B6- Gut Parasites And Giardia SAV Flashcards
Which 2 gut parasites are common in the whole world because they are zoonotic
Cryptosporidium and giardia (micro is also zoonotic)
How does this compare to entamoeba histolytica
Low levels in eu and us more in developing countries eg due to poor sanitation of water
Which way do they all transmit
Faecal oral with resistant cysts
Although giardia is extracellular where is it
Close to epi surfaces (contacts with them)
What is acute vs chronic diarrhoea
Acute is below 14 days
Chronic is over 30 and seem more in immunocompromised
What are the 2 main cryptosporidium
Parvum and hominis
What do they cause if severe infections
Profuse watery diarrhoea, vomiting, malabsorption and death (in under 2 second biggest death after rv)
What proteases do they have for ezcystarion
Serine protease
What is gp900 and TRAP proteins for and found to be from
Found in invading sporozoites and required for host cell invasion
From microneme release of apical organelles
Which cells do they infect
Small intestine
What transporter in c.Parvum found for feeding on nutrients in the parasitophorous vacuole
CpABC transporters (another virulence factor)
Which pid affecting cd4 are eveidence for crucial role of cd4 cells in crypto
Scid and cd4 lymphophenia severity of disease
What cells induced by the th1 in particular also important in the crypto response
CD8 and NK cells potentially
What happens in hiv infection for collapse
Hiv load comes in
Not fully removed by your immune system so persists and replicates
High viral load causes loss first of mucosal cd4 and then blood cd4
Below what cell count of CD4 sees increased micro and crypto
100 mm^4
Where can excystarion occur to release 4 sporozoites in crypto
Stomach acid ph
What histological changes seen in infection
Villous atrophy and immune infiltration
Which neuropeptide triggered by crypto from monocytes/macrophages is released which increase Cl secretion for diarrhoea
Neuropeptide P
In what disease is neuropeptide p seen more of
AIDS
Give some examples of proteins crypto has which disrupts tj and cytoskeleton for permeability and proinflam responses (for diarrhoea)
Aminopeptidases
Recognition of c Parvum by enterocyte tlr important for the release of chemotactic cytokines for neutrophils like RANTES and il8, why?
Because macrophages are isolated from them since at the apical site
Need neutrophil response
Which hiv protein downrwgs the tlr4 responses of crypto
Tat protein
Which cytokines important for reduced crypto burden and is low in hiv and chronic uncontrolled cryptosporidiosis
Il15
What does it do and where from
Activated monocytes release it and
Induces the ilc1/NK response
causes NK cell prolif and crypto toxicity
How does malnutrition affect complement mediated opsonisation and phagocytosis
Reduced mbl which binds crypto needed for complement mediated opsonisation and phagocytosis
Which amp defensin is anticrypto
B defensin 2
Balance of th1 with what necessary to stop inflammatory induced diarrhoea
Th2 responses/ th2 cytokines eg il13 needed for m2 phenotype
How could this link to Microbiota potentially
Since they can release tslp and il25 from cells causing ilc2 responses
Which anti apoptotic gene upreg in crypto in infection as evasion mechanism for survival in enterocytes
Osteoprotegerin (acts as a decoy receptor for trail = antiapoptotic )
Where is EH usually situated
Outer mucus layer on the colon (not intracellular)
What % of cases are noninvasive amebiasis and what is this
90%
Where you get non dysenteric diarrhoea (non bloody) , might be asymptomatic or also get abdominal pain and spread cysts
What happens to invasive 10%
Induced colitis
Can either cause bloody diarrhoea with flask shaped lesions forming as they invade the submucosa (this can form chronic lesions)
Or can even disseminate into the portal circulation where it can reach liver and cause liver abscesses which you can die from
What immediate innate are important in EH which can be modulated by microbiota
Mucus barrier effective
Amps
Tj integrity
Iga
Which enzymes do eh have for degrading mucus
Glycosidases and cysteine proteinases
What can this be excacerbated by host dependant to therefore increase interaction with epi cells and inflam
Diet- low fibre = more mucin degrading
What inflam response can occur if they make contact
Proinflam cytokines the usual leading to neutrophil and mac
Ifny also involved causing ros and no (antiparasitic)
Aswell as degranulation
Which ilc is involved in response and can lead to so much inflammation and damage it will cause dissemination potentially
Ilc3
Binding of what to epi cells leads to these inflam responses
Gal/galnac-lectins
What does eh do to Microbiota that potentially exacerbates penetration
Dysbiosis eg increased p copri - makes sense due to inflammatory environment link with this (th17/3 inducing) - associated with RA commonly
Also reduced butyrate clostridium and bacteroides which are immunomod
What is meant by contact dependant cell lysis which allows there dissemination/mucosal lesion formation
They insert an ion pore (amebopore) disrupting the membrane and causing death
Why would il17 be important here (and Microbiota)
Potent Siga responses important for eh
How is it suggested they can be resistant to ox stresses from inflammation they cause
Oxygen reductases they have
How do they affect effective iga and complement
Cysteine protease mediated degradation
Degrade c3b and c3a
Is Giardia invasive
No it will stay on the si lumen and interact with si by central sucking disc
In most cases what are the symptoms
Asymptomatic or acute/cleared diarrhoea, cramps, nausea
Can this become chronic / what chronic effects can happen
Yes it can,
Due to impairment of absorption
With recurring episodes of diarrhoea, can lead to cramps, anorexia/weight loss and nutritional disorders bc of malnutrition
Why can trophozoites often unlike EH interact with epi cells
Because low mucus barrier in si
