Decoupling immunomodulatory properties from lipid binding in the α-pore-forming toxin Sticholysin II.

Sticholysin II (StII), a pore-forming toxin from the marine anemone Stichodactyla helianthus, enhances an antigen-specific cytotoxic T lymphocyte (CTL) response when co-encapsulated in liposomes with a model antigen. This capacity does not depend exclusively on its pore-forming activity and is partially supported by its ability to activate Toll-like receptor 4 (TLR4) in dendritic cells, presumably by interacting with this receptor or by triggering signaling cascades upon binding to lipid membrane. In order to investigate whether the lipid binding capacity of StII is required for immunomodulation, we designed a mutant in which the aromatic amino acids from the interfacial binding site Trp110, Tyr111 and Trp114 were substituted by Ala. In the present work, we demonstrated that StII3A keeps the secondary structure composition and global folding of StII, while it loses its lipid binding and permeabilization abilities. Despite this, StII3A upregulates dendritic cells maturation markers, enhances an antigen-specific effector CD8+ T cells response and confers antitumor protection in a preventive scenario in C57BL/6 mice. Our results indicate that a mechanism independent of its lipid binding ability is involved in the immunomodulatory capacity of StII, pointing to StII3A as a promising candidate to improve the reliability of the Sts-based vaccine platform.

The Vacuolar Pathway in Macrophages Plays a Major Role in Antigen Cross-Presentation Induced by the Pore-Forming Protein Sticholysin II Encapsulated Into Liposomes.

Cross-presentation is an important mechanism for the differentiation of effector cytotoxic T lymphocytes (CTL) from naïve CD8+ T-cells, a key response for the clearance of intracellular pathogens and tumors. The liposomal co-encapsulation of the pore-forming protein sticholysin II (StII) with ovalbumin (OVA) (Lp/OVA/StII) induces a powerful OVA-specific CTL activation and an anti-tumor response in vivo. However, the pathway through which the StII contained in this preparation is able to induce antigen cross-presentation and the type of professional antigen presenting cells (APCs) involved have not been elucidated. Here, the ability of mouse bone marrow-derived dendritic cells (BM-DCs) and macrophages (BM-MΦs) stimulated with Lp/OVA/StII to activate SIINFEKL-specific B3Z CD8+ T cells was evaluated in the presence of selected inhibitors. BM-MΦs, but not BM-DCs were able to induce SIINFEKL-specific B3Z CD8+ T cell activation upon stimulation with Lp/OVA/StII. The cross-presentation of OVA was markedly decreased by the lysosome protease inhibitors, leupeptin and cathepsin general inhibitor, while it was unaffected by the proteasome inhibitor epoxomicin. This process was also significantly reduced by phagocytosis and Golgi apparatus function inhibitors, cytochalasin D and brefeldin A, respectively. These results are consistent with the concept that BM-MΦs internalize these liposomes through a phagocytic mechanism resulting in the cross-presentation of the encapsulated OVA by the vacuolar pathway. The contribution of macrophages to the CTL response induced by Lp/OVA/StII in vivo was determined by depleting macrophages with clodronate-containing liposomes. CTL induction was almost completely abrogated in mice depleted of macrophages, demonstrating the relevance of these APCs in the antigen cross-presentation induced by this formulation.

GM3(Neu5Gc) ganglioside: an evolution fixed neoantigen for cancer immunotherapy.

Numerous molecules have been considered as targets for cancer immunotherapy because of their levels of expression on tumor cells, their putative importance for tumor biology, and relative immunogenicity. In this review we focus on the ganglioside GM3(Neu5Gc), a glycosphingolipid present on the outer side of the plasma membrane of vertebrate cells. The reasons for selecting GM3(Neu5Gc) as a tumor-specific antigen and its use as a target for cancer immunotherapy are discussed, together with the development of antitumor therapies focused on this target by the Center of Molecular Immunology (CIM, Cuba).

Immunologic Response Elicited in Breast Cancer Patients Receiving a NeuGcGM3-based Vaccine as Adjuvant Therapy.

