Rob's Fungal Immunity

Question 1

Which fungi classes cause disease in humans

Answer 1

3 phyla causing disease in humans Zygomycota Basidiomycota `Ascomycota (bottom 2 more closely related)

Question 2

Give an example of ascomycota

Answer 2

Candida and Aspergillus

Question 3

Give examples of basidiomycota

Answer 3

Mushrooms(cryptococci)

Question 4

List Fungi causing infections

Answer 4

Aspergillus (ascomycota) Cryptococcus (basidiomycota) Candida albicans (ascomycota)

Question 5

How can aspergillus cause problems

Answer 5

Have spores called conidium.Normally fine, most people inhale every day Only a problem if you have no neutrophils Can germinate (leading to fungal ball) and cause bleeding in LUNGS

Question 6

How can Cryptococcus neoformans cause disease

Answer 6

Mushroom group (microscopic) .Fimbrae that allow it to adhere to surfaces .Commonest cause of death in HIV patients (subsaharan Africa) .Inhaled through lungs but can disseminate to brain if lack of CD4+ T cells. Leads to cryptococcal meningitis. Can then develop cryptococcomas (fungal ball) , and stroke like symptoms.

Question 7

What is cryptococcoma

Answer 7

Ball of fungus which has germinated. CNS (cryptococcus neoformans)

Question 8

How can candida albicans cause disease

Answer 8

Candida is commensal on skin and gut But in immunocompromised/catheterised, can develop invasive infeection. Can get into the back of the eye creates mass =candida endophthalmitis, for example

Question 9

Outline cellular immunity to fungal infection

Answer 9

Innate immune system very important. Loss of neutrophils is a key risk factors .Most fungi encountered at mucosal surface (in gut, yeast or on lungs as moulds). Opsonisation, phagocytes and complemet all important. Dendritic cells present antigen to T cells Can lead to Th1, Th2 and Th17 responses(these then determine innate response-circle).

Question 10

Why are NK cells important in cellular immunity to fungal infection

Answer 10

They produce IFN-g which primes macrophage to deal with fungus

Question 11

Outline how fungi change shape Candida, cryptococcus and aspergillus

Answer 11

Can start as unicellular organisms then become mutlicellular ▪Candidal dimorphism (starts of as budding yeast but when it is involved in invasioive infections changes into hyphal forms, which are muticellular filamentoius structurees) allows tissue invasion ▪Crytpococcus divides in the host as a yeast. Forms a capsule to evade phagocytosis ▪Aspergillus species inhaled as conidia, invade tissues as hyphae

Question 12

How can fungi be sensed

Answer 12

Toll like receptors (innate receptor). Losing the toll systems put you at high risk of fungal disease

Question 13

What are c-type lectins

Answer 13

Part of immunoglobulin super family.Detect carbohydrate on fungal cell wall. Important for phagocytosis of fungi (TLR cannot do it alone, need c -type lectins).

Question 14

What receptors are important in fungal infection

Answer 14

TLR, c-type lectins and scavenger receptors

Question 15

T/F scavenger receptors normally phagocytose non-inflammatory materials

Answer 15

T

Question 16

What deficiencies could result in chronic mucocutaneous candidasis

Answer 16

c-type lectin is really importnat in fungal immunity. Mutations and thus deficiency of Dectin 1[Dectin 1 (a c-type lectin). It binds candida. Without dectin 1 ,cannot produce IL-6 or bind], and CARD9, a protein in the downstream signalling pathays for many c-type lectins, can result in chronic mucocutaneous candidiasis.

