Armed and targeted measles virus for chemovirotherapy of pancreatic cancer

No curative therapy is currently available for locally advanced or metastatic pancreatic cancer. Therefore, new therapeutic approaches must be considered. Measles virus (MV) vaccine strains have shown promising oncolytic activity against a variety of tumor entities. For specific therapy of pancreatic cancer, we generated a fully retargeted MV that enters cells exclusively through the prostate stem cell antigen (PSCA). Besides a high-membrane frequency on prostate cancer cells, this antigen is expressed on pancreatic adenocarcinoma, but not on non-neoplastic tissue. PSCA expression levels differ within heterogeneous tumor bulks and between human pancreatic cell lines, and we could show specific infection of pancreatic adenocarcinoma cell lines with both high- and low-level PSCA expression. Furthermore, we generated a fully retargeted and armed MV-PNP-anti-PSCA to express the prodrug convertase purine nucleoside phosphorylase (PNP). PNP, which activates the prodrug fludarabine effectively, enhanced the oncolytic efficacy of the virus on infected and bystander cells. Beneficial therapeutic effects were shown in a pancreatic cancer xenograft model. Moreover, in the treatment of gemcitabine-resistant pancreatic adenocarcinoma cells, no cross-resistance to both MV oncolysis and activated prodrug was detected.

The prostate stem cell antigen represents a novel glioma-associated antigen

Gliomas of WHO grades III-IV are malignant brain tumors mostly resistant to conventional therapies. Therefore, novel strategies for the treatment of gliomas are warranted. Although immunotherapy is gaining increased attention for the treatment of malignant gliomas and in particular of glioblastoma multiforme (GBM), this approach requires the identification of appropriate antigens. Our aim was to investigate the expression of the prostate stem cell antigen (PSCA), a highly N-glycosylated phosphatidylinositol (GPI)-anchored cell surface protein, in gliomas of different WHO grades in order to evaluate its potential as a diagnostic marker and as a target for immunotherapy. Tumor specimens and controls were assessed by quantitative RT-PCR, Western blotting and immunohistochemistry. The samples investigated in the study consisted of 210 human glial tumors, among which 31 were oligodendrogliomas, 9 ependymomas and 170 were astrocytomas (including 134 glioblastomas). PSCA was absent in normal brain tissue, but was detected in WHO grade III-IV gliomas. Weak PSCA protein expression was also recognized in some WHO grade I and WHO grade II tumors. The difference between WHO grade I-II tumors and WHO grade III-IV tumors was statistically significant (p<0.001). Our results suggest that increased PSCA expression levels are linked to gliomas of WHO grades III and IV, and may represent a suitable additional target for immunotherapy of gliomas.

Detection of autoantibodies to tumour-associated antigens in sera of patients with systemic autoimmunity using a novel protein microblot array

It is well known that sera of patients with systemic autoimmunity contain autoantibodies to nuclear antigens. It is also known that patients with systemic autoimmunity have an increased risk for the development of tumours. Interestingly, tumour patients frequently develop autoantibodies and there is a growing list of potential tumour-associated antigens. It is, however, not known whether or not patients with systemic autoimmunity also develop antibodies to tumour-associated antigens. Here we describe the development of a novel multiprotein array allowing us to screen for autoantibodies to 30 different tumour-associated antigens in parallel. Using this novel assay, we found that the frequency of autoantibodies to the selected tumour-associated antigens is increased between 2- and 14-fold in patients with systemic autoimmunity compared with an age-matched control group.

Bortezomib significantly impairs the immunostimulatory capacity of human myeloid blood dendritic cells

Bortezomib is a potent drug for the treatment of multiple myeloma. Its anti-tumor activity is mediated by proteasome inhibition leading to decreased cell proliferation and induction of apoptosis. However, an unimpaired proteasomal function plays a crucial role for the induction of anti-tumor immunity by dendritic cells (DCs), which are currently used for therapeutic vaccination against various tumors including myeloma. In the present study, we investigated the impact of bortezomib on the immunostimulatory capacity of 6-sulfo LacNAc (slan) DCs, which represent a major subset of human blood DCs. We demonstrated that this proteasome inhibitor efficiently impairs the spontaneous in vitro maturation of slanDCs and the release of tumor necrosis factor (TNF)-alpha as well as interleukin (IL)-12 upon lipopolysaccharide (LPS) stimulation. Functional data revealed that bortezomib profoundly inhibits slanDC-induced proliferation and differentiation of CD4(+) T cells. In addition, the capacity of slanDCs to promote interferon-gamma secretion and tumor-directed cytotoxicity of natural killer (NK) cells is markedly impaired by bortezomib. These results provide evidence that bortezomib significantly reduces the ability of native human blood DCs to regulate innate and adaptive anti-tumor immunity and may have implications for the design of therapeutic strategies combining DC vaccination and bortezomib treatment.

Identification of SOX2 as a novel glioma-associated antigen and potential target for T cell-based immunotherapy

Prognosis for patients suffering from malignant glioma has not substantially improved. Specific immunotherapy as a novel treatment concept critically depends on target antigens, which are highly overexpressed in the majority of gliomas, but the number of such antigens is still very limited. SOX2 was identified by screening an expression database for transcripts that are overexpressed in malignant glioma, but display minimal expression in normal tissues. Expression of SOX2 mRNA was further investigated in tumour and normal tissues by real-time PCR. Compared to cDNA from pooled normal brain, SOX2 was overexpressed in almost all (9 out of 10) malignant glioma samples, whereas expression in other, non-malignant tissues was almost negligible. SOX2 protein expression in glioma cell lines and tumour tissues was verified by Western blot and immunofluorescence. Immunohistochemistry demonstrated SOX2 protein expression in all malignant glioma tissues investigated ranging from 6 to 66% stained tumour cells. Human leucocyte antigen-A^*0201-restricted SOX2-derived peptides were tested for the activation of glioma-reactive CD8+ cytotoxic T lymphocytes (CTLs). Specific CTLs were raised against the peptide TLMKKDKYTL and were capable of lysing glioma cells. The abundant and glioma-restricted overexpression of SOX2 and the generation of SOX2-specific and tumour-reactive CTLs may recommend this antigen as target for T-cell-based immunotherapy of glioma.

