Characterization of two putative Dichelobacter nodosus footrot vaccine antigens identifies the first lysozyme inhibitor in the genus

Sci Rep. 2019 Jul 11;9(1):10055. doi: 10.1038/s41598-019-46506-z.

Abstract

The Gram-negative anaerobic bacterium Dichelobacter nodosus (Dn) causes footrot in ruminants, a debilitating and highly contagious disease that results in necrotic hooves and significant economic losses in agriculture. Vaccination with crude whole-cell vaccine mixed with multiple recombinant fimbrial proteins can provide protection during species-specific outbreaks, but subunit vaccines containing broadly cross-protective antigens are desirable. We have investigated two D. nodosus candidate vaccine antigens. Macrophage Infectivity Potentiator Dn-MIP (DNO_0012, DNO_RS00050) and Adhesin Complex Protein Dn-ACP (DNO_0725, DNO_RS06795) are highly conserved amongst ~170 D. nodosus isolates in the https://pubmlst.org/dnodosus/ database. We describe the presence of two homologous ACP domains in Dn-ACP with potent C-type lysozyme inhibitor function, and homology of Dn-MIP to other putative cell-surface and membrane-anchored MIP virulence factors. Immunization of mice with recombinant proteins with a variety of adjuvants induced antibodies that recognised both proteins in D. nodosus. Notably, immunization with fimbrial-whole-cell Footvax vaccine induced anti-Dn-ACP and anti-Dn-MIP antibodies. Although all adjuvants induced high titre antibody responses, only antisera to rDn-ACP-QuilA and rDn-ACP-Al(OH)3 significantly prevented rDn-ACP protein from inhibiting lysozyme activity in vitro. Therefore, a vaccine incorporating rDn-ACP in particular could contribute to protection by enabling normal innate immune lysozyme function to aid bacterial clearance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesins, Bacterial / immunology*
  • Animals
  • Antibodies, Bacterial / blood
  • Antibody Formation
  • Bacterial Proteins / immunology*
  • Bacterial Vaccines / immunology*
  • Dichelobacter nodosus / physiology*
  • Fimbriae, Bacterial / immunology
  • Foot Rot / immunology*
  • Mice
  • Muramidase / antagonists & inhibitors
  • Peptidylprolyl Isomerase / immunology*
  • Phylogeny
  • Protein Conformation
  • Recombinant Proteins / immunology*
  • Ruminants
  • Vaccination

Substances

  • Adhesins, Bacterial
  • Antibodies, Bacterial
  • Bacterial Proteins
  • Bacterial Vaccines
  • Recombinant Proteins
  • Muramidase
  • lysozyme C, human
  • Peptidylprolyl Isomerase