title: Construction of a camelid VHH yeast two-hybrid library and the selection of VHH against haemagglutinin-neuraminidase protein of the Newcastle disease virus.
abstract: BACKGROUND
  Newcastle disease (ND), which is caused by the Newcastle disease virus (NDV), is one of the most important avian diseases in poultry. Since its discovery in 1926, ND has caused great economic losses to the world poultry industry and remains a threat to chickens and wild birds. Although a stringent vaccination policy is widely adopted to control ND, ND outbreaks still occur, and virulent NDV is sporadically isolated from chickens and wild birds. To study the pathogenesis of ND and provide tools to prevent its prevalence, novel antibody fragments should be developed. The variable domains of the heavy chain of the heavy-chain antibodies (VHH) are the smallest naturally occurring antibodies derived from camelid heavy-chain antibodies. The comparatively small size, high affinity, high solubility, low immunogenicity and ability to bind epitopes inaccessible to conventional antibodies of VHH make them ideal candidates for a considerable number of therapeutic and biotechnological applications. However, an anti-NDV VHH has not been reported to date.
  
  
  RESULTS
  In this study, a VHH yeast two-hybrid library was constructed from NDV vaccine immunized C. bactrianus, and seven VHH fragments to the haemagglutinin-neuraminidase (HN) protein of NDV were successfully screened and characterized for the first time. These selected VHH clones were all expressed as soluble protein in E. coli. ELISA, dot blot, immunocytochemistry and pull down results showed that the screened VHHs could interact with NDV virion, among which five had neutralizing activity. In addition, the seven VHHs could inhibit the haemagglutination activity of different NDV strains.
  
  
  CONCLUSIONS
  We constructed an NDV-immunized VHH yeast two-hybrid library and screened and characterized seven VHHs targeting NDV HN protein for the first time. The seven VHHs may have great potential for NDV diagnosis, pathogenesis and therapeutics.
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. gaoxiaolong1017@163.com.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Gao
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. 821995274@qq.com.
authors.forename: Xiangyun
authors.initials: X
authors.lastname: Hu
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. 957594922@qq.com.
authors.forename: Lina
authors.initials: L
authors.lastname: Tong
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. 394010364@qq.com.
authors.forename: Dandan
authors.initials: D
authors.lastname: Liu
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. 13946753@qq.com.
authors.forename: Xudong
authors.initials: X
authors.lastname: Chang
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. 1091382540@qq.com.
authors.forename: Haixin
authors.initials: H
authors.lastname: Wang
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. 345489586@qq.com.
authors.forename: Ruyi
authors.initials: R
authors.lastname: Dang
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. 93341378@qq.com.
authors.forename: Xinglong
authors.initials: X
authors.lastname: Wang
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. 2803779262@qq.com.
authors.forename: Sa
authors.initials: S
authors.lastname: Xiao
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. duenqi227@126.com.
authors.forename: Enqi
authors.initials: E
authors.lastname: Du
authors.affiliation: College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi Province, 712100, P. R. China. yzq1106@nwsuaf.edu.cn.
authors.forename: Zengqi
authors.initials: Z
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002162:Camelus; D005260:Female; D015723:Gene Library; D015707:HN Protein / Q000276:immunology*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008969:Molecular Sequence Data; D009522:Newcastle disease virus / Q000276:immunology*; D020798:Two-Hybrid System Techniques
chemical_list: D015707:HN Protein; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region