This study aimed to investigate the immunogenicity of a cancer vaccine consisting of the NeuGcGM3 ganglioside combined with the outer membrane protein complex of Neisseria meningitides to form very small size particles. The vaccine is administered together with Montanide ISA51, as adjuvant treatment for breast cancer patients. After surgical resection and standard first-line chemo/radiotherapy, breast cancer patients in stage II-III were enrolled in a phase III clinical trial and allocated into 2 strata, according to the number of positive lymph nodes [stratum I (0-3); stratum II (≥4)]. Subsequently, patients were randomly assigned to receive the vaccine or placebo. The treatment consisted of 5 vaccine doses (200 µg) every 2 weeks and thereafter monthly reimmunizations to complete 15 doses. The vaccine was well-tolerated and high titers of immunoglobulin M and immunoglobulin G anti-NeuGcGM3 antibodies were similarly detected in each stratum. Hyperimmune sera were able to specifically recognize and kill the NeuGcGM3-expressing L1210 tumor cell line, and these functional capacities were significantly associated with a better clinical outcome in patients of stratum II. Besides, postimmune sera had the capacity to revert in vitro the immunosuppression induced by NeuGcGM3, as measured by the prevention of CD4 downmodulation on human T lymphocytes. Vaccination had no impact on the frequency of regulatory T cells or circulating NK cells. This study demonstrated, for the first time, the immunogenicity of the NeuGcGM3/VSSP/Montanide ISA 51 vaccine in the adjuvant setting and describes the functionality of induced anti-NeuGcGM3 antibodies as potential surrogate biomarkers of clinical benefit.

Novel Adjuvant Based on the Pore-Forming Protein Sticholysin II Encapsulated into Liposomes Effectively Enhances the Antigen-Specific CTL-Mediated Immune Response.

Vaccine strategies to enhance CD8+ CTL responses remain a current challenge because they should overcome the plasmatic and endosomal membranes for favoring exogenous Ag access to the cytosol of APCs. As a way to avoid this hurdle, sticholysin (St) II, a pore-forming protein from the Caribbean Sea anemone Stichodactyla helianthus, was encapsulated with OVA into liposomes (Lp/OVA/StII) to assess their efficacy to induce a CTL response. OVA-specific CD8+ T cells transferred to mice immunized with Lp/OVA/StII experienced a greater expansion than when the recipients were injected with the vesicles without St, mostly exhibiting a memory phenotype. Consequently, Lp/OVA/StII induced a more potent effector function, as shown by CTLs, in vivo assays. Furthermore, treatment of E.G7-OVA tumor-bearing mice with Lp/OVA/StII significantly reduced tumor growth being more noticeable in the preventive assay. The contribution of CD4+ and CD8+ T cells to CTL and antitumor activity, respectively, was elucidated. Interestingly, the irreversibly inactive variant of the StI mutant StI W111C, encapsulated with OVA into Lp, elicited a similar OVA-specific CTL response to that observed with Lp/OVA/StII or vesicles encapsulating recombinant StI or the reversibly inactive StI W111C dimer. These findings suggest the relative independence between StII pore-forming activity and its immunomodulatory properties. In addition, StII-induced in vitro maturation of dendritic cells might be supporting these properties. These results are the first evidence, to our knowledge, that StII, a pore-forming protein from a marine eukaryotic organism, encapsulated into Lp functions as an adjuvant to induce a robust specific CTL response.

Superior Efficacy and Safety of a Nonemulsive Variant of the NGcGM3/VSSP Vaccine in Advanced Breast Cancer Patients.

NGcGM3 ganglioside is a tumor-specific antigen expressed in human breast tumors. The NGcGM3/VSSP vaccine, consisting in very small-sized proteoliposomes (VSSP) obtained by the incorporation of NGcGM3 into the outer membrane protein complex of Neisseria meningitidis, has been previously tested in a Phase II trial in patients with metastatic breast cancer (MBC) but emulsified with Montanide ISA 51. An Expanded Access study was carried out in MBC patients aiming to find if a nonemulsive formulation of NGcGM3/VSSP, without Montanide ISA 51, could be more safe and effective. A total of 104 patients were vaccinated with the nonemulsive formulation (900 µg), subcutaneously (SC), or with the emulsive formulation (200 µg), intramuscularly (IM). An intent-to-treat analysis of efficacy was performed with all patients, and 93 patients were split off according to the site of metastases (visceral/nonvisceral). Of note, SC-treated patients exhibited a superior median overall survival (OS) than IM-treated patients (23.6 vs. 8.2 months; log rank P = 0.001). Even though in the subset of patients with nonvisceral metastases SC vaccination duplicated the median OS compared to the alternative option (31.6 vs. 16.5 months), this difference did not reach statistical significance (log rank P = 0.118). Curiously, in patients with visceral metastases, the advantage of the nonemulsive formulation was more apparent (median OS 21.0 vs. 6.2 months; log rank P = 0.005). The vaccine was safe for both formulations.

