boosting the immune system

Question 1

4 ways to boost the immune system

Answer 1

Vaccination

Cytokine therapy

Replacement of missing components

Blocking immune checkpoints

Question 2

what cells does the adaptive immune response use

Answer 2

B
T

Question 3

how do you get the repetoire of antigen receptors in the adaptive immune response

Answer 3

genes for segments of receptors are rearranged

nucleic acids deleted/added at sites of rearrangement randomly

create trillions of receptors

can get autoreactive cells - need to delete/tolerise autoreactive cells

they can differentiate between very small molecular differences

Question 4

summarise clonal expansion

Answer 4

T cell with right specificity - proliferate and differentiate into effector cells (cytokine secreting, cytotoxic)

B cell with right specificity prolif and either:
* diff into T cell independent plasma and memory cells (IgM)
* do germinal centre reaction with T cell help via CD40L-> T cell dependent IgG/A/E(M) mempry and plasma

plasma secrete high affinity specific Ab

Question 5

summarise T cell immunological memory

Answer 5

residual pool of specific T and B cells with enhanced capacity to respond

• memory T cells stay long time w/o ag - becayuse have low level proliferation in response to cytokines = longevity
• different pattern of expression of cell surface protein involved in chemotaxis/cell adhesion -> memory cells access non-lymphoid tissues - where see infection
• more rapid response to ag than naive cells

pre-fromed pool of high affinity specific Ab

Question 6

what happens to number of CD8 T cells in and after infection

Answer 6

get massive number of specific CD8 cells through clonal expansion

then after primary infection - number drops
-> left with memory cells

same with CD4 cells - just less clonal expansion

Question 7

summarise germinal centre reaction

Answer 7

when B cell see ag

go to germinal centre

T cell help via CD40L:

• -> isotope switching
  -> T cell dependent IgG/A/E(M) memory and plasma
• and stim maturation of receptors - receptors mutate and highest affinity are selected

->

• diff into plasma cells - receptors secreted as Ab
• or stay as T cell dependent memory cells

Question 8

Summarise B cell memory

Answer 8

Pre-formed antibody
Circulating high affinity IgG antibodies

Longevity
Long lived memory B cells and plasma cells

Memory B cells are more easily and rapidly activated than naïve cells

Question 9

3 key features we want from a vaccine

Answer 9

1. MEMORY – preformed antibodies, memory T cells, memory B cells, to provide protective immunity
2. No adverse reactions
3. Practical considerations – one shot, easy storage, inexpensive…

Question 10

theory behind influenza vaccine

Answer 10

Haemagglutinin is the receptor vinding and membrane fusion glycoprotein of the influenza virus

and is what neutralising Ab target - need vaccine to target this

Question 11

summarise influenza haemagglutination inhibition assay

Answer 11

**Red cell in well – sink -> red spot**

Sialic acid receptors on RBC bind to haemagluttinin of influenza virus to ‘haemagluttinate’

If **virus receptors bind to haemagluttanin -> haemaglutinate – haemaglutination across cell**

**If Ab – block this reaction – go back to red cells **

Question 12

theory of the TB vaccine (BCG)

Answer 12

T cells protect against primary TB and progression of TB to active - T cell mediated type 4 response

Injected with tuberculin (mantoux test) intradermally

Look at arm 48-72hrs later

If immunity get T cell infiltration around the tuberculin -> induration (swelling that can be felt)

+ve after infection/vaccination

Now do IGRA or ?spot

Question 13

What are the types of vaccine

Answer 13

1. Live vaccines
2. Inactivated/Component vaccines
   Conjugates+ Adjuvants increase immunogenicity
3. RNA vaccines
4. Adenoviral vector vaccines
5. Dendritic cell vaccines

Question 14

summarise live attenuated vaccines

Answer 14

live organism -> immune response

modified (attenuated) to limit pathogenesis (less virulent)

Question 15

egs of live vaccines

Answer 15

MMR
BCG

Yellow fever
Zostavax

Typhoid (oral)
Polio (Sabin oral)

Influenza (Fluenz tetra nasal spray
for children 2-17 years)

Question 16

advantages of live vaccines

Answer 16

Establishes infection – ideally mild symptoms

Raises broad immune response to multiple antigens – more likely to protect against different strains

Activates all phases of immune system.
T cells, B cells – with local IgA, humoral IgG
local and systemic immunity - important when cell mediated reactions needed

strong immune response

May confer lifelong immunity, sometimes just after one dose

Question 17

disadvantages with live vaccines

Answer 17

Possible reversion to virulence (recombination, mutation).
* Vaccine associated paralytic poliomyelitis (VAPP, ca. 1: 750,000 recipients) – very rare

can cause illness

cant give to immunosuppressed, or if live with immunosuppressed

Spread to contacts
* Spread to immunosuppressed/immunodeficient patients

Storage problems and handling difficult - not stable, potential for contamination

interverence by viruses/vaccines and passive immunity

Question 18

what are the inactivated vaccines

Answer 18

Influenza (inactivated quadrivalent)

Cholera,

Bubonic plague,

Polio (Salk),

Hepatitis A,

Pertussis,

Rabies.

