Diagnostic potential of an iron-regulated hemin-binding protein HbpA that is widely conserved in Leptospira interrogans.

Like most bacteria, Leptospira spp. requires iron for growth. However, they face conditions of iron limitation due to the low solubility of the ferric iron and additionally due to the observation that most of the available iron is held as protein-bound iron by the mammalian host. Our experimental observations with pathogenic Leptospira showed that they do not elaborate siderophores upon iron limitation. In Leptospira interrogans serovar Lai, we demonstrated direct acquisition of iron via an iron-regulated hemin-binding protein HbpA. PCR analysis and Southern hybridization studies revealed that the hbpA gene was conserved in the serovars belonging to L. interrogans species and was absent in the non-pathogenic Leptospira biflexa serovar Patoc and Leptospira meyeri serovar Ranarum. Here, we extended the PCR-based detection of the hbpA gene to clinical isolates and demonstrated the hbpA amplicon in all the serovars belonging to L. interrogans species from a total collection of 91 clinical isolates obtained from different geographical regions. In addition, we detected anti-HbpA antibodies in the serum of patients with leptospirosis. PCR-based detection of hbpA in clinical isolates of serovars and the in vivo expression of HbpA reflects the diagnostic potential of this antigen.