Study of a toxin-alkaline phosphatase conjugate for the development of an immunosensor for tetrodotoxin determination

This paper describes a direct competitive immunoenzymatic spectrophotometric assay (ELISA) for tetrodotoxin (TTX) determination and the adaptation of this method for use in an electrochemical assay format. The novelty of this work involves the use of the antigen labelled with alkaline phosphatase (AP); this conjugate was prepared in our laboratory as there is no commercially available conjugate of any kind for TTX. The new conjugate was characterized in terms of its affinity for the specific antibody as well as the residual concentration and the residual activity of the enzyme (AP) incorporated as label. The proposed method based on the new conjugate showed satisfactory results for TTX determination: for the spectrophotometric method the dynamic range was 4-15 ng mL(-1) with a limit of detection (LOD) of 2 ng mL(-1) (R=0.9247), whereas for the electrochemical protocol the dynamic range was 2-50 ng mL(-1) and the LOD was 1 ng mL(-1).

An electrochemical immunosensor for aflatoxin M1 determination in milk using screen-printed electrodes

The production and assembling of disposable electrochemical AFM1 immunosensors, which can combine the high selectivity of immunoanalysis with the ease of the electrochemical probes, has been carried out. Firstly immunoassay parameters such as amounts of antibody and labelled antigen, buffer and pH, length of time and temperature of each steps (precoating, coating, binding and competition steps) were evaluated and optimised in order to set up a spectrophotometric enzyme-linked immunosorbent assay (ELISA) procedure. This assay exhibited a working range between 30 and 160 ppt in a direct competitive format. Then electrochemical immunosensors were fabricated by immobilising the antibodies directly on the surface of screen-printed electrodes (SPEs), and allowing the competition to occur between free AFM1 and that conjugated with peroxidase (HRP) enzyme. The electrochemical technique chosen was the chronoamperometry, performed at -100 mV. Furthermore, studies of interference and matrix effects have been performed to evaluate the suitability of the developed immunosensors for the analysis of aflatoxin M1 directly in milk. Results have shown that using screen-printed electrodes aflatoxin M1 can be measured with a detection limit of 25 ppt and with a working range between 30 and 160 ppt. A comparison between the spectrophotometric and electrochemical procedure showed that a better detection limit and shorter analysis time could be achieved using electrochemical detection.

T-cell engineering by a chimeric T-cell receptor with antibody-type specificity for the HIV-1 gp120

Immune-based approaches of cell therapy against viral pathogens such as the human immunodeficiency virus type 1 (HIV-1) could be of primary importance for the control of this viral infection. Here, we designed a chimeric cell surface receptor (105TCR) to provide primary human T-lymphocytes with antibody-type specificity for the HIV-1 envelope glycoprotein. This receptor includes the single chain Fv domain of the neutralizing anti-gp120 human monoclonal antibody F105, CD8alpha hinge and the transmembrane and the cytoplasmic domains of TCRzeta. Our results show that 105TCR is expressed at the cellular surface and is capable of recognizing the HIV-1 envelope glycoprotein inducing highly efficient effector T-cell responses, including extracellular signal-regulated kinase phosphorylation and cytokine secretion. Moreover, human primary CD8+ T-lymphocytes transduced by oncoretroviral and lentiviral vectors containing the 105TCR gene are able to mediate in vitro-specific cytolysis of envelope-expressing cells and HIV-1-infected CD4+ T-lymphocytes. These findings suggest that 105TCR is particularly suited for in vivo efficacy studies.

Disposable immunosensor for the determination of domoic acid in shellfish

The construction of an electrochemical immunosensor coupled to differential pulse voltammetry (DPV) for the detection of domoic acid (DA), a neurotoxic aminoacid responsible for the human syndrome known as "Amnesic Shellfish Poisoning" (ASP), is proposed here. The method involves the use of disposable screen-printed electrodes (SPEs) for the immunosensor development based on a "competitive indirect test". Domoic acid conjugated to bovine serum albumin (BSA-DA) was coated onto the working electrode of the SPE, followed by incubation with sample (or standard toxin) and anti-DA antibody. An anti-goat IgG-alkaline phosphatase (AP) conjugate was used for signal generation. A spectrophotometric enzyme-linked immunosorbent assay (ELISA) was used in a preliminary phase of development, prior to transferring the assay to the SPEs. Results showed a detection limit equal to 5 ng/ml of toxin. The electrochemical system is simple and cost-effective due to the disposable nature of the SPEs, and the analysis time is 150 min, shorter than that for the spectrophotometric method. The suitability of the assay for DA quantification in mussels was also evaluated. Samples were spiked with DA before and after the sample treatment to study the extraction efficiency and the matrix effect, respectively. After treatment, samples were analysed using a 1:250 v/v dilution in PBS-M (phosphate saline buffer pH 7.4 + CH3OH 10%) to minimise the matrix effect and allow for the detection of 20 microg/g of DA in mussel tissue. This represents the maximum acceptable limit defined by the Food and Drug Administration [Compliance Programme 7303.842. Guidance Levels, Table 3, p. 248, http://www.fda.org]. The optimised ELISA systems were then used, in parallel with a conventional HPLC method, to detect and confirm DA in shellfish extract in order to verify the performance of the electrochemical system. Very good recoveries were obtained, demonstrating the suitability of the proposed assay for accurate determination of the DA concentration in mussel samples.