Inhibition of malignant glioma cell growth by a survivin mutant retrovirus

Glioblastoma multiforme (GBM) is a highly malignant brain tumor that is resistant to conventional radiotherapy and chemotherapy. The median survival time of patients with GBM has remained less than 2 years despite concerted efforts to improve therapy. As a new approach to treat GBM we generated retroviral particles encoding mutant survivin for transduction of glioma cells. We demonstrate here that retroviral overexpression of a nonphosphorylatable Thr-34 --> Ala mutant of survivin (survivinT34A), in the glioma cell lines U373 and H4 resulted in a marked increase in the percentage of cells bearing multiple nuclei, which was accompanied by significantly decreased cell proliferation, and in greater numbers of cells with hypodiploid DNA content. Administration of the broad caspase inhibitor z-Val-Ala-Asp(OMe)-fluoromethyl-ketone did not reduce the cell death rate. Yet increased nuclear translocation of apoptosis-inducing factor (AIF) was observed in cells transduced with survivinT34A, indicating caspase-independent cell death. Transduction of retroviral vectors encoding wild-type survivin also led to the appearance of multinuclear cells. In contrast to mutant survivin, overexpressed wild-type survivin did not increase the cell death rate and no enhanced nuclear AIF translocation was observed. We suggest that retroviral vectors delivering mutant survivinT34A might be employed for the treatment of glioblastoma.

Identification of an HLA-A*0201-restricted T-cell epitope derived from the prostate cancer-associated protein prostein

The development of T-cell-based immunotherapies of cancer largely depends on the availability of tumour-associated antigens capable of eliciting tumour-directed cytotoxic T-cell responses. In prostate cancer, the number of antigens defined as suitable targets of cytotoxic T lymphocytes (CTLs) is still limited. Recently, prostein was identified as a transmembrane protein that is highly restricted to prostate tissues. In our study, prostein transcripts were found to be abundant in both malignant and nonmalignant prostate tissue samples. To identify immunogenic CD8+ T-cell epitopes, human leucocyte antigen-A^*0201-binding peptides were selected from the amino-acid sequence of prostein and were used for the in vitro stimulation of CD8+ T lymphocytes. Specific CTLs were raised against the prostein-derived peptide CLAAGITYV that were capable of lysing prostate cancer cells, indicating that this peptide is naturally generated by tumour cells. Our data suggest that prostein is a suitable candidate to be included in a T-cell-based immunotherapy of prostate cancer.

Efficient transduction and long-term retroviral expression of the melanoma-associated tumor antigen tyrosinase in CD34(+) cord blood-derived dendritic cells

Differentiation of genetically modified CD34(+) hematopoietic stem cells into dendritic cells (DCs) will contribute to the development of immunotherapeutic anticancer protocols. Retroviral vectors that have been used for the transduction of CD34(+) cells face the problem of gene silencing when integrated into the genome of repopulating stem cells. We reasoned that a high copy number of retroviral DNA sequences might overcome silencing of transgene expression during expansion and differentiation of progenitor cells into functional DCs. To prove this, we utilized a retroviral vector with bicistronic expression of the melanoma-associated antigen tyrosinase and the enhanced green fluorescent protein (EGFP). Human cord blood CD34(+) cells were transduced with vesicular stomatitis virus G-protein (VSV-G) pseudotyped Moloney murine leukemia virus (MoMuLV) particles using 100-150 multiplicity of infection. During expansion of transduced cells with immature phenotype, transgene expression was strongly silenced, but upon differentiation into mature DCs, residual transgene expression was retained. Intracellular processing of the provirally expressed tyrosinase was tested in a chromium release assay utilizing a cytotoxic T cell clone specific for a HLA-A*0201-restricted tyrosinase peptide. We suggest that retroviral transduction of tumor-associated antigens in hematopoietic progenitor cells and subsequent differentiation into DCs is a suitable basis for the development of potent anti-tumor vaccines.

An in vitro vitellogenin bioassay for oestrogenic substances in the medaka (Oryzias latipes)

We developed an in vitro bioassay for oestrogenic compounds based on vitellogenin as a biomarker. To quantify the induction of vitellogenin in medaka (Oryzias latipes) we established a sandwich enzyme-linked immunosorbent assay (ELISA). This ELISA was carried out with two different monoclonal antibodies specific for the yolk precursor protein vitellogenin and the high molecular weight yolk proteins (lipovitellin) of medaka. Purified lipovitellin of medaka was used as a standard for the ELISA and could be quantified down to a concentration of 9 ng/ml. The calibration curve was linear up to at least 600 ng/ml and the intra-assay coefficient of variance was 3.2%. The application of the sandwich ELISA was tested using blood samples of males and females as well as primary hepatocyte cultures of medaka. Vitellogenin synthesis in cultured liver cells of males was induced by 1 and 100 nM of the xenoestrogen 17alpha-ethynylestradiol (EE(2)). The first production of vitellogenin was detected 6 days after hormone application. In contrast, isolated liver cells of sexually mature females, which were treated in the same manner, showed vitellogenin expression from the beginning of cultivation and its synthesis increased and remained high at 100 nM EE(2). However, the induction of vitellogenin synthesis in male hepatocytes in vitro could be maintained for at least one month and this indicated viable and differentiated liver cells. The hepatocyte cultures of male medaka in combination with the sandwich ELISA were shown to be a suitable tool to detect and quantify oestrogenic activity of chemicals.

Increased survivin transcript levels: an independent negative predictor of survival in soft tissue sarcoma patients

Survivin, a recently identified inhibitor of apoptosis protein (IAP), is expressed in diverse embryonic tissues and in various human cancers. We have investigated the quantitative expression of survivin mRNA by a sensitive TaqMan-based RT-PCR assay in tissue samples from 94 patients with soft tissue sarcomas (STS). Survivin transcript levels were measured and normalized to GAPDH transcripts. By using a multivariate Cox regression analysis, we found an inverse correlation between the level of survivin mRNA (ratio >2 zmol survivin/amol GAPDH) and the rate of overall survival (p = 0.009, RR = 2.7). Survivin transcript variants as detected by qualitative RT-PCR analysis were revealed in 36 of 56 STS patients (64%). Only survivin DeltaEx3 and/or full-length survivin variants but not survivin 2B were identified. Our results suggest that a higher level of survivin mRNA is an independent predictor of survival for STS patients.

Increased survivin transcript levels: an independent negative predictor of survival in soft tissue sarcoma patients

Survivin, a recently identified inhibitor of apoptosis protein (IAP), is expressed in diverse embryonic tissues and in various human cancers. We have investigated the quantitative expression of survivin mRNA by a sensitive TaqMan-based RT-PCR assay in tissue samples from 94 patients with soft tissue sarcomas (STS). Survivin transcript levels were measured and normalized to GAPDH transcripts. By using a multivariate Cox regression analysis, we found an inverse correlation between the level of survivin mRNA (ratio >2 zmol survivin/amol GAPDH) and the rate of overall survival (p = 0.009, RR = 2.7). Survivin transcript variants as detected by qualitative RT-PCR analysis were revealed in 36 of 56 STS patients (64%). Only survivin DeltaEx3 and/or full-length survivin variants but not survivin 2B were identified. Our results suggest that a higher level of survivin mRNA is an independent predictor of survival for STS patients.

