Effect of Gemcitabine based chemotherapy on the immunogenicity of pancreatic tumour cells and T-cells

PURPOSE

Chemotherapy for advanced pancreatic cancer has limited efficacy due to the difficultly of treating established tumours and the evolution of tumour resistance. Chemotherapies for pancreatic cancer are typically studied for their cytotoxic properties rather than for their ability to increase the immunogenicity of pancreatic tumour cells. In this study Gemcitabine in combination with immune modulatory chemotherapies Oxaliplatin, zoledronic acid and pomalidomide was studied to determine how combination therapy alters the immunogenicity of pancreatic tumour cell lines and subsequent T-cell responses.

METHODS

Pancreatic tumour cell lines were stimulated with the chemotherapeutic agents and markers of immune recognition were assessed. The effect of chemotherapeutic agents on DC function was measured using uptake of CFSE-stained PANC-1 cells, changes in markers of maturation and their ability to activate CD8+ T-cells. The effect of chemotherapeutic agents on T-cell priming prior to activation using anti-CD3 and anti-CD28 antibodies was determined by measuring IFN-γ expression and Annexin V staining using flow cytometry.

RESULTS

These agents demonstrate both additive and inhibitory properties on a range of markers of immunogenicity. Gemcitabine was notable for its ability to induce the upregulation of human leukocyte antigen and checkpoints on pancreatic tumour cell lines whilst inhibiting T-cell activation. Pomalidomide demonstrated immune modulatory properties on dendritic cells and T-cells, even in the presence of gemcitabine.

DISCUSSION

These data highlight the complex interactions of different agents in the modulation of tumour immunogenicity and immune cell activation and emphasise the complexity in rationally designing chemo immunogenic combinations for use with immunotherapy.

Drug-Disease Interaction and Time-Dependent Population Pharmacokinetics of Isatuximab in Relapsed/Refractory Multiple Myeloma Patients

Isatuximab, a monoclonal antibody (mAb) of immunoglobulin G (IgG) isotype, specifically targets the cluster of differentiation 38 antigen overexpressed in malignant plasma cells. Isatuximab is used to treat multiple myeloma (MM), characterized by the excessive production of abnormal "myeloma proteins" (M-proteins) that may interact with therapeutic IgG mAb on the neonatal Fc receptor (FcRn)-mediated recycling pathway. The clinical pharmacology profile of isatuximab was investigated by population pharmacokinetics (PKs) modeling in 476 patients with MM who received 1-20 mg/kg isatuximab either as single agent or in combination with pomalidomide-dexamethasone in 4 clinical trials. Isatuximab PKs were characterized by a two-compartment model with parallel time-varying linear clearance (CL) and nonlinear elimination. Due to a mechanism-based drug-disease interaction, patients secreting IgG M-protein exhibited a twofold lower drug exposure compared with patients with non-IgG MM. No dose adjustment was required based on MM immunoglobulin type because efficacy and safety profiles were comparable between IgG and non-IgG MM subpopulations. β2-microglobulin, body weight, sex, drug material, and race have a limited effect on drug exposure and do not require any dose adjustment. A typical 50% decrease in linear CL from initial treatment to steady-state was predicted, and this decrease correlated with the best overall response rate and was slower for patients with IgG MM. These findings suggest that the time-dependent effect of isatuximab is likely mediated by a combined factor of both disease state evolution and the perturbation of the FcRn-mediated recycling pathway.

Acetaldehyde suppresses HBV-MHC class I complex presentation on hepatocytes via induction of ER stress and Golgi fragmentation

Alcohol consumption worsens hepatitis B virus (HBV) infection pathogenesis. We have recently reported that acetaldehyde suppressed HBV peptide-major histocompatibility complex I (MHC class I) complex display on hepatocytes, limiting recognition and subsequent removal of the infected hepatocytes by HBV-specific cytotoxic T lymphocytes (CTLs). This suppression was attributed to impaired processing of antigenic peptides by the proteasome. However, in addition to proteasome dysfunction, alcohol may induce endoplasmic reticulum (ER) stress and Golgi fragmentation in HBV-infected liver cells to reduce uploading of viral peptides to MHC class I and/or trafficking of this complex to the hepatocyte surface. Hence, the aim of this study was to elucidate whether alcohol-induced ER stress and Golgi fragmentation affect HBV peptide-MHC class I complex presentation on HBV+ hepatocytes. Here, we demonstrate that, while both acetaldehyde and HBV independently cause ER stress and Golgi fragmentation, the combined exposure provided an additive effect. Thus we observed an activation of the inositol-requiring enzyme 1α-X-box binding protein 1 and activation transcription factor (ATF)6α, but not the phospho PKR-like ER kinase-phospho eukaryotic initiation factor 2α-ATF4-C/EBP homologous protein arms of ER stress in HBV-transfected cells treated with acetaldehyde-generating system (AGS). In addition, Golgi proteins trans-Golgi network 46, GM130, and Giantin revealed punctate distribution, indicating Golgi fragmentation upon AGS exposure. Furthermore, the effects of acetaldehyde were reproduced by treatment with ER stress inducers, thapsigargin and tunicamycin, which also decreased the display of this complex and MHC class I turnover in HepG2.2.15 cells and HBV-infected primary human hepatocytes. Taken together, alcohol-induced ER stress and Golgi fragmentation contribute to the suppression of HBV peptide-MHC class I complex presentation on HBV+ hepatocytes, which may diminish their recognition by CTLs and promote persistence of HBV infection in hepatocytes.NEW & NOTEWORTHY Our current findings show that acetaldehyde accelerates endoplasmic reticulum (ER) stress by activating the unfolded protein response arms inositol-requiring enzyme 1α-X-box binding protein 1 and activation transcription factor (ATF)6α but not phospho PKR-like ER kinase-p eukaryotic initiation factor 2α-ATF4-C/EBP homologous protein in hepatitis B virus (HBV)-transfected HepG2.2.15 cells. It also potentiates Golgi fragmentation, as evident by punctate distribution of Golgi proteins, GM130, trans-Golgi network 46, and Giantin. While concomitantly increasing HBV DNA and HBV surface antigen titers, acetaldehyde-induced ER stress suppresses the presentation of HBV peptide-major histocompatibility complex I complexes on hepatocyte surfaces, thereby promoting the persistence of HBV infection in the liver.

Protective effects of ulinastatin on pulmonary damage in rats following scald injury

Organ protection is desirable in severe burn/scald injuries, and damage mechanisms and thus effective therapies following scald injury have not been fully elucidated. Our aim was to examine the beneficial effects of ulinastatin on pulmonary damage associated with scald injury. Lewis rats were subjected to 30% total body surface area (TBSA) scald injury and were randomly divided into a burn control (S group) and an ulinastatin-treated group (U group). Lung malondialdehyde (MDA) and superoxide dismutase (SOD) levels were determined, and the lungs were examined histologically with immunohistochemistry (IHC) as well for the major histocompatibility complex (MHC) class I chain-related antigen A (MICA) and Bcl-2 at 24, 48 and 72 h after the injury. The expression of spleen human leucocyte antigen-DR (HLA-DR) was detected by immunohistochemistry analysis. Selectins and adhesion molecules in lungs and serum were also detected. The lung injury degree was represented as wet/dry (W/D) values and alveolar thickness. Ulinastatin decreased MDA levels and ameliorated the down-regulation of SOD activity. MICA was up-regulated after the scald, and this up-regulation was greatly diminished by ulinastatin. Bcl-2 was up-regulated after the scald, especially in the U group. The spleen HLA-DR expression demonstrated the immunoregulatory effects of ulinastatin, which effectively protected the pulmonary tissues from scald-induced injury. Our results demonstrated that pulmonary damage was associated with autoimmunity and oxidant attack after severe scald. Ulinastatin exhibits significant protective effects on these effects.

MHC class I dimer formation by alteration of the cellular redox environment and induction of apoptosis

Many MHC class I molecules contain unpaired cysteine residues in their cytoplasmic tail domains, the function of which remains relatively uncharacterized. Recently, it has been shown that in the small secretory vesicles known as exosomes, fully folded MHC class I dimers can form through a disulphide bond between the cytoplasmic tail domain cysteines, induced by the low levels of glutathione in these extracellular vesicles. Here we address whether similar MHC class I dimers form in whole cells by alteration of the redox environment. Treatment of the HLA-B27-expressing Epstein-Barr virus-transformed B-cell line Jesthom, and the leukaemic T-cell line CEM transfected with HLA-B27 with the strong oxidant diamide, and the apoptosis-inducing and glutathione-depleting agents hydrogen peroxide and thimerosal, induced MHC class I dimers. Furthermore, induction of apoptosis by cross-linking FasR/CD95 on CEM cells with monoclonal antibody CH-11 also induced MHC class I dimers. As with exosomal MHC class I dimers, the formation of these structures on cells is controlled by the cysteine at position 325 in the cytoplasmic tail domain of HLA-B27. Therefore, the redox environment of cells intimately controls induction of MHC class I dimers, the formation of which may provide novel structures for recognition by the immune system.