A novel biweekly multidrug regimen of gemcitabine, oxaliplatin, 5-fluorouracil (5-FU), and folinic acid (FA) in pretreated patients with advanced colorectal carcinoma

Previous results suggest that GEM affects 5-fluorouracil (5-FU) metabolism and pharmacokinetics in cancer patients, while combined with oxaliplatin, levo-folinic acid, and 5-FU (GOLF regimen), at doses achievable in cancer patients, determines high cytotoxic and proapoptotic antitumour activity in colon cancer cells in vitro. On these bases we designed a phase I-II clinical trial testing the GOLF regimen in patients with metastatic colorectal carcinoma, who had received at least a prior line of chemotherapy. In total, 29 patients (20 males and nine females) enrolled in the study received every 2 weeks, gemcitabine (patients #1-3 received 600 mg m(-2); patients # 4-6 received 850 mg m(-2); while patients # 7-29 received 1000 mg m(-2)) on the day 1, levo-folinic acid (100 mg m(-2)) on the days 1 and 2; 5-fluorouracil (400 mg m(-2)) in bolus injection, followed by a 22-h continuous infusion (800 mg m(-2)) on the days 1 and 2, and oxaliplatin (85 mg m(-2)), 6 h after the 5-FU bolus on day 2. The most frequent side effect was grade I-II haematological toxicity. In total, 28 patients were evaluable for response: three achieved a complete response, nine a partial response, 10 had a stable disease, and six progressed. The average time to progression and overall survival of the patients was, respectively, 7.26 and 22 months. Our GOLF combination is well tolerated and seems promising for the treatment of advanced colorectal cancer.

Glycosaminoglycan distribution in cartilage as determined by delayed gadolinium-enhanced MRI of cartilage (dGEMRIC): potential clinical applications

OBJECTIVE

We sought to describe a range of in vivo observations of glycosaminoglycan distribution in knee cartilage using the delayed gadolinium-enhanced MRI of cartilage technique.

CONCLUSION

The index of glycosaminoglycan distribution, T1(Gd), can exceed 500 msec (denoting high glycosaminoglycan) or can be less than 300 msec, with focal areas as low as 240 msec. Compartmental differences, as well as focal defects within the knee, were observed in patients who had sustained injuries to the ligaments and menisci of the knee or who had chronic osteoarthritis. Overall, these results suggest the need for further research into the biochemical changes seen during disease progression and the effects of therapeutic interventions.

Production of antibodies and development of highly sensitive formats of enzyme immunoassay for saxitoxin analysis

In this paper the production of antibodies against saxitoxin (STX) is described, as is the optimization and comparison of two competitive ELISA formats (direct and indirect) for the detection of this toxin. Tests were performed in a 96-well microplate using the toxin-specific polyclonal antibodies produced in our laboratory, obtained from rabbits immunized with saxitoxin-keyhole limpet hemocyanin (STX-KLH). In indirect ELISA format saxitoxin, conjugated to bovine serum albumin (STX-BSA) was coated onto the microtitre plate and incubated with standard toxin and anti-STX antibody. A goat anti-rabbit IgG Peroxidase conjugate was used to enable detection. In the direct ELISA format, STX standard, STX conjugate to horseradish peroxidase (STX-HRP), and enzyme substrate/chromogen solution were sequentially added to the microplate after antibody coating.Results showed the saxitoxin detection limit to be 3 and 10 pg mL(-1) for direct and indirect ELISA formats, respectively. The suitability of the assay for quantification of saxitoxin in mussels was also studied. Samples were spiked with saxitoxin before and after sample treatment to study the extraction efficiency and matrix effect, respectively. After treatment, samples were analysed at 1:1000 v/v dilution in PBS to minimize the matrix effect and to detect the regulatory limit of 40-80 micro g saxitoxin per 100 g mussels as stipulated by the Food and Drug Administration. The efficiency of extraction of saxitoxin was from 72 to 102%. These data were confirmed by liquid chromatography coupled with fluorimetric detection, the technique currently used for quantitative determination of toxins in seafood.

