Antigen quantification asin vitroalternative for potency testing of inactivated viral poultry vaccines

Abstract

Routine batch control of licensed inactivated viral vaccines for poultry usually includes a potency assay as a measure of vaccine efficacy. Potency assays often consist of vaccination-challenge experiments in the target species or in laboratory animals. Instead of measuring the protection of vaccinated animals against virulent pathogens, the serological response after vaccination can be quantified for some vaccines. In vitro antigen quantification assays would be attractive alternatives for the current potency assays because the time and costs involved could be greatly reduced and animal use could be avoided. Such in vitro assays will only be acceptable when the correlation between results and efficacy or potency has been demonstrated convincingly. The results of our studies on antigen quantification assays indicate that, in principle, quantification of viral antigens from inactivated oil-adjuvanted vaccines is feasible and reproducible using specially developed antigen capture ELISAs in combination with specific software for statistical analysis of the ELISA data. We have developed methods to quantify the haemagglutination-neuraminidase (HN) and fusion (F) proteins of Newcastle disease virus (NDV), the viral protein 3 (VP3) of the infectious bursal disease virus (IBDV), and the spike-1 (S1) protein of the infectious bronchitis virus (IBV). Vaccination experiments with inactivated ND vaccines indicate that the in vitro quantified HN- or F-proteins of NDV are reliable indicators of the serological response after vaccination.

Detection and estimation of avian infectious bronchitis virus antigen by a novel indirect liquid-phase blocking enzyme-linked immunosorbent assay using chicken and rabbit affinity purified immunoglobulins

“…A large number of animals would be spared and the time and the costs involved would be greatly reduced. One major requirement for this is the availability of an assay, which could reliably measure the antigen concentration (Maas et al, 2000). In the current study, this problem was investigated with a novel liquid-phas e blocking ELISA developed to assess IBV antigen concentration in samples of allantoic fluid taken after propagation of different IBV strains.…”

“…Diagnosis of IBV is generally made by observation of clinical history, seroconversion (Marquardt et al, 1981; or IBV antigen detection by a number of methods such as virus isolation (Gelb, 1989), immunofluorescence and immunoperoxidase assays (Chubb, 1986;Naqi, 1990;Yagyu & Ohta, 1990;Bhattacharjee et al, 1994), different types of antigen-capture enzyme-linked immunosorbent assays (ELISAs) (Yagyu & Ohta, 1987;Nagano et al, 1990;Naqi et al, 1993;Ignjatovich & Ashton, 1996;Maas et al, 2000;Bronzoni et al, 2001) or polymerase chain reaction (PCR) (Lin et al, 1991;Kwon et al, 1993;Capua et al, 1999). Of all these methods, the ELISA is considered to be the least laborious, time consuming and expensive.…”

Strategies and challenges for eliciting immunity against avian influenza virus in birds

“…However, such assessment is time consuming and expensive. Initial assessments can be achieved by indirect methodologies using cost‐effective alternatives such as evaluating bird response to the vaccine using serological assays such as virus‐neutralization or hemagglutination inhibition (HI) titers from serum of vaccinated birds, or by evaluating the vaccine itself by determining the amount of HA protein per inactivated vaccine dose or infectious titer of live vaccines (106–108). In one report, Garcia et al (109) determined that an inactivated AI vaccine containing 0.4 μg of HA per dose could protect chickens against HPAI challenge with A/Chicken/ Queretaro/19/95 H5N2, but the best protection was achieved with 3–8 μg (6).…”

Non-animal replacement methods for veterinary vaccine potency testing: state of the science and future directions

“…An in vitro ELISA antigen quantification assay for inactivated NDV vaccine has been developed and validated by the EDQM [18,87,88,89]. The successful transition from an in vivo assay to an in vitro ELISA was aided by the fact that there was a strong correlation between antigen content and antibody response.…”

“…89]. Additional antigen quantification assays have been developed for infectious bursal disease virus and IBV vaccines; however inadequate funding has prevented further validation [18,87,131]. Although the technology is now available, sufficient resources and efforts must still be adequately applied to validate these replacement potency assays and gain regulatory approval.…”