Question 19

what are the component/subunit vaccines

Answer 19

Protein component of the microorganisms or synthetic virus like particles

Hepatitis B (HbS antigen),

HPV (capsid),

Influenza (recombinant quadrivalent - less commonly used)

DNA for hepB Sag – put in yeast – this produce protein – used in vaccine

Question 20

what are the inactivated toxin vaccines

Answer 20

diptheria

tetanus

inactivated toxic components

Question 21

advantages of inactivated vaccines

Answer 21

No risk of reversion to virulent form

Can be used with immunodeficient patients

Storage easier

Lower cost

Stable

constituents clearly defined

Question 22

disadvantages of the inactivated vaccines

Answer 22

Often do not follow normal route of infection
May not get breadth of immune response that need, don’t work as well

Some components have poor immunogenicity

May need multiple injections - shorter lasting immunity

May need modification to enhance immunogenicity
* conjugate to protein carrier
* adjuvant - keep vaccine at injection site, activates APC

local reactions common

Question 23

what are conjugate vaccines

Answer 23

Polysaccharide plus protein carrier

ie poorly immunogenic ag paired with highly immunogenic protein

Polysaccharide alone -> T cell independent B cell response – transient

Addition of protein carrier promotes T cell immunity which enhances the B cell/antibody response

Question 24

examples of conjugate vaccines

Answer 24

often used in children

HiB

meningococcus

pneumococcus (Prevenar)

Question 25

why add adjuvent to vaccines

Answer 25

**increase immune response w/o alter specificity** -> promote adaptive immune response mimic PAMPs on TLR and other PRR (pattern recognition receptors) eg * Aluminium salts (humans) * Lipids – monophosphoryl lipid A (humans HPV) * Oils -Freund’s adjuvant (animals)

Question 26

summarise mRNA vaccine in context of covid

Answer 26

covid has spike proteins - bind to ACE2 - allow infection neutralising Ab against spike 1. infect E coli with plasmid containing DNA for spike 2. harvest plasmids 3. excise DNA 4. transcribe to mRNA 5. complex with lipids to make the vaccine 6. -> T and B response 7. Inject mRNA/lipid complexes *(Non-infectious, Non-integrating, Degraded within days)* 8. mRNA enter cells 9. translated to spike - synthesised and expressed on cell surface 10. stim immune reesponse - T and B cells pfizer and moderna?

Question 27

summarise adenoviral vector vaccines in context of covid

Answer 27

1. DNA of spike protein inserted into viral vector 2. AZ Covid vaccine vector: ChAdOx1-S // Sputnik Covid vaccine vector: Adenovirus types 26 and 5 3. Infect cells in vivo 4. Transcription/translation to produce protein 5. Stimulates T cells and B cells -> antibodies

Question 28

summarise dendritic cell vaccines

Answer 28

acquired defect in DC effect maturation and function, but inhib pathways to present Ag to T cells can take out DC and pulse with tumour specific ag and put them back in for tumour specific Ag or mutated ag in tumours

Question 29

summarise provenge

Answer 29

dendritic cell vaccine personalised immunotherapy against prostate ca 1. remove White cells - **leukophoresis** 2. **APC harvested** and incubated with recombinant protein - **PAP-GMCSF** *(Prostatic acid phosphatase-granulocyte macrophage colony stimulating factor)* 3. **APC infused back** into patient 4. -> immune response against cancer

Question 30

examples of the use of cytokine therapy

Answer 30

**Interleukin 2 – stimulate T cell response** - in T cell will be a tumour specific response which is boosted by stim the whole T cell response * Renal cell cancer **Interferon gamma – enhance macrophage function** * Chronic granulomatous disease – mutation interfere with ox phos of granulocytes * Can use in immunodeficiency **Interferon alpha – direct antiviral effect** * Hepatitis B * Hepatitis C (with ribavirin)

Question 31

what components of the immune response can be replaced

Answer 31

stem cell transplant Ab specific Ig adoptive cell transfer

Question 32

summarise haematopoietic stem cell transplant as a way of boosting the immune system

Answer 32

can use donor or autologous offers complete and perm cure transplant into marrow treated by radio/chemo indications: * life threatening primary immunodeficiencies - SCID, leukocyte adhesion deficit * haematological ca * severe autoimmune *get rid of all bad cells and start again* risk - some chance of malignancy early on

Question 33

summarise Ab replacement therapy for boosting immune system

Answer 33

Human normal immunoglobulin Prepared from pools of >1000 donors Contains **preformed IgG antibody to a wide range of unspecified organisms** Blood product so...: * Donors screened for Hep B, Hep C and HIV * Further treated to kill any live virus Administration - **IV or SC**

