Antineoplastic chemotherapeutic agents may indirectly activate dendritic cells (DCs) by inducing the release of “danger” signals from dying tumor cells. Whereas the direct cytotoxic or inhibitory effect of conventional chemotherapy on DCs has been reported, modulation of DC function by chemotherapeutic agents in low noncytotoxic concentrations has not yet been investigated. We have tested the effects of different classes of antineoplastic chemotherapeutic agents used in low noncytotoxic concentrations on the Ag-presenting function of DCs. We revealed that paclitaxel, doxorubicin, mitomycin C, and methotrexate up-regulated the ability of DCs to present Ags to Ag-specific T cells. Stimulation of DC function was associated with the up-regulation of expression of Ag-processing machinery components and costimulatory molecules on DCs, as well as increased IL-12p70 expression. However, the ability of DCs treated with paclitaxel, methotrexate, doxorubicin, and vinblastine to increase Ag presentation to Ag-specific T cells was abolished in DCs generated from IL-12 knockout mice, indicating that up-regulation of Ag presentation by DCs is IL-12-dependent and mediated by the autocrine or paracrine mechanisms. At the same time, IL-12 knockout and wild-type DCs demonstrated similar capacity to up-regulate OVA presentation after their pretreatment with low concentrations of mitomycin C and vincristine, suggesting that these agents do not utilize IL-12-mediated pathways in DCs for stimulating Ag presentation. These findings reveal a new mechanism of immunopotentiating activity of chemotherapeutic agents—a direct immunostimulatory effect on DCs (chemomodulation)—and thus provide a strong rationale for further assessment of low-dose chemotherapy given with DC vaccines for cancer treatment.

The dose-delivery schedule of conventional chemotherapy, which determines its efficacy and toxicity, is based on the maximum tolerated dose. This strategy has lead to cure and disease control in a significant number of patients but is associated with significant short-term and long-term toxicity. Recent data demonstrate that moderately low-dose chemotherapy may be efficiently combined with immunotherapy, particularly with dendritic cell (DC) vaccines, to improve the overall therapeutic efficacy. However, the direct effects of low and ultra-low concentrations on DCs are still unknown. Here we characterized the effects of low noncytotoxic concentrations of different classes of chemotherapeutic agents on human DCs in vitro. DCs treated with antimicrotubule agents vincristine, vinblastine, and paclitaxel or with antimetabolites 5-aza-2-deoxycytidine and methotrexate, showed increased expression of CD83 and CD40 molecules. Expression of CD80 on DCs was also stimulated by vinblastine, paclitaxel, azacytidine, methotrexate, and mitomycin C used in low nontoxic concentrations. Furthermore, 5-aza-2-deoxycytidine, methotrexate, and mitomycin C increased the ability of human DCs to stimulate proliferation of allogeneic T lymphocytes. Thus, our data demonstrate for the first time that in low noncytotoxic concentrations chemotherapeutic agents do not induce apoptosis of DCs, but directly enhance DC maturation and function. This suggests that modulation of human DCs by noncytotoxic concentrations of antineoplastic drugs, i.e. chemomodulation, might represent a novel approach for up-regulation of functional activity of resident DCs in the tumor microenvironment or improving the efficacy of DCs prepared ex vivo for subsequent vaccinations.

Salmonella, one of the most important pathogens transmitted by food, especially poultry, has the ability to form biofilms on surfaces. Its adhesion can be influenced by different physicochemical properties of these surfaces, while Salmonella uses fimbriae and produces cellulose as the main matrix components of biofilms. Their synthesis is co-regulated by a LuxR-type regulator, the agfD (aggregative fimbriae, curli), and adrA genes, respectively. Thus, this study investigated the production of biofilm by Salmonella spp. isolated from raw poultry (breast fillet), purchased in Botucatu, Sao Paulo, Brazil, on glass, polyvinyl chloride, and stainless steel at different temperatures (16°, 20°, 28°, and 35°C). We analyzed the frequency of the agfD and adrA genes and the rdar morphotype at 28°C and 35°C in isolated strains. We found Salmonella in 112 of 240 poultry samples (46.7%), and 62 strains previously isolated from the same kind of food were included in the study on biofilm development, gene expression, and rdar morphotype. All of them were positive for both genes, and 98.3% were able to produce biofilm in at least one temperature. The rates of rdar morphotype at 28°C and at 35°C were 55.2% (96 strains) and 2.3% (4 strains), respectively. Glass was the best material to avoid biofilm production, while Salmonella grew even at 16°C on stainless steel. These results point out the need for more effective sanitizing processes in the slaughter plants in order to avoid the permanence of these bacteria in food and eventual human foodborne diseases.

We have recently reported that chemotherapeutic agents in ultra low noncytotoxic concentrations may block the ability of tumor cells to suppress functional activation of dendritic cells (DCs). HCT-116 human colon cancer cells were treated with 0.5 nM paclitaxel (PAC) or 2 nM doxorubicin (DOX) with the aim of defining the immunogenic changes induced by ultra low noncytotoxic concentrations of antineoplastic chemotherapeutic agents. Genetic alterations were screened by DNA microarray that revealed increased expression of genes involved in antigen processing and presentation, including the heat-shock protein, calmodulin, and proteasome 26 genes. As the proteins encoded by these genes are involved in the cytosolic route of antigen processing machinery, we next evaluated whether PAC and DOX in noncytotoxic concentrations changed expression of MHC class I antigen processing machinery (APM) components in three different colon cancer cell lines. Our results showed that PAC and DOX increased the intracellular expression of APM proteins, including calmodulin, LMP2, LMP7, TAP1 and tapasin. The biological significance of modulation of antigen processing and presentation proteins in tumor cells by ultra low nontoxic concentrations of chemotherapeutic drugs was revealed when non-treated and treated tumor cells were used as a source of tumor antigens for the generation of tumor-specific cytotoxic T cells (CTLs) in vitro. We demonstrated that (i) DCs that engulf tumor cells pretreated with noncytotoxic concentrations of chemotherapeutic agents induced CTLs with a higher cytotoxic potential than DCs loaded with nontreated tumor cells, and (ii) CTLs induced by tumor lysate-pulsed DCs killed live tumor cells more efficiently if these tumor cells were pretreated with noncytotoxic concentrations of chemotherapeutic drugs. These results demonstrate that chemomodulation of human tumor cells with noncytotoxic concentrations of chemotherapeutic agents increases tumor immunogenicity and results in the generation of more efficient DC vaccines and CTLs, which can be used for cell-based anticancer immunotherapies.

In this study we investigated the effect of beta-glucan derived from Saccharomyces cerevisiae on fungicidal activity, cytokine production and natural killer activity. Spleen and peritoneal cells from female C57BL/6 mice, previously injected (24 or 48 h) with 20 or 100 microg of glucan by i.p. route, were assayed. In vivo beta-glucan administration primed spleen cells for a higher production of IL-12 and TNF-alpha when S. aureus was used as a stimulus. In addition, beta-glucan increased NK spleen cells activity against YAC target cells. Some immunomodulatory activities not yet described for beta-glucan were observed in this work.