Development of an immune complex vaccine to control variant infectious bursal disease virus (IBDV) infections in the broiler chicken industry in Canada

传染性法氏囊病病毒(IBDV)首先在美国特拉华州冈博罗镇附近被发现(冈博罗病)。传染性法氏囊病病毒属于禽科禽鸟病毒属，引起传染性法氏囊病(IBD)，是3-6周龄雏鸡的一种急性高度传染性疾病。IBDV感染最严重的后果是法氏囊功能丧失。IBD是最重要的禽类获得性免疫抑制性疾病之一，给全球养禽业造成了巨大的损失。新出现的IBDV不能通过用“经典”IBDV毒株制成的疫苗进行免疫控制，因此被称为变种IBDV(VIBDV)。由于对vIBDV的认识，加拿大对IBD的控制变得复杂起来。我们之前的研究发现，萨斯喀彻温省43%的肉鸡群或场所(或52%的牛棚)感染了vIBDV。可见，感染vIBDV的鸡具有饲料转化率低、死亡率高、法氏囊萎缩和产肉量减少等特点。这导致萨斯喀彻温省肉鸡业每年损失390多万公斤肉鸡产量。这批损失的鸡肉每年的批发市场价值超过1300万美元。此外，近年来，由于免疫抑制，细菌性肝炎引起的肉鸡身体受到越来越多的谴责。我们的研究表明，目前加拿大肉鸡养殖业针对IBDV的疫苗接种计划在控制VIBDV方面并不有效，因为美国来源的疫苗与加拿大肉鸡行业流通的VIBDV之间存在抗原差异。此外，我们还发现，目前肉鸡行业使用的疫苗不能提供针对加拿大VIBDV的保护。最近，我们的研究发现了一个未知的现象，即用载体疫苗免疫肉鸡会导致免疫抑制，这可能会进一步增加对vIBDV感染的易感性。由于这些原因，我们建议开发一种使用加拿大分离株的IBDV疫苗，以控制加拿大肉鸡业中的vIBDV。

Infectious bursal disease virus (IBDV) was first recognized in the USA near the town of Gumboro, Delaware (Gumboro disease). Infectious bursal disease virus belongs to the genus Avibirnavirus of the family Birnaviridae and causes infectious bursal disease (IBD), an acute highly contagious disease of 3- to 6-week-old chickens. The most severe consequence of IBDV infection is the functional loss of the bursa of Fabricius. IBD is one of the most important avian acquired immunosuppressive diseases and has led to large losses to the poultry industry worldwide. IBDVs emerged that could not be controlled by immunization with vaccines prepared from ''classic'' IBDV strains, and were called variants IBDVs (vIBDVs). The control of IBD in Canada has been complicated by the recognition of vIBDVs. Our previous research has identified 43% of broiler flocks or premises (or 52% of barns) in Saskatchewan are infected with vIBDV. It is apparent that flocks with vIBDV infection have a poor feed conversion ratio, high mortality, bursal atrophy and decreased meat production. This has led to an annual loss of over 3.9 million kilograms of broiler production per year in the Saskatchewan broiler chicken industry. This mass of chicken meat lost had a wholesale market value of over $13 million per year. Moreover, in recent years, increased condemnations of broiler carcasses due to bacterial hepatitis was recognized due to immunosuppression. Our research has demonstrated that current vaccination programs against IBDV in the broiler breeder industry in Canada are not effective in controlling vIBDV because of antigenic differences between US-sourced vaccines and vIBDVs circulating in the broiler chicken industry in Canada. Furthermore, we have discovered that current vaccines used in the broiler chicken industry are not able to provide protection against the Canadian vIBDV. Recently, our research revealed an unrecognized phenomenon that the immunization of broilers with vectored vaccine induces immunosuppression that may further increase susceptibility to vIBDV infection. Because of these reasons, we are proposing to develop a IBDV vaccine using Canadian isolates to control vIBDV in the broiler chicken industry in Canada.