HmuY is an important virulence factor for Porphyromonas gingivalis growth in the heme-limited host environment and infection of macrophages

Porphyromonas gingivalis, the main etiologic agent and key pathogen responsible for initiation and progression of chronic periodontitis, is a haem auxotroph, and the uptake of this compound is essential for its survival and the ability to establish an infection. The aim of this study was to examine the role of a hemophore-like HmuY protein in P. gingivalis growth and infection of macrophages. Inactivation of the hmuY gene caused reduced P. gingivalis growth in vitro in the presence of serum as a heme sole source, as well as in vivo co-cultures with THP-1-derived macrophages. This resulted in diminished invasion efficiency of macrophages by live bacteria lacking functional hmuY gene. Both features were partially restored after addition of the purified HmuY protein, which was internalized when added either together with the hmuY mutant strain or alone to macrophage cultures. We conclude that HmuY is an important virulence factor of P. gingivalis for infection of macrophages in a heme-limited host environment.