detected in acute sera from DHF/DSS but not in sera from DF patients. However, 1 year after illness, ADCC activity was observed in all cases. This preliminary report represents one of the few studies of ADCC in dengue patients and suggests that ADCC could be implicated in dengue pathogenesis.

Cytokine GM-CSF genetic adjuvant facilitates prophylactic DNA vaccine against pseudorabies virus through enhanced immune responses

Granulocyte/macrophage colony-stimulatory factor (GM-CSF) is an attractive adjuvant for a DNA vaccine on account of its ability to recruit antigen-presenting cells (APCs) to the site of antigen synthesis as well as its ability to stimulate the maturation of dendritic cells (DCs). This study evaluated the utility of GM-CSF cDNA as a DNA vaccine adjuvant for glycoprotein B (gB) of pseudorabies virus (PrV) in a murine model. The co-injection of GM-CSF DNA enhanced the levels of serum PrV-specific IgG with a 1.5-to 2-fold increase. Moreover, GM-CSF co-injection inhibited the production of IgG2a isotype. However, it enhanced production of an IgG1 isotype resulting in humoral responses biased to the Th2-type against PrV antigen. In contrast, the co-administration of GM-CSF DNA enhanced the T cell-mediated immunity biased to the Th1-type, as judged by the significantly higher level of cytokine IL-2 and IFN-gamma production but not IL-4. When challenged with a lethal dose of PrV, the GM-CSF co-injection enhanced the resistance against a PrV infection. This suggests that co-inoculation with a vector expressing GM-CSF enhanced the protective immunity against a PrV infection. This immunity was caused by the induction of increased humoral and cellular immunity in response to PrV antigen.

Immune responses in advanced colorectal cancer following repeated intradermal vaccination with the anti-CEA murine monoclonal antibody, PR1A3: results of a phase I study

BACKGROUND AND AIMS

The aim was to determine the toxicity, clinical and immune responses to the murine monoclonal anti-carcinoembryonic antigen (CEA) antibody, PR1A3, in patients with advanced colorectal cancer.

MATERIALS AND METHODS

Fifteen patients with advanced colorectal cancer received either 0.5-, 1.0- or 5.0-mg doses of PR1A3 mixed with 10% w/v Alum adjuvant (Superfos Biosector, Denmark) intradermally at 4-week intervals for 3 months. Patient serum was assessed for anti-idiotypic (Ab2), anti-anti-idiotypic (Ab3) and human anti-mouse antibody (HAMA) reactivity. Peripheral blood mononuclear cell (PBMC) proliferation with phytohaemagglutinin (PHA), CEA and PR1A3, stimulated IL-2, IL-4 and IFN-gamma levels and PR1A3-stimulated IL-2 receptor expression during immunotherapy were determined. Comparisons were made with 16 age-matched controls without malignant disease.

RESULTS

Hyperimmune sera from 12 of the 15 patients showed Ab2 reactivity with no detectable Ab3 responses. Strong HAMA reactivity was recorded in 7 of the 15 cases with no adverse clinical effect. Delayed-type hypersensitivity (DTH) responses developed in 12 of the 15 patients. Pre-treatment PBMC proliferation with PHA was subnormal in each patient compared with controls, becoming normal (or supranormal) in all patients during immunisation (P<0.001). PBMC proliferation with CEA and PR1A3 increased during immunotherapy (P<0.001) along with stimulated production of IL-2, IFN-gamma and IL-2 receptor expression. Progressive disease was observed in 14 of the 15 patients with minimal toxicity.

CONCLUSION

PR1A3 generated limited idiotypic responses but robust DTH reactivity in most patients. In vitro PBMC proliferation with mitogens and recall antigens is greatly increased during the course of immunisation, with a shift in stimulated cytokine profile.

