Immunochemical-based assays in the bioanalysis of immunoglobulins

Label-free sensitive luminescence biosensor for immunoglobulin G based on Ag6Au6 ethisterone cluster-estrogen receptor α aggregation and graphene

A specific and label-free "on-off-on" luminescence biosensor based on a novel heterometallic cluster [Ag₆Au₆(ethisterone)₁₂]-estrogen receptor α (Ag₆Au₆Eth-ERα) aggregation utilizing graphene oxide (GO) as a quencher to lead a small background signal was firstly constructed to detect immunoglobulin G (IgG) with a simple process and high selectivity. The efficient photoluminescent (PL) Ag₆Au₆Eth-ERα aggregation is strongly quenched by GO. In the presence of IgG, the PL of this system will be restored, and perceivable by human eyes under UV lamp excitation (365 nm). The quenching mechanism of GO on Ag₆Au₆Eth-ERα and enhancement mechanism of IgG on Ag₆Au₆Eth-ERα-GO were investigated in detail. Under the optimum conditions, the biosensor for high sensitive IgG detection expressed a wider linear range of 0.0078-10 ng/mL and a lower detection limit of 0.65 pg/mL with good stability and repeatability, which provided a new approach for label-free IgG detection.

Bacterial cell microarrays for the detection and characterization of antibodies against surface antigens

Bacterial cell surface antigens interact with the host immune system resulting in the production of antibodies. Detection of antibodies against surface antigens has applications in diagnosis of many bacterial infections, assessment of immune status and epidemiological studies. We developed a microarray platform, for antibody detection, by printing Gram-negative and Gram-positive whole bacterial cells on nitrocellulose coated glass substrates. Antibody binding was detected using fluorophore labeled secondary antibodies. The sensitivity of antibody detection was found to be 0.1 microg/ml. Using bacterial cell microarrays it was also possible to successfully detect antibodies against Francisella tularensis in canine serum samples declared positive for tularemia based on microagglutination antibody titer. Use of bacterial cells as the antigen source in immunoassays has the advantages of simulating in vivo presentation of surface antigens and also eliminating the need for antigen purification. The microarray format gives the added advantage of simultaneous detection of antibodies against multiple bacteria employing only small amounts of samples and reagents.

A direct comparison of the antigen-specific antibody profiles of intravenous immunoglobulins derived from US and UK donor plasma

BACKGROUND AND OBJECTIVES

Intravenous immunoglobulin (IVIG) is used in a range of immunodeficiency states that require a broad spectrum of protective antibodies to a range of common pathogens. A comparison of the antigen-specific antibody profile of preparations of an IVIG (Vigam) derived from US and UK sourced plasma was performed, and these preparations were also compared with three other IVIG products from different manufacturers.

MATERIALS AND METHODS

Antibodies against a range of bacterial and viral pathogens were measured by immunoassay.

RESULTS

Similar profiles were found for Vigam made from UK and US source plasma and also for the other three IVIGs tested, but some specific differences were observed.

CONCLUSIONS

IVIG preparations have a similar therapeutic spectrum of antibodies when prepared from plasma sourced either from the UK or the US.

Application of surface biopassivated disposable poly(dimethylsiloxane)/glass chips to a heterogeneous competitive human serum immunoglobulin G immunoassay with incorporated internal standard

A microfluidic platform for a heterogeneous competitive immunoassay of human immunoglobulin G (IgG) employing Cy5-human IgG as tracer and Cy3-mouse IgG as internal standard was developed. The device consisted of microchannels made of poly(dimethylsiloxane) and glass which were patterned with antibodies against human IgG and mouse IgG. Electrokinetic sample transport was employed in order to exploit the small difference between the net mobilities of analyte and tracer, thereby achieving favorable conditions for the performance of the competitive immunoreaction. The overall quality of the disposable chip and performance of the immunoassay were controlled by monitoring the fluorescence of bound tracer and bound internal standard. Analyses with an insufficient internal standard response were discarded, and immunoassay data evaluation was based on the ratio of tracer and internal standard fluorescence. Using synthetic samples in the range from 0 to 80 microg/mL IgG and alkaline running conditions, a concentration-dependent response with reproducible Cy5/Cy3 signal ratios (average relative standard deviation of 6.8%) was obtained. Chips stored with solution in the channels at 4 degrees C over a two-month period were found to perform like freshly prepared chips, whereas chips stored dry at -20 degrees C and rehydrated prior to use could not be employed. The analysis of patient sera showed that the immunoassay platform behaved differently in the presence of serum-based samples. Using the same conditions as for the synthetic samples, no concentration dependence was noted. With a large excess of tracer, however, an IgG concentration dependence was observed, permitting distinction of samples of patients with normal IgG serum levels (8-16 mg/mL) from those with elevated IgG concentrations (>16 mg/mL).

IVIG-pools: regulatory gifts--transiting from harmony toward harmonious immunoglobulins: why? and why not?

Based on 'initial conditions' which depend on each donors' exposure to a unique environment, a pooled intravenous immunoglobulin (IVIG) product transfers its immunoglobulin molecule repertoire, unchanged, to the altered host. The relay function of the cell-bound receptors, especially that of the inhibitory Fc(gamma)RIIB, may then allow sufficient amplification to make regulatory activity possible. To the clinician, IVIG may be considered a tool to promote reversal of the dysregulation causing autoimmune disease. Generically, IVIG may be seen as a promoter allowing a progression from harm by an inflammatory/fibrotic reaction, then down-regulating toward restitutio ad integrum. By modifying natural processes, IVIG may play minor roles in promoting defense against spontaneous bleeding and, perhaps, stimulating remyelination. The wide spectrum of IVIG specificities, by reflecting evolutionary epitope selection, may not further destabilize cell/molecule disarray in the affected host. Benefit to the patient by IVIG treatment cannot be predicted nor can potentially severe or even fatal accidents entirely be excluded. Important aspects of IVIG treatment still await clarification including dosage, timing and the isotype form. In the foreseeable future it does not seem that biotechnological advances will match the physiologic harmony of IVIG, leaving antibody characteristics aside.