The ferrous iron transporter IRP1-3 is required for Bordetella pertussis pathogenesis

JUAN HILARIO, CAFIERO; ALVAREZ HAYES, J; LAMBERTI YANINA; MARIA EUGENIA RODRIGUEZ

Buenos Aires

Simposio; 11th International Bordetella Symposium; 2016

Bordetella Scientific Committee

Bordetella pertussis (Bp) survives inside macrophages in compartments with early endosomecharacteristics. IRP1-3 is one of Bp high affinity iron transporters and the only active at the pHinside early endosomes. To control a bacterial infection, IFN-γ is produced by the host, whichdepletes iron from phagocytic cells, in order to restrict the growth of intracellular pathogens. Thismight determine that during Bp intracellular survival there is low iron availability. Objective:Determine the role of IRP1-3 in Bp pathogenesis. Materials and methods: A Bp IRP1-3 null mutantstrain and a complemented strain were constructed. The growth in SS liquid medium of these andthe parental (wt) strain were measured in parallel and showed no differences. Iron depletedcultures of the strains were used in an infection assay of PMA differentiated IFN-γtreated THP-1cells. Immunofluorescence microscopy was used to analyze the uptake of bacteria. Theintracellular survival of the strains inside THP-1 cells was analyzed in a polymyxin B protectionassay, and the CFU/THP-1 was enumerated at 2, 24 and 48 hours post infection (pi) andnormalized to the attachment level of each strain. To analyze the role of IRP1-3 in vivo, BALB/cmice were infected intranasally with either Bp wt or Bp∆IRP1-3 and the lung colonization wasevaluated at 0 and 6 days pi. Results: Bp∆IRP1-3 adhered significantly less (p<0.01) than the wtand the complemented strain to THP-1 cells, suggesting that either IRP1-3 is an adhesin or thatthis transporter affects other adhesins on the bacterial surface. Furthermore, Bp∆IRP1-3 survivedless than the wt strain at 24 and 48 hours pi (p<0.01), indicating that IRP1-3 is required forintracellular survival. In a mice infection, the mutant strain colonized in a lesser extent the lungsthan the wt strain at day 6 pi (p<0.001), confirming that IRP1-3 plays a role in Bp infectiousprocess. Conclusion: Overall, these suggest that IRP1-3 is a relevant factor in Bp pathogenesis