title: Immunological identification and characterization of extracellular serine protease-like protein encoded in a putative espP2 gene of Haemophilus parasuis.
abstract: Haemophilus parasuis is known to produce a group of virulence-associated autotransporter (AT) proteins, VtaAs; however, no other ATs have been characterized yet. On the basis of the reported sequence of a putative espP2 gene for extracellular serine protease (ESP)-like protein of H. parasuis, this putative AT gene was successfully amplified from H. parasuis serotype 5 field strain HPS0819, cloned and sequenced. The confirmed ORF sequence showed 100% identity with the reported putative espP2 gene. The recombinant ESP-like protein purified from Escherichia coli with a pET expression system was used for immunological characterization. An approximately 85 kDa antigen was detected in cultured H. parasuis by using antiserum to the purified ESP-like protein, and antibodies against the recombinant ESP-like protein were detected in a selected serum from pigs with experimental H. parasuis infection. The results indicated that H. parasuis could produce ESP-like protein in vitro and in vivo. In an immune protection study using guinea pigs, 6 out of 10 animals immunized with the recombinant ESP-like protein survived after challenge with 5 × 10(9) bacteria of strain HPS0819, whereas 7 out of 10 animals immunized with formalin-inactivated H0819 bacterin survived after challenge. The results suggest that ESP-like protein could be one of the vaccine antigen candidates for H. parasuis infection.
authors.affiliation: State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou 730046, China.
authors.forename: Nian-Zhang
authors.initials: NZ
authors.lastname: Zhang
authors.forename: Yue-Feng
authors.initials: YF
authors.lastname: Chu
authors.forename: Peng-Cheng
authors.initials: PC
authors.lastname: Gao
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
authors.forename: Ying
authors.initials: Y
authors.lastname: He
authors.forename: Zhong-Xin
authors.initials: ZX
authors.lastname: Lu
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006168:Guinea Pigs; D006192:Haemophilus Infections / Q000382:microbiology; D044137:Haemophilus parasuis / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D057057:Serine Proteases / Q000235:genetics / Q000378:metabolism*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D057057:Serine Proteases