Dilated bile canaliculi and attenuated decrease of nerve-dependent bile secretion in connexin32-deficient mouse liver

Gap junction channels in the rodent liver are composed of connexin26 (Cx26) and connexin32 (Cx32) proteins. Gap junctional intercellular communication in the mouse liver enhances the effects of hormonal or sympathetic stimulation of glucose release from glycogen stores. To determine whether contraction of bile canaliculi and bile secretion are dependent on the function of gap junction channels, we compared wild-type and connexin32-deficient mice. Confocal laser scanning microscopy of the wild-type mouse liver confirmed the close association of connexin26 and -32 proteins with the zona occludens-1 protein and actin filaments of the bile canaliculi. The decrease of bile flow after electrical stimulation of sympathetic nerves in the perfused liver was attenuated in the Cx32-deficient liver compared with wild-type controls. The amount of secreted bile, however, was similar in wild-type and Cx32-deficient livers. Furthermore, Cx32-deficient mice exhibited dilated bile canaliculi, suggesting that the contraction of bile canaliculi could be impaired in these animals.

Generation of survivin-specific CD8+ T effector cells by dendritic cells pulsed with protein or selected peptides

The identification of tumor-associated antigens recognized by CD8+ cytotoxic T cells paved the way to new concepts in adjuvant anticancer therapy. However, the number of tumor-associated proteins found to be expressed in the majority of human cancers is still rather limited. Recently, the newly identified apoptosis inhibitor protein survivin has been recognized as a widely occurring tumor-associated protein. In the present study, we demonstrate that survivin is capable of inducing specific CD8+ effector T cells in vitro. T cells from healthy donors were subjected to several cycles of stimulation by autologous dendritic cells (DCs) pulsed with soluble recombinant survivin protein. Activation of CD8+ cytotoxic T cells by survivin-derived peptides cross-presented by DCs was demonstrated by lysis of autologous survivin-expressing B cell transfectants. Using a peptide-motif scoring system, two survivin peptides (ELTLGE-FLKL and TLPPAWQPFL) were predicted and proved to bind to the HLA-A*0201 molecule. Both peptides were shown to induce CD8+ effector T cells when presented on DCs; one peptide could be verified to result from natural intracellular processing of survivin. These findings recommend survivin as a new and widely applicable target for protein- and peptide-based immunotherapy of tumors.

M-DC8+ leukocytes--a novel human dendritic cell population

Dendritic cells (DC) constitute a heterogeneous leukocyte population having in common a unique capacity to induce primary T cell responses and are therefore most attractive candidates for immunomodulatory strategies. Two populations of blood DC (CD11c+ CD123(dim) and CD11c- CD123(high)) have been defined so far. However, their direct isolation for experimental purposes is hampered by their low frequency and by the lack of selective markers allowing large scale purification from blood. Here we describe the monoclonal antibody (mAb) M-DC8, which was generated by immunizing mice with highly enriched blood DC. This mAb specifically reacts with 0.2-1% of blood leukocytes and enables their direct isolation by a one-step immunomagnetic procedure from fresh mononuclear cells. These cells can be differentiated from T cells, B cells, NK cells and monocytes using lineage-specific antibodies. M-DC8+ cells express HLA class II molecules, CD33 and low levels of the costimulatory molecules CD86 and CD40. Upon in vitro culture M-DC8+ cells spontaneously mature into cells with the phenotype of highly stimulatory cells as documented by the upregulation of HLA-DR, CD86 and CD40; in parallel CD80 expression is induced. M-DC8+ cells display an outstanding capacity to present antigen. In particular, they proved to be excellent stimulators of autologous mixed leukocyte reaction and to activate T cells against primary antigens such as keyhole limpet hemocyanin. Furthermore, they induce differentiation of purified allogeneic cytotoxic T cells into alloantigen-specific cytotoxic effector cells. While the phenotypical analysis reveals similarities with the two known blood DC populations, the characteristic expression of FcgammaRIII (CD16) and the M-DC8 antigen clearly defines them as a novel population of blood DC. The mAb M-DC8 might thus be a valuable tool to determine circulating DC for diagnostic purposes and to isolate these cells for studies of antigen-specific T cell priming.

Expansion of CD60 helper lymphocytes detected in peripheral lymphocytes of HIV-1 infected individuals is not paralleled in lymph nodes

BACKGROUND AND OBJECTIVE

A significant expansion of CD8 cells with capability of Th2 type helper function had been observed in hemophiliacs with HIV infection. These cells were characterised by the surface co-expression of CD8 and CD60 antigen. Our objective was to investigate this lymphocyte subset in relation to other subsets in homosexuals and drug users in two compartments: blood and lymph nodes. Blood and lymph nodes from not HIV-infected persons served as control.

RESULTS

CD8+CD60+ cells were expanded in perpheral blood of HIV - infected patients as compared to age matched controls (10.0 versus 4.1%, p <0.05). This difference was not observed in lymph node cell suspensions (6.2 vs. 4.3% of all lymph node cells; p = n.s.). The CD 4/CD8 ratio was significantly less impaired in lymph nodes than in blood (2.27 vs. 0.83; p <0.05). Cytotoxic T cells were more abundant in the lymph nodes of patients with early stage HIV disease when compared two late stage patients (4.3 vs 2.1%; p <0.05). Immunohistochemistry on frozen lymph node cuts showed presence of CD60 cells mainly in the interfollicular and paracortical area. In 3 of 10 HIV infected patients these cells were also found in the germinal centers. In controls no CD60 cells were detected in the follicles. Numbers and percentages of CD60 cellls and CD8+CD60+ cells in blood and in lymph nodes did not correlate with HIV - stage, CD4 count or plasma viral load. No correlation with lymph node viral load was seen.

CONCLUSIONS

Our data confirm that like in hemophiliacs expansion of CD8+CD60+ is also found in the blood of other HIV risk groups and seems not to be specific for hemophiliacs. However, the higher percentage in peripheral blood is not paralleled in lymph nodes. Redistribution phenomena seem to be the most plausible explanation. According to these data, a major impact of CD8+CD60+ cells in the immunopathogenesis of HIV infection does not seem likely.

Antibody response to the tumor-associated inhibitor of apoptosis protein survivin in cancer patients

Antibody reactivity against survivin, a recently identified tumor-associated protein, was determined in sera from patients with lung (n = 51) or colorectal cancer (n = 49). The same collection of sera was tested for the presence of antibodies against p53. Eleven sera from lung cancer patients and four sera from colorectal cancer patients reacted with purified recombinant survivin in an ELISA (21.6% and 8.2%, respectively), whereas four sera from lung cancer patients and nine sera from colorectal cancer patients contained anti-p53 antibodies (7.8% and 18.4%, respectively). The increase in prevalence when anti-survivin and anti-p53 antibodies were determined in parallel was statistically significant (29.4% versus 7.8%, P = 0.005 in lung cancer population; 26.6% versus 8.2%, P = 0.015 in colorectal cancer population). The high prevalence of anti-survivin antibodies makes these antibodies an attractive novel marker for the diagnosis of lung and colorectal cancer, particularly in patients lacking anti-p53 antibodies.