An six-amino acid motif in the alpha3 domain of MICA is the cancer therapeutic target to inhibit shedding

Expression of the MHC class I chain related molecules A and B (MICA/B) on tumor cell surface can signal the immune receptor NKG2D for tumor immune destruction. However, MIC was found to be shed by tumors in cancer patients, which negatively regulates host immunity and promotes tumor immune evasion and progression. The mechanisms by which tumors shed MIC are not well understood although diverse groups of enzymes are suggested to be involved. The functional complexity of these enzymes makes them unfeasible therapeutic targets for inhibiting MIC shedding. Here we identified an six-amino acid (6-aa) motif in the alpha3 domain of MIC that is critical for the interaction of MIC with ERp5 to enable shedding. Mutations in this motif prevented MIC shedding but did not interfere with NKG2D-mediated recognition of MIC. Our study suggests that the 6-aa motif is a feasible target to inhibit MIC shedding for cancer therapy.

Treatment of ovarian cancer cell lines with 5-aza-2'-deoxycytidine upregulates the expression of cancer-testis antigens and class I major histocompatibility complex-encoded molecules

PURPOSE

To test the hypothesis that decrease in DNA methylation will increase the expression of cancer-testis antigens (CTA) and class I major histocompatibility complex (MHC)-encoded molecules by ovarian cancer cells, and thus increase the ability of these cells to be recognized by antigen-reactive CD8(+) T cells.

METHODS

Human ovarian cancer cell lines were cultured in the presence or absence of varying concentrations of the DNA demethylating agent 5-aza-2'-deoxycytidine (DAC) for 3-7 days. The expression levels of 12 CTA genes were measured using the polymerase chain reaction. The protein expression levels of class I MHC molecules and MAGE-A1 were measured by flow cytometry. T cell reactivity was determined using interferon-gamma ELISpot analysis.

RESULTS

DAC treatment of ovarian cancer cell lines increased the expression of 11 of 12 CTA genes tested including MAGE-A1, MAGE-A3, MAGE-A4, MAGE-A6, MAGE-A10, MAGE-A12, NY-ESO-1, TAG-1, TAG-2a, TAG-2b, and TAG-2c. In contrast, DAC treatment decreased the already low expression of the MAGE-A2 gene by ovarian cancer cells, a finding not previously observed in cancers of any histological type. DAC treatment increases the expression of class I MHC molecules by the cells. These effects were time-dependent over a 7-day interval, and were dose-dependent up to 1-3 microM for CTA and up to 10 microM for class I MHC molecules. Each cell line tested had a unique pattern of gene upregulation after exposure to DAC. The enhanced expression levels increased the recognition of 2 of 3 antigens recognized by antigen-reactive CD8(+) T cells.

CONCLUSIONS

These results demonstrate the potential utility of combining DAC therapy with vaccine therapy in an attempt to induce the expression of antigens targeted by the vaccine, but they also demonstrate that care must be taken to target inducible antigens.

The adaptor complex AP-2 regulates post-endocytic trafficking through the non-clathrin Arf6-dependent endocytic pathway

The ADP-ribosylation factor 6 (Arf6) GTPase functions as a key regulator of endocytic trafficking, participating in clathrin-independent endocytosis in most cell types. Unexpectedly, we found that siRNA-mediated depletion of clathrin or of adaptor protein 2 (AP-2)-complex subunits alters trafficking of Arf6 pathway cargo proteins, such as major histocompatibility complex class I (MHCI) and beta1 integrin. Internalization of these cargoes from the plasma membrane was not affected in cells depleted of clathrin, but was modestly delayed in cells lacking AP-2. Furthermore, depletion of clathrin or AP-2 altered the intracellular distribution of MHCI and beta1 integrin, inducing clustering in a perinuclear region. Despite this altered localization in both depleted populations, enhanced lysosomal targeting of MHCI was observed uniquely in cells that lack AP-2. Total levels of MHCI were modestly but consistently reduced in AP-2-depleted cells, and restored by the lysosomal inhibitor bafilomycin A. Furthermore, the half-life of surface-derived MHCI was reduced in AP-2-depleted cells. Consistent with enhanced degradative sorting, colocalization of Arf6 cargo with the late endosome and lysosome markers CD63 and Lamp1 was increased in cells depleted of AP-2 but not clathrin. These studies indicate a role for AP-2 in maintaining normal post-endocytic trafficking through the Arf6-regulated, non-clathrin pathway, and reveal pervasive effects of clathrin and AP-2 depletion on the endosomal and lysosomal system.

Histone deacetylase inhibitors induce TAP, LMP, Tapasin genes and MHC class I antigen presentation by melanoma cells

Histone deacetylase inhibitors (HDACi), including trichostatin A (TSA) and valproic acid, can alter the acetylation of histones in chromatin and enhance gene transcription. Previously we demonstrated that HDACi-treated tumor cells are capable of presenting antigen via the MHC class II pathway. In this study, we show that treatment with HDACi enhances the expression of molecules (TAP1, TAP2, LMP2, LMP7, Tapasin and MHC class I) involved in antigen processing and presentation via the MHC class I pathway in melanoma cells. HDACi treatment of B16F10 cells also enhanced cell surface expression of class I and costimulatory molecules CD40 and CD86. Enhanced transcription of these genes is associated with a significant increase in direct presentation of whole protein antigen and MHC class I-restricted peptides by TSA-treated B16F10 cells. Our data indicate that epigenetic modification can convert a tumor cell to an antigen presenting cell capable of activating IFN-gamma secreting T cells via the class I pathway. These findings suggest that the abnormalities, observed in some tumors in the expression of MHC class I antigen processing and presentation molecules, may result from epigenetic repression.

Anti beta2-microglobulin monoclonal antibodies induce apoptosis in myeloma cells by recruiting MHC class I to and excluding growth and survival cytokine receptors from lipid rafts

We recently showed that monoclonal antibodies (mAbs) against beta2-microglobulin (beta2M) have a remarkably strong apoptotic effect on myeloma cells. The mAbs induced apoptosis by recruiting major histocompatibility complex (MHC) class I to lipid rafts, activated c-Jun N-terminal kinase (JNK), and inhibited phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) pathways. Growth and survival cytokines such as interleukin-6 (IL-6) and insulin-like growth factor-I (IGF-I), which could protect myeloma cells from dexamethasone-induced apoptosis, did not affect mAb-mediated cell death. This study was undertaken to elucidate the mechanisms underlying anti-beta2M mAb-induced PI3K/Akt and ERK inhibition and the inability of IL-6 and IGF-I to protect myeloma cells from mAb-induced apoptosis. We focused on lipid rafts and confirmed that these membrane microdomains are required for IL-6 and IGF-I signaling. By recruiting MHC class I into lipid rafts, anti-beta2M mAbs excluded IL-6 and IGF-I receptors and their substrates from the rafts. The mAbs not only redistributed the receptors in cell membrane, but also abrogated IL-6- or IGF-I-mediated Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3), PI3K/Akt, and Ras/Raf/ERK pathway signaling, which are otherwise constitutively activated in myeloma cells. Thus, this study further defines the tumoricidal mechanism of the mAbs and provides strong evidence to support the potential of these mAbs as therapeutic agents for myeloma.

Constitutive internalization of murine MHC class I molecules

The total number of cell surface glycoprotein molecules at the plasma membrane results from a balance between their constitutive internalization and their egress to the cell surface from intracellular pools and/or biosynthetic pathway. Constitutive internalization is net result of constitutive endocytosis and endocytic recycling. In this study we have compared spontaneous internalization of murine major histocompatibility complex (MHC) class I molecules (K(d), D(d), full L(d), and empty L(d)) after depletion of their egress to the cell surface (Cycloheximide [CHX], brefeldin A [BFA]) and internalization after external binding of monoclonal antibody (mAb). MHC class I alleles differ regarding their cell surface stability, kinetics, and in the way of internalization and degradation. K(d) and D(d) molecules are more stable at the cell surface than L(d) molecules and, thus, constitutively internalized more slowly. Although the binding of mAbs to cell surface MHC class I molecules results in faster internalization than depletion of their egress, it is still slow and, thereby, can serve as a model for tracking of MHC class I endocytosis. Internalization of fully conformed MHC class I molecules (K(d), D(d), and L(d)) was neither inhibited by chlorpromazine (CP) (inhibitor of clathrin endocytosis), nor with filipin (inhibitor of lipid raft dependent endocytosis), indicating that fully conformed MHC class I molecules are internalized via the bulk pathway. In contrast, internalization of empty L(d) molecules was inhibited by filipin, indicating that non-conformed MHC class I molecules require intact cholesterol-rich membrane microdomains for their constitutive internalization. Thus, conformed and non-conformed MHC class I molecules use different endocytic pathways for constitutive internalization.

