禽腺病毒第四血清型（Fowl adenovirus-4，FAdV4）是屬於禽腺病毒第I群，為無封套模的雙股DNA病毒，直徑大小約70–90 nm。FAdV4感染的臨床症狀主要為心包積液綜合症（Hydropericardium Syndrome，HPS）和包涵體肝炎（Inclusion Body Hepatitis，IBH)。HPS及IBH是一種潛伏期短，發病急，發病之後迅速波及全群的病毒，會造成雞群大量死亡和巨大的經濟損失。本研究選殖FAdV4誘發中和抗體之Hexon蛋白基因，利用大腸桿菌表現系統表現Hexon蛋白，同時利用雞肝細胞（Leghorn male hepatocellular, LMH)培養FAdV4病毒，作為疫苗抗原。結果顯示以LMH細胞培養野外分離株FAdV4/N經10代馴化其病毒量可達107.6 TCID50/mL。以大腸桿菌表現系統表現FAdV4-Hexon蛋白其表現量可達180 μg/mL。動物試驗方面，以105 TCID50 FAdV4/N病毒株與50 μg Hexon次單位蛋白混和後添加佐劑製成疫苗免疫無特定性病原雞隻，免疫後14天中和抗體可高於2048倍。在攻毒試驗結果顯示本疫苗達到完全保護的效果，免疫組雞隻全數健存，並且在攻毒14天後就偵測不到排毒。本研究發現FAdV4不活化疫苗加入次單位Hexon蛋白具有輔助免疫反應提升的效果。本研究開發以LMH細胞株用於量產FAdV4，經細胞馴化之病毒除具有具經濟價值之病毒生長力價外，並保有良好的抗原性，加入Hexon次單位蛋白可降低FAdV4病毒於疫苗中的使用量，以降低生產成本並提升疫苗之保護力。

Fowl adenovirus serotype 4 (FAdV4) belongs to avian adenovirus group I and is a double-stranded DNA virus without envelope. The diameter is about 70-90 nm. Clinical symptoms of FAdV4 infection is mainly Hydropericardium Syndrome (HPS) and Inclusion Body Hepatitis (IBH). HPS and IBH have a short incubation period and acute onset. The virus quickly spreads through the whole organism, resulting in a large number of deaths and huge economic losses. In this study, the FAdV4 virus was cultured with chicken liver cells and was successfully passaged in LMH cells. Titer of the virus gradually increased, reaching 107.6 TCID50/mL at passage 10. The Hexon protein gene of FAdV4 was selected and expressed using the E. coli expression system, in which the protein expression reached 180 μg/mL. The inactivated 105 TCID50 FAdV4 virus along with 50 μg/mL recombination Hexon protein and adjuvant were prepared as a vaccine and used to immunize chickens. The neutralizing antibody titer, reached over 2048x dilution 14 days after immunization. When immunized chickens were challenged, complete protection was observed and no virus was detected 14 days after challenge. The present results revealed that FAdV4 virus and Hexon protein retains high antigencity and can elicit high neutralizing antibody titers. Therefore, it suggests that Hexon protein of FAdV4 could be a good candidate to be developed as a vaccine in the future.

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