Vaccine-induced T cell-mediated immunity plays a critical role in early protection against pseudorabies virus (suid herpes virus type 1) infection in pigs

The aim of our study was to evaluate the relative importance of antibody and T cell-mediated immunity in protection against pseudorabies virus (suid herpes virus type 1) infection in pigs. We induced different levels of immune responses by using: (1) a modified live vaccine; (2) the same modified live vaccine with an oil-in-water (o/w) adjuvant; (3) an inactivated vaccine; and (4) the same inactivated vaccine with an o/w adjuvant. Subsequently, we challenged pigs with virulent pseudorabies virus (PRV). We demonstrated that best-protected pigs stood out by maintaining strong T cell-mediated immune (CMI) responses after challenge. Of the immune parameters tested, protection against virus shedding was correlated best with the magnitude of the IFN-gamma response of in vitro re-stimulated peripheral blood mononuclear cells (PBMC) with an additional role for PRV-specific IgG2 antibodies. The use of an o/w adjuvant resulted in higher antibody and CMI responses, in particular with an increased frequency of memory T helper blast cells of in vitro re-stimulated PBMC. However, this adjuvant-induced enhancement of the immune response had a limited additional effect on the efficacy of inactivated vaccines. This study suggests a major contribution of the CMI response in early protection against PRV infection and that PRV-induced IFN-gamma responses may serve as a suitable indicator for assessing the immune status of vaccinated pigs.

The flow cytometric PKH-26 assay for the determination of T-cell mediated cytotoxic activity

We present a rapid flow cytometric and non-radioactive functional assay developed for the determination of the cytotoxic activity of T lymphocytes, natural killer cells, and lymphokine-activated killer cells. In contrast to indirect evaluation of cytotoxicity using radioactive assays, this assay is based on the quantitative and qualitative flow cytometric analysis of cell damage on a single cell level. Target cells are stained with PKH-26, a lipophilic dye that stably integrates into the cell membrane, without disturbing its surface marker expression. It, thus, permits the distinction between target and effector cells. After short term in vitro incubation (1.5-3h), AnnexinV-FITC (ann-FITC) staining allows to discriminate between apoptotic and non-apoptotic target cells. Data analysis is performed first by gating on PKH-26 positive target cells, followed by the analysis of the ann-FITC positive subpopulation. The percentage of cytotoxicity in the PKH-26 gated cell population is calculated by subtracting unspecific ann-FITC positive target cells, measured in appropriate controls without effector cells. Using in vitro generated antigen-specific cytotoxic T lymphocytes, we demonstrate that this flow cytometric assay is sensitive, correlates well with the standard 51Cr release assay, and is easy to handle.

CD4+-dependent immunity to Onchocerca volvulus third-stage larvae in humans and the mouse vaccination model: common ground and distinctions

Onchocerciasis is a major filarial disease and is the second most common cause of infectious blindness in the world. Disease development after infection with Onchocerca volvulus varies widely and is determined by the host's immune response to the parasite. Vector control and administration of ivermectin has reduced infection and disease rates significantly. However, limitations of these programmes, including ivermectin's selective activity on microfilariae, the need for 10-15 years of annual treatments, logistical obstacles and the potential emergence of drug-resistant strains demand alternative strategies. A vaccine that targets O. volvulus infective third-stage larvae (L3) could provide an additional tool to guarantee successful elimination of infection with O. volvulus. An essential step in the development of immunoprophylactic procedures and reagents is the identification of host immune responses toward antigens of O. volvulus L3 and L3 developing to the fourth-stage larvae that are associated with protection against these stages of the parasite. This review summarises the recent advancements in understanding the immune mechanisms in particular the CD4(+) responses to L3 stages in humans and in the mouse vaccination model. Comparison between the two uncovered common immunological elements in naturally exposed humans and mice vaccinated with radiation attenuated L3 or recombinant O. volvulus antigens, as well as significant differences. These studies promisingly suggest that the O. volvulus mouse model is a very useful adjunct to the studying of natural infection in humans and could provide us with the tools to identify the target molecules and the effector immune correlates of protection in humans responsible for attrition of L3 stages. Since some of these antigens may exist in other nematodes, any insight gained into the mechanisms of vaccine-induced anti-O. volvulus L3 protective immunity in both humans and mice could be applicable to the development of vaccines against other nematode infections.

