Targeting the HUβ Protein Prevents Porphyromonas gingivalis from Entering into Preexisting Biofilms

Abstract

ABSTRACT The oral cavity is home to a wide variety of bacterial species, both commensal, such as various streptococcal species, and pathogenic, such as Porphyromonas gingivalis , one of the main etiological agents of periodontal disease. Our understanding of how these bacteria ultimately cause disease is highly dependent upon understanding how they coexist and interact with one another in biofilm communities and the mechanisms by which biofilms are formed. Our research has demonstrated that the DNABII family of DNA-binding proteins are important components of the extracellular DNA (eDNA)-dependent matrix of bacterial biofilms and that sequestering these proteins via protein-specific antibodies results in the collapse of the biofilm structure and release of the resident bacteria. While the high degree of similarity among the DNABII family of proteins has allowed antibodies derived against specific DNABII proteins to disrupt biofilms formed by a wide range of bacterial pathogens, the DNABII proteins of P. gingivalis have proven to be antigenically distinct, allowing us to determine if we can use anti- P. gingivalis HUβ antibodies to specifically target this species for removal from a mixed-species biofilm. Importantly, despite forming homotypic biofilms in vitro , P. gingivalis must enter preexisting biofilms in vivo in order to persist within the oral cavity. The data presented here indicate that antibodies derived against the P. gingivalis DNABII protein, HUβ, reduce by half the amount of P. gingivalis organisms entering into preexisting biofilm formed by four oral streptococcal species. These results support our efforts to develop methods for preventing and treating periodontal disease. IMPORTANCE Periodontitis is one of the most prevalent chronic infections, affecting 40 to 50% of the population of the United States. The root cause of periodontitis is the presence of bacterial biofilms within the gingival space, with Porphyromonas gingivalis being strongly associated with the development of the disease. Periodontitis also increases the risk of secondary conditions and infections such as atherosclerosis and infective endocarditis caused by oral streptococci. To induce periodontitis, P. gingivalis needs to incorporate into preformed biofilms, with oral streptococci being important binding partners. Our research demonstrates that targeting DNABII proteins with an antibody disperses oral streptococcus biofilm and prevents P. gingivalis entry into oral streptococcus biofilm. These results suggest potential therapeutic treatments for endocarditis caused by streptococci as well as periodontitis.