Virus mutations and their impact on vaccination against infectious bursal disease (Gumboro disease)

Development of a Viral-Like Particle Candidate Vaccine Against Novel Variant Infectious Bursal Disease Virus

Infectious bursal disease (IBD), an immunosuppressive disease of young chickens, is caused by infectious bursal disease virus (IBDV). Novel variant IBDV (nVarIBDV), a virus that can evade immune protection against very virulent IBDV (vvIBDV), is becoming a threat to the poultry industry. Therefore, nVarIBDV-specific vaccine is much needed for nVarIBDV control. In this study, the VP2 protein of SHG19 (a representative strain of nVarIBDV) was successfully expressed using an Escherichia coli expression system and further purified via ammonium sulfate precipitation and size-exclusion chromatography. The purified protein SHG19-VP2-466 could self-assemble into 25-nm virus-like particle (VLP). Subsequently, the immunogenicity and protective effect of the SHG19-VLP vaccine were evaluated using animal experiments, which indicated that the SHG19-VLP vaccine elicited neutralization antibodies and provided 100% protection against the nVarIBDV. Furthermore, the protective efficacy of the SHG19-VLP vaccine against the vvIBDV was evaluated. Although the SHG19-VLP vaccine induced a comparatively lower vvIBDV-specific neutralization antibody titer, it provided good protection against the lethal vvIBDV. In summary, the SHG19-VLP candidate vaccine could provide complete immune protection against the homologous nVarIBDV as well as the heterologous vvIBDV. This study is of significance to the comprehensive prevention and control of the recent atypical IBD epidemic.

Humoral and mucosal immune responses in challenged chickens vaccinated with Infectious bursal disease vaccine using gums from Cedrela odorata and Khaya senegalensis as delivery agents

The emergence of antigenic variants and very virulent strains of infectious bursa disease virus (IBDV) in vaccinated flocks considerably stimulated research in IBDV vaccine administration. The mucoadhesive and immunopotentials of Cedrela odorata and Khaya senegalensis were explored in vaccine delivery against clinical IBDV in broiler chickens. A total of 400 chicks were successfully brooded and raised from day old for commencement of this experiment. The birds were randomly distributed into eight groups with an average of 50 birds per group comprising: Gums-Gumboro Vaccine Ocular (infected) (GGVOC), Gumboro Vaccine alone Ocular (infected) (GVOC), Gums alone Ocular (infected) (GOC), Gums-Gumboro Vaccine Oral (infected) (GGVOR), Gumboro Vaccine alone Oral (infected) (GVOR), Gums alone Oral (infected) (GOR), No-Vaccine-No-Gums (infected) (NVNG/i), and No-Vaccine-No-Gums (not infected) (NVNG). On a weekly basis, 1.5mls of blood were collected from 5 birds and 3 birds euthanized per group for serological analysis and mucosal washings (trachea and intestine) respectively. Data obtained were analyzed and sample to positive ratio calculated. The post 1st vaccination trachea IgG antibody response was moderately higher in the ocular groups than the oral groups. It was also high in the VOC, GVOC, GOC, VOR groups than the GVOR groups. The antibody response (IgG) pre and post 1st vaccination, post 2nd vaccination and post infection from serum, trachea and intestinal washes showed that by week 1 Post 1st vaccination, there was insignificant increase in titer serum response of the gum-vaccine ocular group compared to the vaccine ocular alone while both groups were insignificantly higher than the oral group. Overall, serum titer showed a rapid response with spiked significant response by 48h pi in the gum vaccine groups (especially GVOR), which peaks by day 3 and remains insignificantly higher throughout the day 7 pi compared to vaccine alone groups. In conclusion, use of the mucilage from C. odorata and K. senegalenses in equal proportion has given better enhancement of the response to IBDV vaccination and premise for further investigations for improvement against IBD.

Circulation of very virulent avian infectious bursal disease virus in Finland

In the spring of 2014 infectious bursal disease (IBD) was confirmed in a Finnish layer flock exhibiting clinical signs and increased mortality. Organ and blood samples were sent for diagnosis to the Finnish Food Safety Authority Evira. IBD virus (IBDV) was detected in RT-PCR studies. Altogether hens from six layer farms associated with increased mortality (7-10%, worst case 30%) were diagnosed with IBD during 2014. Antibodies were also detected with IBD-ELISA tests in hens on two farms. Phylogenetic analysis showed that the causative agent of the 2014 IBD outbreak was a non-reassortant very virulent type IBDV. The representative virus strains from previous IBD outbreaks in 1978, 1987 and 1993 were also included in the analysis. The strains isolated in 2014 and 1993 were very similar indicating circulation of a very virulent IBDV for over 20 years in the country. In spite of the comprehensive phylogenetic analysis, the definitive origin of the viruses from 2014 and previous outbreaks remains unclear.