An improved flow cytometric assay for the determination of cytotoxic T lymphocyte activity

The cytotoxic activity of T lymphocytes, natural killer and lymphokine-activated killer cells is usually tested by radioactive assays, which detect the release of cytoplasmic contents after plasma membrane disintegration of dying cells. In contrast to this indirect evaluation of cytotoxicity, we describe here an improved fluorescence assay that is based on the direct quantitative and qualitative flow cytometric analysis of cell damage at a single cell level. Target cells are stained with PKH-26, a lipophilic dye that stably integrates into the cell membrane and permits distinction between target and effector cells. After 3 h of in vitro incubation, costaining with AnnexinV-FITC (ann-FITC) and propidium iodide (PI) permitted discrimination between vital, early apoptotic and necrotic cells. Data analysis is performed first by gating on PKH-26-positive target cells followed by the analysis of ann-FITC- and PI-positive subpopulations. The percentage of cytotoxicity in the PKH-26-gated cell population is calculated by subtracting non-specific ann-FITC- or PI-positive target cells, measured in appropriate controls without effector cells. Membrane staining of target cells such as primary melanoma cells or leukemic blasts revealed high and stable loading of PKH-26 without altering the viability or the immunogenicity of the cells. Using in vitro-generated antigen-specific cytotoxic T lymphocytes (CTL), we could demonstrate that this flow cytometric assay is sensitive and correlates well with the standard 51Cr release assay. In conclusion, the improved fluorescence assay is a simple and highly reproducible procedure for evaluating the specific cytotoxicity of T cells.

Inhibition of tumour growth and metastasis of human fibrosarcoma cells HT-1080 by monoclonal antibody BCD-F9

BCD-F9 is a murine IgG(2a) monoclonal antibody (mAb) that recognises a conformational epitope found on the surface of many human tumour cells. The aim of this study was to investigate the ability of BCD-F9 to recognise a variety of neoplastic cell lines and to test BCD-F9 in vivo for anticancer activity in subcutaneous (s.c.) and metastatic tumour models. Intravenous (i.v.) administration of BCD-F9 in CD-1 nude mice xenografted s.c. with human HT-1080 cells led to a significant inhibition of tumour growth. We demonstrated that BCD-F9 administrated i.v. significantly prolonged the life-span of CD-1 nude mice inoculated i.v. with the same tumour cell line that induces aggressive lung metastases in the untreated mice. We also investigated the antitumour activity of BCD-F9 in vitro in antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent complement-mediated cytotoxicity (ADCMC) assays. The effector cell subpopulations were obtained by macrophage stimulation (thioglycollate) or natural killer (NK) cell enrichment (negative selection). BCD-F9 was found to be effective in mediating tumour cell killing in vitro by ADCC and ADCMC mechanisms. These results suggest that the mAb BCD-F9 can have a potential use in immunotherapy for treatment of tumours of different origin.

Natural cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) is not impaired in patients suffering from chronic hepatitis C

BACKGROUND/AIMS

Recent observations suggest that natural killer (NK) cell activity might be impaired in chronic hepatitis C. However, to date antibody-dependent cellular cytotoxicity (ADCC) has not been studied in chronic hepatitis C in detail.

METHODS

Therefore, we investigated spontaneous and cytokine-induced (interleukin-2 and interferon-gamma) natural cytotoxicity and ADCC in 29 patients suffering from chronic hepatitis C and 19 healthy controls. Cytotoxicity was determined with a flow-cytometric assay, which can also assess monocyte cytotoxicity. As target cells we used the colorectal tumor cell line HT29 and the lymphoma cell line Raji.

RESULTS

We found no significant differences with respect to spontaneous cytotoxicity (HCV versus healthy controls (32 vs. 46%) and 17-1A specific ADCC (59 vs. 48%), even if isolated monocytes or NK cells were studied. Preincubation and stimulation of effector cells with cytokines increased both natural cytotoxicity and ADCC by 20-30%. However, natural cytotoxicity and ADCC after stimulation did not differ between the two groups.