Modulation of HLA-G expression

Recent studies demonstrated that HLA-G transcription is in some cells silenced by epigenetic mechanisms as DNA methylation and histone modification. Accordingly HLA-G gene transcriptions can be activated in such cells by demethylating agent or by inhibitors of histone deacetylation. In addition to epigenetic alterations HLA-G gene transcription can be activated by stress. In the present study these aspects of HLA-G expression are re-examined and a new inhibitor of histone deacetylation (valproic acid) and hypoxia mimetic chemical (CoCl2) are included. The highest activation of HLA-G transcription was achieved by treatment of choriocarcinoma JAR and lymphoblastoid RAJI cell lines with demethylating agent 5-aza-2 - deoxycytidine. Treatment of JAR and RAJI cells with histone deacetylase inhibitors (sodium butyrate and valproic acid) also enhanced HLA-G transcription. Nevertheless this increase in HLA-G expression was low as compared with activation by 5-aza-2 - deoxycytidine. The hypoxia mimetic agents (desferrioxamine or CoCl2) had no detectable effect on HLA-G gene transcription in examined cells. Relatively high increase of HLA-G transcription was detected in JAR and RAJI cells exposed to heat shock treatment. Interestingly heat shock induced high expression of HLA-G6 transcript in JAR cells. Heat shock treatment had no effect on alternative splicing of constitutively expressed HLA-G mRNA in choriocarcinoma cell line JEG-3. HLA-G1 protein expression was induced in JAR and RAJI cell lines by 5-aza-2 - deoxycytidine. In agreement with the differences in the levels of HLA-G transcripts JAR cells express more of HLA-G1 protein than RAJI cells.

Telomerase vaccination has no detectable effect on SCID-repopulating and colony-forming activities in the bone marrow of cancer patients

OBJECTIVES

The telomerase reverse transcriptase hTERT is a widely expressed tumor-associated antigen recognized by cytotoxic T lymphocytes (CTL). We have previously shown that vaccination of cancer patients against hTERT induces functional anti-tumor CTL in vivo, but it is not known whether hTERT vaccination harms normal cells expressing the enzyme, especially hematopoietic stem cells and progenitors.

PATIENTS AND METHODS

We employed colony-forming cell (CFC) assays, long-term in vitro cultures, and nonobese diabetic/severe combined immunodeficient (NOD/SCID) repopulation studies to evaluate the effects of hTERT vaccination on hematopoietic progenitors and stem cells in cancer patients following treatment.

RESULTS

Using bone marrow samples obtained from cancer patients before and after vaccination, we found that there was no significant decline in the frequency of granulocyte, macrophage or erythroid CFCs using CFC assays or long-term in vitro cultures. In NOD/SCID mice, human hematopoietic reconstitution was easily detected, without quantitative or qualitative differences between pre- and postvaccine samples.

CONCLUSION

These findings suggest that induction of tumor-lytic hTERT-specific T cells in vivo by vaccination does not result in a detectable decline in hematopoietic potential despite the expression of hTERT and major histocompatibility complex class I in bone marrow progenitors and stem cells. Thus, even for self-antigens such as telomerase, tumor immunity does not necessarily involve autoimmunity in normal tissues that share the target.

The role of TNF in hepatic histopathological manifestations and hepatic CD8+ T cell alloresponses in murine MHC class I disparate GVHD

Transfer of B6 T cells to major histocompatibility complex (MHC) class I disparate bm1 x B6 F1 mice leads to the development of hepatic graft-versus-host disease (GVHD) characterized by an active hepatitis with portal and lobular inflammation as well as bile duct inflammation and venulitis. The present studies determined the role of tumor necrosis factor (TNF) in hepatic GVHD. B6 responder cells were cultured with irradiated MHC class I disparate bm1 or syngeneic spleen cells (SpC) in the presence or absence of TNF receptor inhibitor [TNFR-immunoglobulin (Ig)]. Recipient bm1 x B6 F1 mice were irradiated (600 cGy) and reconstituted with 5 x 10(6) T cell-depleted B6 bone marrow cells and 1 x 10(7) B6 SpC. Mice were injected with an adenovirus encoding TNFR-Ig [TNF inhibitor-encoding adenovirus (Adv-TNFi)] or beta-galactosidase (Adv-betagal). Severity of liver GVHD was assessed by a composite histopathological score consisting of the sum of scores for venulitis, lobular hepatitis, and bile duct inflammation. Addition of TNFR-Ig reduced cell proliferation in mixed lymphocyte cultures using B6 responder SpC by 71% +/- 12.8% and interferon-gamma responses by 78% +/- 18%. GVHD-induced "wasting disease" was reduced in Adv-TNFi recipients [4.4%+/-5.2% weight loss (n=11)] compared with Adv-betagal recipients [16.1%+/-7.6% weight loss (n=11; P=0.0004)] 9 days post-transplant. Composite histopathological scores and individual venulitis scores were reduced with the addition of Adv-TNFi. Hepatic CD8+ T cells in the recipients of Adv-TNFi were reduced as compared with recipients of Adv-betagal. In conclusion, Adv-TNFi reduces MHC class I disparate alloproliferative responses and hepatic GVHD.

Using a small molecule inhibitor of peptide: N-glycanase to probe its role in glycoprotein turnover

Peptide:N-glycanase (PNGase) is ostensibly the sole enzyme responsible for deglycosylation of unfolded N-linked glycoproteins dislocated from the ER to the cytosol. Here we show the pan-caspase inhibitor, Z-VAD-fmk, to be an active site-directed irreversible inhibitor of yeast and mammalian PNGase at concentrations below those used to inhibit caspases in vivo. Through chemical synthesis we determined that the P1 residue, electrophile position, and leaving group are important structural parameters for PNGase inhibition. We show that Z-VAD-fmk inhibits PNGase in living cells and that degradation of class I MHC heavy chains and TCRalpha, in an identical cellular setting, is markedly different. Remarkably, proteasome-mediated turnover of class I MHC heavy chains proceeds even when PNGase is completely inhibited, suggesting that the function of PNGase may be to facilitate more efficient proteasomal proteolysis of N-linked glycoproteins through glycan removal.

Induction of HLA-G expression in a melanoma cell line OCM-1A following the treatment with 5-aza-2′-deoxycytidine

The non-classical HLA class I antigen HLA-G is an immune modulator which inhibits the functions of T cells, NK cells, and the Dendritic cells (DC). As a result, HLA-G expression in malignant cells may provide them with a mechanism to escape the immune surveillance. In melanoma, HLA-G antigen expression has been found in 30% of surgically removed lesions but in less than 1% of established cell lines. One possible mechanism underlying the differential HLA-G expression in vivo and in vitro is that the HLA-G gene is epigenetically repressed in melanoma cells in vitro. To test this hypothesis, we treated the HLA-G negative melanoma cell line OCM-1A with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-AC) and analyzed whether HLA-G expression can be restored. Our data strongly suggest that HLA-G is silenced as a result of CpG hypermethylation within a 5' regulatory region encompassing 220 bp upstream of the start codon. After treatment, HLA-G mRNA expression was dramatically increased. Western blot and flow cytometry showed that HLA-G protein was induced. Interestingly, HLA-G cell surface expression on the 5-AC treated OCM-1A cells is much less than that on the HLA-G positive JEG-3 cells while a similar amount of total HLA-G was observed. Possible mechanisms for the difference were analyzed in the study such as cell cold-treatment, peptide loading and antigen processing machinery components (APM) as well as beta2 microglobulin (beta2-m) expression. Data revealed that the APM component calreticulin might be involved in the lower HLA-G surface expression on OCM-1A cells. Taken together, our results indicated that DNA methylation is an important epigenetic mechanism by which HLA-G antigen expression is modulated in melanoma cells in vitro. Furthermore, to the first time, we hypothesized that the deficiency of calreticulin might be involved in the low HLA-G surface expression on the 5-AC treated OCM-1A cells.

Modified anthrax fusion proteins deliver HIV antigens through MHC Class I and II pathways

T cell-based HIV vaccine candidates have focused on eliciting both CD4- and CD8-mediated responses. One challenge in vaccine development is the successful introduction and presentation of exogenous antigen to elicit an immune response. Modified bacterial toxins have been studied extensively as intracellular delivery agents because of their unique capability to translocate antigen across the cell membrane without affecting cell viability. Modified anthrax toxin lethal factor (LFn) fusion protein is able to effectively induce anti-HIV cytotoxic T lymphocytes in the absence of protective antigen (PA) and is being evaluated as a vaccine candidate. Here we describe, for the first time, the processing and presentation of LFn fusion proteins by the MHC Class II pathway. The ability of LFn--HIV to induce both CD8- and CD4-mediated responses may have relevance in current approaches to vaccine design. Furthermore, the translocation and presentation of antigens occurs in the absence of PA, which proposes a modified molecular mechanism of antigen presentation by the anthrax toxin model. Additionally, we found that LFn--HIV is specific and sensitive in detecting HIV-specific CD4(+) and CD8(+) T cell responses in T cell assays, further broadening the value of this antigen delivery system as a useful immunologic tool.