Markers of cardiac oxidative stress and altered morphology after intraperitoneal cocaine injection in a rat model

This study was designed to assess the parameters of myocardial oxidative stress and related cardiac morphological changes following intraperitoneal cocaine exposure in rats. The cardiac levels of reduced glutathione(GSH), oxidised glutathione(GSSG), ascorbic acid (AA), and the production of malondialdehyde (MDA) were measured, as well as the variations of activity in the enzyme systems involved in cell antioxidant defence, glutathione peroxidase (GSH-Px), glutathione reductase (GR) and superoxide dismutase (SOD). After chronic cocaine administration for 30 days GSH was significantly depleted in the heart from 30 min (P < 0.001) to 24 h (P < 0.001) after exposure, and GSSG was increased for a similar time (P < 0.05 at 30 min and P < 0.01 at 24 h). SOD increased during the first hour (P < 0.001), GR and GSH-Px both increased from 30 min to 24 h, and these increases were statistically significant (P < 0.01 and P < 0.001 at 30 min and P < 0.01 and P < 0.001 at 24 h, respectively). The AA levels increased after 1 h (P < 0.01), remaining significantly so for 24 h (P < 0.001) and MDA increased from 30 min to 24 h, all values being highly significant (P < 0.001). The body weight was significantly (P < 0.001) reduced in both cocaine groups (40 mg/kg x 30 days and 40 mg/kg x 10 days + 60 mg/kg x 20 days). The heart weight (P < 0.01) and its percentage of the body weight (P < 0.001) were significantly higher in these two groups than in the controls. Similarly, in the noradrenaline 4 mg/ kg x 30 days group, the body weight was significantly (P < 0.001) reduced and the heart weight (P < 0.01) and its percentage of body weight (P < 0.001) were significantly higher than in the controls. In comparing the cocaine and noradrenaline experiments, the frequency and extent of cardiac lesions obtained with 40 mg/kg x 10 days + 60 mg/kg x 20 days of cocaine were similar to those with 8 mg/kg of noradrenaline at 24 h. In this experimental model, cocaine administration compromised the antioxidant defence system of the heart associated with a significant increase of heart weight and the percentage of body weight.

Tumour-associated antigen (TAA)-specific cytotoxic T cell (CTL) response in vitro and in a mouse model, induced by TAA-plasmids delivered by influenza virosomes

We investigated influenza virosomes as a TAA-gene delivery system for use in TAA-directed anti-cancer vaccine therapy. An engineered plasmid (GC90) expressing the parathyroid hormone-related peptide (PTH-rP), a protein secreted by prostate and lung carcinoma cells, was included in influenza virosomes (GC90V). The ability of GC90V to elicit a PTH-rP-specific cytotoxic T cell (CTL) response was demonstrated in BALB/c mice immunised with intranasal (i.n.) GC90V+/-adjuvant subcutaneous (s.c.) interleukin-2 (IL-2). A PTH-rP-specific CTL response with antitumour activity was also demonstrated in human peripheral blood mononuclear cells (PBMC) stimulated in vitro with GC90V infected autologous dendritic cells (DC). These results provide a rationale for investigating GC90V in clinical trials of anticancer vaccine therapy.

A parathyroid-hormone-related-protein (PTH-rP)-specific cytotoxic T cell response induced by in vitro stimulation of tumour-infiltrating lymphocytes derived from prostate cancer metastases, with epitope peptide-loaded autologous dendritic cells and low-dose IL-2

