P. 49-59Bacteria have evolved a set of highly specialized proteins to capture iron in irondepleted
environments. The acquisition and uptake of iron present in the extracellular milieu of
eukaryotic organisms is indispensable for the growth and survival of microbial pathogens in the
course of infection. Haemophilus parasuis is the causative agent of Glässer disease, which is
responsible for considerable financial losses in pig-rearing worldwide. To gain insight into the
mechanisms involved in siderophore-mediated iron uptake in H. parasuis, genes in the H. parasuis
ferric hydroxamate uptake (Fhu) region were amplified in the work being reported here. As has been
described in A. pleuropneumoniae, an Fhu genomic region was also present in H. parasuis, being
composed of four potential consecutive open reading frames (ORF) designated as fhuC, fhuD, fhuB,
and fhuA, respectively. By immunoblotting, using a cross-reactive polyclonal antibody raised
against Actinobacillus pleuropneumoniae FhuA protein, it was demonstrated that this protein was
constitutively expressed in H. parasuis and its level of expression was not modified under
conditions of restricted iron availability. This is the first report describing the presence of the fhu
genes in H. parasuis. Our results indicate that FhuA protein expression is not affected under ironrestricted
conditions, however, it is one of the targets of the humoral immune responseS
