Bordetellae and their interactions with the host: Improving the fight against infection.

Open Access
Author:
Goodfield, Laura Lynn
Graduate Program:
Immunology and Infectious Diseases
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 12, 2014
Committee Members:
  • Eric Thomas Harvill, Dissertation Advisor
  • Eric Thomas Harvill, Committee Chair
  • Margherita Teresa Anna Cantorna, Committee Member
  • Girish Soorappa Kirimanjeswara, Committee Member
  • Mary J Kennett, Committee Member
  • David Peter Hughes, Special Member
Keywords:
  • Bordetella
  • Whooping cough
  • host-pathogen interactions
  • vaccination
  • microfold cell
  • respiratory pathogen
Abstract:
The classical bordetellae are comprised of respiratory pathogens that infect a wide range of hosts. This dissertation focuses on surveying Bordetella species and investigating host-pathogen interactions. Chapter 2 identifies 22 different PFGE types of B. pertussis, including newly identified PFGE types, which were isolated during outbreaks in California and Washington from 2010-2012. Although the isolates are genetically distinct, they have similarities in susceptibility to antibiotics and in vivo growth in the murine respiratory tract. Three (ptxA, fim2, and fim3) of 5 genes encoding vaccine antigens were conserved while two others contained mutations (prn and fhaB) in approximately half of the isolates. Investigation of current vaccine efficacy revealed that the current acellular pertussis vaccine reduced colonization of clinical B. pertussis strains in the murine respiratory tract, though not necessarily to the same extent as it reduced that of the laboratory strain. These data provide evidence that the current vaccine is still effective, but the circulating B. pertussis isolates have evolved since the generation of the vaccine. Chapter 3 investigates an avirulent B. bronchiseptica strain isolated from human sputum. This B. bronchiseptica strain 99R-0433 is beta-hemolytic when grown on a blood agar plate and appears to be negative for O-antigen serotypes O1 and O2. Additionally, in contrast to B. bronchiseptica strain RB50, which is an efficient colonizer of the murine respiratory tract, B. bronchiseptica strain 99R-0433 cannot colonize the murine respiratory tract of wild type or immunodeficient mice. Based on genome wide SNP analysis, B. bronchiseptica strain 99R-0433 is divergent from other Bordetella isolates. Furthermore, B. bronchiseptica strain 99R-0433 lacks several important virulence factors including pertactin, tracheal colonization factor, dermonecrotic toxin, adenylate cyclase toxin, Type VI secretion system, and O-antigen. Using this strain as a tool, we can begin to understand which virulence factors are required for different aspects of pathogenesis. Investigating the host side, Chapter 4 discusses the interactions between Bordetella species and microfold (M) cells. The data provide evidence that B. bronchiseptica is capable of colocalizing with M cells in vivo and in vitro, and Bordetella species associate with and are translocated by M cells in a Bvg-dependent manner. Following infection with Bordetella species, induction of tumor necrosis factor α and interleukin-6 by M cells are observed. These preliminary data provide support for determining whether M cells play a role in the initiation of an immune response. Chapter 5 questions the experimental mouse model of a high dose inoculation system and discusses the capabilities of using B. bronchiseptica at a low dose inoculum in order to mimic natural conditions. The low dose inoculum grows in the nasal cavity and results in high bacterial numbers of approximately 100,000 by 7 days post-inoculation, and the bacteria are capable of persisting long term to day 56. Toll like receptor-4 (TLR4) signaling is required for the control of bacterial growth in the nasal cavity in a low dose inoculum, which is in contrast to high dose inoculation systems. In contrast, Tumor necrosis factor-α (TNFα) signaling is not required for control of bacterial numbers following a low dose inoculation. Cell recruitment analysis revealed that while a high dose inoculum induces ~6,500 leukocytes to the nasal cavity 7 days post-inoculation, the low dose inoculum does not induce recruitment of leukocytes or neutrophils beyond a basal level (< 3,000). Finally, despite the inability of the low dose to induce leukocytosis to the nasal cavity, serum antibody levels are the same in both high and low dose inoculated mice. Through these studies, we can understand the breadth of Bordetella species and their interactions with the host system while beginning to elucidate remaining questions concerning their pathogenesis.