Adjuvants and myeloid-derived suppressor cells: enemies or allies in therapeutic cancer vaccination.

Adjuvants are a critical but largely overlooked and poorly understood component included in vaccine formulations to stimulate and modulate the desired immune responses to an antigen. However, unlike in the protective infectious disease vaccines, adjuvants for cancer vaccines also need to overcome the effect of tumor-induced suppressive immune populations circulating in tumor-bearing individuals. Myeloid-derived suppressor cells (MDSC) are considered to be one of the key immunosuppressive populations that inhibit tumor-specific T cell responses in cancer patients. This review focuses on the different signals for the activation of the immune system induced by adjuvants, and the close relationship to the mechanisms of recruitment and activation of MDSC. This work explores the possibility that a cancer vaccine adjuvant may either strengthen or weaken the effect of tumor-induced MDSC, and the crucial need to address this in present and future cancer vaccines.

Induction of leukocyte infiltration at metastatic site mediates the protective effect of NGcGM3-based vaccine.

While the NGcGM3/VSSP vaccine, a preparation consisting in very small sized proteoliposomes (VSSP) obtained by the incorporation of the NGcGM3 ganglioside into the outer membrane protein (OMP) complex of Neisseria meningitides, is currently studied in late stage clinical trials in breast cancer and melanoma patients, mechanisms involved in the vaccine's antitumor effect are insufficiently understood. Here we have addressed the role of adaptive and innate immune cells in mediating the protective effect of the vaccine. To this aim we selected the 3LL-D122 Lewis lung spontaneous metastasis model. Unexpectedly, inoculation of the vaccine in tumor bearing C57BL/6 mice, either by subcutaneous (sc) or intraperitoneal (ip) routes, induced similar anti-metastatic effect. Regardless the T-independent nature of NGcGM3 ganglioside as antigen, the antimetastatic effect of NGcGM3/VSSP is dependent on CD4(+) T cells. In a further step we found that the vaccine was able to promote the increase, maturation, and cytokine secretion of conventional DCs and the maturation of Bone Marrow-derived plasmacytoid DCs. In line with this result the in vivo IFNα serum level in ip vaccinated mice increased as soon as 2h after treatment. On the other hand the infiltration of NK1.1(+)CD3(-) and NK1.1(+)CD3(+) cells in lungs of vaccinated mice was significantly increased, compared with the presence of these cells in control animal lungs. In the same way NGcGM3/VSSP mobilized acquired immunity effector cells into the lungs of vaccinated tumor bearing mice. Finally and not less noteworthy, leukocyte infiltration in lungs of tumor bearing mice correlates with vaccine induced inhibition of lung metastization.

Very small size proteoliposomes abrogate cross-presentation of tumor antigens by myeloid-derived suppressor cells and induce their differentiation to dendritic cells.

