Biomedical subjects

G Braslawsky

Publications and source records attributed to G Braslawsky.

8 recordsLinked to original sources

PubMed2001

Modification of the Fc region of a primatized IgG antibody to human CD4 retains its ability to modulate CD4 receptors but does not deplete CD4(+) T cells in chimpanzees.

Keliximab, a Primatized IgG1 CD4 mAb, was reconfigured to an IgG4 antibody. The gamma4 constant region was further modified by substituting glutamic acid for serine at position 235 in the CH2 domain (IgG4-E), to remove residual binding to Fcgamma receptors, and substitution of serine with proline at position 228 in the hinge region (IgG4-PE) for greater stability. Pharmacokinetic analysis in rats gave a t(1/2) of approximately 4 days for IgG4-E and 9 days for IgG4-PE, consistent with a greater stability of the IgG4-PE molecule. The effects on T cell subsets were assessed in chimpanzees given escalating doses of IgG4-PE: 0.05 mg/kg on Day 16, 1.5 mg/kg dose on Day 43, and 15 mg/kg on Day 85. Receptor modulation was observed at the two highest doses, but no depletion of T cells at any dose. The in vitro and in vivo results demonstrate the potential of this IgG4-PE mAb for use in human trials.

Amino Acid Substitution↗

PubMed2001

Future approaches for treating hematologic disease.

The approval of monoclonal antibodies for therapy of hematologic malignacies (Rituxan, Mylotarg, Campath) renewed the interest in antibodies as potential new treatment options for cancer patients. Antibodies are effective in inhibiting tumor cell growth , inducing apoptosis, and activating host effector mechanisms for tumor cell killing. Monoclonal antibodies can be clinically effective as monotherapy, as targeting agents delivering either potent cytotoxic drugs or radionuclides as well as in combination with conventional chemotherapies. Advances in antibody engineering provided new capabilities to reduce immunogenicity, alter half life, increase effector functions, and increase tumor targeting for optimal therapeutic modalities requiring chronic dosing regimens. During the next decade, as new tumor-specific surface antigens are discovered and the linkage between genes and function is better understood, new targets will be identified for regulating tumor cell growth by engineered antibodies with agonist or antagonist activity. Additionally, antibody engineering will allow for more efficient radionuclide or cytotoxic drug targeting or lead to more selective activation of relevant host effector mechanisms, leading to a safe and effective therapy of cancer.

Animals↗

PubMed1998

Tumor regression in mice following vaccination with human papillomavirus E7 recombinant protein in PROVAX.

Induction of CD8+ cytotoxic T lymphocytes (CTLs) specific for human papillomavirus (HPV) antigens provides an attractive strategy for immunotherapy of HPV-related cancers in humans. In this study, we investigated the potential of utilizing soluble E7 protein of HPV 16 in an adjuvant formulation, PROVAX as a vaccine against a progressively growing E7 transfected K1735-X21 (H-2k) metastatic melanoma cells (HOPE2) in a mouse model. Vaccination of HOPE2 tumor bearing mice (C3H) with E7 protein in PROVAX resulted in significant inhibition of tumor growth, compared to mice vaccinated with E7 in Alum or saline. In vivo depletion of CD8+ or CD4+ cells indicated that CD8+ cells are the major effector cells in mediating the anti-tumor activity in this model. Furthermore, E7-specific CTL activity in vitro was detected in tumor bearing mice vaccinated with E7-PROVAX. Our studies suggest that recombinant HPV antigens in combination with PROVAX could serve as an effective subunit vaccine to stimulate tumor specific CD8+ T cell mediated immunity against HPV-related cancers.

Adjuvants, Immunologic↗

PubMed1998

Enhancement of cell-mediated immunity in melanoma patients immunized with murine anti-idiotypic monoclonal antibodies (MELIMMUNE) that mimic the high molecular weight proteoglycan antigen.

The purpose of this study was to determine whether a combination of two anti-idiotypic antibodies that mimic the high molecular weight proteoglycan antigen found on most melanoma tumors was capable of enhancing cellular immunity in vaccinated high-risk patients with melanoma. Twenty-eight stage I-IV high-risk patients with melanoma were immunized with a mixture of variable concentrations of MELIMMUNE-1 and MELIMMUNE-2, along with the adjuvant SAF-m, using two immunization schedules. Peripheral blood mononuclear cells were collected before the first immunization and 4 weeks after the final immunization and tested for in vitro proliferation to MELIMMUNE-1 and MELIMMUNE-2 and for cytotoxicity against 51Cr-labeled target cell lines. Additionally, supernatants from in vitro proliferation cultures were tested for interleukin 10 and IFN-gamma levels. Significant in vitro proliferation to MELIMMUNE-1 and MELIMMUNE-2 were observed in postimmunization samples but not in prevaccination samples. The mean stimulation index for MELIMMUNE-2 (33.7 +/- 0.6) was significantly higher than that for MELIMMUNE-1 (13.9 +/- 0.3; P < 0.025). Supernatants obtained from 78% of the in vitro stimulated cultures pre- or postvaccination contained significant levels of interleukin 10 (range, 0.43-142 pg/ml), whereas IFN-gamma levels were elevated in 53% of postvaccination samples (range, 3-245 pg/ml) but not prevaccination samples. More importantly, we were able to generate specific CTL responses in 43% of the patients, which correlated with elevated IFN-gamma levels. These results indicate that MELIMMUNE enhances cell-mediated immunity in patients with melanoma.