Give some issues in so it can cause to histology and enzymes
Shortening of microvilli so malabsorption
Cell apoptosis via direct contact
Also affects enzymes like lactase gaining access to the si and therefore also causing increase diarrhoea due to water flow
What can malabsorption and diarrhoea lead to in long run
IBS, cognitive impairment, tiredness and stunted development
What ilc response is there like EH and which cytokines is particularly important
Ilc3
Il17 required for pigr expression as iga most important adaptive protection against Giardia
Is the effects of the Microbiota dysbiosis Giardia causes known
No but it is present
Why is flagella and adhesive disc essential
Peristalsis induced by NO release on surface = sm contraction
What same proteases as EH do they have and disrupts tj and also appptosis of cells and most importantly degrades iga
Cysteine proteases
Which amps essential for anti Giardia
Defensins and cathelicidins (showing role of il22 and also Microbiota)
cathelcidin ll37 speicfically induced by b producta and b theta via hif 1a
What chemical from cells and immune cells inhibits excystation and trophozoites proliferation - particularly important innate control of Giardia
NO
Which KO of mice caused chronic infection with increased trophozoites in small intestine
Iga, pigr and J chain (showing importance of Siga and the role of Microbiota)
Other than vsp immune evasion, what do they have to control NO production
Arginine deaminases reducing levels of no
Whcih genetic pid can therefore affect severity/chronic of Giardia
X linked b cell immunodeficiency
VSP GIARDIA ANTIGEN SWITCH
Explain the structure of vsp proteins on surface of Giardia
Intracellular C domain ( cytoplasmictail) and is conserved
Tmd
Then middle part of extracellular is semi conserved
N terminus is variable and has cxxc motifs
How many expressed on trophozoites at once
1 or 2
Why are they important
Very immunogenic (both cell and humoral)
What enzymes does it protect parasite from
Intestinal and pancreatic proteases
Around how many genes compared to trypanosoma
300 genes (all transcribed) vs 1000 vsg copies
How is it similar only way to trypanosoma vsg
Called ‘true’ ag switch where there are homologous genes that can be expressed alternatively
Explain the rnai process used for mono allelic exp
Hairpin premirna from rna dep rna pol is transcribed
This then goes to cytoplasm meeting dicer rnase which processes it to ds mirna
Dsmirna binds argonaute ago protein and form mirna-risc complex which either cleaves the transcript or blocks translation via complementary binding
Downregulation of which proteins in this process of mirna silencing causes multiple allele expressions in Giardia showing rnai is important
Dicer ko or rdrp (ago would kill them)
Rdrp required for production of hairpin loop mirna
What special motifs did a bioinformatics study find that 73 out of total vsp have which make them able to be presented on cell surface and complete switching
2 conserved motifs that were not present in around half (suggesting they don’t have effect)
Why is using bio informatics on vsp difficult
Different studies will annotate diff proteins as vsp depending on the tools they use. Hard to figure out
Give example of why 3’ utr specifically isn’t used in Giardia repression (saraiya 2014 study into whole coding sequence mirna binding to vsp)
Vsp-2 doesn’t even have a 3’ targeting site for mirna but still silenced
What happened to vsp117 silenced by no overlapping 6mirna compared to only 2 non overlapping
There was additive effect where vsp 117 silenced to only 2% exp vs 48% for 2 mirna
What does this indicate
Giardia relies on multiple mirna targeting sites within the orf to fully silence as only having 1 on 3’ utr is insufficient
In comparison to vsg, are vsp in subtelmoeres?
No only 3 are out of 75 working
Explain what they found in gerbils suggesting vsp could be used in future for vaccines
injection of trophozoites exp all of them (rnai mutants) protected from secondary infections
What did using oral vaccines injecting all vsp protein repertoires (solely the proteins) done in dogs and cats also find
That they were protected from subsequent infections with giardiasis and chronic infection
and it also reduced spread to children from dogs in shanty towns ie affecting zoonotic transmission rates
Why would using vsp- coated vlps with Ha and na be useful for influenza
Highly immunogenic ie
Found better igG and iga responses orally to HA and NA
Also it protects them from being degraded by enzymes
How are these gut protozoans different to MICROSPORIDIA
MICROSPORIDIA is opportunistic- meaning that it won’t cause symptoms in healthy
These are obligate pathogens and can cause complications
Which nutrient from diet could impact host ability to fight infection via redox activity in macrophages for example
Can be pumped into the phagosome and kill them via ros generation
What vaccine was initially found worked for crypto in calves but wasn’t replicated
Y-irradiated oocysts
Why would th1 cytokines like ifny be important for crypto
Can starve the vacuole of tryptophan via breakdown
Also induced production of NO/ROS VIA INOS = kill cells and crypto
How would entamoeba even get to the liver
Trophozoites into the portal vein through intestinal lesions
Which is the most common protozoan found in stool
Giardia
How do Giardia excysting trophozoites replicate
They adhere close to surface and replicate extracellularly before encystation
Which enzyme does Giardia have which maybe makes NO response less important
arginine deaminase which degrades arginine required for NO production
How does mirna work in mammals
Mirna sites usually near 3’ utr and there is cleavage of the poly A tail causing de adenylation exonuclease activity
Since b-defensin 2 is important for cryptococcus, which probiotic could be useful and why
Ecoli nissle 1917- shown to induce the release of b-defensin 2 via nfkb induction (similar to the tlr9 mediated degranulation)
