Vet. Res. 37 (2006) 49-59
DOI: 10.1051/vetres:2005039

Molecular characterization of Haemophilus parasuis ferric hydroxamate uptake (fhu) genes and constitutive expression of the FhuA receptor

Maria Luisa del Río^a, Jesús Navas^b, Ana Judith Martín^a, César B. Gutiérrez^a, José-Ignacio Rodríguez-Barbosa^c and Elías F. Rodríguez Ferri<sup>a

a</sup>  Microbiology and Immunology Section, Department of Animal Health, Faculty of Veterinary Medicine, Leon, Spain
^b  Department of Molecular Biology, School of Medicine, Santander, Spain
^c  Research Unit, Arrixaca University Hospital, Murcia, Spain

(Received 16 December 2004; accepted 20 June 2005; published online 13 December 2005)

Abstract - Bacteria have evolved a set of highly specialized proteins to capture iron in iron-depleted 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 iron-restricted conditions, however, it is one of the targets of the humoral immune response.

Key words: Haemophilus parasuis / ferric hydroxamate uptake / iron

Corresponding author: Elías F. Rodríguez Ferri dsaerf@unileon.es

© INRA, EDP Sciences 2005