Campylobacter

what is the #8 cause of human mortality

campylobacter

which countries are the most impacted by campylobacter

low- middle- income countries; mostly due to insufficient access to clean water/sanitation facilities, cohabitation with livestock

which patients are most impacted by campylobacter

pediatric patients

how many species does the campylobacter genus contain?

>25; about ½ of the species are pathogenic to humans

does campylobacter cause much disease in its animal hosts?

no

what are the two species of campylobacter that cause the most disease?

C. jejuni (70-85%) and C. coli (10-25%) in the US

what animal species is C. jejuni associated with?

poultry and cattle

what animal species is C. coli associated with

swine

shape of campylobacter

helical, amphitrichous flagella

gram stain of campylobacter

gram-negative

what type of media does campylobacter require

• relatively rich nutrient media

• DOES NOT CONSUME GLUCOSE

• consumes amino acids, fatty acids, and tricarboxylic acids for carbon

oxygen requirements of campylobacter

obligate microaerophile (5% O2)

temperature requirements of campylobacter

thermophilic with optimal growth at 42C (grows well in birds and birds are hot)

what is the most common source of campylobacter in the US

consumption of undercooked meat; often associated with poultry, byt can come from other sources

Infectious does of Campy

very low

what area of the body does campy colonize

the lower gastrointestinal tract

what does campy colonization of the lower GI tract cause

inflammatory diarrhea

symptoms associated with inflammatory diarrhea

stomach cramps, bloody stool, and fever

what causes inflammatory diarrhea

pissed off immune system → damage GI tract, blood in stool, high fevers, malaise

what does secretory diarrhea look like

osmotic imbalance; efflux of water and nutrients into the GI lumen → you pass loose stools

what can persistent campy infection in children lead to?

• environmental enteric dysfunction

• decreased nutrient acquisition, growth, cognitive development

long term implications of campy infection

• reactive arthritis

• IBD

• IBS

• colorectal cancer

• brain abcsesses

• meningitis

GI tract defenses to protect from campy

• low pH

• digestive enzymes and bile salts

• host and microbiota reduce nutrient availability

• mucus coating that is constantly shed

sensitivity of E. coli, salmonella, etc. to low pH and implications of pH tolerance on infectious dose

• very sensitive to low pH

• need a very high infectious dose

diameter of large intestine

5-10 cm

size of bacterium

1 × 5 um → this is very tiny → have to travel a long way from the lumen of the intestine to reach the wall

how do campylobacter move from the lumen to epithelial surface

flagella

speed of campylobacter moving through intestinal lumen

20 cell lengths/second (1 second 40 yard dash); THIS IS ONE OF THE FASTEST ORGANISMS EVER

how many times thicker is mucus than water

100x

speed of campy through mucus

70 um/second; slower than its speed through the lumen, but still 3-7x faster than other GI pathogens

components of mucus serve as ___________ for campy

chemoattractants

what characteristic of campy contributes to its ability to penetrate mucus

helical shape

in general, can commensal gut bacteria penetrate the mucus secreted by goblet cells that lines GI epithelium

no

where to campy cells really like to be

in the crypts of the GI epithelium

what does efficient infection of campy require?

the ability to invade paracellularly (apical invasion is not preferred, fibronectin is more abundant at the basolateral surface)

what protein does campy secrete in order to invade paracellularly

High-temperature requirement protein A (HtrA)

what does HtrA protein do?

• cleaves tight junction components such as occluding, claudin-8, and E. cadherin

• can reduce misfolded proteins

• involved in adherance

simple explanation of the process campy goes through to invade paracellularly

bacteria swims to the colon crypts → the bacteria excretes HrtA → cell junctions are disrupted → campy goes further down

what does campy use to attach to the epithelium

• does hot encode “typical” adhesins or pili

• does encode:

  • CafF

  • FlpA

  • JlpA

  • Flagella?

CadF

campylobacter adhesin to fibronectin; surface protein that binds to fibronectin; helps bacteria adhere to the basolateral side of cells

FlpA

fibronectin-like protein A; surface protein; separate from CadF, but likely binds to fibronectin

JlpA

jejuni lipoprotein A; surface lipoprotein that binds surface associated host protein

flagella and what type of secretion system are evolutionarily related?

T3SS

effector protein

a protein secreted by a bacteria that causes an effect; generally the bacteria trying to get the host cell to do something for it

through what structure does campylobacter secrete its effectors

through its flagella

what are the effector proteins secreted by campylobacter

campylobacter invasioin antigens (Cia proteins)

What induces expression and translocation of Cia proteins

host components; the expression/translocation of Cia proteins often does not occur until there is some contact with host components

what are the Cia protein types?

