Abstract
Since 2015, China has experienced outbreaks of severe hydropericardium syndrome (HPS), associated with a novel genotype and hypervirulent fowl adenovirus serotype 4 (FAdV-4) infection, with a prevalence in various provinces of the country. This has resulted in huge economic losses in the poultry industry. The novel FAdV-4 showed new genome characters, such as the natural deletion of open reading frame (ORF) 19 and ORF 27 (1966 bp), and high pathogenicity toward chickens. These are coupled with severe hydropericardium, inclusion body hepatitis, and mortality rates ranging from 30% to 90%. Although several inactivated and subunit vaccines against the traditional FAdV-4 have been developed, no commercial vaccine against the emerged disease caused by the novel strain has been available until now. The potential risks of infection with this novel hypervirulent FAdV-4 urgently require an effective vaccine. Thus, an inactivated oil-emulsion FAdV-4 vaccine formulated with the novel genotype virus was developed in this study. The vaccine provided a high level of antibody, preferential T helper 2 (Th2) (interleukin-4 secretion) not Th1 (interferon-γ secretion) response, and full protection against a lethal dose of the novel hypervirulent FAdV-4. Therefore, the novel genotype FAdV-4 vaccine is proposed as an attractive candidate to prevent and reduce the spread of HPS in the poultry industry of China.
Highlights
Fowl adenoviruses (FAdVs), members of the genus Aviadenovirus, are separated into five species
Hepatitis-hydropericardium syndrome (HHS), inclusion body hepatitis (IBH), and gizzard erosion (GE) in chickens and other birds are always associated with singleor co-infection of FAdVs [2,3]
The first FAdVs infection case was reported in Pakistan in 1987 [4], and subsequent outbreaks have been reported in Germany [5,6], Canada [7], Poland [8], Hungary [9], Chile [10], South America [11], Mexico [12], India [13], Korea [14], Japan [15], and China [16], resulting in significant economic losses to the poultry industry
Summary
Fowl adenoviruses (FAdVs), members of the genus Aviadenovirus, are separated into five species (designated FAdV-A to FAdV-E). These are based largely on molecular criteria and restriction enzyme digest patterns or twelve serotypes (designated FAdV-1 to 8a and -8b to 11) based on the results of serum cross-neutralization tests [1]. Almost all the FAdVs could induce IBH with or without mortality, while fowl. Since the identification of the causative agent of HPS and IBH, various live and killed vaccines against FAdV-4 have been developed that have provided considerably effective protection against the conventional hypervirulent strain [17,18,19]. Several subunit vaccines were constructed, notably rPenton and rFiber-2, which can provide a 90% and 96.4%
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