Question 17

What is worse, dectin 1 or CARD9 deficiency

Answer 17

CARD9, because this is the signalling molecule for the actiation of many receptors

Question 18

Why is CARD9 required in fungal immunity

Answer 18

Functional Card9 is Required for TNFα Production in Response to βGlucan ,and is also Required for T cell Th17 Differentiation in Humans. (SHOWS THAT DEFECTIVE INNATE RECEPTORS MEANS THAT ADAPTIVE IMMUNE SYSTEM CAN THEN NOT BE TRAINED TO DEAL WITH THE FUNGI

Question 19

Why is Th17 response importnat in fungal disease

Answer 19

Mucosal protection .But in CARD9 deficiency, Th17 does not differentiate properly (showing that innate immune reponse interacts with adaptive one) and you get chornic mucocutaneous candidasis

Question 20

Explain why fungal infections are important in stem cell transplantation, give an example of one that is important.

Answer 20

Apergillosis (stem cell transplantation occurs in leukaemia. All your own bone marrow wiped out with txic drugs. Give someone else’s bone marrow. That bone marrow will act as your bone marrow, creating your red and white cells. But it will also attack your own immune system to destroy all of the bone marrow cancer) But during that period of the transplanted bone marrow killing your bone marrow and then producing new cells, there are less neutrophils and less innate immunity, and these patents very susceptible to fungal infection including aspergillosus .TLR4 polymophoisms can alter risk of pulmonary aspergillosis in transpantation

Question 21

What proteins are important in risk of invasive aspergillosis in stem cell transpantation

Answer 21

Dectin 1 and TLR4

Question 22

Mutations in which haemostasis related protein increases susceptibility to fungal disease

Answer 22

Plasminogen (as well as dectin1, TLR4)

Question 23

Why will fungal immunogenics be important

Answer 23

E.g in transplant patients you can look at their TLR4 phenotype and see if this is going to place them at a risk of a certain infection and then give prophylactic medication (ABs)

Question 24

What are important innate immunity cells in fungus infection

Answer 24

Both macrophages and neutrophils contribute to fungal immunity However for Aspergillus neutrophils are of primary importance

Question 25

What happens if you took neutrophil away from lung and put aspergillus there

Answer 25

It would grow as it would in a test tube Basically, without neutrophils aspergillus will grow so easily and body doesn’t really do anything with it

Question 26

Outline one way in which neutrophils deal with fungi

Answer 26

Neutrophl extracellular nets DNA released by dead neutrophils and this binds the aspergillus (in this cause aspergillus fumigatus) and is very sticky This is the reason for very sticky mucus in these sorts of infections

Question 27

Other function of neutrophil DNA other than coding for proteins

Answer 27

Neutrophil extracellular trap And, when released from cells, acts as a DAMP (along with histones, actin etc.)

Question 28

When do Th1 responses occur and when do Th2 responses occur generally

Answer 28

Th2 is development of allergic response i.e. eosinophil and mast cell degranulation Th2 is promoted by worms and parisitic infections because they are too big to phagocytose, so Th1 response isn’t approrpiate Th1 response occur against intracellular parasites such as bacteria and viruses which can be phagocytosed

Question 29

What are the important cytokines for Th1 and Th2

Answer 29

Th1: TNF-a, IFN-g and IL-6 and IL-12 stimulates macropahges Th2: IL4/IL-10 for eosinophil and mast cells

Question 30

Outline the T helper response to fungi

Answer 30

DEPENDS on fungal morphogenesis. At first, the fungi might be in the yeast form but then can take different forms (hyphae form/capsule) Dendritic cells take up antigen. For the yeast form of candida, leads to Th1 (as it’s smaller and can be phagocytosed) In the hyphae form of candidam there is Th2 response as now the yeast is filamentous and big so requires allergic response not phagocytic Same for aspergillus conida (Th1) vs aspergillus hyphae (Th2)

Question 31

What is the relevance of both Th1 and Th2 responses to fungal infection

Answer 31

They have both invasive infectious disease AND drive allergy including asthma

Question 32

Outline novel methods of treating fungal disease based on immunotherapy and gene editing (not necessary just incase you stressed)