A nonhuman primate model for the selective elimination of CD8+ lymphocytes using a mouse-human chimeric monoclonal antibody

Nonhuman primates provide valuable animal models for human diseases. However, studies assessing the role of cell-mediated immune responses have been difficult to perform in nonhuman primates. We have shown that CD8+ lymphocyte-mediated immunity in rhesus monkeys can be selectively eliminated using the mouse-human chimeric anti-CD8 monoclonal antibody cM-T807. In vitro, this antibody completely blocked antigen-specific expansion of cytotoxic T cells and decreased major histocompatibility complex class I-restricted, antigen-specific lysis of target cells but did not mediate complement-dependent cell lysis. In vivo administration of cM-T807 in rhesus monkeys resulted in near total depletion of CD8+ T cells from the blood and lymph nodes for up to 6 weeks. This depletion was not solely complement-dependent and persisted longer in adults than in juveniles. Preservation of B cell and CD4+ T cell function in monkeys depleted of CD8+ lymphocytes was demonstrated by their ability to develop humoral immune responses to the administered chimeric monoclonal antibody. Furthermore, during CD8+ lymphocyte depletion, monkeys developed delayed-type hypersensitivity reactions comprised only of CD4+ T cells but not CD8+ T cells. This CD8+ lymphocyte depletion model should prove useful in defining the role of cell-mediated immune responses in controlling infectious diseases in nonhuman primates.

Th2 cells as effectors in postirradiation pulmonary damage preceding fibrosis in the rat

PURPOSE

Radiation-induced pneumonitis and subsequent pulmonary fibrosis are important dose-limiting complications of radiotherapy. Their pathogenesis is known only in part. T-lymphocytes comprise a significant part of the infiltrating cells but little is known about their role. The aim of this study was to define the function of T-lymphocytes during development of postirradiation pneumonitis and pulmonary fibrosis.

MATERIALS AND METHODS

Rats received a unilateral lung irradiation of 20 Gy. Kinetics of T-lymphocytes isolated from irradiated and non-irradiated lungs were analysed. Subsequent CD4 depletion experiments were performed to affirm the importance of CD4+ T-cells in the development of lung fibrosis. Finally, the T helper-cell subtype of the T-lymphocytes was analysed by determining the cytokine mRNA by RT-PCR.

RESULTS

A selective increase of CD4+ T-cells was observed peaking 4 weeks after irradiation in the irradiated lungs. When rats were depleted of these cells, the postirradiation thickening of parenchyma was significantly reduced as determined by morphometric analysis of lung tissue sections. In addition, it was found that IL-4 mRNA was selectively increased in the CD4+ T-cells isolated from irradiated lungs, which indicates a lymphocyte reactivity dominated by Th2 cells.

CONCLUSION

The results suggest a critical role for Th2 CD4+ T-lymphocytes in the pathogenesis of radiation-induced pneumonitis preceding lung fibrosis.

Differential expression of alpha2-6 sialylated polylactosamine structures by human B and T cells

We found that human peripheral B and T cells differed in the surface expression of alpha2-6 sialylated type 2 chain glycans. In contrast to B cells, T cells expressed only sialoglycans with repeated N-acetyllactosamine (Galss1-4GlcNAc) disaccharides. This finding was based on the specificity of the monoclonal antibodies HB6, HB9 (CD24), HD66 (CDw76), FB21, and CRIS4 (CDw76) with the alpha2-6 sialylated model gangliosides IV6NeuAcnLc4Cer (2-6 SPG), VI6NeuAcnLc6Cer (2-6 SnHC), VIII6NeuAcnLc8Cer (2-6 SnOC), and X6NeuAcnLc10Cer (2-6 SnDC). We found that, in addition to their common requirement of an alpha2-6 bound terminal sialic acid for binding, the antibodies displayed preferences for the length of the carbohydrate backbones. Some of them bound mainly to 2-6 SPG with one N-acetyllactosamine (LacNAc) unit (HB9, HD66); others preferentially to 2-6 SnHC and 2-6 SnOC, with two and three LacNAc units, respectively (HB6 and FB21); and one of them exclusively to very polar alpha2-6 sialylated type 2 chain antigens (CRIS4) such as to 2-6 SnOC and even more polar gangliosides with three and more LacNAc units. These specificities could be correlated with the cellular binding of the antibodies as follows: whereas all antibodies bound to human CD 19 positive peripheral B cells, their reactivity with CD3 positive T cells was either nearly lacking (HD66, HB9), intermediate (about 65%: HB6, FB21) or strongly positive (CRIS4, 95%). Thus, the binding of the antibodies to 2-6 sialylated glycans with multiple lactosamine units appeared to determine their binding to T-cells.

Control of viremia in simian immunodeficiency virus infection by CD8+ lymphocytes

Clinical evidence suggests that cellular immunity is involved in controlling human immunodeficiency virus-1 (HIV-1) replication. An animal model of acquired immune deficiency syndrome (AIDS), the simian immunodeficiency virus (SIV)-infected rhesus monkey, was used to show that virus replication is not controlled in monkeys depleted of CD8+ lymphocytes during primary SIV infection. Eliminating CD8+ lymphocytes from monkeys during chronic SIV infection resulted in a rapid and marked increase in viremia that was again suppressed coincident with the reappearance of SIV-specific CD8+ T cells. These results confirm the importance of cell-mediated immunity in controlling HIV-1 infection and support the exploration of vaccination approaches for preventing infection that will elicit these immune responses.

A novel dendritic cell population in human blood: one-step immunomagnetic isolation by a specific mAb (M-DC8) and in vitro priming of cytotoxic T lymphocytes

Originating from a common progenitor cell, dendritic cells (DC) appear to develop along early branched pathways into various yet ill-defined subpopulations residing at various sites throughout the body where they capture and present antigen in the most professional fashion. Here we give evidence for a unique subpopulation of human DC circulating in blood that account for 0.5-1% of blood leukocytes only, their most specific characteristic being the expression of a cell surface protein recognized by a novel monoclonal antibody (M-DC8) which enables their isolation by a one-step immunomagnetic procedure. The isolated cells (> 97% pure) present morphologically as typical dendritic cells. They express the Fc(gamma)RIII (CD16), so far not found on DC, and avidly phagocytose latex beads as well as opsonized erythrocytes. These cells not only present antigens efficiently to naive T cells but also induce purified CD8+ T cells to become alloantigen-specific cytotoxic cells. Furthermore, when loaded with a tyrosinase-derived peptide they stimulate T cells from normal donors and melanoma patients to exhibit MHC-restricted specific cytotoxicity against melanoma cells.