BACKGROUND: Myeloid-derived suppressor cells (MDSCs) are among the major obstacles that adjuvants for cancer vaccines have to overcome. These cells cross-present tumor-associated antigens (TAA) to naive T lymphocytes with a tolerogenic outcome. Very Small Size Proteoliposomes (VSSP) is used as adjuvant by four therapeutic cancer vaccines currently in Phase I and II clinical trials. We previously found that VSSP reduces the suppressive function of MDSCs, then activating antigen-specific CTL responses in tumor-bearing (TB) mice, with the consequent reduction of tumor growth. However the mechanistic explanation for the immunomodulatory effect of this adjuvant in TB hosts has not been addressed before. METHODS: TB mice were inoculated with VSSP and MDSCs isolated and characterized by their expression of Arg1 and Nos2 genes by RT-PCR. The effect of VSSP on antigen cross-presentation by MDSCs, regulatory T cells (Tregs) expansion and MDSCs differentiation towards dendritic cells (DCs) was analyzed by FACS. Student's t test or ANOVA and Tukey's tests were used for statistical analyses. RESULTS: After inoculating VSSP into TB mice, a significant reduction of Arg1 and Nos2 gene expression was observed in recovered MDSCs. Concurrently the ability of these cells to induce down-regulation of CD3ζ chain on T cells was lost. Likewise in mice inoculated with the adjuvant lower percentages of Tregs were detected. In vitro, VSSP treatment was enough to differentiate MDSCs into phenotypically mature DCs, eliminating the former suppressive effect. Noteworthy, in vivo administration of VSSP to OVA-expressing (EG.7) TB mice abrogated this model antigen cross-presentation by splenic MDSCs. Similar results were obtained even when OVA antigen was administered into these TB mice formulated in VSSP. On the contrary, immunization with the same protein in polyI:C did not change the percentage of MDSCs expressing SIINFEKL/H-2K(b) complexes, whereas a concomitant injection of VSSP aborted the limitations of polyI:C in this setting. CONCLUSIONS: Altogether, these results indicate that VSSP has the peculiar capacity of inhibiting TAA cross-presentation and certain suppressive mechanisms on MDSCs which in turn, combined with the ability to induce differentiation of these cells into antigen-presenting cells (APCs), sustains this adjuvant as an ideal immunomodulator for cancer immunotherapy.

NGlycolylGM3/VSSP Vaccine in Metastatic Breast Cancer Patients: Results of Phase I/IIa Clinical Trial.

Patients treated with vaccines based on NGlycolil gangliosides have showed benefit in progression free survival and overall survival. These molecules, which have been observed in breast cancer cells, are minimally or not expressed in normal human tissue and have been considered as antigen tumor-specific. For this reason they are very attractive to immunotherapy. A phase I/II clinical trial was carried out in metastatic breast cancer patients with the NGlycolylGM3/VSSP vaccine administered by subcutaneous route. Selecting the optimal biological doses of the vaccine in these patients was the principal objective based on the immunogenicity, efficacy and safety results. Six levels of doses of vaccine were studied. Treatment schedule consisted of five doses every two weeks and then monthly until reaching a fifteenth doses. Doses levels studied were 150, 300, 600, 900, 1200 and 1500 µg. Five patients in each level were included except at the 900 µg dose, in which ten patients were included. Immunogenicity was determined by levels of antibodies generated in patients after vaccination. The response criteria of evaluation in solid tumors (RECIST) was used to evaluate antitumoral effect. Safety was evaluated by Common Toxicity Criteria of Adverse Event (CTCAE). The vaccine administration was safe and immunogenic in all does levels. Most frequent adverse events related to vaccination were mild or moderate and were related to injection site reactions and "flu-like" symptoms. Vaccination induced specific anti-NeuGcGM3 IgM and IgG antibodies responses in all patients. Disease control (objective response or stable disease) was obtained in 72.7% of evaluated patients. Median overall survival was 15.9 months. Two patients of two different dose levels achieved overall survival values of about six years. The dose of 900 µg was selected as biological optimal dose in which overall survival was 28.5 months.

Effect of vaccination with N-glycolyl GM3/VSSP vaccine by subcutaneous injection in patients with advanced cutaneous melanoma.

NeuGc-containing gangliosides have been described in melanoma cells and are an attractive target for cancer immunotherapy because they are minimally or not expressed in normal human tissues. Melanoma patients treated with a vaccine based on N-glycolyl gangliosides have shown benefit in progression free survival and overall survival. We conducted a multicenter Phase I/II clinical trial in patients with metastatic cutaneous melanoma treated with the N-gycolyl GM3/very-small-size proteoliposomes vaccine by the subcutaneous route. Selecting the optimal biological dose of the vaccine was the principal objective based on immunogenicity, efficacy, and safety results. Six dose levels were studied and the treatment schedule consisted of five doses administered every 2 weeks and then monthly until 15 doses had been given. Dose levels evaluated were 150, 300, 600, 900, 1200, and 1500 µg with five patients included in each dose level except the 900 µg dose (n = 10). Immunogenicity was determined by antibody titers generated in patients after vaccination. Antitumor effect was measured by response criteria of evaluation in solid tumors and safety was evaluated by common toxicity criteria of adverse events. The vaccine was safe and immunogenic at all doses levels. The most frequent adverse events related to vaccination were mild to moderate injection site reactions and flu-like symptoms. Vaccination induced specific anti-NeuGcGM3 immunoglobulin M and immunoglobulin G antibody responses in all patients. Disease control (objective response or stable disease) was obtained in 38.46% of patients. Global median overall survival was 20.20 months. Two patients achieved overall survival duration of about 4 and 5 years, respectively. The 900 µg dose resulted in overall survival duration of 19.40 months and was selected as the biological optimal dose.

