Bordetella pertussis is the human adapted pathogen that causes the disease known a “whooping cough”. B. pertussis is a non-invasive, extracellular pathogen that colonizes the upper respiratory tract (URT) during pathogenesis.

• Name 2 innate immune mechanisms that B. pertussis must evade in order to successfully colonize the URT.
• Name 2 secreted products expressed by B. pertussis during URT colonization that knockout the above 2 innate immune mechanisms that you listed.

B. pertussis infection is viewed as a two stage pathogenesis process involving first colonization of the URT and second toxin mediated tissue damage. Name two virulence factors that are expressed by B. pertussis that are responsible for toxin mediated tissue damage.

BvgAS, the virulence gene regulation locus of pathogenic Bordetella, is a 2 component sensory transduction system. How was BvgAS implicated in phase variation that occurs with Bordetella pertussis with respect to the virulence phenotype?

In a study designed to determine whether BvgAS of B. pertussis is responsible for phenotypic modulation of virulence, Miller et al. designed an experimental approach to find mutants that were insensitive to environmental modulators of BvgAS.

• In the genetic construct generated for the above goal by Miller (strain VIR102 of B. pertussis), why was the pertussis encoding toxin gene fused with the gene encoding chloramphenicol acetyltransferase that confers resistance to the antibiotic chloramphenicol?
• Why was hemolytic activity also assayed along with chloramphenicol resistance?
• Why in the genetic construct that they generated (VIR102) did they delete the wild type BvgAS from the chomosome and then integrate back into the chromosome a plasmid vector containing wild type BvgAS? How did this allow them to prove that BvgAS mediates phenotypic modulation?

The apparent function of BvgAS in Bordetella pathogens is to determine if Bordetella is within or outside a mammalian host. The Bvg minus phase in B. bronchiseptica results in the expression of several products required for survival of B. bronchiseptica when it is free living in the environment. What is the function of the Bvg minus phase products expressed by B. pertussis

During B. bronchiseptica infection of rabbits, serum from the infected rabbits have antibodies against FHA, fimbriae, adenylcyclase, but not flagella. What conclusion can you draw from this finding with respect to BvgAS?

In the “skinny pig” (the ugly hairless guinea pig) aerosol transmission model it was found that B. bronchiseptica having a wild type BvgAS locus, but not those having a Bvgc (constitutive Bvg+ phase) locus were transmission competent. Given that Bvgc is as virulent as wild type, and Bvg- is avirulent, what conclusions were drawn from this observation?