Antibodies, Anti-Idiotypic↗

PubMed1995

The induction of cytotoxic T cells and tumor regression by soluble antigen formulation.

CTLs specific for tumor antigens play a major role in the immunity against cancer. We have shown that class I-restricted CTLs can be induced by injecting soluble antigens mixed in an antigen formulation (AF) that consists of squalane, Tween 80, and Pluronic L121 (S. Raychaudhuri et al., Proc. Natl. Acad. Sci. USA, 89: 8308-8312, 1992). In this study, using ovalbumin and the ovalbumin-expressing transfectoma (EG7) as a tumor model system, we examined the in vivo antitumor effect of antigen-AF mixture. Vaccination of mice with ovalbumin in AF 2 or 3 days after EG7 tumor challenge showed significant inhibition of tumor growth compared to mice vaccinated with ovalbumin in alum or in saline. Depletion of CD8+ cells at the time of immunization completely abrogated the AF-induced tumor protection, indicating that CD8+ T cells are the major effectors in tumor protection in vivo. Depletion of CD4+ cells led to a marginal loss of tumor protection, which may be the result of inhibition of ovalbumin-specific CTL response due to the lack of T-helper activity. Our results demonstrate that AF can be used in subunit vaccines to stimulate CTLs and tumor regression in vivo.

Animals↗

PubMed1993

Granulocyte-macrophage colony-stimulating factor plays a role in the functional activity of mast cells.

A peptide homologous to a region of murine granulocyte-macrophage colony-stimulating factor (mGM-CSF), P27-38, which was shown to be a GM-CSF antagonist, inhibited the function of serotonin release from murine mast cells. Peptide P27-38 inhibited immunoglobulin E (IgE)-mediated serotonin release in a dose-dependent manner when induced by either specific antigen or anti-IgE antibody. In contrast, non-receptor-mediated release of serotonin by agents such as compound 48/80 or the calcium ionophore A23187 were not affected by the GM-CSF antagonist. Similar effects were observed with GM-CSF-neutralizing antibodies. The inhibitory effect of P27-38 and the neutralizing antibodies on serotonin release could be reversed by the addition of exogenous GM-CSF to the stimulated mast cells, indicating that the inhibitory activity was probably due to an effect on endogenously produced GM-CSF. These findings suggest that GM-CSF produced by stimulated mast cells is involved in the regulation of their activity in an autocrine manner.

Amino Acid Sequence↗

PubMed1976

Tumor bound immunoglobulins: the relationship between the in vivo coating of tumor cells by potentially cytotoxic anti-tumor antibodies, and the expression of immune complex receptors.

In this study we investigated the relationship between binding of anti-tumor antibodies by polyoma-virus-induced SEYF- a tumor cells and the expression of immune-complex receptors on these cells. It was shown that in vivo propagated cells became progressively coated with IgG. The increase in the IgG coating of SEYF-a cells, occurring during the second week of propagation, was directly correlated with an increase in the coating of cells with potentially cytotoxic anti-tumor antibodies. The activity of these antibodies was demonstrated by cell lysis following addition of exogenous complement. Cell populations propagated in vivo for longer periods (3 weeks or more) became less sensitive to exogenous complement although their IgG coating remained high, and although higher titers of anti-tumor antibodies could be eluted from them. This indicated that antibodies coating young tumor cell populations have the capacity to activate complement whereas those coating older tumor cell populations are incapable of complement activation. Previous findings that SEYF-a cell populations are able to bind unrelated immune complexes were confirmed in the present study. We also found that the capacity of these populations to bind such unrelated complexes decreased with propagation time in vivo. The involvement of anti-tumor antibodies in this phenomenon was indicated by the finding that such antibodies inhibited binding of unrelated immune complexes by young cells but not by old cells. Furthermore, treatments causing dissociation of Ig from the cell surface restored, to some extent, the capacity of anti-tumor antibodies to inhibit immune complex binding by old SEYF-a populations.

Animals↗

PubMed1975

Intramitochondrial bodies in a human cell line carrying oncornavirus-like particles.

Electron-dense particles 80-100 nm in diameter were observed in electron micrographs of mitochondria in transformed mouse fibroblasts and in a human amnion cell line infected with supernatants of a human mammary carcinoma cell culture. Intramitochondrial particles were more numerous in the human cell cultures early after subculture. These particles were morphologically similar to those reported in mitochondria of Rous sarcoma virus-infected cells.

Amnion↗