Lai Lijin, Li Rui, Chen Yanan, Deng Junyuan, Yu Siyao, Lin Qiuyan, Chen Libin, Ren Tao
College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China.
National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, Guangzhou, China.
Vet Res. 2025 Jul 8;56(1):144. doi: 10.1186/s13567-025-01577-x.
The H9N2 subtype of avian influenza is highly contagious, and although it is classified as a low-pathogenic avian influenza virus, its tendency to recombine with other subtypes of avian influenza viruses has made it a potential problem for the poultry industry. Vaccines currently used to prevent this disease are all inactivated, making it difficult to stimulate long-lasting immunity, and have a very weak ability to trigger cellular immunity, thus failing to address the problem of virus shedding. Live-attenuated vaccines are capable of stimulating cellular immunity but carry the risk of recombination with wild-type strains. In this study, we successfully rescued a replication-deficient H9N2 strain (H9-SD18GD12HA) using reverse genetic techniques, which was obtained by replacing the neuraminidase (NA) gene with the open reading frame of the hemagglutinin (HA) gene with the PR8 strain as the backbone. Dynamic growth results showed that H9-SD18GD12HA can proliferate only under NA-containing conditions and therefore cannot grow in normal animals or cells. After immunization of chickens with H9-SD18GD12HA using eye and nose drops, both humoral and cellular immunity were stimulated, and some degree of reduction in virus shedding was observed. These results indicate that H9-SD18GD12HA has good immunogenicity, does not proliferate in vivo, and has the potential to be developed into a novel live-attenuated vaccine for the H9N2 subtype of avian influenza.
H9N2亚型禽流感具有高度传染性，尽管它被归类为低致病性禽流感病毒，但其与其他亚型禽流感病毒重组的倾向已使其成为家禽业的一个潜在问题。目前用于预防这种疾病的疫苗均为灭活疫苗，难以刺激产生持久免疫力，且触发细胞免疫的能力非常弱，因此无法解决病毒脱落问题。减毒活疫苗能够刺激细胞免疫，但存在与野生型毒株重组的风险。在本研究中，我们利用反向遗传技术成功拯救了一株复制缺陷型H9N2毒株（H9-SD18GD12HA），它是以PR8毒株为骨架，用血凝素（HA）基因的开放阅读框替换神经氨酸酶（NA）基因而获得的。动态生长结果表明，H9-SD18GD12HA仅在含有NA的条件下才能增殖，因此无法在正常动物或细胞中生长。用H9-SD18GD12HA滴鼻点眼免疫鸡后，既能刺激体液免疫又能刺激细胞免疫，且观察到病毒脱落有一定程度的减少。这些结果表明，H9-SD18GD12HA具有良好的免疫原性，在体内不增殖，有潜力被开发成为一种新型的H9N2亚型禽流感减毒活疫苗。