Very small size proteoliposomes derived from Neisseria meningitidis: an effective adjuvant for antigen-specific cytotoxic T lymphocyte response stimulation under leukopenic conditions.

Leukopenia is a severe condition resulting from both pathological processes and some treatments, like chemotherapy in cancer patients. However, the activation of the patient immune system is required for the success of immunotherapeutic strategies, as cancer vaccines. In this regard, leukopenia constitutes a major hurdle to overcome, mainly due to the impairment of cytotoxic T lymphocyte (CTL) responses. Adjuvants are basic components of vaccine formulations, which might be useful to stimulate immunity under this immunosuppressed condition. To this aim, we tested the capacity of a novel nanoparticulated complex, very small size proteoliposomes (VSSP), to promote CTL even in a leukopenic scenario. Noteworthy, we observed that a VSSP-based OVA vaccine induced a normal antigen-specific CTL response in mice rendered leukopenia by the administration of high doses of the chemotherapeutic agent cyclophosphamide (CY), while under the same conditions the OVA antigen formulated in the TLR-3 agonist polyinosinic-polycytidylic acid (P(I:C)) was ineffective. Moreover, an appropriate combination of VSSP with the P(I:C) vaccine was able to restore the CD8(+) T cell effector function in leukopenic mice. VSSP induced not only a faster repopulation of immune cells in CY-receiving animals, but also enhanced the recovery of memory T lymphocytes and myeloid dendritic cells (DCs) while simultaneously abrogated the immunosuppressive capacity of myeloid-derived suppressor cells (MDSCs). Our results suggest that VSSP could be a particularly suitable immunomodulator to be used in CTL-promoting active immunotherapy strategies operating in severe immune compromised scenarios.

Bivalent binding by intermediate affinity of nimotuzumab: a contribution to explain antibody clinical profile.

Nimotuzumab is an EGFR-targeting antibody that has demonstrated encouraging clinical results in the absence of severe side-effects observed with other approved anti-EGFR antibodies. We investigated whether different clinical behavior of nimotuzumab is related to its bivalent/monovalent binding profile. Binding properties of nimotuzumab and cetuximab, the most development of anti-EGFR antibodies, were studied in vitro using chip surfaces and cells with varying EGFR expression levels. Experimental observations demonstrated that in contrast to cetuximab, the intrinsic properties of nimotuzumab required bivalent binding for stable attachment to the cellular surface, leading to nimotuzumab selectively binding to cells that express moderate to high EGFR expression levels. At these conditions, both antibodies bound bivalently, and accumulated to similar degrees. When EGFR density is low, nimotuzumab monovalent interaction was transient, whereas cetuximab continued to interact strongly with the receptors. We compared the in vitro anti-tumor efficacy of nimotuzumab and cetuximab. Cetuximab decreased the cell viability and induced apoptosis for all the tested cell lines, effects which did not depend on EGFR expression level. In contrast, nimotuzumab also provoked significant anti-cellular effects, but its anti-tumor capacity decreased together with EGFR expression level. Cetuximab Fab fragment was able to impact tumor cell survival, whereas nimotuzumab fragment totally lost this effect. Tumor-xenograft experiments using cells with a high EGFR expression revealed similar tumor growth inhibiting effects for both antibodies. This study suggests an explanation for nimotuzumab clinical profile, whereby anti-tumor activity is obtained in absence of severe toxicities due to its properties of bivalent binding to EGFR.

Inhibition of tumor-induced myeloid-derived suppressor cell function by a nanoparticulated adjuvant.