Depletion of CD8+ T lymphocytes by murine monoclonal CD8 antibodies and restored specific T cell proliferation in vivo in a patient with chronic hepatitis C

Cellular immune mechanisms, especially those mediated by CD8+ T cells, are important in the pathogenesis and control of viral infections. On the other hand, as shown for chronic lymphocytic choriomeningitis virus infection in the mouse, CD8+ T cells may not only hinder the elimination of a virus, but make the host unresponsive to a second viral infection. In hepatitis C virus (HCV) infections, at least 50% of the patients become chronically infected, despite the detection of HCV-specific CTL and a specific proliferative response to HCV Ags in PBL and in lymphocytes isolated from the liver. To better understand the immunopathologic mechanisms of CD8+ cells in vivo and to search for a potential treatment, we applied murine CD8 mAbs to a patient with therapy-resistant chronic HCV. A drastic reduction of CD8+ circulating lymphocytes, a reduction of CD8 molecule density, and complement fixation on CD8+ cells were observed. The reduction of CD8+ cells was compensated partially by an elevation of CD4+ cells. High concentrations of neutralizing human anti-mouse Abs were induced. After the Ab infusions, the CD4/CD8 ratio in peripheral blood increased from 1.6 to values of about 3 during therapy, and gradually decreased to 2.3 1 yr after the last mAb infusion. A continuing decrease of serum aminotransferases and clinical improvement was observed. Interestingly, after initiation of treatment, a significant proliferative response to HCV-specific Ags became measurable.

Depletion of CD8+ T lymphocytes by murine monoclonal CD8 antibodies and restored specific T cell proliferation in vivo in a patient with chronic hepatitis C

Cellular immune mechanisms, especially those mediated by CD8+ T cells, are important in the pathogenesis and control of viral infections. On the other hand, as shown for chronic lymphocytic choriomeningitis virus infection in the mouse, CD8+ T cells may not only hinder the elimination of a virus, but make the host unresponsive to a second viral infection. In hepatitis C virus (HCV) infections, at least 50% of the patients become chronically infected, despite the detection of HCV-specific CTL and a specific proliferative response to HCV Ags in PBL and in lymphocytes isolated from the liver. To better understand the immunopathologic mechanisms of CD8+ cells in vivo and to search for a potential treatment, we applied murine CD8 mAbs to a patient with therapy-resistant chronic HCV. A drastic reduction of CD8+ circulating lymphocytes, a reduction of CD8 molecule density, and complement fixation on CD8+ cells were observed. The reduction of CD8+ cells was compensated partially by an elevation of CD4+ cells. High concentrations of neutralizing human anti-mouse Abs were induced. After the Ab infusions, the CD4/CD8 ratio in peripheral blood increased from 1.6 to values of about 3 during therapy, and gradually decreased to 2.3 1 yr after the last mAb infusion. A continuing decrease of serum aminotransferases and clinical improvement was observed. Interestingly, after initiation of treatment, a significant proliferative response to HCV-specific Ags became measurable.

Local production of interleukin-4 during radiation-induced pneumonitis and pulmonary fibrosis in rats: macrophages as a prominent source of interleukin-4

Fibrosis of lung tissue is a frequent and serious consequence of radiotherapy of mammary carcinoma. The pathogenesis of radiation-induced pulmonary fibrosis remains unclear. Cytokines such as transforming growth factor beta (TGFbeta) and interleukin-4 (IL-4) have been reported to stimulate collagen synthesis in fibroblasts in vitro. The aim of this study was to document the presence of IL-4 during the development of post-irradiation lung fibrosis. Right lungs of male Fischer rats were irradiated with a single dose of 20 Gy and IL-4 expression in the irradiated lungs was monitored for a period of three months. IL-4 gene transcription as determined by ribonuclease protection assay (RPA) as well as IL-4 synthesis as shown by Western blotting increased in the irradiated lungs reaching a plateau concentration within 3 weeks after irradiation. Enhanced IL-4 production was still detected at day 84 after irradiation. The cellular origin of IL-4 was analyzed by in situ hybridization and two-color immunofluorescence on lung tissue sections and on cytospin preparations of leukocytes obtained from bronchoalveolar lavages. These experiments revealed a substantial IL-4 production by macrophages during development of post-irradiation lung fibrosis.

Structural diversity of monoclonal CD4 antibodies and their capacity to block the HIV gp120/CD4 interaction

A number of monoclonal antibodies have been raised against CD4, the receptor on T cells for the HIV envelope glycoprotein gp120. In the present paper we describe biological activities and sequence analysis of seven CD4 MAb. Five of these MAb preparations compete with HIV/gp120 for CD4 binding. The sequences of the variable regions for these MAb were determined in order to ascertain any correlation with selective V gene usage. A relationship was found between the expressed variable region genes and the CD4 recognition pattern. The VH genes that are used can be subdivided into two major groups expressing either a VH gene belonging to the J558 family or to the VGam family. The usage of the VL genes varies, indicating that the epitope specificity is predominantly determined by the rearranged VH genes. The distinct cross-reactivity pattern of these MAb also correlates with their capacity to block binding of recombinant gp120 to CD4 in vitro. Although five of these MAb were able to block gp120 binding none of the CDR sequences shows a relevant homology to the gp120 sequence. This indicates a steric hinderence mechanism for blocking gp120 binding and not a direct interaction with the receptor binding site on CD4. The data also confirm the failure of these MAb as a potential target for receptor mimicry.

Treatment of severe cutaneous lupus erythematosus with a chimeric CD4 monoclonal antibody, cM-T412

BACKGROUND

Monoclonal CD4 antibodies are among the most potent immunomodulatory agents in various experimental models of autoimmune disease, including murine lupus erythematosus.

OBJECTIVE

The aim of this study was to evaluate the toxicity and therapeutic efficacy of a chimeric monoclonal CD4 antibody, cM-T412, in patients with cutaneous lupus erythematosus (LE).

METHODS

Five patients with severe cutaneous LE lesions received intravenously a total of 275, 400, or 475 mg of cM-T412 in single doses of 20 to 50 mg during a period of 5 to 8 weeks.

RESULTS

CD4 antibody treatment induced a long-lasting decrease in disease activity. It resulted in healing of LE skin lesions, a reconstituted responsiveness to conventional treatment, or both. Despite a substantial depletion of circulating CD4+ T lymphocytes, no clinical signs of immunosuppression were noted.

CONCLUSION

Monoclonal CD4 antibodies should be considered as a novel treatment for the management of severe cutaneous LE.

