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B Gansbacher

Publications and source records attributed to B Gansbacher.

64 records · Page 4Linked to original sources
PubMed1990

Retroviral vector-mediated gamma-interferon gene transfer into tumor cells generates potent and long lasting antitumor immunity.

Retroviral vectors were used to introduce the gamma-interferon (IFN-gamma) gene into CMS-5 cells, a weakly immunogenic tumor of BALB/c origin. After selection in G418-containing medium, colonies were isolated, cloned, and expanded to cell lines. IFN-gamma secretion was assessed using a bioassay and enzyme-linked immunosorbent assay, and high (25 units/ml) and low (5 units/ml) IFN-gamma producers were isolated. Tumor growth was followed after intradermal injection, and spleen cells were isolated at different time points. IFN-gamma secretion by tumor cells abrogated their tumorigenicity and induced a persistent and specific antitumor immunity. In contrast to the normally observed cellular immunosuppression in unmodified CMS-5 tumor-bearing mice, IFN-gamma-producing tumors induced a long lasting state of T-cell immunity, as judged by rejection of a CMS-5 tumor challenge and persistence of specific cytotoxic activity in the spleen cell population. High levels of tumor-specific cytotoxic activity could also be detected if IFN-gamma-secreting tumor cells, but not unmodified CMS-5 cells, were used as targets at a time point when immunosuppression was usually seen. These studies highlight the potential advantages of localized IFN-gamma secretion to induce potent antitumor immune responses.

Animals↗
PubMed1990

Interleukin 2 gene transfer into tumor cells abrogates tumorigenicity and induces protective immunity.

To study the effects of localized secretion of cytokines on tumor progression, the gene for human interleukin 2 (IL-2) was introduced via retroviral vectors into CMS-5 cells, a weakly immunogenic mouse fibrosarcoma cell line of BALB/c origin. Secretion of low levels of IL-2 from the tumor cells abrogated their tumorigenicity and induced a long-lasting protective immune response against a challenge with a tumorigenic dose of parental CMS-5 cells. Co-injection of IL-2-producing CMS-5 cells with unmodified tumor cells inhibited tumor formation even when highly tumorigenic doses of CMS-5 cells were used. Cytolytic activity in mice injected with parental CMS-5 cells was transient and was greatly diminished 3 wk after injection, as commonly observed in tumor-bearing animals. However, in mice injected with IL-2-producing cells, tumor-specific cytolytic activity persisted at high levels for the duration of the observation period (at least 75 d). High levels of tumor-specific cytolytic activity could also be detected in parental CMS-5 tumor-bearing animals 18 d after inoculation with tumor cells, if IL-2-producing CMS-5 cells but not unmodified parental tumor cells were used as targets. These studies highlight the potential advantages of localized secretion of cytokines mediated via gene transfer to induce potent anti-tumor immune responses.

Animals↗
PubMed1990

Interferon-alpha with zidovudine: safety, tolerance, and clinical and virologic effects in patients with Kaposi sarcoma associated with the acquired immunodeficiency syndrome (AIDS)