Answer 32

IMMUNOTHERAPY. T cell adoptive therapy. In the stem cell transplant example, we said that patients were susceptible to aspergillus (and candida) after stem cell transplant. After taking stem cells from the donor, you can select for T cells with specific fungus binding receptors, and give these to the patient if they get fungal infection after the HSC transplant has occurred. Gene editing: There is mutation in NADPH oxidase which is present on plasma membrane of phagosome to generate reactive oxidants in the RESPIRATORY BURST to kill organisms phagocytosed by neutrophils for example. A boy who had mutation in this protein had chronic granulomatous disorder. They took out his bone marrow and gene edited all of the cells using a virus to correct the mutation. Then then killed all his other bone marrow cells that weren’t gene edited, re-infused the edited bone marrow cells which now contain functional NADH oxidase. There was also a restoration of neutrophil NET formation :)

Question 33

What is the importance of T cell interferon gamma

Answer 33

Adaptive T cell interferon-gamma responses augment host immunity to fungi

Question 34

For candida and aspergillus, neutrophls are importnat. What about for cryptococcus

Answer 34

Cryptococcus more in HIV patients. CD4+ T cells more important

Question 35

Give examples of aspergillu environmental organisms

Answer 35

Aspergillus niger Aspergillus fumigatus Inhaled leading to fungal allergic airway disease. Spores get into lungs really easily

Question 36

T/F people with asthma due to fungi like aspergillus are getting it due to immunosupression

Answer 36

F they are getting it because of an exaggerated immune response

Question 37

Outline a type of fungal disease fo each category of hypersensitivity reacton

Answer 37

Type 1 (IgE/histamine mediated) –> allergic rhinitis, allergic asthma, ABPA Type 2 –> unknown Type III–> hypersensitivity pneumoniits/aspergilloma Type IV –> hypersensitivity pneumonitis

Question 38

T/f there is just one allergen in fungi that causes hypersensitive response

Answer 38

F

Question 39

Outline why fungal allergens are confusing for immune system

Answer 39

Cross reactivtiy between candida allegens in the gut and breathed in allergens in the lung (immune system doesn’t know which it is responding to) And Because they are eukaryotic, some allergens from fngi have promoted autoimmue response against self antigens in the lung

Question 40

What leads to allergic and what leads to invasive fungal disease

Answer 40

Wheter host response is ineffective or exaggerated

Question 41

What type of hypersensitivity reactions are occurring in fungal infections

Answer 41

I, III and IV

Question 42

What is the primary driver of allergic fungal disease

Answer 42

Aspergillus

Question 43

What is ABPA

Answer 43

Allergic bronchopulmonary aspergillosus which causes IgE response and is a form of bronchiectasis High eosinophil levels in peripheral blood Loads of mucus Overexagerated immune response

Question 44

Which conditions presispose to ABPA

Answer 44

Asthma or cystic fibrosis

Question 45

Radiological features of ABPA

Answer 45

• Dilated bronchi with thick walls • Ring or linear opacities • Upper or central region predeliction • Proximal bronchiectasis • Lobar collapse due to mucous impaction (hyper dense mucus) • Fibrotic scarring

Question 46

What happens to size of airways with ABPA

Answer 46

DILATION (this is bronchiectasis) Bronchiectasis is a long-term condition where the airways of the lungs become abnormally widened, leading to a build-up of excess mucus that can make the lungs more vulnerable to infection Because of mucus plugging

Question 47

Management of ABPA

Answer 47

Corticosteroids Itraconazole for steroid sparing effect (a triazole) Recombinant IgE monoclonal antibodies

Question 48

What is an anti-IgE antibody

Answer 48

Omalizumab

Question 49

What is hypersensitivity pneumonitis

Answer 49

Fibrotic lung disease Evidence for fungal sensitisation

Question 50

What is diagnosis of fungal hypersensitivity driven by

Answer 50

Diagnosis driven by skin test, IgE and IgM in clinical relevant populations