Reciprocal activating interaction between dendritic cells and pamidronate-stimulated gammadelta T cells: role of CD86 and inflammatory cytokines

We investigated the interactions between human monocyte-derived dendritic cells (DCs) and Ag-activated circulating TCR-gammadelta-expressing lymphocytes (Vdelta2). Coculture of immature DCs (iDCs) with peripheral blood Vdelta2 T cells activated with either pyrophosphomonoesters (isopentenyl pyrophosphate; IPP) or aminobiphosphonates (pamidronate; PAM) led to a significant up-modulation of CD86 and MHC class I molecules and to the acquisition of functional features typical of activated DCs. DC activation induced by both IPP- and PAM-stimulated gammadelta T cells was mostly mediated by TNF-alpha and IFN-gamma secreted by activated lymphocytes. However, the effect of PAM-activated gammadelta T cells, but not that of IPP-activated cells, required cell-to-cell contact. Reciprocally, activation of Vdelta2 T cells by PAM, but not by IPP, was dependent on cell contact with iDCs. In fact, when PAM-stimulated DC-gammadelta T cell cocultures were separated by a semipermeable membrane or treated with blocking anti-CD86 Abs, induction of CD25 and CD69 as well as IFN-gamma and TNF-alpha secretion by Vdelta2 cells were strongly reduced. These results demonstrate for the first time a bidirectional activating interaction between iDCs and PAM-stimulated gammadelta T lymphocytes, thus suggesting a potential adjuvant role of this early cross-talk in the therapeutic activity of aminobiphosphonate drugs.

Collapse and restoration of MHC class-I-dependent immune privilege: exploiting the human hair follicle as a model

The collapse of major histocompatibility complex (MHC) class-I-dependent immune privilege can lead to autoimmune disease or fetal rejection. Pragmatic and instructive models are needed to clarify the as yet obscure controls of MHC class I down-regulation in situ, to dissect the principles of immune privilege generation, maintenance, and collapse as well as to develop more effective strategies for immune privilege restoration. Here, we propose that human scalp hair follicles, which are abundantly available and easily studied, are ideally suited for this purpose: interferon-gamma induces ectopic MHC class I expression in the constitutively MHC class-I-negative hair matrix epithelium of organ-cultured anagen hair bulbs, likely via interferon regulatory factor-1, along with up-regulation of the MHC class I pathway molecules beta(2)microglobulin and transporter associated with antigen processing (TAP-2). In the first report to identify natural immunomodulators capable of down-regulating MHC class I expression in situ in a normal, neuroectoderm-derived human tissue, we show that ectopic MHC class I expression in human anagen hair bulbs can be normalized by treatment with alpha-MSH, IGF-1, or TGF-beta1, all of which are locally generated, as well as by FK506. These agents are promising candidates for immune privilege restoration and for suppressing MHC class I expression where this is clinically desired (eg, in alopecia areata, multiple sclerosis, autoimmune uveitis, mumps orchitis, and fetal or allograft rejection).

B cell chronic lymphocytic leukaemia cells have reduced capacity to upregulate expression of MHC class I in response to interferon-γ

AIMS

An important consideration in the design of a tumour vaccine is the ability of tumour-specific cytotoxic T lymphocytes (CTL) to recognise unmanipulated tumour cells in vivo. To determine whether B-CLL might use an escape strategy, the current studies compared B-CLL and normal B cell MHC class I expression.

METHODS

Flow cytometry, TAP allele PCR and MHC class I PCR were used.

RESULTS

While baseline expression of MHC class I did not differ, upregulation of MHC class I expression by B-CLL cells in response to IFN-gamma was reduced. No deletions or mutations of TAP 1 or 2 genes were detected. B-CLL cells upregulated TAP protein expression in response to IFN-gamma. Responsiveness of B-CLL MHC class I mRNA to IFN-gamma was not impaired.

CONCLUSIONS

The data suggest that MHC class I molecules might be less stable at the cell surface in B-CLL than normal B cells, as a result of the described release of beta(2)m and beta(2)m-free class I heavy chains from the membrane. This relative MHC class I expression defect of B-CLL cells may reduce their susceptibility to CTL lysis in response to immunotherapeutic approaches.

Modulation of major histocompatibility complex Class I molecules and major histocompatibility complex—bound immunogenic peptides induced by interferon-α and interferon-γ treatment of human glioblastoma multiforme

OBJECT

Little is known about the quantitative modulation of major histocompatibility complex (MHC) Class I expression on human gliomas that is effected by interferons; even less is known about the immunogenic peptides that are accommodated in the peptide-binding motifs of MHC Class I alleles in these brain tumors. In this article the authors investigated the ability of interferon (IFN)alpha and IFNgamma to upregulate MHC Class I expression and to modulate acid-eluted Class I-bound peptides on human glioblastoma multiforme (GBM) cells in vitro.

METHODS

Early-passage primary human GBM cell cultures and U87MG GBM cells were incubated with varying doses of INFalpha or IFNgamma ranging between 0 and 2000 U/ml. Upregulation of MHC Class I expression was assayed by immunocytochemical analysis, flow cytometry, and Western blot analysis. Modulation of acid-eluted MHC Class I-bound peptides from the IFN-treated GBM cells was examined with the aid of mass spectroscopy. The in vitro expression of the MHC Class I molecule was upregulated by both IFNalpha and IFNgamma in a dose-dependent manner. Interferon-gamma exhibited a more potent effect on MHC Class I upregulation, peaking at 10 U/ml; whereas the effect of IFNalpha was less marked, reaching a plateau at 500 U/ml. In addition, a native peptide eluted from MHC Class I molecules of human GBM cells was identified and found to be consistently upregulated by IFN treatment.

CONCLUSIONS

Interferon-alpha and IFN-gamma can significantly upregulate the MHC Class I molecules that are expressed on the cell surface of human GBM cells as well as the potentially immunogenic peptides bound to the MHC. These results may help explain the molecular basis for increased immunogenicity with IFN treatment of human GBMs and might provide added insight into the design of future antitumor vaccines for human brain tumors.

Inosine stimulates chemotaxis, Ca2+-transients and actin polymerization in immature human dendritic cells via a pertussis toxin-sensitive mechanism independent of adenosine receptors

Inosine is an endogenous purine nucleoside, which is formed by adenosine deaminidase during adenosine breakdown and is released into the extracellular space from the sympathetic nervous system or injured cells. Here, we studied the biological activity of inosine on human dendritic cells (DC), which are specialized antigen presenting cells characterized by their ability to migrate from the blood to peripheral tissues, and then to secondary lymphoid organs where they initiate adaptive immune responses. In immature DC, inosine concentration-dependently stimulated Ca(2+)-transients, actin polymerization, and chemotaxis. Experiments with adenosine receptor antagonists and pertussis toxin (PTX) as well as desensitization studies suggested that the activity of inosine was mediated by a G protein-coupled receptor pathway independent of adenosine receptors. DC, induced to mature by lipopolysaccharide, lost their ability to respond towards inosine with these activities. Moreover, inosine did neither influence membrane expression of CD54, CD80, CD83, CD86, HLA-DR, and MHC class I molecules nor modulated secretion of interleukin (IL)-12, IL-10, and tumor necrosis factor alpha in immature and lipopolysaccharide-matured DC. In aggregate, our study indicates that inosine may be involved in the trafficking control system of immature DC, and mediates its chemotactic activity by a PTX-sensitive mechanism independent of adenosine receptors.

IFN- mediates the up-regulation of HLA class I on melanoma cells without switching proteasome to immunoproteasome

Treatment of melanoma cell lines with IFN-gamma induces the switch from proteasome (PS) to immunoproteasome (iPS). This finding has profound implications for the immunobiology of melanoma cells since certain peptides (such as Melan-A(mart1)(27-35)) are cleaved differently by iPS, thus implying a different ability to be presented by HLA class I molecules. IFN-alpha is a cytokine not only produced during infectious diseases, but also used in the treatment of certain cancers. Nevertheless, the effects of IFN-alpha on the switch of PS to iPS are largely unknown. A comparison of the effect of both IFN-alpha and IFN-gamma was thus carried out on melanoma cell lines. RT-PCR showed that mRNA for iPS subunits (i.e. LMP-2, LMP-7 and MECL-1) was detectable both in untreated and IFN-treated melanoma cells. Immunoblotting analysis revealed that while IFN-gamma was able to consistently induce the switch from PS to iPS, IFN-alpha treatment did not, possibly due to post-transcriptional event(s) blocking the expression of iPS-specific subunits. Finally, Melan-A(mart1)(27-35) peptide was found only in the HPLC-MS spectra from both untreated and IFN-alpha-treated cells, but not upon IFN-gamma treatment. Altogether, these data demonstrate that IFN-alpha does not induce the switch from PS to iPS.

