雞傳染性喉氣管炎疫苗的免疫具有增加家H9N2亞型禽流感病毒感染的風險

導讀

在家禽養殖過程中禽流感病毒和傳染性喉氣管炎病毒都是常見的能夠導致家禽嚴重呼吸系統疾病，造成家禽行業嚴重經濟損失的病毒。近期，來自埃及的科學家們通過研究發現，家禽在免疫了傳染性喉氣管炎病毒活疫苗後，會導致家禽更容易感染H9N2亞型禽流感病毒。該研究結果目前已在線發表至《Veterinary Microbiology》雜誌，題為「Enhanced infection of avian influenza virus H9N2 with infectious laryngeotracheitis vaccination in chickens」。

在試驗過程中，研究人員首先對試驗雞隻進行傳染性喉氣管炎活病毒疫苗免疫，之後對免疫後的雞進行H9N2亞型禽流感病毒的接種，通過與對照組（只接種H9N2病毒）對比發現，免疫了傳染性喉氣管炎病毒的雞隻在接種了H9N2亞型的禽流感病毒後的發病率和死亡率顯著提升。該試驗說明，傳染性喉管炎活病毒疫苗在臨床應用的過程中，潛在提升家禽H9N2亞型禽流感病毒感染的風險。

該研究成果在一定程度對雞傳染性喉氣管炎和H9N2亞型禽流感病毒的防控提出了新的挑戰，同時，也進一步揭示了臨床上家禽H9N2亞型流感病毒感染，發病及致死的原因。

Abstract

Avian influenza and infectious laryngeotracheitis viruses are common causes of respiratory diseases in chickens with economical importance worldwide. In this study, we investigated the effect of experimental co-infection of avian influenza virus-H9N2 (AIV-H9N2) with infectious laryngeotracheitis virus (ILTV) live-attenuated vaccine (LAR-VAC) on chickens. Four experimental groups were included in this study: negative control group, AIV-H9N2 group, AIV-H9N2+LAR-VACgroup, and LAR-VACgroup. AIV-H9N2 was inoculated intranasally to challenged groups at 35 days of age. On the same day, LAR-VACwas ocularly administered to vaccinated groups. Chickens were observed for clinical signs, changes in body weight and mortality rates. Tissue samples, sera, tracheal and cloacal swabs, and blood were also collected at 3, 6, 9 and 12 days post-infection (PI). A significant increase in clinical signs and mortality rates were observed in the AIV-H9N2?+?LAR-VACgroup. Moreover, chickens coinfected with AIV-H9N2 and LAR-VACshowed a significant decrease in body weight and lymphoid organs indices. The tracheal gross and histopathological lesions and the shedding titer and period of AIV-H9N2 were significantly higher in AIV-H9N2?+?LAR-VACgroup when compared to other groups. Furthermore, AIV-H9N2 infection leads to humoral and cellular immunosuppression as shown by a significant decrease in the CD4+/CD8+ratio and antibody responses to ILTV and a significant increase in H/L ratio. In conclusion, this is the first report of co-infection of AIV-H9N2 and ILTV vaccine in chickens, which leads to increased pathogenicity, pathological lesions, and AIV-H9N2 shedding titer and period, which can lead to severe economic losses due to poor weight gain and mortality.

本期編輯：木木

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