Current strategies to prevent or treat human papillomavirus type 16 (HPV-16) infection are promising, but remain costly. More economical but efficient vaccines are thus needed. In this study, we evaluated the protective effects of mucosally coadministered live Lactococcus lactis strains expressing cell wall-anchored E7 Ag and a secreted form of IL-12 to treat HPV-16-induced tumors in a murine model. When challenged with lethal levels of tumor cell line TC-1 expressing E7, immunized mice showed full prevention of TC-1-induced tumors, even after a second challenge, suggesting that this prophylactic immunization can provide long-lasting immunity. Therapeutic immunization with L. lactis recombinant strains, i.e., 7 days after TC-1 injection, induced regression of palpable tumors in treated mice. The antitumor effects of vaccination occurred through a CTL response, which is CD4+ and CD8+ dependent. Furthermore, immunized mice developed an E7-specific mucosal immune response. These preclinical results suggest the feasibility of the low-cost mucosal vaccination and/or immunotherapy strategies against HPV-related cervical cancer in humans.

BackgroundColloidal silver has been used as an antimicrobial and disinfectant agent. However, there is scarce information on its antitumor potential. The aim of this study was to determine if colloidal silver had cytotoxic effects on MCF-7 breast cancer cells and its mechanism of cell death.MethodsMCF-7 breast cancer cells were treated with colloidal silver (ranged from 1.75 to 17.5 ng/mL) for 5 h at 37°C and 5% CO2 atmosphere. Cell Viability was evaluated by trypan blue exclusion method and the mechanism of cell death through detection of mono-oligonucleosomes using an ELISA kit and TUNEL assay. The production of NO, LDH, and Gpx, SOD, CAT, and Total antioxidant activities were evaluated by colorimetric assays.ResultsColloidal silver had dose-dependent cytotoxic effect in MCF-7 breast cancer cells through induction of apoptosis, shown an LD50 (3.5 ng/mL) and LD100 (14 ng/mL) (*P < 0.05), significantly decreased LDH (*P < 0.05) and significantly increased SOD (*P < 0.05) activities. However, the NO production, and Gpx, CAT, and Total antioxidant activities were not affected in MCF-7 breast cancer cells. PBMC were not altered by colloidal silver.ConclusionsThe present results showed that colloidal silver might be a potential alternative agent for human breast cancer therapy.

Interleukin-12 (IL-12), a heterodimeric cytokine, plays an important role in cellular immunity to several bacterial, viral, and parasitic infections and has adjuvant activity when it is codelivered with DNA vaccines. IL-12 has also been used with success in cancer immunotherapy treatments. However, systemic IL-12 therapy has been limited by high levels of toxicity. We describe here inducible expression and secretion of IL-12 in the food-grade lactic acid bacterium Lactococcus lactis. IL-12 was expressed as two separate polypeptides (p35-p40) or as a single recombinant polypeptide (scIL-12). The biological activity of IL-12 produced by the recombinant L. lactis strain was confirmed in vitro by its ability to induce gamma interferon (IFN-␥) production by mouse splenocytes. Local administration of IL-12-producing strains at the intranasal mucosal surface resulted in IFN-␥ production in mice. The activity was greater with the single polypeptide scIL-12. An antigen-specific cellular response (i.e., secretion of Th1 cytokines, IL-2, and IFN-␥) elicited by a recombinant L. lactis strain displaying a cell wall-anchored human papillomavirus type 16 E7 antigen was dramatically increased by coadministration with an L. lactis strain secreting IL-12 protein. Our data show that IL-12 is produced and secreted in an active form by L. lactis and that the strategy which we describe can be used to enhance an antigen-specific immune response and to stimulate local mucosal immunity.

Genital human Papillomavirus infection is common and only a minor fraction of infected subjects develop progressing cervical epithelial lesions or cancer. Bypassing local immune responses is important for the development of cervical cancer. In this work we determined the cytokine pattern in samples from patients with cervical cancer. Thus, we examined the local mRNA expression profile of helper T cell type 1 (Th1), Th2, and Th3 cytokines in HPV-positive cervical cancer biopsies by reverse transcription-polymerase chain reaction. Our data indicate that 80% of the tumors expressed low levels of CD4 mRNA, with all of them expressing higher CD8 mRNA levels. Most tumors expressed interleukin (IL)-4 and IL-10 mRNAs and, most importantly, all of them expressed transforming growth factor (TGF)-beta1 and interferon gamma mRNA. None of the tumors studied expressed IL-12, IL-6, or tumor necrosis factor (TNF) mRNA. Immunohistochemical analysis identified IL-10 only in tumor cells and koilocytic cells, but not in tumor-infiltrating lymphocytes, suggesting that IL-10-producing cells are those transformed by HPV. We found a correlation between immunostaining for IL-10 protein and the level of IL-10 mRNA expression. Moreover, supernatants from HPV-transformed cell cultures contained IL-10 and TGF- beta1. Our findings indicate a predominant expression of immunosuppressive cytokines, which might help downregulate tumor-specific immune responses in the microenvironment of the tumor. This information may be useful for cervical cancer immunotherapies or for therapeutic vaccine design against Human Papillomavirus.