The interaction between cancer vaccine adjuvants and myeloid-derived suppressor cells (MDSCs) is currently poorly understood. Very small size proteoliposomes (VSSP) are a nanoparticulated adjuvant under investigation in clinical trials in patients with renal carcinoma, breast cancer, prostate cancer, and cervical intraepithelial neoplasia grade III. We found that VSSP adjuvant induced a significant splenomegaly due to accumulation of CD11b(+)Gr-1(+) cells. However, VSSP-derived MDSCs showed a reduced capacity to suppress both allogeneic and Ag-specific CTL response compared with that of tumor-induced MDSCs. Moreover, splenic MDSCs isolated from tumor-bearing mice treated with VSSP were phenotypically more similar to those isolated from VSSP-treated tumor-free mice and much less suppressive than tumor-induced MDSCs, both in vitro and in vivo. Furthermore, different from dendritic cell vaccination, inoculation of VSSP-based vaccine in EG.7-OVA tumor-bearing mice was sufficient to avoid tumor-induced tolerance and stimulate an immune response against OVA Ag, similar to that observed in tumor-free mice. This effect correlated with an accelerated differentiation of MDSCs into mature APCs that was promoted by VSSP. VSSP used as a cancer vaccine adjuvant might thus improve antitumor efficacy not only by stimulating a potent immune response against tumor Ags but also by reducing tumor-induced immunosuppression.

NGcGM3 ganglioside: a privileged target for cancer vaccines.

Active specific immunotherapy is a promising field in cancer research. N-glycolyl (NGc) gangliosides, and particularly NGcGM3, have received attention as a privileged target for cancer therapy. Many clinical trials have been performed with the anti-NGc-containing gangliosides anti-idiotype monoclonal antibody racotumomab (formerly known as 1E10) and the conjugated NGcGM3/VSSP vaccine for immunotherapy of melanoma, breast, and lung cancer. The present paper examines the role of NGc-gangliosides in tumor biology as well as the available preclinical and clinical data on these vaccine products. A brief discussion on the relevance of prioritization of cancer antigens in vaccine development is also included.

Direct validation of NGcGM3 ganglioside as a new target for cancer immunotherapy.

OBJECTIVE: The target concept means not only an aberrant expression of a particular molecule in tumour tissues but also evidence of a clear therapeutic advantage, as a consequence of immune-intervention, in an antigen-positive relevant tumour model. Since we reported the presence of NGcGM3 ganglioside in human breast tumours years ago and though Phase I clinical trials of a ganglioside containing vaccine have been conducted, a definitive direct validation of this peculiar molecule as target for cancer immunotherapy has remained unperformed. METHODS: Two animal models were used: leghorn chickens and C57BL/6 mice. The murine 3LL-D122 cell line, the derived subcutaneous tumours and metastatic lung lesions were processed for gangliosides identification. Active immunotherapy experiments in the 3LL-D122 spontaneous lung metastasis model were performed with NGcGM3/VSSP vaccine prepared by conjugation of NGcGM3 with the outer membrane proteins of Neisseria meningitides. RESULTS: The 3LL-D122 Lewis lung carcinoma results were consistent with an increased expression of NGcGM3 from primary tumours to metastatic lesions, as observed in human breast cancer samples. Both vaccines, prepared with synthetic or natural-source-derived ganglioside, showed similar anti-tumour and immunogenicity profiles. Finally, a clear involvement of NK1.1(+) cells and CD8(+) T cells in the anti-metastatic effect elicited by the vaccine was manifested. CONCLUSIONS: While 'proof of concept' Phase II and III clinical trials with the NGcGM3/VSSP vaccine in cancer patients are currently ongoing these results reasonably sustain the validation of this peculiar ganglioside as a novel target for cancer immunotherapy.

Differential influence of the tumour-specific non-human sialic acid containing GM3 ganglioside on CD4+CD25- effector and naturally occurring CD4+CD25+ regulatory T cells function.

Increasing evidences suggest that the aberrant expression of certain gangliosides on malignant cells could affect host's anti-tumour-specific immune responses. We have recently documented the relevance of the N-glycolylated variant of GM3 ganglioside (NGcGM3), a tumour-specific non-human sialic acid containing ganglioside, for tumour progression. However, evidences about the implication of host's immunity in NGcGM3-promoted cancer progression had not been obtained previously. In this work, we compared tumour growth of X63 myeloma cells pre-treated or not with an inhibitor of the glucosylceramide synthase enzyme, in wild or CD4+ T cell-depleted BALB/c mice. Results clearly showed a relationship between the agonistic effect of NGcGM3 in tumour growth and the presence of CD4+ T lymphocytes. For the first time, a description of a ganglioside-differential effect over purified CD4+CD25- and naturally occurring regulatory CD4+CD25+ T cells is provided. While NGcGM3 similarly down-modulated the CD4 expression in both cell populations, the inhibitory capacity of the CD4+CD25+ lymphocytes and their proliferation, induced by an anti-CD3 mAb and IL2, were not modified. In a different fashion, a reduction in proliferative capacity and a noteworthy secretion of anti-inflammatory cytokines were detected when CD4+CD25- T cells were cultured in the presence of NGcGM3. Considering the relevance of dendritic cells (DC) on primary activation of T cells, the effect of NGcGM3 over DC differentiation and TLR4-mediated maturation was also assessed. Our results indicate that NGcGM3 contributes to cancer progression mainly by influencing DC and CD4+CD25- T lymphocyte functions, rather than increasing the inhibitory capacity of naturally occurring regulatory T cells.