CONCLUSIONS

Our data obtained with a long-term cytotoxicity assay do not reveal impaired cytolytic capacity of the innate immune system in chronic hepatitis C, even when isolated monocytes and NK cells were studied as effector cells.

Antibody-dependent cell-mediated cytotoxicity can be induced by MUC1 peptide vaccination of breast cancer patients

Human polymorphic epithelial mucin (PEM, MUC1) is a high molecular weight transmembrane glycoprotein expressed on the apical cell surface of glandular epithelium and is over-expressed and hypo-glycosylated in adenocarcinomas. The extracellular part of the molecule consists mainly of a variable number of 20 amino acid repeats that contain cryptic epitopes exposed in malignancy. The objective of our study was to determine whether humanized MUC1 MAbs and Abs induced by vaccination of breast cancer patients with MUC1 peptides can effect an antibody-dependent cell-mediated cytotoxicity (ADCC). An in vitro assay has been set up in which the breast tumor cell line ZR-75-1 is used as target and PBMC of healthy donors as effector cells. Different target and effector cells, as well as various MUC1 MAbs were tested to optimize the efficacy of the in vitro assay. The humanized MAb HuHMFG-1, which recognizes the PDTR sequence in the MUC1 tandem repeat, induced a strong cell-mediated cytotoxicity. Nine MUC1-expressing tumor cell lines, including 3 bone marrow-derived cell lines, as well as 2 MUC1-transfected cell lines were susceptible to different extent to MUC1 Ab-dependent killing. Large variations in the killing capacity of PBMC from healthy donors were found. The NK cells were the essential effector cells for the MUC1 Ab-dependent killing. Plasma samples with induced high levels of MUC1 Ab were obtained from breast cancer patients repeatedly immunized with a KLH-conjugated 33-mer or 106-mer MUC1 tandem repeat. Pre- and post-vaccinated plasma samples of these patients were compared in the ADCC assay and it could be clearly demonstrated that the induced MUC1 Abs can effect tumor cell killing. MUC1 Ab-dependent cell-mediated tumor cell killing may occur in vivo and the ADCC assay can be applied to monitor MUC1 vaccination trials.

A novel technique for the fluorometric assessment of T lymphocyte antigen specific lysis

The 51Cr release assay has traditionally been used to investigate effector cell cytotoxic function against labeled targets, but this method has inherent problems that include hazards associated with radioactivity, cell labeling and high spontaneous release. Here we describe a novel flow cytometric assay which addresses and improves upon the problems currently encountered with the 51Cr release assay. The fluorometric assessment of T lymphocyte antigen specific lysis (FATAL) assay employs dual staining (PKH-26 and CFSE) to identify and evaluate the target population. We found that the PKH-26/CFSE combination efficiently labeled target cells. Evaluation of the spontaneous leakage from dye labeled target cells was forty fold lower than the spontaneous leakage seen with the 51Cr release assay. The FATAL assay permitted a more accurate assessment of the effector: target ratio, and detected low levels of cytotoxic T lymphocyte (CTL) mediated lysis. There was a strong correlation between the 51Cr release and FATAL assays, when performed in parallel with identical effector and target cells (r(2)=0.998, P=<0.0001). This novel method of detecting cytolysis represents a qualitative and quantitative improvement over standard 51Cr release analysis. The FATAL assay will be of value to further investigate mechanisms of cytolysis by effector cell populations.