Human papillomavirus type 16 (HPV-16) is the major causative agent of cervical cancer. To date, vaccine strategies against HPV-16 are based on the ability of the E7 oncoprotein to elicit an immune response against this virus. In this study, the use of an inducible or a constitutive system to produce the HPV-16 E7 protein in Lactococcus lactis, a non-pathogenic and non-invasive Gram-positive bacterium, was compared. The highest E7 production was obtained with the inducible system. When mice were immunized intranasally with recombinant lactococci expressing either inducible or constitutive E7, an antigen-specific cellular response (i.e. secretion of IL2 and IFN-ª cytokines) was evoked and was substantially higher in mice receiving L. lactis expressing E7 with the inducible system. As bacterial antigen location may influence the immune response, recombinant L. lactis strains that produced E7 in three cellular locations, intracellular, secreted or cell-wall-anchored were evaluated. The highest immune response was elicited by administration of L. lactis producing an inducible cell-wall-anchored form of E7 protein. These promising results represent a step towards the development of a new, safe mucosal vector to treat HPV-related cervical cancer. INTRODUCTIONEpidemiological data have clearly shown that human papillomavirus type 16 (HPV-16) infection is the main aetiological factor for cervical cancer (CxCa) (Furumoto & Irahara, 2002). Worldwide, $400 000 women die annually from CxCa (Parkin et al., 1999). A prophylactic and/or therapeutic vaccine against this virus is thus a priority to prevent or to treat, respectively, CxCa. A prophylactic vaccine based on highly purified virus-like particles has recently been successfully used in trials in women, with a significant reduction observed in the incidence of both HPV-16 infection and related CxCa (Koutsky et al., 2002). However, such vaccines could probably not be used therapeutically in alreadyinfected patients because the virion capsid proteins are not detected in CxCa. The HPV-16 E7 protein, constitutively produced in cervical carcinomas, is required for the transformation process (Baker et al., 1987;Bedell et al., 1987;Dyson et al., 1989;Tanaka et al., 1989) and is considered a good antigen candidate for the development of a therapeutic vaccine against CxCa.Several studies have investigated the use of bacteria as E7 antigen delivery vehicles to elicit an immune response against HPV-16. In these studies, the vectors used were attenuated strains of pathogenic bacteria such as Salmonella and Mycobacterium spp. (Londoño et al., 1996; Jabbar et al., 2000). Although these recombinant strains elicited immune responses, invasiveness of the vectors and risks of reversion to pathogenicity limit their use in vulnerable groups such as immunocompromised patients or children. There is thus a need for the development of a new generation of safe delivery vehicles.Lactic acid bacteria (LAB) are promising candidates as safe vehicles for in vivo delivery of antigens. Compared with att...

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The human papillomavirus type-16 (HPV-16) E7 protein is considered a major viral oncoprotein involved in cervical cancer (CxCa) and a potential candidate for the development of a vaccine against this neoplasia. Here, two lactic acid bacteria (the model one Lactococcus lactis and a probiotic one Lactobacillus plantarum) were engineered to deliver an E7 mutant protein (E7mm), which has a reduced transforming activity and consequently, could fit better to therapeutic use in humans than the native form of E7. An efficient cell-surface display of E7mm was obtained in L. lactis using an expression cassette encoding a precursor composed of (i) the signal peptide and the first 15 amino acids of the mature part of the lactococcal Usp45 protein; (ii) E7mm and (iii) the cell-wall anchor of the Streptococcus pyogenes M6 protein (CWA(M6)). This hybrid precursor was produced but not cell-wall anchored in Lb. plantarum. We thus replaced CWA(M6) by the cell-wall anchor of a Lb. plantarum protein which allows an efficient cell-wall anchoring of E7mm in this bacterium. The E7mm production and cell-surface display in both L. lactis and a probiotic bacterium, Lb. plantarum, represent one more step towards the development of a safe and effective treatment against CxCa.

We investigated the potential of a rapid colorimetric microassay based on the reduction of dimethylthiazoldiphenyltetrazolium bromide (MTT) for determining the growth of Mycobacterium avium-M. intracellulare complex (MAC) and MICs of clofazimine, resorcinomycin A, and the quinolone PD 127391 against MAC. The reduction of MTT was directly proportional to the number of viable bacteria. A comparison of the MTT reduction test with the [ 3 H]glycerol uptake assay showed the former to possess higher analytical sensitivity for detecting MAC growth in microtiter plates. The MTT reduction test avoids the use of radioisotopes and costly material and equipment; it is reliable, reproducible, and convenient for rapid routine susceptibility testing of MAC.