Haemophilus parasuis, the etiological agent of Gl¨asser’s disease in pigs, possesses
iron acquisition pathways mediated by a surface receptor that specifically bind
porcine transferrin. This receptor is composed of transferrin-binding protein A
(TbpA) and TbpB. As it has been reported for other gram-negative organisms, H.
parasuis TbpA could be useful as a candidate target for H. parasuis vaccination. In
this study, a 600-bp tbpA fragment of the gene encoding TbpA from H. parasuis
serovar 5, the Nagasaki strain, was amplified by PCR and cloned into a pBAD/
Thio-TOPO expression vector, generating the pBAD-Thio-TbpA-V5-His (TbpAHis)
construction. Escherichia coli LMG194-competent cells were transformed
with this construction, followed by the induction of protein expression with
arabinose. A band (38.5 kDa) corresponding to a 200-amino acid recombinant
TbpA (rTbpA) fragment was seen on the sodium dodecyl sulfate polyacrylamide
gel electrophoresis and confirmed by immunoblotting. Polyclonal antibodies
raised against this fragment were specific for H. parasuis and Actinobacillus
pleuropneumoniae, reacted at the cell surface with H. parasuis, and a significant
bactericidal activity was also detected. Therefore, this rTbpA fragment induces an
immunological response and might be useful as an antigen for vaccination against
Gl¨asser’s disease
