Influenza A virus-specific CD8.sup.+ T-cell responses : from induction to function

Seasonal influenza virus infection is a leading cause of illness and mortality in young children and the elderly each year. Current influenza vaccines generate protective antibody responses; however, these must be given annually to provide protection against serologically distinct viruses. By contrast, CD8.sup.+ T cells are capable of recognizing conserved antigenic determinants within the influenza virion and, as such, may provide protection against a number of variant strains of the virus. CD8.sup.+ T cells play a critical key role in controlling and resolving influenza virus infections via the production of cytokines and cytolytic mediators. This article focuses on the induction of the influenza-specific CD8.sup.+ T-cell response and how these cells acquire and maintain effector function after induction. Moreover, we discuss how cytotoxic T-lymphocyte function correlates with protection following vaccination.

A Pb<sup>2+sup>-ion electrochemical biosensor based on single-stranded DNAzyme catalytic beacon

A novel strategy for selective and sensitive electrochemical lead ion (Pb<sup>2+sup>) biosensor was developed based on the single-stranded DNAzyme catalytic beacon. A DNAzyme that requires Pb<sup>2+sup> for activation was selected and labeled with redox-active ferrocene (Fc) for signal transducer. The Fc-labeled single-stranded DNAzyme (Fc-ssDNAzyme) was self-assembled through SAu bonding on a gold electrode surface. In the presence of Pb<sup>2+sup>, the ssDNAzyme was activated and catalyzed the hydrolytic cleavage of the substrate strand, resulting in the removal of the substrate strand along with the Fc from the Au electrode surface. The dissociation of Fc caused a decrease of electrochemical signal ("signal-off"). Under the optimal conditions, the electrochemical signal of Fc decreased directly with the increasing Pb<sup>2+sup> concentration, exhibiting a linear response in the range of 0.5nM to 5μM with a detection limit of 0.25nM. This strategy is simple, sensitive and selective with the minimal reagents and working steps, thereby holds great potential for Pb<sup>2+sup> detection in real environmental sample analysis.

On-site determination of Pb<sup>2+sup> and Cd<sup>2+sup> in seawater by double stripping voltammetry with bismuth-modified working electrodes

To meet the urgent requirement of determining trace Pb2+ and Cd2+ in seawater on site, herein we developed a simple but novel electrochemical method, named as double stripping voltammetry, using only a portable heavy metal analyzer. The proposed method consisted of three steps: First, the targeted heavy metal ions in bulk solution were concentrated onto an ionic liquid-graphite-based paste working electrode (ILGPE), which exhibits a dramatic ability of accumulation, by electrodeposition in the presence of Bi3+. Second, the three-electrode arrangement, including the ILGPE loaded with the reduced products, was transferred into 1.0mL acetate buffer solution, followed by a stripping procedure. Third, the measurement was performed with the other stripping voltammetry procedure by using a glassy carbon electrode as working electrode. Under optimum conditions, the linear range values for Pb2+ and Cd2+ in seawater were 0.2-3.2 μg/L and 0.1-3.2 μg/L, respectively. The concentrations of Pb2+ and Cd2+ in five real samples collected from coastal sites of Qingdao City were determined on site, and the results were in good agreement with that obtained with the atomic absorption spectroscopy method. In addition, the analytical performance of working electrode modified with Bi film by in situ mode was investigated in comparison with that by ex situ mode. The results showed that the in situ mode was much better than the ex situ one.