Activation of gene transcription by IL-4, IL-13 and IFN-gamma through a shared DNA binding motif

Both interleukin-4 (IL-4) and interleukin-13 (IL-13) induce the transcription factor NF-IL4 (nuclear factor IL-4) which preexists in an inactive form and binds to an IL-4 responsive element (IL-4RE) in the promoter regions of IL-4/IL-13-dependent genes. UV-crosslinking and SDS gel electrophoresis indicate that NF-IL4 consists of at least two DNA-binding components of 50 kDa and 100-130 kDa. The IL-4 responsive element is also recognized by an interferon-gamma (IFN-gamma)-induced DNA binding protein for which a Mr of 50 kDa has been determined. A common DNA binding motif for different transcription factors might provide the basis for the frequently observed functional antagonism between IL-4/IL-13 and IFN-gamma. The activation of transcription factors by IL-4/IL-13 and IFN-gamma could be blocked by inhibitors of tyrosine kinases and ser/thr phosphatases but not by a PKC inhibitor, suggesting related signal transduction pathways for these cytokines.

Recombinant CD4-IgE, a novel hybrid molecule, inducing basophils to respond to human immunodeficiency virus (HIV) and HIV-infected target cells

Basophils and mast cells, as the main effector cells in IgE-mediated type I hypersensitivity, are involved in the elimination of parasites and, according to recent findings, may also play an important role in the defense against bacterial and viral infections. Using a genetic engineering approach we wanted to redirect this potent IgE-mediated defense system against intruding human immune deficiency virus. We constructed a recombinant CD4-IgE molecule, consisting of the two N-terminal domains of CD4 and the CH2-4 domains of the IgE heavy chain, thus providing the IgE with specificity for the gp120 of human immunodeficiency virus (HIV). The binding properties of hybrid CD4-IgE to the high-affinity receptor for IgE (Fc epsilon RI) on basophils as well as to the low-affinity receptor (Fc epsilon RII or CD23) for IgE on lymphoid cells were found to be similar to those of native IgE. At the same time, the CD4 domains of the recombinant molecule retained the gp120 binding specificity with an affinity similar to that of the native CD4. By functional tests, we demonstrated that CD4-IgE armed basophils can be triggered by free HIV and by HIV-infected cells to release their mediators. We further show that HIV-triggered basophils lead to a decreased replication of HIV in susceptible T cells. We, therefore, conclude that the type I hypersensitivity effector cells can be engaged in the elimination of HIV-infected cells, at least in vitro. Because of the strong binding of the CD4-IgE construct to the Fc epsilon RI, we assume that CD4-IgE has a short t1/2 in serum, but may similarly to IgE exhibit prolonged resident time on basophils and mast cells, which are located close to mucosal surfaces or in the connective tissue. Thus CD4-IgE could play an important role in the elimination of HIV also in vivo.

A reduction in allergen-induced Fc epsilon R2/CD23 expression on peripheral B cells correlates with successful hyposensitization in grass pollinosis

BACKGROUND

The cellular basis for the mechanism of specific hyposensitization is still unclear.

OBJECTIVE

We prospectively studied the effect of immunotherapy on allergen-induced proliferation and Fc epsilon R2/CD23 expression of lymphocytes.

METHODS

Mononuclear cells prepared from the peripheral blood of 22 patients with grass pollen (GP) allergy before, during, and after a preseasonal immunotherapy period with GP were stimulated with GP or control antigens. Tritiated thymidine uptake and percentage of CD23+ B cells were determined daily during days 6 to 8 and compared with lymphocyte responsiveness of 11 only symptomatically treated atopic patients and 14 nonatopic individuals.

RESULTS

GP-induced lymphocyte proliferative response of both hyposensitized and symptomatically treated GP-allergic patients decreased markedly before the pollen season and rose again after seasonal allergen exposure, whereas a long-lived decrease in GP-induced Fc epsilon R2/CD23+ B cells was only observed in GP-treated patients. Alterations in Fc epsilon R2/CD23 expression were closely related to changes in symptoms and medication requirement during the following pollen season. In contrast, immunotherapy had no effect on Fc epsilon R2/CD23 expression of B cells without stimulation or on B cells cultured in the presence of control antigens.

CONCLUSION

Because Fc epsilon R2/CD23 expression on B cells is antagonistically regulated by the cytokines interleukin-4 and interferon-gamma, the decrease of allergen-induced Fc epsilon R2/CD23+ B cells indicates an altered cytokine secretion pattern of the allergen-specific T lymphocytes with a predominance of interferon-gamma.

Treatment of myasthenia gravis with anti-CD4 antibody: improvement correlates to decreased T-cell autoreactivity

We treated a patient with severe myasthenia gravis with a chimeric (murine/human) anti-CD4 monoclonal antibody (cM-T412) for 7 days and followed the therapeutic effect by standardized muscle function tests, single-fiber electromyography, and immunologic examinations of disease-specific B- and T-cell functions. Clinical and electrophysiologic improvement began within 4 days, lasted for 3 months, and was maximal between days 16 and 58. The CD4+ lymphocytes decreased to a minimum of 80 cells per microliters of peripheral blood, recovered slowly during the first year of follow-up, and did not correlate with changes in disease severity. T-cell stimulation by human acetylcholine receptor was abolished by the treatment but became detectable at the time of worsening of symptoms. The concentration of acetylcholine receptor antibodies in serum was not decreased by the treatment. The results suggest that anti-CD4 antibody administration could be effective in the treatment of severe myasthenia gravis and indicate that acetylcholine receptor-specific T lymphocytes might contribute to the disturbed neuromuscular transmission in the disease.

Chimeric monoclonal CD4 antibody--a novel immunosuppressant for clinical heart transplantation

The murine CD4 monoclonal antibody (mAb) M-T412 effectively downregulates T-helper-inducer function, while exhibiting high affinity and specificity for an epitope formed by the V1 and V2 domain of CD4. The antibody was chimerized by combining the murine VH and VL parts to the constant region of a human IgG1 kappa immunoglobulin. This chimeric CD4 monoclonal antibody (chim CD4 mAb) cM-T412 was used for adjunct immunosuppression in addition to standard triple-drug therapy for patients after orthotopic (n = 10) and heterotopic (n = 1) heart transplantation (HTx). cM-T412 was administered intraoperatively and postoperatively on days 1-7, 9, 11, 13, 17, and 21. A control group of similar composition (10 orthotopic, 1 heterotopic HTx) was conventionally treated in an adjunct fashion with antithymocyte globulin (ATG) until cyclosporine (CsA) in serum had reached therapeutic levels. Over the total observation time (mean: 600 days), the number of acute rejection episodes per 100 patient days was 0.26 in the cM-T412 group versus 0.41 in the control group, indicating a reduction of nearly 40%. Four of the 11 patients in the CD4 group have thus far not experienced any rejection crisis compared with two out of 11 in the control group. The mean time to the first rejection episode was 43.7 days in the CD4-treated patients versus 25.3 days in the control group. In addition the interval to the second rejection episode was longer in CD4 patients than in controls. Furthermore, patients treated with chim CD4 mAb had fewer episodes of infection during the first year after HTx (0.49 vs. 0.91 per 100 pt. days) and had a better overall survival rate (91% vs. 73%) than control group pts. No anaphylactic reaction was observed. The only adverse event probably related to cM-T412 infusion was a transient decrease of blood pressure in one patient. Although this study has only a limited number of patients, addition of cM-T412 to standard triple drug therapy appears to be an effective, specific, and well tolerated adjunct to current immunosuppression that offers a new approach for an improved immunomodulatory regimen after heart transplantation.

