Agar gel immunodiffusion assay to detect antibodies to Type A influenza virus

Tetraplex Fluorescent Microbead-Based Immunoassay for the Serodiagnosis of Newcastle Disease Virus and Avian Influenza Viruses in Poultry Sera

Virulent Newcastle disease virus (NDV) as well as highly pathogenic avian influenza (HPAIV) subtypes H5 and H7 induce contagious and lethal systemic disease in poultry. In contrast, low pathogenic AIV H5 and H7 may circulate clinically unnoticed in poultry but eventually generate HPAIV. Low pathogenic NDV strains are widely used as live-attenuated vaccines against ND. Serological tools are essential to conduct active surveillance for infections with notifiable AIV-H5, -H7 and to control vaccination against NDV and HPAIV in poultry populations. Here, recombinant nucleocapsid proteins (NP) of AIV and NDV, and haemagglutinin protein fragment-1 (HA1) of AIV subtypes H5 and H7 were expressed in E. coli. Purification and refolding were required before coating fluorescent microspheres via streptavidin-biotin linkage. The tetraplexed inhibition fluorescent microsphere immunoassay (iFMIA) was then assembled for analysis on a Luminex^®-like platform (Bioplex^®) using murine monoclonal antibodies specific for each of the four targets. The assay was evaluated by testing galliform poultry sera derived from experimental infections (n = 257) and from farms (n = 250), respectively. The tetraplex iFMIA compared favorably with commercially available ELISAs and the “gold standard” hemagglutination inhibition assay. Tetraplexed iFMIA provided a specific and sensitive tool to detect and discriminate AIV- and NDV-specific antibodies in the sera of galliform poultry.

Aspects of "antigen-antibody" interaction of chicken infectious bronchitis virus determined by surface plasmon resonance

Authors performed investigation on "antigen-antibody" interaction of chicken infectious bronchitis coronavirus (IBV) by a method based on the surface plasmon resonance (SPR). Presence of space-size effect related to a difference between antigen and antibody particle sizes has been theoretically grounded and experimentally proven. Herewith, the difference between responses of the SPR-sensor to specific and non-specific interactions is considerably less (up to 6.3 times) than the expected one (8 - 11 times). An impact of functionalization of sensor's sensitive element surface, as well as acidity of buffer solution on the activity of antigen-antibody interaction was studied here. The difference between sensor's responses to specific and non-specific interactions increased two-fold from 200 to 432ang sec due to this treatment. When changing the acidity of analyzed solution from pH7.3 to pH6.8, the corresponding difference between sensor's responses increased by 6.3 times from 194 up to 1235ang.sec. Thus, an impact of space-size effect on interaction between IBV antigen and specific antibody can be considerably (almost in 3 times) decreased by reducing the acidity of used buffer solution. The results of our investigation can be successfully applied to develop new methods for detection of pathogens and specific antibodies using SPR.

Successes and Short Comings in Four Years of an International External Quality Assurance Program for Animal Influenza Surveillance

The US National institutes of Health-Centers of Excellence for Influenza Research and Surveillance is a research consortium that funds numerous labs worldwide to conduct influenza A surveillance in diverse animal species. There is no harmonization of testing procedures among these labs; therefore an external quality assurance (EQA) program was implemented to evaluate testing accuracy among labs in the program in 2012. Accurate detection of novel influenza A variants is crucial because of the broad host range and potentially high virulence of the virus in diverse species. Two molecular detection sample sets and 2 serology sample sets (one with avian origin isolates, and one with mammalian origin isolates each) were made available at approximately six month intervals. Participating labs tested the material in accordance with their own protocols. During a five year period a total of 41 labs from 23 countries ordered a total of 132 avian molecular, 121 mammalian molecular and 90 serology sample sets. Testing was completed by 111 individuals. Detection of type A influenza by RT-PCR was reliable with a pass rate (80% or greater agreement with expected results) of 86.6% for avian and 86.2% for mammalian origin isolates. However, identification of subtype by RT-PCR was relatively poor with 54.1% and 75.9% accuracy for avian and mammalian influenza isolates respectively. Serological testing had an overall pass rate of 86.9% and 22/23 labs used commercial ELISA kits. Based on the results of this EQA program six labs modified their procedures to improve accuracy and one lab identified an unknown equipment problem. These data represent the successful implementation of an international EQA program for an infectious disease; insights into the logistics and test design are also discussed.