Bone metastases are one of the most common events in patients with prostate carcinoma. PTH-rP, a protein produced by prostate carcinoma and other epithelial cancers, is a key agent for the development of bone metastases. A PTH-rP-derived peptide, designated PTR-4 was identified, which is capable to bind HLA-A2.1 molecules and to generate PTH-rP-specific cytotoxic T cell (CTL) lines from healthy HLA-A2.1(+) individual peripheral-blood-mononuclear-cells (PBMC). In this model, we investigated the in vitro possibility of generating an efficient PTH-rP specific CTL response by cyclical stimulations with IL-2 and PTR-4 peptide-pulsed autologous dendritic cells (DC), of HLA-A2.1(+) tumour infiltrating lymphocytes (TIL) derived from a patient with metastatic prostate carcinoma. A T cell line generated in this way (called TM-PTR-4) had a CD3(+), CD5(+), CD4(-), CD8(+), CD45(Ro+), CD56(-) immunophenotype and a HLA-A2.1 restricted cytotoxic activity to PTR-4-peptide pulsed CIR-A2 (HLA-A2.1(+)) target cells, PTH-rP(+)/HLA-A2.1(+) CIR-A2 transfected with PTH-rP gene, prostate carcinoma LNCaP cells, and autologous metastatic prostate cancer cells (M-CaP). These lymphocytes were not cytotoxic to HLA-A2.1(+) targets not producing PTH-rP, such as peptide-unpulsed CIR-A2 and colon carcinoma SW-1463, cell lines. Our results provide evidence that PTR-4 peptide-pulsed autologous DC may break the tolerance of human TIL against the autologous tumour by inducing a PTH-rP-specific CTL immune reaction. In conclusion PTR-4 peptide-pulsed autologous DC may be a promising approach for vaccine-therapy and antigen-specific CTL adoptive immunotherapy of hormone-resistant prostrate cancer.

In vitro generation of cytotoxic T lymphocytes against HLA-A2.1-restricted peptides derived from human thymidylate synthase

5-Fluorouracil (5-FU) is a pyrimidine antimetabolite active against colorectal carcinoma and other malignancies of the digestive tract. Over-expression or mutation of thymidylate synthase (TS), the target enzyme of the 5-FU metabolite, 5-fluorodeoxyuridine monophosphate, is strictly correlated with cancer cell resistance to 5-FU. On this basis we investigated whether TS is a potential target for active specific immunotherapy of human colon carcinoma, which acquires resistance to 5-FU. Three TS-derived epitope peptides which fit defined amino acid consensus motifs for HLA-A2.1 binding were synthesized and investigated for their ability to induce human TS-specific cytotoxic T cell (CTL) responses in vitro. CTL lines specific for each peptide were established by stimulating peripheral blood mononuclear cells (PBMC) from an HLA-A2.1+ healthy donor with autologous dendritic cells loaded with TS peptide. Specific CTL lines showed HLA-A2.1-restricted cytotoxicity in vitro to HLA-A2.1+ target cells pulsed with the specific TS peptide and to HLA-class I matching colon carcinoma target cells over-expressing TS enzyme after exposure to 5-FU. Recognition by CTL lines suggests that these TS peptides may be potential candidates for use in a peptide-based vaccine against 5-FU resistant colon carcinoma.

Recruitment of dendritic cells and enhanced antigen-specific immune reactivity in cancer patients treated with hr-GM-CSF (Molgramostim) and hr-IL-2. results from a phase Ib clinical trial

Experimental findings suggest that granulocyte-monocyte-colony stimulating factor (GM-CSF) synergistically interacts with interleukin-2 (IL-2) in generating an efficient antigen-specific immune response. We evaluated the toxicity, antitumour activity and immunobiological effects of human recombinant (hr)-GM-CSF and hr-IL-2 in 25 cancer patients who subcutaneously (s.c.) received hr-GM-CSF 150 microg/day for 5 days, followed by hrIL-2 s.c. for 10 days and 15 days rest. Two of the most common side-effects were bone pain and fever. Of the 24 patients evaluable for response, 3 achieved partial remission, 13 experienced stable disease, and 8 progressed. Cytokine treatment increased the number of monocytes, dendritic cells (DC), and lymphocytes (memory T cells) in the peripheral blood and enhanced the antigen-specific immunoreactivity of these patients. Our results show that the hr-GM-CSF and hr-IL-2 combination is active and well tolerated. Its biological activity may support tumour associated antigen (TAA)-specific anticancer immunotherapy by increasing antigen presenting cell (APC) activity and T cell immune competence in vivo.