IFN-γ production in human NK cells through the engagement of CD8 by soluble or surface HLA class I molecules

The engagement of CD8 on NK cell surface by either surface or soluble HLA class I (sHLA-I) molecules induces synthesis and secretion of IFN-gamma. HLA-I-mediated effects were inhibited by the covering of CD8 with specific anti-CD8 monoclonal antibodies, indicating a direct interaction of HLA-I and CD8. That CD8 ligation induces IFN-gamma production was further supported by the finding that cross-linking of CD8 led to release of IFN-gamma at similar levels to those obtained with HLA-I. The sHLA-I-induced IFN-gamma production via CD8 was strongly down-regulated by the engagement of the inhibitory isoforms of either CD94/NKG2 complex by sHLA-I-non-(A,B,C,G) (putative sHLA-E) or CD158b by sHLA-I-Cw3 allele. Ligation of CD8 did not elicit, different from other activating NK cell surface molecules such as CD16 or CD69, triggering of NK cell-mediated cytolysis. Cyclosporin A, but not concanamycin A, an H+-ATPase vacuolar inhibitor which affects perforin and granzyme release, strongly reduced the sHLA-I-mediated CD8-dependent IFN-gamma production but did not affect cytolytic activity of NK cells, suggesting that different biochemical pathways are involved. Altogether, these findings indicate that CD8 engagement by sHLA-I activates a cyclosporin A-dependent pathway leading to production and secretion of IFN-gamma which may play a role in the regulation of innate immune responses in humans.

Local IFN-gamma therapy of HPV16-associated tumours

We have examined whether peritumoral administration of IFN-gamma can inhibit growth of HPV16-associated, MHC class I- tumour MK16/1/IIIABC (MK16) transplanted in syngeneic mice. It has been found that peritumoral administration of recombinant IFN-gamma performed on days 0-11 after tumour challenge inhibited growth of MK16 s.c. tumour transplants. If the therapy with IFN-gamma was started when the tumours had already reached a palpable size, the IFN-gamma administration was without any effect. To investigate the antitumour effects of IFN-gamma in a clinically more relevant setting, surgical minimal residual tumour disease was utilized. Subcutaneously growing MK16 carcinomas, 8-12 mm in diameter, were removed and the operated mice were injected with IFN-gamma on days 3-14 after the operation at the site of surgery. Treatment with IFN-gamma resulted in a moderate, reproducible, but statistically insignificant inhibition of tumour recurrences. In the next experiments we have addressed the question whether the tumour-inhibitory effect of IFN-gamma was due to the upregulation of MHC class I molecule expression on MK16 tumour cells. IFN-gamma-treated and control mice were sacrificed, their tumours were explanted, and the expression of MHC class I molecules on the MK16 tumour cells was examined. As presumed, the MHC class I expression on the cells of IFN-gamma-treated tumours, as well as on their lung metastases, was upregulated. However, an unexpected moderate upregulation of the MHC class I expression was also observed on MK16 tumours from the control, exogenous IFN-gamma-uninjected mice. Cytofluorometric analysis of the in vivo transplanted MK16 tumours from both groups has excluded that the increased percentage of the MHC class I molecules on the tumour cell populations could be due to the infiltration of the tumours with MHC class I+ leukocytes, since no expression of MHC class II, CD11b, CD80/CD86, and CD11c molecules in the MK16 cell population was observed.

Cytokine dependent inverse regulation of CD54 (ICAM1) and major histocompatibility complex class I antigens by nuclear factor kappaB in HEp2 tumor cell line: effect on the function of natural killer cells

The aim of this study is to investigate the mechanisms by which elevated nuclear factor kappaB (NFkappaB) activity in HEp2 cells can modulate the function and survival of immune effector cells. Inhibition of NFkappaB functional activity by stable expression of IkappaB super-repressor rendered HEp2 cells (HEp2-IkappaB((S32AS36A))) susceptible to natural killer (NK) cell mediated cytotoxicity. Increase in surface ICAM1 expression was greater on HEp2-IkappaB((S32AS36A)) cells than on the surface of vector alone transfected HEp2 cells when these cells were treated with IFN-gamma. In contrast, tumor necrosis factor alpha (TNF-alpha) treatment augmented ICAM-1 expression on the surface of vector-alone transfected HEp2 cells and not on the HEp2-IkappaB((S32AS36A)) cells. Moreover, synergistic augmentation of ICAM-1 by a combination of TNF-alpha and interferon-gamma (IFN-gamma) treatment was completely abrogated on the surface of HEp2-IkappaB((S32AS36A)) cells. The addition of blocking antibody to ICAM-1 surface antigen partially inhibited the increased cytotxicity mediated by interleukin-2 treated NK cells against HEp2-IkappaB((S32AS36A)) cells. In contrast to ICAM-1, the expression of major histocompatibility complex (MHC) class I antigens were downregulated when the function of nuclear NFkappaB was inhibited in HEp2 cells. The addition of IFN-gamma to HEp2-kappaB((S32AS36A)) cells increased the expression of MHC class I antigen and rendered these cells less susceptible to NK cell mediated cytotoxicity. Secretion of IFN-gamma and granulocyte macrophage-colony-stimulating factor (GM-CSF) by NK cells was also significantly increased in the presence of HEp2-IkappaB((S32AS36A)) cells, and the treatment of these tumor cells with IFN-gamma prior to their addition to the cultures of NK cells decreased the released IFN-gamma and GM-CSF by NK cells. However, the levels of NK cell mediated cytotoxicity and IFN-gamma secretion remained significantly higher in the presence of both untreated and IFN-gamma treated HEp2-IkappaB((S32AS36A)) cells when compared with vector-alone transfected HEp2 cells. Thus, NFkappaB regulates inversely the expression of ICAM-1 and MHC class I antigens on HEp2 tumor cells and this may contribute to the resistance of these cells to NK cell mediated cytotoxicity.

Class I HLA oligomerization at the surface of B cells is controlled by exogenous beta(2)-microglobulin: implications in activation of cytotoxic T lymphocytes

Submicroscopic molecular clusters (oligomers) of class I HLA have been detected by physical techniques [e.g. fluorescence resonance energy transfer (FRET) and single particle tracking of molecular diffusion] at the surface of various activated and transformed human cells, including B lymphocytes. Here, the sensitivity of this homotypic association to exogenous beta(2)-microglobulin (beta(2)m) and the role of free heavy chains (FHC) in class I HLA oligomerization were investigated on a B lymphoblastoid cell line, JY. Scanning near-field optical microscopy and FRET data both demonstrated that FHC and class I HLA heterodimers are co-clustered at the cell surface. Culturing the cells with excess beta(2)m resulted in a reduced co-clustering and decreased molecular homotypic association, as assessed by FRET. The decreased HLA clustering on JY target cells (antigen-presenting cells) was accompanied with their reduced susceptibility to specific lysis by allospecific CD8(+) cytotoxic T lymphocytes (CTL). JY B cells with reduced HLA clustering also provoked significantly weaker T cell activation signals, such as lower expression of CD69 activation marker and lower magnitude of TCR down-regulation, than did the untreated B cells. These results together suggest that the actual level of beta(2)m available at the cell surface can control CTL activation and the subsequent cytotoxic effector function through regulation of the homotypic HLA-I association. This might be especially important in some inflammatory and autoimmune diseases where elevated serum beta(2)m levels are reported.

Mild acid treatment induces cross-reactivity of 4H84 monoclonal antibody specific to nonclassical HLA-G antigen with classical HLA class I molecules

Mild acid treatment by releasing beta(2)m and antigenic peptides leaves human leukocyte antigen (HLA) class I free heavy chains attached to the cell surface. Acid treatment thus allows detection of the cell surface class I antigens by monoclonal antibodies (mAbs) specific to HLA-free heavy chains. We found that acid treatment also enables detection of the cell surface non-classical HLA-G class I antigen with mAbs specific for HLA-G free heavy chains, including 4H84 mAb recognizing all isoforms. Furthermore, we found that 4H84 mAb, but not other mAbs specific to HLA-G free heavy chains, binds to the surface of 8 out of 16 acid-treated leukemia cell lines. Nevertheless, HLA-G antigen is not present in any of these leukemia cells. This was demonstrated by failure to detect any antigen with 4H84 mAb in immunoblotting as well as by inability to detect HLA-G mRNA by RT-PCR. The antigen recognized by 4H84 mAb in some acid treated leukemia cells was identified by immunoprecipitation as a 45 kDa protein. A number of observations indicate that 45 kDa proteins are none other than classical class I heavy chains. Acid treatment thus induces the ability of the 4H84 mAb to recognize some classical HLA class I molecules. Remarkably, 4H84 determinant on HLA-G is linear but corresponding determinant present on some partially folded classical HLA class I free heavy chains is conformational. In view of the unexpected cross-reactivity, detection of HLA-G with this mAb must be carefully evaluated to avoid false detection.

