GD Animal Health offers a large number of antigens, monospecific antisera and reference sera – carefully selected to obtain optimum results in laboratory tests. Diagnostics are produced in our own facilities. Our well-defined sera are also used in the Proficiency testing schemes. All antigens, antisera and reference sera are freeze-dried to extend their shelf life and guarantee long-term stability.
Haemagglutination Inhibition (HI) assays
Several avian pathogens, such as Avian Influenza Virus (AI), Newcastle Disease Virus (NDV), Egg Drop Syndrome ’76 Virus (EDS), Mycoplasmas, and Infectious Bronchitis Virus (IBV), haemagglutinate the red blood cells of birds. (Or in some cases other animals.) This haemagglutination usually occurs ‘spontaneously’ as a result of the presence of natural receptors (haemagglutinin) on the virus surface. In the case of Infectious Bronchitis Virus, most antigens need a special treatment to make them haemagglutinating. The Haemagglutination Inhibition (HI) assay is based on the inhibition of this specific haemagglutination by antivirus antibodies in the test sample, which bind and neutralise the viral haemagglutinin receptor.
Antigens and antisera for HI
The HI assay is usually carried out in U or V shaped microtitre plates (8x12) using 25 μL volumes of antigen containing 4 or 8 haemagglutinating units (HAU) and 25 micro-litre volumes of serially diluted samples. Red blood cells are obtained from birds free of antibodies against the virus concerned and used as a 1% or 2% v/v suspension. The antigen is available at GD Animal Health.
GD Animal Health’s antisera for HI assays are monospecific, unless otherwise indicated. The antisera are specially selected to yield higher titres with homologous serotypes than with heterologous serotypes, but care should be taken in interpreting the results of IBV HI assays. GD Animal Health offers HI antisera for the most important haemagglutinating avian pathogens including many Avian Influenza types and Mycoplasma. The Mycoplasma antisera can also be used as positive controls in the rapid plate agglutination assays.
Agar Gel Precipitation (AGP) assays
The Agar Gel Precipitation (AGP) assay is a very specific immunological technique, frequently used in poultry serology. The technique has been described and used for several poultry diseases, either to detect antibodies using a known, specific antigen, or to detect or identify antigens using monospecific antisera. Although it is increasingly being replaced by ELISAs, the AGP assay is the only routine assay in which the specificity of the observed reaction can be directly compared with a known positive control serum. When used in flock monitoring or diagnosis, (herd) sensitivity of the AGP assay is usually adequate.
Antigens and antisera for AGP
The AGP assay visualises the antigen-antibody complexes formed after antigens and samples have diffused in a semisolid medium. GD Animal Health produces the necessary antigens for use in its own laboratory and for sale. GD Animal Health also offers several antisera which can be used as control sera. These antisera have been carefully selected to yield optimum results with the technique used. All antisera for AGP assays are monospecific, directed at groups of antigens. These sera will detect but not differentiate between serotypes of a single viral pathogen. These antisera can also be used to detect or identify unknown antigens in samples obtained in egg or tissue culture (virus isolation).
GD Animal Health reference sera are produced from naturally infected or vaccinated animals with significant antibody levels. These sera are available as assay-independent controls or ‘in-house’ controls for monitoring the performance of third-party immunodiagnostic assays on a day-to-day basis. Our avian and porcine reference sera are not monospecific, but a specificity profile is specified for each serum in a Certificate of Analysis.
Certificate of analysis
A Certificate of analysis is available for each batch of products. This certificate specifies Quality Control data (specificity data and working dilutions) obtained at the GD Animal Health laboratory.
Standard Operating Procedures
Standard Operating Procedures (SOPs) and descriptions are available for most assays in which GD Diagnostics are used.
The GD Animal Health R&D staff and laboratory technicians will be able to answer your technical or practical questions concerning the use of GD Animal Health products and the associated techniques. They also have direct access to the day-to-day results and performance data of reagents and controls and will in all probability be using the same batches you yourself are using. For a more veterinary-diagnostic approach or specific veterinary problems you are welcome to consult the scientific laboratory staff, specialised in the fields of veterinary immunology, virology, bacteriology, pathology and clinical chemistry.