台灣家禽腺病毒之基因、抗原性與致病性分析

Abstract

家禽腺病毒（Fowl adenoviruses, FAdVs）是引起雞隻包涵體性肝炎與肝心綜合症等疾病之重要病原體，對家禽產業造成重大經濟損失，尤其近年來台灣FAdV相關病例有上升趨勢，然而目前對於病毒株之各項特性分析卻相當有限。本研究針對2020至2025年間之疑似病例進行採樣與病毒分離，並進行病毒分子特徵、抗原性與致病性之系統性評估。本研究從台灣田間雞場共分離到10株FAdV，來源涵蓋白肉雞、蛋雞、種雞及有色肉雞，全基因體定序結果顯示，病毒株分屬三個基因型（C、D、E）與五個血清型（FAdV-2、-3、-8a、-8b、-11），其中一株有跨型別基因重組現象。另外，血清交叉中和試驗結果證實各分離株具明顯的抗原性差異，顯示台灣FAdV流行株具高度抗原多樣性與複雜性。接著，本研究選用代表性毒株NTU/C1120/2023進行動物實驗，設計包含單一感染以及和傳染性支氣管炎病毒（infectious bronchitis virus, IBV）之共感染模式。共感染組雞隻表現出更嚴重的臨床症狀、更高的死亡率，並出現明顯的免疫組織與肝臟病變。雖然早期組織與血液中FAdV含量較低，但病毒排毒時間延長，且抗體反應受抑，並進一步以組織病理與免疫組織化學染色確認肝臟為主要病變器官。為了確認FAdV與IBV之間的干擾現象，以雞胚腎細胞進行共感染的細胞實驗，發現IBV可抑制早期FAdV複製，而FAdV則於感染後期促進IBV之複製。綜合本研究結果，顯示目前台灣流行之FAdV株具有高度基因與抗原多樣性，並與IBV存在時間依賴性之干擾現象，這些結果突顯了台灣持續監測FAdV與採取疾病防控策略之重要性。

Fowl adenoviruses (FAdVs) are important avian pathogens associated with inclusion body hepatitis and hydropericardium-hepatitis syndrome, contributing to significant economic losses in the poultry industry. Despite increasing cases in Taiwan, the comprehensive characterization of circulating strains remains limited. This study investigated the molecular features, antigenic properties, and pathogenicity of FAdVs isolated in Taiwan between 2020 and 2025. Among suspected cases from broilers, layers, breeders, and colored broilers farms, 10 FAdVs were isolated. Whole-genome sequencing revealed five serotypes (FAdV-2, -3, -8a, -8b, and -11) across three species (C, D, and E), with one isolate exhibiting intertypic recombination. Cross-neutralization assays confirmed distinct serotypes with minimal antigenic overlap, highlighting the complexity of FAdV circulation in Taiwan. A representative strain (NTU/C1120/2023) was selected for animal studies, including single and co-infection with infectious bronchitis virus (IBV) in SPF chickens. Co-infected birds exhibited more severe clinical signs, higher mortality, and pronounced lesions in lymphoid and liver tissues. Although FAdV loads in tissues and blood were initially lower in co-infected birds, viral shedding was prolonged, and antibody responses were reduced. Histopathology and IHC confirmed extensive hepatic involvement. In vitro studies using chicken embryo kidney cells demonstrated that IBV suppressed early FAdV replication, while FAdV enhanced IBV replication at later stages. Collectively, this study highlights the genetic and antigenic diversity of FAdVs in Taiwan and reveals a dynamic, time-dependent interaction between FAdV and IBV. These findings underscore the need for continuous surveillance and tailored vaccine strategies to mitigate FAdV-associated diseases in poultry.