Tumor necrosis factor-alpha induces coordinated changes in major histocompatibility class I presentation pathway, resulting in increased stability of class I complexes at the cell surface

It is demonstrated that similar to interferon gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) induces coordinated changes at different steps of the major histocompatibility complex (MHC) class I processing and presentation pathway in nonprofessional antigen-presenting cells (APCs). TNF-alpha up-regulates the expression of 3 catalytic immunoproteasome subunits--LMP2, LMP7, and MECL-1--the immunomodulatory proteasome activator PA28 alpha, the TAP1/TAP2 heterodimer, and the total pool of MHC class I heavy chain. It was also found that in TNF-alpha--treated cells, MHC class I molecules reconstitute more rapidly and have an increased average half-life at the cell surface. Biochemical changes induced by TNF-alpha in the MHC class I pathway were translated into increased sensitivity of TNF-alpha--treated targets to lysis by CD8(+) cytotoxic T cells, demonstrating improved presentation of at least certain endogenously processed MHC class I--restricted peptide epitopes. Significantly, it was demonstrated that the effects of TNF-alpha observed in this experimental system were not mediated through the induction of IFN-gamma. It appears to be likely that TNF-alpha--mediated effects on MHC class I processing and presentation do not involve any intermediate messengers. Collectively, these data demonstrate the existence of yet another biologic activity exerted by TNF-alpha, namely its capacity to act as a coordinated multi-step modulator of the MHC class I pathway of antigen processing and presentation. These results suggest that TNF-alpha may be useful when a concerted up-regulation of the MHC class I presentation machinery is required but cannot be achieved by IFN-gamma. (Blood. 2001;98:1108-1115)

Profile of epidermal growth factor receptor (EGFr) expression in human malignancies: effects of exposure to EGF and its biological influence on established human tumour cell lines

The aim of this study was to compare the profile of EGFr expression in transitional cell carcinoma of the bladder (TCC) and in oral squamous cell carcinoma (OSCC). In addition, to study the influence of EGF stimulation on the expression of major histocompatibility complex class I antigens, placental alkaline phosphatase (PLAP) as well as changes in tumour cell sensitivity to cisplatin using immunocytochemical staining, a colorimetric assay and SDS-gel electrophoresis. The results showed that: a) strong EGFr expression could be seen in 22/88 (27%) cases of TCCs. In oral tumours the values for non-invasive ameloblastoma and invasive OSCC were 4/25 (16%) and 30/41 (73%) respectively. b) EGFr expression in tumour cell lines paralleled that of tumour biopsies. The number of lines expressing high and low EGFr expression amongst TCCs were 4 and 4 and in OSCCs were 3 and 1 respectively. c) Exposure of tumour cell lines to EGF led to: i) an increase in EGFr expression (stimulatory indices SI, ranged from 1.06 to 2.58) for TCCs but a decrease in the case of OSCCs (SI ranged from 0.01 to 0.85). The corresponding SI values for class I antigens were 0.95-1.16 and 0.10-0.84. ii) A significant reduction in expression of PLAP by OSCC cell lines. iii) An increased susceptibility of OSCC cell lines to cisplatin by as much as 14% (p<0.001). These data demonstrated the overexpression of EGFr in a significant proportion of TCCs. As for oral tumours it depended on whether they were of an invasive or non-invasive type. In the invasive cases the majority overexpressed EGFr. The exposure of OSCC but not TCC tumour cells to EGF resulted in down regulation of EGFr and class I antigens. The expression of PLAP was also significantly reduced. Exposure of OSCC cells to EGF resulted in their increased susceptibility to cisplatin. The data supports the notion that the mitogenic activation of some tumour cells by EGF resulted in a reduction of their immune visibility, differentiation status and an increase in chemosensitivity.

MAGE-specific cytotoxic T lymphocytes require non-specific CD54 adherence receptors on carcinoma cells

We investigated several factors that could regulate the susceptibility of carcinoma cells to MAGE-2-specific CTL mediated lysis. Cytofluorometric analysis showed that the cytolysis correlated with the expression of CD54. IFN-gamma treatment induced the TAP-1 and LMP-2 genes, continuously up-regulated the HLA class I expression and increased cytolysis. Although HLA class I were highly induced in MRKnu1 cells, CD54 was not induced and the cytolysis was minimal. Cytotolysis of IFN-gamma-treated MKN-1 cells was completely inhibited by a monoclonal anti-CD54 antibody. These results suggest that HLA-restricted CTL lysis requires non-specific CD54 adherence receptors in addition to specific TCR signals.

Ethanol and halothane differently modulate HLA class I and class II oligomerization. A new look at the mode of action of anesthetic agents through fluorescence spectroscopy

The field of research considering the working mechanism of anesthetic agents is a complex one and the site or sites of action of general anesthetics are yet to be elucidated. Through the years, on the molecular level, the discussion has shifted from the lipid theories to the more specific interaction with the proteins responsible for the signal transduction. While this approach led to several models, they offer, at best, partial explanations for the observed phenomena. Anesthetic agents interact with many systems, of which the neuronal is best studied, leaving interaction with the immune defense system relatively unexplored. In this study we focus on the interaction of ethanol and halothane with the co-localization on the membrane of HLA I and II molecules. We show that ethanol tends to randomize the distribution of HLA I and II molecules, while halothane increases the clustering of HLA I proteins. The notion that anesthetics modulate cell function by disrupting clustering and thereby promoting a random distribution is a novel approach that may explain the general involvement of many systems during exposition to anesthetic drugs. In this study we show the disturbance of co-localization of molecules that may form a functional network. The relevance of this finding depends on the importance of these networks for extracellular and intracellular processes.

Role of anti-gB and -gD antibodies in antibody-induced endocytosis of viral and cellular cell surface glycoproteins expressed on pseudorabies virus-infected monocytes

The addition of porcine pseudorabies virus (PrV)-specific polyclonal IgG antibodies to PrV-infected monocytes induces internalization of plasma membrane-anchored viral glycoproteins and major histocompatibility complex (MHC) class I. Using PrV deletion strains, it was shown that gB and gD are essential for the process to occur. The purpose of the current study was to evaluate whether antibodies directed against single viral glycoproteins are able to induce endocytosis. It was shown that monoclonal antibodies directed against viral glycoprotein gB and gD, but not against gC and gE, are able to induce internalization of their respective ligand. Adding a combination of monoclonal antibodies against gB and gD resulted in endocytosis levels, comparable to the endocytosis levels observed when adding porcine PrV-specific polyclonal antibodies. The addition of genistein and tyrphostin 25, two inhibitors of tyrosine kinase activity, abolished endocytosis induced by monoclonal anti-gB and -gD antibodies in a concentration-dependent manner. The addition of similar concentrations of tyrphostin 1, an inactive tyrphostin, had no effect on endocytosis. It was also shown that a mixture of polyclonal, but not monoclonal, antibodies against gB and gD is able to induce cointernalization of MHC class I. This indicates that MHC class I cointernalization results from a passive catching of the molecules rather than from a specific interaction of the MHC class I molecules with one or more viral glycoproteins. In conclusion, it can be stated that antibody-induced crosslinking of gB and gD induces the activation of a tyrosine phosphorylation-dependent signal transduction pathway, leading to their endocytosis. Cointernalization of other viral glycoproteins and MHC class I is most likely caused by a passive catching of these molecules in the gB and gD aggregates.

Decreased expression of interleukin-1alpha, interleukin-1beta, and cell adhesion molecules in muscle tissue following corticosteroid treatment in patients with polymyositis and dermatomyositis

OBJECTIVE

To study the effects of immunosuppressive therapy, in particular, corticosteroids, on morphologic signs of inflammation and expression of cytokines, adhesion molecules, and class I major histocompatibility complex (MHC) antigen in muscle tissue from patients with polymyositis (PM) and dermatomyositis (DM) and to correlate the molecular changes with changes in muscle function.

METHODS

Seven patients with PM and 4 patients with DM underwent muscle biopsy before and after 3-6 months of therapy. Ten of the 11 patients were initially treated with prednisolone 30-60 mg/day. The phenotypes of infiltrating inflammatory cells and the expression of interleukin-1alpha (IL-1alpha) and IL-1beta, adhesion molecules, and class I MHC antigen were studied by immunochemistry. Computerized image analysis was used for quantitation of staining. Muscle function was assessed with a muscle function index score.

