Rapid biotin-avidin method for quantitation of antiviral antibody isotypes

Long period grating working in transition mode as promising technological platform for label-free biosensing

We present the development of a platform for label-free biosensing based on overlayered Long Period Gratings (LPGs) working in transition mode. Nano-scale layers of Polystyrene (PS) with different thicknesses were deposited onto the same LPG to test the performances of the device in different working points of its modified sensitivity characteristic. Adsorption dynamic of biotinylated bovine serum albumin (BBSA) onto the PS overlays was on-line monitored as well as a subsequent streptavidin (SA) binding dynamic on the biotinylated sites of the protein ad-layer. Experimental results show that overlayered LPGs are among the most sensitive refractive index transducers to be employed in label-free biochemical detection and that wide margins of further optimization exist.

Split tolerance of Th1 and Th2 cells in tolerance to Theiler's murine encephalomyelitis virus

Theiler's murine encephalomyelitis virus (TMEV) produces a chronic, inflammatory demyelinating disease in susceptible mouse strains that is used as a model for multiple sclerosis. Because disease susceptibility correlates temporally with the development of virus-specific delayed-type hypersensitivity (DTH) responses, we studied methods and mechanisms by which virus-specific DTH could be specifically inhibited. The intravenous injection of UV-inactivated TMEV coupled to syngeneic splenocytes via a carbodiimide linkage (TMEV-SP), prior to immunization, induced a significant degree of tolerance in virus-specific helper (Th) cells as determined by decreased DTH and T cell proliferative responses, and decreased interleukin (IL)-2 and interferon (IFN)-gamma protein and mRNA levels. In contrast to the reduced levels of Th1-specific lymphokine mRNA levels, IL-4-specific mRNA levels in response to virus stimulation were not affected in tolerant mice. Surprisingly, the total anti-TMEV antibody response in DTH tolerant mice was enhanced 20-100-fold over sham-tolerized controls and was composed of reduced levels of anti-virus IgG2a, but dramatically increased levels of anti-virus IgG1. The "split-tolerance" was antigen specific, dependent on the concentrations of TMEV and carbodiimide used in the coupling procedure, and varied with the number of coupled syngeneic splenocytes administered. The fixative effects of carbodiimide on antigen-presenting function were necessary for the induction of DTH tolerance with TMEV-SP, since intravenous administration of virus coupled to splenocytes via a biotin-avidin linkage led to enhanced virus-specific antibody responses, but was unable to inhibit DTH unless concomitantly fixed with carbodiimide. Collectively, the data indicate that Th1 cells (mediating DTH, IL-2 and IFN-gamma production, and helper function for IgG2a production) were specifically anergized, with concomitant stimulation of Th2 cells (producing IL-4 and mediating helper function for IgG1 antibody production).