Influence of cytokines, monoclonal antibodies and chemotherapeutic drugs on epithelial cell adhesion molecule (EpCAM) and LewisY antigen expression

MoAbs against tumour-associated antigens (TAA) may be useful for the treatment of colorectal cancer. Since an increased expression of TAA may lead to enhanced antibody-dependent cellular cytotoxicity we examined whether the cytokines IL-2, IL-4, IL-6, IL-10, IL-12, interferon-alpha (IFN-alpha), IFN-gamma, granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor and tumour necrosis factor-alpha can influence EpCAM and LewisY expression on the surface of the colorectal carcinoma cell lines HT29, LoVo and SW480. We found that only IFN-alpha increased significantly whereas IL-4 decreased both EpCAM and LewisY expression. IFN-gamma significantly increased LewisY expression only. When tumour cells were treated with MoAb, the LewisY-specific MoAb BR55-2 down-regulated LewisY antigen expression, whereas MoAb 17-1A, which binds to EpCAM, up-regulated this TAA after 3 days of culture. The cytokines IFN-alpha or IFN-gamma combined with MoAb 17-1A enhanced further slightly the expression of EpCAM. In additional experiments with chemotherapeutic drugs commonly used for the treatment of colorectal cancer, we found that 5-fluorouracil, mitomycin-C and oxaliplatin up-regulated EpCAM and LewisY antigen expression. Raltitrexed enhanced LewisY and down-regulated EpCAM expression, whereas CPT-11 had no influence at all. The highest expression for EpCAM on HT29 cells was achieved by the combination of IFN-alpha, 5-fluorouracil and MoAb 17-1A. Our results may be useful for defining combinations of biological and chemotherapeutic drugs for the treatment of colorectal cancer. Further trials should evaluate to what extent these combinations enhance antibody-dependent cellular cytotoxicity.

Mechanism of cytotoxicity induced by chimeric mouse human monoclonal antibody IDEC-C2B8 in CD20-expressing lymphoma cell lines

With a new flow cytometric cytotoxicity assay, we examined the mechanism of action of chimeric mouse human anti-CD20 monoclonal antibody IDEC-C2B8. IDEC-C2B8 alone induced direct cytotoxicity in four of eight examined CD20-expressing lymphoma cell lines (RAJI, DAUDI, JOK-1, and WT100) at a concentration above 100 ng/ml. Moreover, after 4 h incubation in human serum, only a moderate complement-dependent cellular cytotoxicity (CDCC) was observed, whereas cytotoxicity increased markedly after 3 days of culture, indicating that combined direct cytotoxicity and CDCC were responsible. IDEC-C2B8 induced an effective antibody-dependent cellular cytotoxicity (ADCC) in seven of eight tested lymphoma cell lines when peripheral blood mononuclear cells were used as effector cells. ADCC was moderately enhanced by cytokine interleukin-2, whereas interleukin-12, interferon-alpha, and GM-CSF had no influence. Interestingly, we could demonstrate a correlation between CD32 expression on lymphoma cell lines and IDEC-C2B8-induced direct cytotoxicity, indicating that crosslinking of CD20 with CD32 may be involved in the mechanism of cytotoxicity. We propose that direct cytotoxicity, CDCC, and ADCC result in the marked elimination of CD20-expressing tumor cells observed after treatment with IDEC-C2B8.

Augmentation of 17-1A-induced antibody-dependent cellular cytotoxicity by the triple cytokine combination of interferon-alpha, interleukin-2, and interleukin-12

Previously, interferon-alpha (IFN-alpha), interleukin-2 (IL-2), and interleukin-12 (IL-12) were shown to increase the antibody-dependent cellular cytotoxicity (ADCC) induced by the murine monoclonal antibody 17-1A, which recognizes the tumor-associated antigen EpCAM. In this study, the authors wanted to determine whether the combination of these three cytokines would yield greater cytotoxicity than the single cytokines. For cytotoxicity assessment, a new flow cytometric assay was used that allows the analysis of long-term ADCC exerted by macrophages. Peripheral blood mononuclear cells from healthy donors were used as effector cells against the colorectal carcinoma cell line HT29 at a low effector-to-target ratio of 4.5:1. With this test, the effectiveness of the combinations IL-2 and IFN-alpha, IL-2 and IL-12, and IL-12 and IFN-alpha were compared with each other. The combinations IL-2 plus IL-12 and IFN-alpha plus IL-12 were more potent at the concentrations tested. Furthermore, the triple cytokine combination of IFN-alpha, IL-2, and IL-12 revealed significantly greater ADCC than dual cytokine combinations. Next, CD14+, CD4+, and CD4- cells were isolated by paramagnetic beads and magnetic activated cell sorter (MACS) columns. The CD14+ and CD4- cell populations contained the ADCC effectors. The addition of CD4+ cells to CD14+ or CD4- cells resulted in augmented ADCC, indicating that cooperation between immune cells occurs. These results suggest that multiple cytokine combinations with monoclonal antibodies may be more effective for cancer immunotherapy.