• CiaB

• CiaC

• CiaD

• CiaI

what proteins does campy secrete into the host cell

• CiaC

• CiaD

• CiaI

• FlaC

• FspA

FlaC

flagellar component

FspA

flagellar component

how is the epithelium connected to Fibronectin

integrins

What do CadF and FlpA (flagellar components secreted by campy) bind to?

fibronectin associated with alpha5beta1 integrin

What does binding of CadF and FlpA to fibronectin during the focal adhesion provess promote?

FAK phosphorylation and Scr-1 recruitment

what does FAK phosphorylation and Scr-1 recruitment lead to in the focal adhesion process?

paxillin phosphorylation and Rac-1 activation

what does activated Rac-1 do in the focal adhesion process

regulates actin remodeling and membrane ruffles

how does campylobacter invade cells?

membrane ruffling with cell-specific actin involvement; clathrin-coated vesicles are also involved (depleting clathrin can inhibit campy invasion into host cells)

What does CCV stand for

campylobacter-containing vacuole

what is the CCV?

a membrane-enclosed compartment that contains the campylobacter within the cell

despite having _______________, the CCV does not often associate with ____________

early and late endosome markers; lysosomes

what structures allow CCV to associate with the host golgi apparatus

microtubule and dynein association

once the CCV associates with the golgi, where does it go?

it gets further transported to the perinuclear environment

what does Cdt stand for

cytolethal distending toxin

what is CDT

tripartite, AB2, toxin containing CdtA, CdtB, and CdtC

What parts of Cdt facilitate holotoxin binding to host cell lipid rafts?

CdtA and CdtC

what part of the cell does the CDT holotoxin bind to

host cell lipid rafts

what is the function of CdtB in CDT

promoted endocytosis by cytoskeleton rearrangements; it is also a DNase I protein that leads to double-strand breaks in host DNA once it has been transported by the Golgi and ER to the nucleus

What does DNA damage as a result of CDT (specifically CdtB) lead to the release of

causes the cell to release proinflammatory

• IL-1B

• IL-6

• IL-8

does every isolate of campy possess CDT?

No. only 40% of strains do

What is are CDT+ campy strains in mice associated with

• increased tissue invasion and pathology in immunocompromised mice

• colorectal tumor formation in mice prone to tumorigenesis

what signaling leads to the recruitment of neutrophils into colonic crypts?

PI3K-gamma dependent signaling

What can neutrophils do in response to Campylobacter

• phagocytose

• degranulate

• form extracellular traps

are neutrophils able to effectively kill campylobacter?

not always; intracellular survive of campy has been observed

what host receptors sense campy lipoproteins?

• TLR1

• TLR2

• TLR6

What host receptors sense campy LOS?

TLR4

What does sensing of lipoproteins by TLR1/2/6 and LOS sensing by TLR4 lead to?

MyD88-dependent activation of NHkB

what does activation of NFkB lead to?

transcription and release of iL-8. TNF-alpha, IL1b, and monocyte chemoattractant protein 1 (MCP-1)

What is the immune response to Cia proteins?

they stimulate MAP kinase and ERK pathways to drive further IL-8 secretion

what does intracellular campy stimulate

TLR9 and nucleotide-binding oligomerization protein NOD receptors

What does campy-induced release of IL-8, TNF-alpha, IL-1b, and MCP-1 lead to?

potent innate immune cell recruitment to tissues

are monocytes recruited to the site of campy infection?

yes

how are monoytes activated in a campy infection?

activated by LOS in a TLR4-dependent manner

what do monocytes do when they are recruited to the cite of campy infection

• promote cytokine secretion

• promote further recruitment of innate immune cells

effect of differentiated macrophages on Campy

they phagocytose it and kill it in nitric oxide synthase 2-dependent manner

what campy enzyme promotes intracellular survival

catalase

what kind of activation occurs in campy-infected macrophages?

NLRP3 inflammasome activation

autoantibody

induced by mimic in pathogen → cross reaction to nerve glycolipids

complement activation in GB syndrome

deposition of C3b MAC

inflammation in GB syndrome

infiltration of macrophages, production of inflammatory mediators, T cells

in GB syndrome, what structure on campy mimics ________ on _________

LOS mimics GM1a on gangliosides

in GN syndrome what happens as a result of campy LOS mimicking GM1a on gangliosides?

development of autoantibodies

In BG syndrome, what does development of autoantibodies promote

complement activation and recruitment of macrophages and T cells

in GB syndrom, what do complement activation, and the recruitment of macrophages and T cells lead to?

demyelination and axonal degradation

what happens as a result of demyelination and axonal degradation of gangliosides in GB syndrome result in?

peripheral paralysis and potential breathing complications