RESULTS

Pronounced improvement of muscle function during the treatment period was noted in 8 of the 11 patients. The changes in muscle function coincided with an almost complete disappearance of inflammatory cells, including CD3+ T cells, in the patients with clinical improvement. These patients also exhibited decreased expression of IL-1alpha, IL-1beta, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), leukocyte function-associated antigen 1alpha, and very late activation antigen 4alpha. Of note, there was persistent expression of IL-1alpha, ICAM-1, and VCAM-1 in capillaries and of class I MHC antigens on muscle fibers in several of the patients who, after corticosteroid treatment, still had muscle weakness despite the disappearance of inflammatory infiltrates.

CONCLUSION

Changes in the muscle expression of key molecules in the inflammatory process, such as IL-1alpha and IL-1beta, ICAM-1 and class I MHC antigens, showed a consistent but not complete concordance with changes in and status of muscle function in patients with myositis who received the current standard treatment for the disease. These data indicate that it is possible to further evaluate various therapies for myositis using molecular analysis of muscle biopsy specimens obtained on repeated occasions. In addition, the data demonstrate a dissociation between muscle function and degree of inflammatory infiltration in the affected muscles and suggest that the functional defects are more related to the expression of molecules such as IL-1alpha in muscle capillaries than to the mere presence of inflammatory cells in the affected muscles.

Characteristics of human T-lymphotropic virus type-1 (HTLV-1)-infected cell line MT-2, which is not killed by a natural killer cell line NK-92 but is killed by lymphokine-activated killer cells

Natural killer (NK) cell-mediated cytolysis (NK-lysis) is triggered by costimulatory signals of adhesion molecules and is downregulated by negative signals of killer cell inhibitory receptors (KIRs). Recently, a NK cell line, NK-92, was established. This cell line can kill several tumor cells, which possess adhesion molecules CD54 and CD102. However, the NK-92 cannot kill a human T-lymphotropic virus type 1 (HTLV-1)-infected cell line, MT-2, although lymphokine-activated killer (LAK) cells can kill MT-2. In this report we investigated the reason for LAK sensitivity but NK-92 resistance of the MT-2. The MT-2 highly expressed CD54 and CD102, suggesting that the costimulatory signals may be intact. Then we tested the responsibility of the negative signals by determining HLA type of the MT-2 and KIRs of the effector cells. The MT-2 expressed HLA-A24, B40, B51, Cw3, and HLA-G. The NK-92 did not express KIR2DL1, KIR2DL2,3, nor KIR3DL1, but 24% of the cells weakly expressed CD94. The blocking tests against these HLA class I molecules and KIRs did not restore the NK-92 resistance, although blocking against HLA-G slightly increased its lysis. Finally, in order to eliminate the class I molecules from the cell surface, we treated the MT-2 using a buffered citric acid solution (pH 3.8). By using this treatment, the expression of class I molecules and HTLV-1 antigen decreased, and then the MT-2 was killed by the NK-92. These findings suggest that an aberrant class I molecule of the MT-2 transferred a negative signal to the NK-92 and induced the NK-92 resistance. It remains to be elucidated whether or not the HTLV-1 infection contributed to the alteration of the class I molecule.

Antigen presentation by MHC class I and its regulation by interferon gamma

Antigen processing by MHC class I molecules begins with the generation of peptides by proteolytic breakdown of proteins. IFN-gamma upregulates gene expression of several proteasomal subunits as well as the proteasome regulator PA28; this implicated their role in antigen degradation. Crystallographic, mutational and biochemical studies contributed to our understanding of the basic principles of proteasomal protein degradation and the consequences of IFN-gamma induction for proteasome function. In addition, nonproteasomal mechanisms seem to be involved in antigen degradation. Leucine aminopeptidase, which is also upregulated by IFN-gamma, was shown to collaborate with the proteasome for epitope production and unknown proteases seem to compensate for the loss of proteasomal degradation in the presence of proteasome inhibitors. Thus, a rather complex picture emerges for the rules governing peptide production in the presence or absence of IFN-gamma.

Functional comparison of bovine, murine, and human beta2-microglobulin: interactions with murine MHC I molecules

Fetal calf serum is a well known source of bovine beta2-microglobulin (beta2m) which can exchange with endogenous beta2m from, as well as promote peptide binding to, class I major histocompatibility (MHC I) molecules on cells cultured in vitro. Recombinant bovine beta2m was expressed and purified for direct functional comparison to human and murine beta2m for interactions with murine MHC I molecules H-2Kb, Db, Kd, Ld, and Dd. Bovine and human beta2m were equivalent in stabilizing MHC I heavy chains and facilitating peptide loading, suggesting similar affinities for murine MHC I heavy chains. The activity of murine beta2m was significantly weaker, consistent with previous work that demonstrated the lower affinity of murine human beta2m for murine heavy chains compared to human beta2m. Analysis of bovine beta2m in fetal calf serum revealed ten-fold higher concentrations than in adult bovine serum, levels shown to significantly affect MHC I stability and peptide loading. The ramifications for the study of MHC I molecules from cells in culture and the evolutionary implications of the higher affinity interactions of human and bovine beta2m are discussed.

Photoactivated 8-methoxypsoralen treatment causes a peptide-dependent increase in antigen display by transformed lymphocytes

Ex vivo exposure of malignant human T cells to photoactivated 8-methoxypsoralen (8-MOPa), followed by their i.v. return, appears to vaccinate patients against tumor-associated antigens of cutaneous T cell lymphoma in a procedure termed photopheresis. The molecular basis of this Food and Drug Administration-approved therapy, administered in 100 centers worldwide, is unclear. Most of the attention to the mechanism of action of the drug has focused on its capacity to form covalent cross-links with pyrimidine bases of DNA, thereby inhibiting cellular proliferation. Because immunologic factors appear to be important in the clinical response and could potentially serve as a model for immunotherapy of other malignancies, we explored the possibility that 8-MOP-treated cells display increased quantities of antigenic peptides at their cell surface. In this work, human B-lymphoblastoid tissue culture lines were exposed to 8-MOPa and expression of cell surface class I major histocompatibility complex proteins assessed, since CD8 T cells recognize antigenic moieties in the context of class I molecules. A peak 200-300% increase in MHC class I expression in 8-MOPa-treated cells occurred at 20 hr. 8-MOPa was far more effective in inducing this increase in class I MHC than other modalities, including mitomycin C, gamma-irradiation, ultraviolet B or heat or cold shock. This increase in surface class I MHC molecules appears to be driven by the degradation of cytoplasmic proteins into small peptides, followed by the transport of these peptides to MHC class I molecules in the endoplasmic reticulum. The data suggest that 8-MOPa treatment may augment the immunogenicity of tumor and/or antigen-presenting cells by enhancing processing and transport of class I MHC antigenic peptides.

IFN-alpha priming of human monocytes differentially regulates gram-positive and gram-negative bacteria-induced IL-10 release and selectively enhances IL-12p70, CD80, and MHC class I expression

Administration of IFN-gamma and IFN-alpha may protect or induce autoimmune diseases. Although the in vitro regulation of monokine secretion by IFN-gamma have been extensively studied, the regulatory function of IFN-alpha has not yet been elucidated. We compared IFN-alpha and IFN-gamma, added alone or simultaneously before bacterial stimulation, for the control of monokine release and the expression of costimulatory molecules by human monocytes. Our data show that: 1) IFN-alpha primes monocytes for increased production of IL-10 in response to Staphylococcus aureus Cowan I strain (SAC) but not to LPS, leading to a lack of IFN-alpha priming for TNF-alpha secretion; 2) pretreatment of monocytes with IFN-alpha inhibits LPS- or SAC-induced IL-12p40 production but unexpectedly enhances the release of the biologically active form of IL-12 (IL-12p70); 3) IFN-alpha and IFN-gamma exert an antagonistic effect on LPS- and SAC-induced IL-10 as well as IL-12p40 release, whereas they further enhance IL-12p70 production when added simultaneously; 4) in contrast to IFN-alpha, IFN-gamma primes monocytes to enhance LPS- or SAC-induced TNF-alpha and IL-12 production, but surprisingly, it increases IL-10 production by monocytes following LPS but not SAC stimulation; and finally, 5) IFN-alpha pretreatment selectively up-regulates CD80 and MHC class I expression on monocytes. It is proposed that the outcome of the immune response at the site of inflammation may depend on both the type of bacterial injury (gram-positive or -negative) and of locally produced IFNs, and that the differential and opposite effects of type I and type II IFNs on monocytes may account for the beneficial or detrimental effects of IFN-alpha therapy.

Effects of retinoic acid combined with irradiation on the expression of major histocompatibility complex molecules and adhesion/costimulation molecules ICAM-1 in human cervical cancer

OBJECTIVES

Radiation treatment is one of the most standardized and effective modalities for contemporary cervical cancer therapy. In addition, the radiation-potentiating effects of retinoic acid have been recently described. In order to investigate whether enhanced immunogenicity might be responsible for such potentiation, we have evaluated the effects of retinoic acid combined with high doses of gamma-irradiation on the expression of major histocompatibility complex (MHC) Class I and II and intercellular adhesion molecule-1 (ICAM-1) in human cervical carcinoma cell lines.