Question 34

indications for Ab replacement

Answer 34

Primary antibody deficiency * X linked agammaglobulinaemia * X linked hyper IgM syndrome – no germinal centre switch * Common variable immune deficiency Secondary antibody deficiency * Haematological malignancies * Chronic lymphocytic leukaemia * Multiple myeloma * After bone marrow transplantation

Question 35

what is specific Ig replacement

Answer 35

Human immunoglobulin used for **post-exposure prophylaxis (passive immunisation)** Derived from plasma donors with **high titres of IgG antibodies to specific pathogens**

Question 36

diseases where specific Ig replacement is useful

Answer 36

**Hepatitis B immunoglobulin** – needle stick/bite/sexual contact – from **HepBSag+ve** individual **Rabies** immunoglobulin – to bite site following potential rabies exposure **Varicella Zoster** immunoglobulin – women **less than 20 weeks pregnancy or immunosuppressed where aciclovir or valaciclovir is contraindicated** Tetanus immunoglobulin – no specific preparation available in UK – use IVIG for suspected tetanus

Question 37

what are the different types of adoptive T cell transfer

Answer 37

Virus specific T cells Tumour infiltrating T cells (TIL – T cell therapy) T cell receptor T cells (TCR - T cell therapy) Chimeric antigen receptor T cells (CAR – T cell therapy)

Question 38

what is virus specific T cell therapy

Answer 38

for EBV: 1. Take blood from self/donor 2. Take out white cell 3. **Stim blood cells by EBV in vitro** 4. -> EBV specific T cells 5. -> put back in patient Usually after transplant/cancer patient Avoid risk of EBV related illness inc lymphoma also used for severe persistent viral infection in immunocomp

Question 39

what is tumour infiltratijng lymphocyte T cell therapy

Answer 39

Take out tumour Culture with IL2 Select and expand the T cells – assume have specificity for cancer because was in body Put T cells back in patient

Question 40

what is TCR and CAR T cell therapy

Answer 40

Can **take T cell from donor** **Engineer to express specific T cell receptor** **Put in T cells with the receptor** – will **recognise tumour with that specific epitope** Car T cells - Express chimeric ag receptor * Express by normal domain * At end is an **Ab structure (variable segment)** * **Recognise specific Ag** * eg Recognition of CD19 – used for leukaemia

Question 41

use of CAR T cells

Answer 41

used against: * ALL * NHL * autoimmune **variable fragment of CAR recognise CD19** **CAR signals through CD3** in T cells - > T cell response -> kill tumour *less successful for solid tumours*

Question 42

summarise blocking immune checkpoint: PD-1

Answer 42

Immune checkpoint –ve reg immune response PD-1 = program death 1 * Negative response * PD-ligand on APC and tumour cells bind PD-1 –> reg T cell response **Monoclonal Ab – block either PD-1 or PD-ligands** **Blocked program death signal -> live T cell activation**

Question 43

what are monoclonal Ab against PD-1 used for

Answer 43

**Advanced melanoma** **Metastatic renal cell cancer** Increasing indications in oncology – colon and breast *Balance between active and controlled T cell response Too active -> autoimmunity* *High proportions of the patients get control of malignancy but get autoimmune - arthritis/thyroid/lung/gut/pituitary – all immune mediated*

Question 44

summarise monoclonal Ab against CTLA4

Answer 44

CD8 t cell express **CD28** – **activation** signal which **binds to CD80 and CD86** **CD80 and 86 - also bind to CTLA4** which is a **negative signal** Balance = controlled **Ab against CTLA4 takes out -ve signal = T cell activation**

Question 45

Use of monoclonal Ab against CTLA4

Answer 45

advanced melanoma increased indications in onch

Question 46

complications of monoclonal Ab against CTLA4 Ab

Answer 46

autoimmunity - *more than for anti PD-1*

Question 47

benefit of activating T cell response against melanoma

Answer 47

drastic improval in progression free survival

Question 48

what are inactivated vaccines

Answer 48

microorganism destroyed by heat, chemicals, radiation or antibiotics (e.g. Influenza, cholera, polio)

Question 49

how do you attenuate vaccines

Answer 49

**Naturally occurring** (e.g. Poliovirus strain with lack of virulence for brain and spinal cord in monkeys. **Adenovirus** vaccine (types 4 and 7) given **orally was restricted to replication in the GIT**. **Derived from wild type through serial passage in cell cultures prepared from an unnatural host**. -> mutants partially restricted in humans at portal of entry and/or target organs.

Question 50

what are heterotypic vaccines

Answer 50

Pathogens that infect other animals but do not cause disease or cause mild disease in humans

Question 51

eg of heterotropic vaccines

Answer 51

**BCG** more effective when given to children only given to high risk

Question 52

examples of viral vector vaccines

Answer 52

ebola janssen and AZ covid vaccines