OBJECTIVE: To evaluate safety, tolerance, and potential efficacy of interferon-alpha and zidovudine combination therapy in patients with Kaposi sarcoma and the acquired immunodeficiency syndrome (AIDS). DESIGN: Open, phase-I study with randomization between two preparations of interferon-alpha. SETTING: Outpatient clinic of a cancer research center. PATIENTS: Forty-three patients with Kaposi sarcoma associated with AIDS. INTERVENTIONS: Patients were treated with interferon-alpha, 4.5, 9, or 18 million U/d, and zidovudine, 100 or 200 mg orally every 4 hours. MEASUREMENTS AND MAIN RESULTS: Neutropenia was the major dose-limiting toxicity. Fatigue, liver enzyme elevation, anemia, and thrombocytopenia were dose-limiting in some patients. Maximum tolerated dosages for interferon-alpha 2a with zidovudine, respectively, were 4.5 million U/d with 200 mg every 4 hours or 18 million U/d with 100 mg every 4 hours. An interferon-alpha n1 [corrected] dosage of 9 million U/d with zidovudine dosages of either 100 or 200 mg every 4 hours induced dose-limiting toxicity in most patients. Of 37 evaluable patients, 17 (46%; 95% CI, 30% to 62%) showed complete or partial tumor regression. Antitumor effects occurred more frequently in patients with baseline CD4 counts above 200 x 10(6) cells/L (65%) than in patients with lower baseline counts (30%, P = 0.05). Effects on CD4 cells were related to both initial CD4 count and interferon dose. Increased skin test reactivity and decreased serum human immunodeficiency virus (HIV) p24 antigen and virus recovery from blood cells were seen. CONCLUSIONS: Combined therapy with interferon-alpha and zidovudine can be safely administered to patients with AIDS and Kaposi sarcoma. The observed effects on tumor growth, HIV replication, and immune function support further studies of the combination in patients at various stages of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Expression of HLA-DR mRNA in T cells following activation is early and can precede DNA synthesis.

The stimulation of T cells is accompanied by the appearance of a number of activation antigens not found on resting T cells. We have studied the expression of one group of such antigens, the HLA class II antigens (DR, DQ and DP), following stimulation with PHA and PMA. Immunofluorescence studies using monoclonal antibodies indicated that cell surface class II determinants were detectable as little as 30 minutes following stimulation, and that their levels remained constant for about 24 hours, after which they began to increase. Studies on the molecule level demonstrated an increase in the steady state levels of mRNA for DR beta by 15 minutes. Immunoblot analysis of resting T cell lysates using a monoclonal antibody reactive with DR detected a polypeptide of approximately 28 KDa, which agrees with the known molecular mass of the light chain of class II molecules on SDS-PAGE, suggesting that the rapid surface expression might have been due to the presence of pre-formed class II polypeptides. These results demonstrate 1) that T cells defined as resting by conventional criteria contain class II polypeptides and 2) that increases in steady state levels of class II mRNA is a very early event which precedes the initiation of DNA synthesis.

DNA Replication↗
PubMed1989

HLA class II mRNA accumulation by activated human T cells following growth in conditioned medium.

The expression of HLA Class II beta genes by seven CD4- or CD8-positive T cell clones grown in conditioned medium was examined on the mRNA and cell surface levels. Monoclonal antibodies directed against Class II glycoproteins demonstrated the presence of these molecules on the cell surface. In addition, Northern blot analysis demonstrated that cDNA probes for the DR, DP, and DQ beta genes hybridized to mRNA isolated from each clone. Because we were interested in differences in expression of relative levels of DR, DQ and DP, mRNA isolated from the clones was quantified by means of densitometry. Our results demonstrated that different ratios of DR, DQ and DP beta chain messages were expressed by the clones. Subsequent studies established the kinetics of the accumulation of DR beta mRNA messages by T cells during culture and showed that it could be regulated by factors contained within conditioned medium. Our results confirm that the accumulation of Class II mRNA following growth of T cells in conditioned medium appears to be a general feature.

Antigens, Surface↗
PubMed1988

Regulation of HLA-DR, DP, and DQ expression in activated T cells.

