Meng, Lingzhai;Yu, Mengmeng;Wang, Suyan;Chen, Yuntong;Bao, Yuanling;Liu, Peng;Feng, Xiaoyan;He, Tana;Guo, Ru;Zhang, Tao;Hu, Mingxue;Liu, Changjun;Qi, Xiaole;Li, Kai;Gao, Li;Zhang, Yanping;Cui, Hongyu;Gao, Yulong

Chinese Acad Agr Sci, Harbin Vet Res Inst, Avian Immunosuppress Dis Div, State Key Lab Anim Dis Control & Prevent, Harbin 150069, Peoples R China;Natl Poultry Lab Anim Resource Ctr, Harbin 150069, Peoples R China

avian metapneumovirus;attenuated;protection;vaccine candidate;chickens

Avian metapneumovirus (aMPV) is a highly contagious pathogen that causes acute upper respiratory tract diseases in chickens and turkeys, resulting in serious economic losses. Subtype B aMPV has recently become the dominant epidemic strain in China. We developed an attenuated aMPV subtype B strain by serial passaging in Vero cells and evaluated its safety and efficacy as a vaccine candidate. The safety test showed that after the 30th passage, the LN16-A strain was fully attenuated, as clinical signs of infection and histological lesions were absent after inoculation. The LN16-A strain did not revert to a virulent strain after five serial passages in chickens. The genomic sequence of LN16-A differed from that of the parent wild-type LN16 (wtLN16) strain and had nine amino acid mutations. In chickens, a single immunization with LN16-A induced robust humoral and cellular immune responses, including the abundant production of neutralizing antibodies, CD4+ T lymphocytes, and the Th1 (IFN-gamma) and Th2 (IL-4 and IL-6) cytokines. We also confirmed that LN16-A provided 100% protection against subtype B aMPV and significantly reduced viral shedding and turbinate inflammation. Our findings suggest that the LN16-A strain is a promising live attenuated vaccine candidate that can prevent infection with subtype B aMPV.