Zhang Xuxiao, Zhang Fushou, Chen Ning, Cui Xiaoping, Guo Xiaoqin, Sun Zhi, Guo Pengju, Liao Ming, Li Xin
Boehringer Ingelheim Vetmedica (China) Co., Ltd., Taizhou 225300, China.
National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, China.
Vaccines (Basel). 2024 Aug 21;12(8):932. doi: 10.3390/vaccines12080932.
The evolution of the H5 highly pathogenic avian influenza (HPAI) viruses has led to the emergence of distinct groups with genetically similar clusters of hemagglutinin (HA) sequences. In this study, a consensus H5 HA sequence was cloned into the baculovirus expression system. The HA protein was expressed in baculovirus-infected insect cells and utilized as the antigen for the production of an oil emulsion-based H5 avian influenza vaccine (rBacH5Con5Mut). Twenty-one-day-old SPF chickens were immunized with this vaccine and then challenged at 21 days post-vaccination with clade 2.3.2.1, clade 2.3.4.4, and clade 7.2 of H5 HPAI viruses. The sera of vaccinated chickens exhibited high hemagglutination inhibition (HI) titers against the rBacH5 vaccine antigen, while lower HI titers were observed against the different challenge virus H5 hemagglutinins. Furthermore, the rBacH5Con5Mut vaccine provided 100% protection from mortality and clinical signs. Virus isolation results showed that oropharyngeal and cloacal shedding was prevented in 100% of the vaccinated chickens when challenged with clade 2.3.2.1 and clade 2.3.4.4 H5 viruses. When the rBacH5Con5Mut vaccine candidate was administrated at one day of age, 100% protection was demonstrated against the challenge of clade 2.3.4.4 virus at three weeks of age, indicating the potential of this vaccine for hatchery vaccination. Overall, A single immunization of rBacH5Con5Mut vaccine candidate with a consensus HA antigen can protect chickens against different clades of H5 HPAI viruses throughout the rearing period of broiler chickens without a boost, thus fulfilling the criteria for an efficacious broad-spectrum H5 avian influenza vaccine.
H5高致病性禽流感（HPAI）病毒的进化导致出现了具有基因相似的血凝素（HA）序列簇的不同群体。在本研究中，将一个共有H5 HA序列克隆到杆状病毒表达系统中。HA蛋白在杆状病毒感染的昆虫细胞中表达，并用作生产油乳剂H5禽流感疫苗（rBacH5Con5Mut）的抗原。用该疫苗对21日龄的SPF鸡进行免疫，然后在接种疫苗后21天用H5 HPAI病毒的2.3.2.1分支、2.3.4.4分支和7.2分支进行攻毒。接种疫苗的鸡血清对rBacH5疫苗抗原表现出高血凝抑制（HI）效价，而对不同攻毒病毒的H5血凝素观察到较低的HI效价。此外，rBacH5Con5Mut疫苗提供了100%的死亡率和临床症状防护。病毒分离结果表明，在用2.3.2.1分支和2.3.4.4分支H5病毒攻毒时，100%的接种疫苗鸡的口咽和泄殖腔排毒得到预防。当rBacH5Con5Mut候选疫苗在1日龄时给药，对3周龄时2.3.4.4分支病毒的攻毒显示出100%的防护，表明该疫苗用于孵化场接种的潜力。总体而言，用共有HA抗原单次免疫rBacH5Con5Mut候选疫苗可以在肉鸡整个饲养期内保护鸡免受不同分支的H5 HPAI病毒感染，无需加强免疫，从而满足有效广谱H5禽流感疫苗的标准。