Combinations of the cytokines IL-12, IL-2 and IFN-alpha significantly augment whereas the cytokine IL-4 suppresses the cytokine-induced antibody-dependent cellular cytotoxicity of monoclonal antibodies 17-1A and BR55-2

Since some cytokines effectively enhance the cytotoxicity of monoclonal antibodies, we investigated whether a combination of cytokines can augment the antibody-dependent cellular cytotoxicity (ADCC) of monoclonal antibodies 17-1A and BR55-2 against the colorectal carcinoma cell line HT29. Since monocytes/macrophages are important effector cells for ADCC, we used a new flow cytometric cytotoxicity assay, which allows the analysis of long-term-ADCC exerted by these cells. In our previous studies with peripheral blood mononuclear cells from normal donors, we found that IL-2, IL-12 and IFN-alpha increase ADCC. Therefore, we examined whether combination of these three cytokines with IL-2, IL-4, IL-6, IL-10, IL-12, IFN-alpha, IFN-gamma, GM-CSF, M-CSF and TNF-alpha may yield higher ADCC than obtained by the application of single cytokines. Indeed, we found that the combinations IL-2/IFN-alpha, IL-2/IL-12 and IL-12/IFN-alpha potentiated ADCC. Interestingly, the ineffective single cytokines TNF-alpha and GM-CSF in the combinations IL-2/TNF-alpha, IFN-alpha/TNF-alpha and IFN-alpha/GM-CSF also proved to enhance ADCC. In contrast, IL-4 significantly suppressed the IL-2, IL-12 and IFN-alpha-induced ADCC. In addition, the immunosuppressive cytokine IL-10 in higher concentrations significantly suppressed the IL-12-induced-ADCC. Our results may be useful to find combinations of cytokines and mAb for the treatment of cancer.

Immunity to onchocerciasis: cells from putatively immune individuals produce enhanced levels of interleukin-5, gamma interferon, and granulocyte-macrophage colony-stimulating factor in response to Onchocerca volvulus larval and male worm antigens

Antigen-specific interleukin-5 (IL-5), gamma interferon (IFN-gamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF) responses in individuals living in an area of hyperendemicity for onchocerciasis in Cameroon were examined. The responses against antigens prepared from Onchocerca volvulus third-stage larvae (L3), molting L3 (mL3), and crude extract from adult males (M-OvAg) were compared to the responses against antigens from adult female worms and skin microfilariae. Cytokine responses for the putatively immune individuals (PI) and the infected individuals (INF) were compared. A differential cytokine profile of IL-5 (Th2 phenotype) and IFN-gamma (Th1 phenotype) was found in these individuals in response to the antigens. In both the PI and the INF, Th2 responses against all the antigens tested were dominant. However, in the PI group as a whole, there was an enhanced Th2 response against the larval antigens and the adult male and adult female antigens, and a Th1 response in a subgroup of the PI (27 to 54.5%) against L3, mL3, and M-OvAg antigens was present. While the PI produced significantly higher levels of GM-CSF against L3, mL3, and M-OvAg antigens than the INF, there was no difference in the GM-CSF responses of the groups against the other antigens. The present study indicated that, in comparison to the INF, the PI have distinct larva-specific and adult male-specific cytokine responses, thus supporting the premise that immunological studies of the PI would lead to the identification of immune mechanisms and the target genes that play a role in protective immunity.