Immunization with a GM3 ganglioside nanoparticulated vaccine confers an effector CD8(+) T cells-mediated protection against melanoma B16 challenge.

Preventive immunotherapy is an attractive strategy for patients at a high risk of having cancer. The success of prophylactic cancer vaccines would depend on the selection of target antigens that are essential for tumour growth and progression. The overexpression of GM3 ganglioside in murine and human melanomas and its important role in tumour progression makes this self antigen a potential target for preventive immunotherapy of this neoplasm. We have previously shown that preventive administration of a GM3-based vaccine to C57BL/6 mice elicited the rejection of the GM3 positive-B16 melanoma cells in most of the animals. Despite the crucial role of cellular immune response in tumour protection, the involvement of T cells in anti-tumour immunity of ganglioside vaccines is not described. Here, we examined the mechanisms by which this immunogen confers tumour protection. We have found that induction of anti-GM3 IgG antibodies correlated with tumour protection. Surprisingly, CD8(+) T cells, but not NK1.1(+) cells, are required in the effector phase of the antitumour immune response. The depletion of CD4(+) T cells during immunization phase did not affect the anti-tumour activity. In addition, T cells from surviving-immunized animals secreted IFNgamma when were co-cultured with IFNalpha-treated B16 melanoma cells or DCs pulsed with melanoma extract. Paradoxically, in spite of the glycolipidic nature of this antigen, these findings demonstrate the direct involvement of the cellular immune response in the anti-tumour protection induced by a ganglioside-based vaccine.

T cells are crucial for the anti-metastatic effect of anti-epidermal growth factor receptor antibodies.

Experimental evidences supporting the epidermal growth factor receptor (EGFR) as an important molecule for tumor metastasis had been accumulated. Currently, anti-EGFR monoclonal antibodies (mAbs) constitute a promising approach for the treatment of patients with metastatic tumors. However, the mechanisms associated with the potent anti-metastatic effect of these mAbs have not been completely elucidated due to the lack of appropriate syngeneic preclinical models. In this paper, we have investigated the effects of 7A7, an antibody specific to murine EGFR, on the metastatic properties of D122 murine lung carcinoma. 7A7 mAb significantly impaired metastatic spread of D122 cells in C57BL/6 mice by direct anti-proliferative and pro-apoptotic effects on tumor metastasis. 7A7 mAb capacity to inhibit EGFR activation on D122 cells could contribute to its anti-metastatic effect. In addition, 7A7 mAb was able to induce in vitro antibody-dependent cell-mediated cytotoxicity on D122 cells. Interestingly, 7A7 mAb treatment increased the number of natural killer cells, T lymphocytes and dendritic cells infiltrating the metastatic sites. More strikingly, depletion of CD8(+) and CD4(+) T cells in vivo completely abrogated the 7A7 mAb anti-metastatic activity whereas function of natural killer cells was irrelevant. This study supports an in vivo role for T cell response in the mechanism of action of anti-EGFR mAbs, suggesting the induction of an adjuvant effect.

Simple multichannel system for the measurement of the net water flux across biological tissues.

This paper describes the development of a simple system for measurement of net water movement through biological membrane barriers. The system is based on the detection of a water meniscus inside a polyethylene tube, which reflects the water movement inside one hemichamber of a modified Ussing chamber containing a membrane barrier. The detection device consists of a commercial computer-controlled flat bed scanner and specifically developed software. This system allows one to perform a relatively high number of individual experiments per physical unit. It is a flexible and affordable device, which allows comparatively more information per unit to be obtained than previously described methods.