Cloning of PC3B, a novel member of the PC3/BTG/TOB family of growth inhibitory genes, highly expressed in the olfactory epithelium

We identified in the EST database murine and human sequences similar, but not identical, to the members of the PC3/BTG/TOB family of cell cycle inhibitors. A conserved domain (aa 50-68) of the PC3 protein, the prototype member of the family, was used as a query. That domain has been shown by us to be necessary for the antiproliferative activity of PC3. A murine EST clone and a highly homologous human EST clone, containing the entire ORF, were chosen for sequencing. Comparison to databases and a phylogenetic tree analysis indicated that these EST clones are the mouse and human homologues of a gene that represents a novel member of the PC3/BTG/TOB family. This gene, named PC3B, is endowed with marked antiproliferative activity, being able to induce G(1) arrest, and is highly expressed in testis, in oocyte, and in preimplantation embryos. Analysis of its expression during murine development indicated a specific localization in the olfactory epithelium at midgestation, suggesting that PC3B might be involved in the differentiation of this neuronal structure. Human PC3B mapped to chromosome 11q23, as indicated by radiation hybrid analysis.

Arrest of G(1)-S progression by the p53-inducible gene PC3 is Rb dependent and relies on the inhibition of cyclin D1 transcription

The p53-inducible gene PC3 (TIS21, BTG2) is endowed with antiproliferative activity. Here we report that expression of PC3 in cycling cells induced accumulation of hypophosphorylated, growth-inhibitory forms of pRb and led to G(1) arrest. This latter was not observed in cells with genetic disruption of the Rb gene, indicating that the PC3-mediated G(1) arrest was Rb dependent. Furthermore, (i) the arrest of G(1)-S transition exerted by PC3 was completely rescued by coexpression of cyclin D1 but not by that of cyclin A or E; (ii) expression of PC3 caused a significant down-regulation of cyclin D1 protein levels, also in Rb-defective cells, accompanied by inhibition of CDK4 activity in vivo; and (iii) the removal from the PC3 molecule of residues 50 to 68, a conserved domain of the PC3/BTG/Tob gene family, which we term GR, led to a loss of the inhibition of proliferation as well as of the down-regulation of cyclin D1 levels. These data point to cyclin D1 down-regulation as the main factor responsible for the growth inhibition by PC3. Such an effect was associated with a decrease of cyclin D1 transcript and of cyclin D1 promoter activity, whereas no effect of PC3 was observed on cyclin D1 protein stability. Taken together, these findings indicate that PC3 impairs G(1)-S transition by inhibiting pRb function in consequence of a reduction of cyclin D1 levels and that PC3 acts, either directly or indirectly, as a transcriptional regulator of cyclin D1.

Rapid antibody biosensor assays for environmental analysis

Traditionally, biosensor development has focused on molecules with a defined metabolic role that can be exploited by enzyme-based systems. Antibodies have the ability to move beyond this range of analytes, and are particularly useful in detecting small, hapten molecules. Electrochemically based biosensor developments have been less fruitful in this regard, as enzyme labelling is required, and such assays require the separation from bound and unbound species. These separations and the removal of background signals result in the increased complexity of the assay format, making it unsuitable for rapid sensor analysis. We have developed an electrochemical sensor based on antibodies that does not require the separation of bound and unbound molecules in a competition immunoassay format. This removes the need for several washing and separation steps as is normally employed in this type of assay. This allows single-step immunoassays to be performed using this system, and also allows for the real-time monitoring of antibody-antigen interactions. We have shown that such assays are possible in both batch and flow-injection formats and we are currently developing an assay for the pesticide atrazine. Tentative results show that analysis with this system is possible in the p.p.m. to p.p.b. range.

Isolation and characterisation of a ropy Lactobacillus strain producing the exopolysaccharide kefiran

A capsular-polysaccharide-producing strain, LM-17, was isolated from kefir grains and was identified as a slime-forming, rod-shaped Lactobacillus. According to 1H- and 13C-NMR spectral data, the exopolysaccharide produced by the isolated bacterial strain is identical to the glucogalactan extracted from kefir grains and therefore known as kefiran. The kefiran produced was characterised by means of viscosity, optical rotatory power, circular dichroism and IR spectral measurements. A batch procedure was set up for the culture and extraction of the exopolysaccharide in laboratory conditions, resulting in a yield of 2 g/l purified kefiran from the culture supernatant of the LM-17 strain.

High-performance liquid chromatography of flufenamic acid in rat plasma

A simple high-performance liquid chromatographic (HPLC) method for the determination of flufenamic acid in rat plasma is described. After liquid-liquid extraction, the drug is separated by HPLC on a 5-microns octadecylsilica column (Nucleosil C18) with ultraviolet detection at 280 nm. Linear calibration graphs for flufenamic acid were constructed from 0.5 to 15 micrograms/ml. The method has been applied to a pharmacokinetic study in animals.