Relevance of the tumor antigen in the validation of three vaccination strategies for melanoma.

Many preclinical studies of cancer immunotherapy are based on the testing of a single vaccination strategy in several tumor models. Moreover, most of those studies used xenogeneic Ags, which, owing to their high immunogenicity, may not represent realistic models for the validation of cancer immunotherapies. To address these issues, we compared the vaccination efficacy of three well established strategies (i.e., naked DNA; peptide-pulsed dendritic cells (DC), or a mixture of peptide and the Escherichia coli toxin LTR72) using the xenogeneic OVA or the naturally expressed tyrosinase-related protein 2 (TRP-2) tumor Ag in the B16 melanoma model. C57BL/6 mice received one to three s.c. injections of peptide-pulsed DC or DNA, or one to four mucosal administrations of peptide-toxin mixture. One to 2 wk later, the animals were challenged s.c. with B16 or B16 cells expressing OVA (B16-OVA). Vaccination of mice with OVA induced in all cases melanoma-specific CTL and protection against B16-OVA. When TRP-2 was used, all three vaccines elicited B16-specific CTL, but only DC pulsed with the immunodominant T cell epitope TRP-2181-188 allowed protection against B16. Even more importantly, a vaccination regimen with TRP-2-pulsed DC, started 24 h after the injection of a lethal number of B16 cells, caused a therapeutic effect in 60% of the challenged animals. Our results strongly emphasize the relevance of the tumor Ag in the definition of immunotherapeutic strategies for cancer, and support the use of peptide-pulsed DC as cancer vaccine in humans.

Role of antigen-presenting cells in cross-priming of cytotoxic T lymphocytes by apoptotic cells.

Although the mechanisms regulating recognition and phagocytosis of apoptotic cells by scavenger cells are the subject of intense investigation, little is known about the fate of the antigens contained in apoptotic cells and the constraints defining their immunogenicity. We developed a model in C57BL/6 mice to evaluate whether phagocytosis of apoptotic tumor cells yielded antigens able to get access to the MHC class I pathway and activate a specific cytotoxic T lymphocyte response. Our results demonstrate that apoptotic tumor cells are antigenic in vitro and can be immunogenic in vivo. Their immunogenicity depends on the number of cells used for immunization and the antigen-presenting cells involved in processing and presentation of antigens contained in the dying cells. The demonstration of the immunogenicity of apoptotic cells may have direct implications both in autoimmunity and cancer.

Immunogenicity of apoptotic cells in vivo: role of antigen load, antigen-presenting cells, and cytokines.

Apoptosis allows the clearance of unwanted cells from living tissues without causing inflammation. Processing of phagocytosed apoptotic cells yields Ags that access the cytosol and the MHC class I pathway of engulfing cells and are recognized by Ag-specific CTL. We show here that injection of apoptotic RMA cells, a syngeneic T cell lymphoma, into C57BL/6 mice results in priming of a functional and long-lasting tumor-specific immune response. Cross-priming of CTLs by apoptotic cells requires CD4+ T cell help. Apoptotic cells, however, are at least 20-fold less immunogenic than nonreplicating live cells. Immunogenicity of apoptotic cells is proportional to the number of cells injected, correlates with the serum concentration of IL-10 and IL-1beta cytokines, and is enhanced in IL-10 knockout mice. Moreover, immunization with dendritic cells (DCs), but not macrophages (Mphi), pulsed with apoptotic cells primes tumor-specific CTLs and confers protection against a tumor challenge. Our findings demonstrate that tumor cells undergoing apoptosis are, though scarcely, immunogenic in vivo, outline the different roles of Mphi and DCs in the physiologic clearance of unwanted cells, and have implications in designing immunomodulating vaccines.

7.5% hypertonic saline versus 20% mannitol during elective neurosurgical supratentorial procedures.

This prospective randomized clinical study was designed to compare the effects of equal volumes of 7.5% hypertonic saline solution (HS) or 20% mannitol (M) on brain bulk and lumbar cerebrospinal fluid pressure (CSFP) during elective neurosurgical procedures (aneurysm, arteriovenous malformation, or tumor). After informed consent, 50 American Society of Anesthesiologists physical Status I (ASA I) patients were randomly assigned to M (n = 25) or HS (n = 25) groups. Anesthesia protocol was identical for both, and variables monitored included mean arterial blood pressure (MAP), heart rate (HR), central venous pressure (CVP), CSF pressure (CSFP), arterial blood gases (PaCO2 30-35 mm Hg), serum sodium, potassium, and osmolality, and diuresis. The study period started before hypertonic solution administration (T0) and ended at the opening of the dura mater or 60 min after T0. Data were assessed with repeated measures analysis of variance and Student t test with Bonferroni correction (p < or = 0.05). MAP and CVP were the same in the two groups. After treatment, osmolality increased, and the increase at T15 was higher in HS-treated patients [316.6 +/- 9.3 vs. 304.0 +/- 12.0 (SD) mOsmol/kg; p < 0.001]. Sodium decreased after M and increased after HS. During the study, brain bulk was always considered satisfactory. CSFP was not different between M and HS groups and significantly decreased overtime (p = 0.0056) with no difference between treatments. The results of the present study demonstrate that hypertonic saline is as effective as mannitol in reducing the brain bulk and the CSFP during elective neurosurgical procedures under general anesthesia.

Therapeutic management of primary central nervous system lymphoma in immunocompetent patients: results of a critical review of the literature.

BACKGROUND: The optimal treatment for primary central nervous system lymphomas (PCNSL) has not been defined. PATIENTS AND METHODS: Therapeutic results of 1180 immunocompetent patients (pts) with PCNSL reported in 50 series published in English between 1980 and 1995 were analysed. The impact on survival of age, treatment strategy, radiation field and doses, systemic and intrathecal chemotherapy (CHT) and treatment sequence was evaluated. RESULTS: Univariate analyses showed a longer survival in pts of < or = 60 years (P < 0.00001): pts treated with > 40 Gy to whole brain (WB) (P = 0.02): pts receiving > 50 Gy to the tumor bed after a WB dose > 40 Gy (P = 0.02): pts submitted to a combined treatment as opposed to CHT alone (P = 0.007) or radiotherapy alone (P < 0.00001): pts receiving CHT followed by radiotherapy rather than in the reverse sequence (P = 0.05); pts treated with high-dose methotrexate (HDMTX) (P = 0.04) and pts receiving intrathecal CHT (P = 0.03). Multivariate analysis confirmed the independent prognostic value of age, WB dose, HD-MTX and intrathecal CHT. CONCLUSIONS: Current data confirm the prognostic value of age and appear to support the use of systemic CHT consisting of HD-MTX and intrathecal drug administration followed by 41-50 Gy to WB and > 50 Gy to the tumor bed in the treatment of PCNSL in immunocompetent pts.