The future for electrocoagulation as a localised water treatment technology.

Electrocoagulation is an electrochemical method of treating polluted water whereby sacrificial anodes corrode to release active coagulant precursors (usually aluminium or iron cations) into solution. Accompanying electrolytic reactions evolve gas (usually as hydrogen bubbles) at the cathode. Electrocoagulation has a long history as a water treatment technology having been employed to remove a wide range of pollutants. However electrocoagulation has never become accepted as a 'mainstream' water treatment technology. The lack of a systematic approach to electrocoagulation reactor design/operation and the issue of electrode reliability (particularly passivation of the electrodes over time) have limited its implementation. However recent technical improvements combined with a growing need for small-scale decentralised water treatment facilities have led to a re-evaluation of electrocoagulation. Starting with a review of electrocoagulation reactor design/operation, this article examines and identifies a conceptual framework for electrocoagulation that focuses on the interactions between electrochemistry, coagulation and flotation. In addition detailed experimental data are provided from a batch reactor system removing suspended solids together with a mathematical analysis based on the 'white water' model for the dissolved air flotation process. Current density is identified as the key operational parameter influencing which pollutant removal mechanism dominates. The conclusion is drawn that electrocoagulation has a future as a decentralised water treatment technology. A conceptual framework is presented for future research directed towards a more mechanistic understanding of the process.

Large-scale expansion of cytomegalovirus-specific cytotoxic T cells in suspension culture.

Clinical trials in recent years involving the adoptive transfer of antigen-specific cytotoxic T lymphocytes (CTL) have shown promise in restoring immunity against viral infection and reducing tumor burden in patients with solid and hematological malignancies. However, the large cell number required to achieve efficacy, 10(9) to 10(11), makes routine application of adoptive immunotherapy impractical. Investigation into new methods of CTL expansion may be useful in addressing this problem. Use of stirred suspension bioreactors are one such method that may allow large-scale T-cell expansion. Suspension cultures offer advantages over conventional static culture methods, including providing a homogeneous culture environment, and the potential for optimization and control of culture conditions. We generated cytomegalovirus (CMV)-specific CTL and investigated the potential of stirred bioreactor systems for expansion of large cell numbers. We found that CTL can be readily expanded ( > 200-fold) from cryopreserved stocks by nonspecific stimulation in the presence of allogeneic feeder cells and interleukin-2 (IL-2). Activated CTL inoculated into either suspension or static cultures could be subsequently expanded tenfold, and showed similar growth kinetics and metabolism independent of the culture vessel used. Furthermore, CTL remained specific for CMVpp65 peptide through the expansion phases, as demonstrated by pp65-tetramer staining ( > 95% tetramer(+)) and cytotoxicity assays. This study indicates that suspension reactor systems may be useful in large-scale expansion of antigen-specific CTL lines or clones, and may facilitate the advancement of routine adoptive immunotherapy.

Rapid, large-scale generation of highly pure cytomegalovirus-specific cytotoxic T cells for adoptive immunotherapy.

Adoptive transfer of donor-derived cytomegalovirus (CMV)-specific cytotoxic T cell (CTL) clones can restore immunity in allogeneic stem cell transplant recipients, providing protection against CMV disease. Current methods for selecting and expanding CMV-specific T cell clones are technically difficult, making adoptive T cell therapy impractical for routine clinical use. In this study, we describe a method for ex vivo generation and expansion of high-purity CMV-specific CTL using peptide-pulsed dendritic cells as antigen-presenting cells. Generation of CMV-specific CTL in numbers sufficient for clinical use in the time span of 4 weeks was accomplished in 6 of 8 CMV-seropositive donors. Examination of pp65 specificity by HLA/peptide tetramer staining demonstrated that a purity of greater than 95% peptide-specific cells could be obtained after two weekly stimulations and retained after further expansion for 3-4 weeks. Median expansion of total cell number was greater than 500-fold and expansion of peptide-specific CTL by tetramer staining was greater than 1.7 x 10(5)-fold. Four weeks after initiating CTL culture, we were able to generate greater than 10(9) total cells that specifically lysed target cells loaded with CMV peptide and cells infected with CMV. This simple and rapid method for generating high-purity CMV-specific CTL for adoptive immunotherapy is currently being examined for routine clinical use for allogeneic stem cell transplantation.