METHODS

The expression of surface antigens (MHC Class I and II and ICAM-1) was evaluated by FACS analysis in untreated control cells and in cells following their exposure to retinoic acid, high doses of gamma-irradiation (i.e., 5000 and 10,000 cGy), or the combination of the two procedures.

RESULTS

HT-3 and SiHa cervical cancer cells expressed variable levels of MHC Class I and ICAM-1 antigens while Class II surface antigens were not detectable. Exposure to either 5000 or 10,000 cGy completely inhibited cell replication in both cell lines and significantly and consistently increased the expression of all surface antigens present on the cells prior to irradiation. Irradiation was unable to induce neoexpression of antigens previously not expressed by these cells (i.e., MHC Class II). In a similar fashion, retinoic acid was also able to significantly increase the expression of MHC Class I and ICAM-1 antigens when compared to untreated tumor cells but was not able to induce the expression of HLA Class II surface antigens. Exposure to the combination of radiation plus retinoic acid significantly upregulated HLA Class I and ICAM-1 molecules in an additive manner when compared to the levels obtainable with the exposure to radiation or retinoic acid alone.

CONCLUSIONS

These data indicate that the combination of these two treatments could induce an additive effect on the expression of immunologically important surface antigens in human cervical cancer cells. These findings, together with the powerful antiproliferative effect of retinoids and irradiation on tumor cells, suggest that the combined regimen may be a promising and more effective combination for the treatment of cervical cancer.

NK cells can recognize different forms of class I MHC

NK recognition and lysis of targets are mediated by activation receptor(s) whose effects may be over-ridden by inhibitory receptors recognizing class I MHC on the target. Incubation of normal lymphoblasts with a peptide that can bind to their class I MHC renders them sensitive to lysis by syngeneic NK cells. By binding to class I MHC, the peptide alters or masks the target structure recognized by an inhibitory NK receptor(s). This target structure is most likely an "empty" dimer of class I heavy chain and beta2m as opposed to a "full" class I trimer formed by binding of specific peptide that is recognized by CTL.

Partial purification and characterization of a novel murine factor that augments the expression of class I MHC antigens on tumor cells

A soluble factor which augments the expression of major histocompatibility complex class I (MHC I) antigens on a number of murine tumor cell lines, has been isolated from the culture supernatants of mixed lymphocyte reaction of spleen cells derived from C57B1/6, Balb/c and Swiss mice. The factor, termed MHC-augmenting factor (MHC-AF) has been partially purified by Sephadex G-100 column chromatography and reverse phase HPLC. MHC-AF activity is associated with an 18 kDa molecule. MHC-AF activity was resistant to pH 2.0 treatment and partially purified MHC-AF preparations did not have any activity in L929 cell/vesicular stomatitis virus (VSV) interferon bioassay system. Antibodies to IFN-gamma did not block the activity of MHC-AF. These results indicate that a MHC-AF distinct from IFN-gamma, is produced by mouse spleen cells undergoing a mixed lymphocyte reaction.

Regulation of major histocompatibility complex class I expression by NF-kappaB-related proteins in breast cancer cells

Downregulation of MHC Class I antigens has been observed in many cancers and usually results from a decreased gene transcription. A reporter CAT gene dependent on the MHC Class I kappaB site or on a longer promoter is transactivated by NF-kappaB complexes containing p65 or RelB. p100 as well as IkappaB-alpha are potent inhibitors of this transcription and p100 sequesters RelB and p65 complexes in the cytoplasm of breast cancer cells. However, although p100 is highly expressed in a number of breast cancer cell lines, MHC Class I antigen expression was observed on all the cell lines we analysed and could be further induced by stimulation with the cytokines IFN-gamma or TNF-alpha. Stable transfection of a unresponsive mutated IkappaB-alpha Ser 32-36 expression vector showed that TNF-alpha induced MHC Cl I expression in an NF-kappaB-dependent way while IFN-gamma did it independently of any NF-kappaB activation.

Characterization of the interactions between MHC class I subunits: a systematic approach for the engineering of higher affinity variants of beta 2-microglobulin

Human beta 2m (h beta 2m) binds to murine MHC I molecules with higher affinity than does murine beta2m and therefore can be used as a model system to define and dissect the interactions between beta2m and MHC I heavy chains that promote the stability of the complex. In the present study we compare three-dimensional crystal structures of human and murine MHC I molecules and use functional studies of chimeric human:murine beta 2m variants to define a region of beta2m that is involved in the higher affinity of h beta 2m for murine MHC I heavy chains. Further examination of the three-dimensional structure in this region revealed conformational differences between human and murine beta2m that affect the ability of an aspartic acid residue at position 53 (D53) conserved in both beta 2ms to form an ionic bond with arginine residues at positions 35 and 48 of the heavy chain. Mutation of residue D53 to either asparagine (D53N) or valine (D53V) largely abrogated the stabilizing effects of h beta 2m on murine MHC I expression in a predictable manner. Based on this observation a variant of h beta 2m was engineered to create an ionic bond between the heavy chain and beta 2m. This variant stabilizes cell surface H-2Dd heavy chains to a greater extent than wild-type h beta 2m. Studying these interactions in light of the growing database of MHC I crystal structures should allow the rational design of higher affinity h beta 2m variants for use in novel peptide-based vaccines capable of inducing cell-mediated immune responses to viruses and tumors.

Downmodulation of HLA class I expression by dexamethasone in MCF-7 cell line

Several reports have shown the importance of MHC class I antigens in enabling the host to regulate tumour growth in vivo. Glucocorticoid hormones have strong immunosuppressive effects and are known to be regulators of gene transcription. In this report the expression of Major Histocompatibility Complex (MHC) class I antigens in six breast carcinoma cell lines have been studied before and after treatment with the synthetic glucocorticoid dexamethasone. Hence, HLA class I expression in the MCF-7 cell line was down-regulated in the presence of dexamethasone. This down-modulation of expression appeared to be mediated by transcriptional mechanisms, as revealed by HLA-class I mRNA levels.

IFN-gamma is not required in the IL-12 response to vesicular stomatitis virus infection of the olfactory bulb

In this report, the role of IFN-gamma in host defense to exogenous IL-12 and clearance of vesicular stomatitis virus (VSV) from the central nervous system was examined. Wild-type and IFN-gamma knockout mice infected with VSV were treated with IL-12 or medium. In both groups, IL-12 treatment resulted in 1) substantially decreased VSV titers in brain homogenates and diminished immunohistochemical detection of VSV Ags in tissue sections; 2) induction of types 1, 2, and 3 nitric oxide synthase; and 3) induction of MHC molecules and rapid infiltration of both T cells and NK cells. These results suggest that IFN-gamma production, both systemically and in the olfactory bulb, contributes to but is not essential for clearance of VSV from the brain. Neutralization of TNF-alpha in IFN-gamma knockout mice mice treated with IL-12 was accompanied by the same immunohistochemical changes, implying that neither IFN-gamma nor TNF-alpha was required. In vitro studies using purified IL-12 or IFN-gamma in culture medium induced nitric oxide synthase isoforms in neurons, glia, and macrophages, and MHC II on glia and macrophages. These data suggest that IL-12 directly activates neurons to promote viral clearance in vivo.

Chronic administration of dexamethasone results in Fc receptor up-regulation and inhibition of class I antigen expression on macrophages from MRL/lpr autoimmune mice

The MRL/lpr mouse develops, after approximately 8 weeks of age, a severe autoimmune syndrome with many features resembling human systemic lupus erythematosus, including autoantibodies against DNA and basement membranes resulting in immune complexes, vasculitis, and multiorgan disease. While this murine model of lupus has been used for the identification of therapeutics with potential efficacy in human autoimmune disease, the long-term impact of chronic immunosuppressive therapy on macrophage function in this paradigm is not understood. To this end, MRL/lpr mice were treated prophylactically with dexamethasone at 0.01, 0.1, and 1 mg/kg of body weight for 20 weeks or were allowed to develop autoimmune disease and, at 15 weeks of age, treated therapeutically with 1-mg/kg dexamethasone for 8 additional weeks. Analysis of surface antigens on resident peritoneal macrophages demonstrated a progressive loss in class I expression with a concomitant increase in Fc receptor expression. Neither phagocytosis nor CD11b expression was modulated with chronic steroid treatment. Furthermore, dexamethasone treatment was associated with a reduction in anti-DNA antibodies and total immunoglobulin G and yet an elevation in serum cholesterol due to an increase in high-density lipoproteins. Therefore, the MRL/lpr mouse serves not only as a small-animal model of autoimmune disease but also as one in which the negative and positive sequelae associated with chronic immunosuppression can be further understood.