Expression and characterization of cM-T413, a chimeric anti-CD4 antibody with in vitro immunosuppressive activity

Anti-CD4 monoclonal antibodies (mAbs) have shown considerable promise in the treatment of rheumatoid arthritis, psoriasis, and allograft rejection and may have potential use in blocking HIV-1 infection. One such anti-CD4 mAb we have developed, chimeric M-T412 (or cM-T412), has been used in clinical trials to treat rheumatoid arthritis, generalized postular psoriasis, and other autoimmune diseases. Here we report the cloning and expression of a second chimeric anti-CD4 mAb using M-T413, a murine mAb that blocks HIV-1 infection of H9 cells. We cloned the immunoglobulin light and heavy chain variable regions of M-T413, combined them with the human kappa (light chain) or G1, G2, G3 and G4 (heavy chain) constant regions in human expression vectors, and expressed these chimeric mAbs in 653 cells. Like chimeric M-T412 IgG1, the chimeric M-T413 mAbs inhibit T-cell proliferation in the mixed lymphocyte response and thus can act to immunosuppress CD4+ T-cell response. In contrast to M-T412, however, the M-T413 chimeric mAbs have reduced activity in an antibody-dependent cell-mediated cytotoxicity (ADCC) assay using human CD4+ target and effector cells. We conclude that the chimeric M-T413 mAbs have potential utility in treating autoimmune disease and may be useful as prophylactics in preventing HIV-1 infection.

Human interleukin-13 activates the interleukin-4-dependent transcription factor NF-IL4 sharing a DNA binding motif with an interferon-gamma-induced nuclear binding factor

The effects of interleukin-13 (IL-13) and interleukin-4 (IL-4) on cellular functions were shown to be quite similar. We provide evidence that in monocytes as well as in T lymphocytes both IL-4 and IL-13 activate the same recently identified transcription factor NF-IL4 which binds to the specific responsive element IL-4RE. In addition, we show that a nuclear factor activated by interferon-gamma also interacts with the IL-4RE. It differs from NF-IL4 in the electrophoretic mobility of the complex with DNA, in its DNA-binding specificity and in the proteins interacting with the DNA sequence. Sensitivity against various enzyme inhibitors suggests that components of the signal transduction pathway are shared by all three cytokines.

CDw60: a marker for human CD8+ T helper cells

The existence of helper cells among the CD8+ T cell subset has been recognized for a long time. However, the phenotype of these cells has remained elusive. In this study, we provide evidence that the expression of the CDw60 antigen on human CD8+ T cell allows one to distinguish between CD8+ T helper cells and CD8+ T cells with cytotoxic and suppressor capacity. CDw60 monoclonal antibodies (mAb) recognize the 9-O-acetylated disialosyl group on ganglioside GD3 expressed on 20-40% of CD8+ cells. By use of the direct and indirect mAb-rosetting technique, we were able to isolate the CDw60+CD8+ and CDw60-CD8+ cells at high purity. The alloantigen-specific cytotoxic activity of CD8+ cells resided entirely in the CDw60- population. Helper and suppressor capacity of both CD8 subsets was assayed by the pokeweed mitogen-induced differentiation of B cells into immunoglobulin-secreting cells. These studies clearly indicate that the CDw60+CD8+ subset provided substantial help to B lymphocytes, whereas the CD8+ cells with the CDw60- phenotype were suppressing B cell differentiation. Both subsets produced similar amounts of interleukin 2 (IL-2) after stimulation with phytohemagglutinin. Activation with phorbol myristate acetate in combination with Ca-ionophore induced IL-4 secretion in both populations, but preferentially in the CDw60+ subset, whereas the vast majority of interferon gamma was produced by the CDw60-CD8+ cells. When used in combination with other markers, CDw60 may prove to be useful in defining CD8+ subsets with reciprocal functional activities.

Treatment of rheumatoid arthritis with a chimeric CD4 monoclonal antibody (cM-T412): immunopharmacological aspects and mechanisms of action

To investigate the mechanisms of action underlying the therapeutic effect of CD4 monoclonal antibody therapy in rheumatoid arthritis (RA), clinical responses were compared with several laboratory parameters. Twenty-nine RA patients received either 10 mg, 50 mg or 100 mg of cM-T412, a chimeric CD4 MoAb, for 7 days. The CD4 binding sites on circulating lymphocytes were saturated directly with cM-T412 and serum levels of unbound cM-T412 accumulated towards day 7 of treatment only in the patients treated with 50 and 100 mg. The treatment induced an instant and prolonged depression of the number of circulating CD4+ cells, similar for all dosages. Clinical improvement was observed predominantly in the patients treated with 50 or 100 mg cM-T412 daily and did not correlate with changes in counts of circulating leucocyte subsets nor with changes in serum cytokine levels. An antiglobulin response against cM-T412 developed in a majority of the patients. Side effects on the first day of treatment were correlated with an increase of serum IL-6 levels. This study indicates that a favourable clinical effect of cM-T412 administration was associated with the presence of unbound cM-T412 in the circulation of RA patients. Therefore penetration of unbound cM-T412 into the site of inflammation might determine the therapeutic effect in RA.

Allergy-associated I epsilon and Ec epsilon receptor II (CD23b) genes activated via binding of an interleukin-4-induced transcription factor to a novel responsive element

Interleukin-4 (IL-4) has important regulatory functions in the immune system, particularly in the generation of immunoglobulin E, the principal mediator of allergic responses. The molecular basis of IL-4 action has remained elusive so far. Here we report on a novel human transcription factor, termed nuclear factor IL-4 (NF-IL4), which is posttranslationally activated by IL-4 in lymphoid and monocytic cells. Homologous binding sequences for NF-IL4 were identified in the promoter regions of the IL-4 controlled CD23b and I epsilon genes. We defined a palindromic 9-bp consensus sequence (5'-TYCYRRGAA-3') as IL-4-responsive element (IL-4RE). Point mutation analysis of the CD23b promoter showed that binding of NF-IL4 to the IL-4RE is essential for the initiation of gene transcription in response to IL-4. NF-IL4 was not activated by Ca2+ ionophore, phorbol ester and cAMP either alone or in combination suggesting a non classical pathway for IL-4 signal transduction.

