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的Gumboro镇附近被发现（Gumboro病）。传染性法氏囊病病毒属于双核糖核酸病毒科的禽双核糖核酸病毒属，并引起传染性法氏囊病（IBD），这是一种3至6周龄鸡的急性高度接触性疾病。IBDV感染的最严重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疾病之一，在世界范围内给养禽业造成了巨大损失。出现了不能通过用从“经典"IBDV毒株制备的疫苗免疫来控制的IBDV，并且被称为变异体IBDV（vIBDV）。由于vIBDV的识别，加拿大IBD的控制变得复杂。我们以前的研究已经确定萨斯喀彻温省43%的肉鸡群或场所（或52%的谷仓）感染了vIBDV。显然，感染vIBDV的鸡群具有较差的饲料转化率、高死亡率、法氏囊萎缩和产肉量降低。这导致萨斯喀彻温省肉鸡产业每年损失超过390万公斤的肉鸡产量。每年损失的大量鸡肉的批发市场价值超过1 300万美元。此外，近年来，由于免疫抑制，认识到由于细菌性肝炎引起的肉鸡尸体死亡增加。我们的研究表明，目前在加拿大的肉鸡养殖业中针对IBDV的疫苗接种计划在控制vIBDV方面无效，因为美国来源的疫苗与加拿大肉鸡业中流行的vIBDV之间存在抗原差异。此外，我们已经发现，目前用于肉鸡产业的疫苗不能提供针对加拿大vIBDV的保护。最近，我们的研究揭示了一个未被认识的现象，即用载体疫苗免疫肉鸡诱导免疫抑制，这可能进一步增加对vIBDV感染的易感性。由于这些原因，我们建议使用加拿大分离株开发IBDV疫苗，以控制加拿大肉鸡产业中的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.