Bordetella

Question 1

What are possible reasons for the recent increase in the incidence of B. pertussis infections?

Answer 1

1. improved surveillence and diagnostic techniques
2. Low immunisation rates among adults and adolescents.
3. waning immunity after vaccination with acellular vaccine.
4. Acellular vaccines protect individuals from symptoms and not colonization leading to a large reservoir of residents who can spread the infection.
5. Strain evolution in circulating strains causing loss or reduced expression of antigens in acellular vaccine.
6. New bordetalla species causing whooping cough-like symptoms.

Question 2

Which are the major antigens used in modern acellular vaccines against whooping cough

Answer 2

1. Pertussis toxin (PTX)
2. Pertactin
3. Fimbriae
4. Filamentous hemagglutinin

Question 3

Why is whooping cough frequently not diagnosed early enough for antibiotics therapy?

Answer 3

1. The symptoms for whooping cough appear after serveral days (10-14 days) but bacteria can only be detected within 2weeks of infection. this makes early diagnosis difficult.
2. Early symptoms are non specific

Question 4

Please describe the major properties of the adenylate cyclase toxin of B. pertussis

Answer 4

It is secreted by type I secretion system
it is part of RTX family of toxins
it is chemically bound by acylation of lysine residues
it is a protective antigen
it is made up of two functional domains (C-terminal responsible for receptor binding and pore formation in cell membrane while N-terminal with calmodulin dependent-adenylate cyclase invades eukaryotic cells leading to cAMP formation)

Question 5

Please describe the chemical composition of the tracheal cytotoxin of B. pertussis and its presumed
role in virulence

Answer 5

it is a spontaneously released muramyl peptide generated during normal cell wall remodelling and recycled by transport into cytosol by AmpG transport protein.

with Lipopolysacchaide, it synergestically stimulates the production of proinflammatory cytokines and induced nitric oxide synthase.
Production of nitric oxide causes tissue distruction and extrusion of cilliated cells from the epithelial surface.

Question 6

Which cell type is the major target for adhesion and colonization by B. pertussis?

Answer 6

Ciliated epithelail cells in the upper respiratory tract (Trachea).

Question 7

Please describe briefly how expression of most virulence genes is regulated in B. pertussis
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Answer 7

Multi-domain BvgS histidine kinase has input and receiver domains, + phosphorelay domains

• Signal from periplasm -> phosphate is transferred along the BvgS phosphorelay system, then transferred to receiver domain of the BvgA response regulator
• This activates the output/DNA binding domain of the BvgA response regulator
• DNA-binding domain becomes a positive or negative transcription factor
• The amount of phosphorylated BvgA response regulator determines which class of genes are expressed

Question 8

Which groups of genes can be classified according to their BvgAS-mediated expression pattern and
provide examples for each group

Answer 8

vag genes (virulence activated genes)
class i- PTX and CYA
class ii- FHA and FIM
class iii- BipA

vrg genes(virulence represses genes)
classiv- B. bronchoseptica motility gene.

Question 9

Compare briefly some important genomic properties of the classical Bordetellae

Answer 9

1. pertusis and parapertusis which both independently evolved from bronchoseptica show their are still under selection pressure.
   a. they both have a smaller genome than bronchoseptica.
   b. they both have a higher number of pseuogenes
   c. have higher number of transposable genomic elements.

Thus, both
species have probably started to specialize to a single host species relatively recently and
still are in an ongoing state of genome erosion in which they get rid of genes not necessary
anymore or even disturbing. Mobile genetic elements may help in this process of genome
reduction by causing genomic rearrangements and deletions

Question 10

Please denominate three Bordetella species pathogenic for animals and which animals are infected
by them

Answer 10

B. avium- birds
B. bronchoseptica- rabbit, sheep (vareity of mammals)
B. parapertusis- sheep
B. hinzii- rabbit