CDw60 glycolipid antigens of human leukocytes: structural characterization and cellular distribution

Monoclonal CDw60 antibodies recognize glycolipid antigens with restricted surface expression on human leukocytes. They allow us to define new functional subpopulations of T lymphocytes and are able to induce costimulatory signals. In this report, we describe the molecular composition of CDw60 glycolipid antigens derived from different human leukocyte subpopulations. The glycolipids were isolated and their structures were identified by immunochemical methods. All molecules containing the CDw60 determinant were found in the disialoganglioside fraction. They were O-acetylated derivatives of the gangliosides II3 (Neu5Ac)2-LacCer (GD3), IV3 (Neu5Ac)2-nLc4Cer (DSPG), and VI3 (Neu5Ac)2-nLc6Cer (DSnHC), respectively. The most common CDw60 glycolipid antigen in human leukocytes was 9-O-acetyl GD3. In a comparison of various cell types, the highest concentration of 9-O-acetyl GD3 on a per cell basis was determined in granulocytes and in blood T lymphocytes, whereas B lymphocytes, thymus cells, and monocytes contained considerably smaller amounts of this molecule. Polar CDw60 antigens such as 9-O-acetyl DSPG and 9-O-acetyl DSnHC were only detected in granulocytes.

Spontaneous tumor cell cytotoxicity mediated by peripheral blood mononuclear leukocytes of the dog

Peripheral blood samples from 37 dogs of different breeds were separated into mononuclear leukocytes, strongly plastic adherent cells, plastic nonadherent cells, nylon wool nonadherent lymphocytes (NAL), Percoll density gradient enriched lymphocyte fractions and monoclonal antibody M-T606-negative cells. The inherent ability of each cell fraction to exert spontaneous cell-mediated cytotoxicity (SCMC) was tested in an 18-hour chromium release assay using two allogeneic and one xenogeneic tumor cell line(s) as the targets. Among the lymphocytes enriched by Percoll density gradient centrifugation natural killer cells could be clearly identified due to their morphology (large granular lymphocytes) and increased cytotoxic potency. Even high SCMC was mediated by effector cell populations showing plastic or nylon wool adherence and a high proportion of peroxidase-positive cells. Immunomagnetic selection of monoclonal antibody M-T606-nonreactive canine NAL regularly resulted in a strong increase in cytotoxicity mediated by M-T606- cells. Cytotoxic activity was found in cell-free supernatants from effector:target cell mixtures indicating the release of soluble leukolysins.

Effects of isotype and Fc region on in vitro function of a mouse/human chimeric CD4 antibody

Murine CD4 mAbs have shown potential for the treatment of allograft rejection and autoimmune disorders including rheumatoid arthritis. Clinical usefulness of the murine mAbs has been limited by immunogenicity and a short circulating half-life. Mouse/human chimeric antibodies have been constructed, composed of the variable region of M-T412 (a murine G2a mAb specific for the human CD4 molecule) and human G1 (cM-T412 G1) or G4 (cM-T412 G4) Fc regions. F(ab')2 and F(ab) fragments of the murine G2a and chimeric G1 mAbs were generated by enzymatic digestion. The chimeric mAbs and all fragments retained the avidity and specificity of the murine M-T412 and were evaluated in in vitro assays measuring Ig production by pokeweed mitogen (PWM)-stimulated peripheral blood mononuclear cells (PBMC), sIL-2R produced by phytohemagglutinin-stimulated PBMC, and proliferation in response to tetanus toxoid, CD3 mAb plus IL-2, and mixed lymphocyte response (MLR). When PBMC were stimulated with tetanus toxoid, 10 ng/ml of cM-T412 G1 inhibited proliferation by 90%, while neither the cM-T412 G4, M-T412 G2a, nor any mAb fragment produced > 65% inhibition, even at 1000-fold higher concentrations. A similar pattern of inhibition was observed in MLR assays. In contrast, the F(ab')2 fragment of the cM-T412 G1 was as effective as the whole antibody in inhibiting PWM-stimulated IgM synthesis and PBMC proliferation in response to stimulation by a CD3 mAb plus IL-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Combinatorial functions of two chimeric antibodies directed to human CD4 and one directed to the alpha-chain of the human interleukin-2 receptor

The general feasibility of chimerization of monoclonal antibodies (mAbs) has already been shown for a large number of them. In order to evaluate in vitro parameters relevant to immunosuppressive therapy, we have chimerized and synthesized two anti-CD4 mAbs recognizing two different epitopes on the human T-lymphocyte antigen, CD4. The chimerized mAbs are produced at levels corresponding to those of the original hybridoma cell lines. With respect to activation of human complement, the individual Abs are negative; however, when used in combination, complement activation was performed. When applied in combination, they were found to modulate the CD4 antigen, whereas the individual mAb do not display this property. Individually they mediate an up to 60% inhibition of the mixed lymphocyte reaction (MLR). However, by combination of an anti-CD4 mAb with one directed against the alpha-chain of the human IL2 receptor, nearly 100% inhibition of the MLR was achieved, even with reduced dosage of the mAbs. Our data suggest that the combination of an anti-CD4 mAb and an anti-IL2R alpha chain mAb is more effective with respect to immunosuppression than each mAb by itself, indicating that this mAb cocktail could be a new strategy for immunosuppressive therapy.

The monoclonal CD4 antibody M-T413 inhibits cellular infection with human immunodeficiency virus after viral attachment to the cell membrane: an approach to postexposure prophylaxis

Infectious cellular uptake of human immunodeficiency virus (HIV) is initiated by a complex sequence of interactions between the viral envelope gp120/gp41 complex and the cellular CD4 receptor resulting in the exposure of a hydrophobic region of gp41 that mediates the irreversible fusion of the virus with the cell membrane. Here we show that viral penetration into a susceptible cell can be inhibited by the high-affinity monoclonal CD4 antibody (CD4 mAb) M-T413 even when it is added as late as 30-120 min after the initial contact of virus with the cell membrane. Inhibition of infection was assessed by monitoring cultures for 34 days after exposure to virus using four different methods simultaneously, including detection of viral DNA by PCR. The interval during which HIV remains sensitive to postbinding neutralization by CD4 mAb depends on strain of virus and type of target cell. Preparations of recombinant soluble CD4 (and the immunoadhesin CD4-IgG1) were much less efficient when compared with mAb M-T413, particularly in blocking infection by fresh HIV-1 isolates. Also cellular transmission of HIV, as determined by syncytia formation within 24 hr, was prevented by mAb M-T413 when added within 45 min of contact of infected H9 cells with uninfected C8166 cells. Together with the favorable clinical experience obtained with CD4 mAbs as immunomodulatory drugs, these data suggest that infusion of CD4 mAb M-T413 may be a therapeutic modus for immediate prophylactic intervention after occupational exposure to HIV and for prevention of intrapartum mother-to-infant HIV transmission.