Class II expression following restimulation of a population of T cells which had first been activated and then allowed to revert to small resting cells via IL-2 deprivation was followed on the cell surface and mRNA levels. Our interest was to determine the kinetics of class II expression during in vitro growth, the triggers which can induce them, and also whether similar or different patterns are observed for the three class II antigens, DR, DQ, and DP. The cells responded rapidly to restimulation with conditioned medium containing IL-2 as assessed by increased incorporation of [3H]TdR into DNA. Cell surface expression of HLA-DR reached peak levels by Day 1, and greater than 90% of the cells continued to express DR until Day 4, when the number of positive cells gradually began to decline. The expression of DP also increased, though maximum levels were not reached until Day 3, when it began to decline. The percentage of cells positive for DP was, however, consistently lower than that of DR. DQ was expressed by very few cells, but appeared to increase until Day 4 and then decline. Tac expression was dramatically up-regulated following IL-2 stimulation, remaining high until Day 4, and then declining more precipitously than any of the other antigens. Class I antigen expression was relatively constant during the entire culture period, though a slight decline was noted between Day 5 and 6 when proliferation and viability were at their lowest levels. On the molecular level, DR beta mRNA accumulation peaked at Day 3, then rapidly declined. Reculture in IL-2 on Day 4 resulted in transient reaccumulation of message. Study of DP beta and DQ beta mRNA demonstrated strong expression on Days 3 and 4 and no obvious up-regulation after restimulation with IL-2 on Day 4. The kinetics of Tac mRNA accumulation and the response to restimulation with IL-2 closely resembled that of DR. Finally we compared the ability of different signals to up-regulate class II mRNA and surface expression and to restimulate proliferation. Our results indicated that PHA was more effective then medium alone, but far less effective than was IL-2. PMA was essentially no different than medium alone.

Blotting, Northern↗
PubMed1986

Effect of PHA-activated T cells on B-cell differentiation.

Recent studies indicate that human T cells expressing the T4 determinant are comprised of functionally distinct subsets. We investigated if activation of OKT4+ cells with the mitogen PHA affected their ability to regulate the proliferation and polyclonal differentiation of autologous B cells. OKT4+ cells were preactivated with PHA and then cocultured with autologous B cells in the presence or absence of PWM. B-cell proliferation and differentiation to immunoglobulin-secreting cells (IgSC) were assessed by [3H]thymidine incorporation and reverse haemolytic plaque assay, respectively. In the absence of PWM, the PHA-activated OKT4+ cells demonstrated radioresistant help and radiosensitive suppression of IgSC responses. Addition of PWM to cocultures of irradiated PHA preactivated OKT4 cells and autologous B cells resulted in further suppression of IgSC responses, suggesting that PWM activated yet another suppression mechanism. Addition of PWM caused diminished B-cell proliferation as well. These data demonstrate functional heterogeneity within the OKT4 subset, and suggest that the particular immunoregulatory activity displayed is influenced by the state and mode of activation of these cells.

Antibodies, Monoclonal↗
PubMed1981

Generation of discriminatory PL against HLA-D antigens not detected by serology.

A family was studied in which the father and the mother were both homozygous for the HLA-DR antigens. All children responded to the parents in MLC, even though each had a copy of the parental DR antigen, implying that they recognized a difference. When the father or the mother was sensitized in PLT against any child, all siblings could restimulate equally well. However, by sensitizing a family member with one copy of the DR phenotype against another family member with the alternate form of the phenotype, discriminatory PL could be produced. This may help define the subtypic specificities of PL antigens.

Epitopes↗
PubMedDate not supplied

Cytokine gene therapy: a new strategy for the management of cancer patients.

Cytokine gene therapy has recently become a new potential prospect in the management of cancer patients. This has stemmed from clinical considerations based on the evidence that high-dose interleukin-2 (IL-2) may be effective in a proportion of patients, that foreign genetic material may be successfully inserted into the genome of normal and neoplastic cells, and by extensive studies in experimental models which have shown that cytokine-gene-transduced tumor cells may reveal a diminished or abolished tumorigenicity. Evidence has also been provided that the IL-2 released constitutively by engineered tumor cells may induce the generation of specific cytotoxic T lymphocytes and of an antitumor memory response. Here, we will review the data which have led to the activation of the first pilot vaccination protocols with IL-2 gene-transduced allogeneic cell lines for advanced-stage melanoma and renal cell carcinoma patients. New directions in delivery modalities, as well as future strategies will also be discussed.

Animals↗