Immunogenicity of Novel Live Vaccine Based on an Artificial rHN20 Strain against Emerging Fowl Adenovirus 4.

Yu Zhang,Kai Li,Aijing Liu,Rongrong Guo,Yanping Zhang,Zhuangzhuang Xu,Yulong Gao,Qing Pan,Xiaole Qi,Xiaomei Wang,Li Gao,Changjun Liu,Hongyu Cui

doi:10.3390/v13112153

Abstract

In recent years, hepatitis-hydropericardium syndrome (HHS), caused by novel fowl adenovirus 4 (FAdV-4), has caused serious economic losses to the poultry industry. Vaccines are important for preventing and controlling HHS. Current FAdV-4 vaccine research and development are mainly focuses on inactivated vaccines and relatively fewer live vaccines. We previously demonstrated that the hexon gene is the key gene responsible for the high pathogenicity of FAdV-4 and constructed a non-pathogenic chimeric virus rHN20 strain based on the emerging FAdV-4. In this study, the immunogenicity of artificially rescued rHN20 was evaluated in chickens using different routes and doses as a live vaccine. The live rHN20 vaccine induced high titers of neutralizing antibodies against FAdV-4 and fully protected the immunized chickens against a lethal dose of FAdV-4. Furthermore, immunized chickens showed no clinical symptoms or histopathological changes in the FAdV-4-targeted liver, and the viral load in the tissues of immunized chickens was significantly lower than that of chickens in the challenge control group. Collectively, the live rHN20 vaccine effectively protected our sample against FAdV-4 infection and can be considered a live vaccine candidate for preventing HHS in the poultry industry.

Highlights

In 2015, severe hepatitis-hydropericardium syndrome (HHS) was observed in 3–5-week-old chickens and was determined to be caused by a novel fowl adenovirus 4 (FAdV-4) on chicken farms in China, resulting in mortality rates of 30–100% [5,6,7]
Large necrotic focal areas and steatotic vacuoles were present in chicken liver liver cells from the challenge controls, whereas each immunization group was indistincells from the challenge controls, whereas each immunization group was indistinguishable guishable from the non-inoculated controls. These results suggest that live rHN20 not from non-inoculated controls
Few live attenuated vaccines based on the emerging novel Fowl adenoviruses (FAdVs)-4 have been evaluated [17,18]

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Fowl adenoviruses (FAdVs) are members of the Aviadenovirus genus and Adenoviridae family and are classified into five species (FAdV-A–E) and 12 serotypes (FAdV-1–7, 8a, 8b, and 9–11) [1]. The pathogenicity of different serotypes or even different strains of FAdVs is not completely consistent. FAdV-4 shows the highest virulence [2,3,4]. In 2015, severe hepatitis-hydropericardium syndrome (HHS) was observed in 3–5-week-old chickens and was determined to be caused by a novel FAdV-4 on chicken farms in China, resulting in mortality rates of 30–100% [5,6,7].

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Conclusion