Immuno 6 - Immune Modulating therapies 1

Question 1

• Clonal expansion following exposure to antigen

o T cells proliferate/differentiate into

o B cells proliferate/differentiate into

Answer 1

o T cells proliferate/differentiate into effector cells (cytokine secreting, cytotoxic)

o B cells proliferate/differentiate into
 T-cell independent (IgM) plasma (and memory) cells
 T-cell dependent (IgG, IgA, IgE) plasma (and memory) cells (in germinal centre reaction – affinity maturation and isotype switching)

Question 2

T cell memory cell receptors

Answer 2

o Different pattern of expression of cell surface proteins involved in chemotaxis / cell adhesion = allow memory cells to access non-lymphoid tissues (where microbes enter)

Question 3

What is a hemagglutination inhibition assay?

Answer 3

• Influenza – antibodies more important than T cell after vaccination
o Haemagglutinin (HA) is the receptor-binding and membrane fusion glycoprotein of influenza virus (i.e. a target for infectivity-neutralising Abs  this is the aim of vaccination)
o These antibodies can be detected using a haemagglutinin inhibition assay
 If normal red cells in a dish  clump at the bottom forming a red spot
 If add influenza virus to RBCs, the HA will make cells stick together  diffuse coloration across the well (hemagglutination)
 If add serum of someone who has a lot of ABs against HA with the virus and red cells, it will inhibit the HA from causing haemagglutination  cells clumping at the bottom as if the virus was not present

 Antibodies prevent haemagglutination

 Higher the dilution with an inhibitory effect, the greater level of antibodies the patient has against HA
ection + levels of IgG antibodies to haemagglutinin (HA)

Question 4

TB vaccination BCG vaccine

which is more important in developing immunity - antibodies or T cells?

Answer 4

T cells more important than antibodies after vaccination

Question 5

Mantoux test type of hypersensitivity reaction

Answer 5

Type IV hypersensitivity reaction

T cell mediated

Question 6

Live vaccines advantages and disadvantages

Answer 6

o Advantages:
 Establishes infections (ideally mild symptoms)
 Raises broad immune response to multiple antigens (offer protection against different strains)
 Activates all phases of immune system (T cells, B cells – local IgA, humoral IgG, etc.)
 Often confer life-long immunity after one dose

o Disadvantages:
 Storage problems
 Possible reversion to virulence
• Vaccine associated paralytic poliomyelitis
 Spread to contacts (i.e. spread to immunocompromised/immunosuppressed)
 Careful in immunodeficient/pregnant patients

Question 7

Inactivated/component/ toxoid vaccines advantages and disadvantages

Answer 7

o Advantages:
 No mutation or reversion to virulent form
 Can be used in immunodeficient patients
 Easier storage
 Lower cost
 Can eliminate wild-type virus from community

o Disadvantages:
 Often do not follow normal route of infection
 Some components may have poor immunogenicity
 Poorer + shorter immunity
• May need multiple injections
• May require conjugates or adjuvants to enhance immunogenicity

Question 8

•	Conjugate vaccines 
o	Activated vaccines
o	Inactivated vaccines 
o	Component/subunit vaccines 
o	Toxoids (inactivated toxins)

Answer 8

• Conjugate vaccines = (polysaccharide encapsulated bacteria) = NHS = N meningitidis, H influenzae, Strep pneumonia

o	Activated vaccines 
	MMR-VBOY
	MMR
	VZV
	BCG (TB)
	Oral – polio (Sabin), typhoid
	Yellow fever
	Influenza

o Inactivated vaccines = influenza, cholera, polio (injection-Salk), HAV, Pertussis, Rabies, bubonic plague, anthrax

o Component/subunit vaccines = Hepatitis B (HbS antigen), HPV (capsid), influenza (haemagglutinin, neuraminidase)

o Toxoids (inactivated toxins) = diphtheria, tetanus

Question 9

How do conjugate vaccines work?

Answer 9

o Attach protein carrier (strong antigen reaction) to target (polysaccharide, poor antigen target)
 Because you don’t get a good T cell response to capsules but you do get a good T cell response to proteins

o Polysaccharide  induces a T cell-independent B cell response (transient)

o Protein carrier  promotes T cell-dependent B cell response (long-term) – promotes T cell immunity which enhances the B cell/antibody response

Question 10

How do adjuvants stimulate activation of the innate immunity?

Answer 10

Activation of innate immunity produces cytokines to promote adaptive immunity

Mimic action of PAMPs (pathogen associated molecular patterns) on TLR (toll-like receptors) and other PRR (pattern recognition receptors)

Provide a steady stream of antigens

Aluminium salts (humans)
Lipids – monophosphoryl lipid A (humans HPV)
Oils -Freund’s adjuvant (animals)

Question 11

How are the mrna vaccines produced?

Answer 11

o Infect E. coli with plasmids containing DNA for spike protein
 Harvest plasmids from cultures  Excise DNA + transcribe to mRNA

 complex with lipids to create the vaccine  inject Mrna/lipid complexes (non infectious/non-integrating/degraded within days)

 mrna enters cells (e.g. muscle cells, endoethelial cells, fibroblasts, dendritic cells)  mrna transcribed + spike protein synthesised/expressed on surface

 stimulates immune response incl. B cells/antibodies + T cells

Question 12

How do dendritic cell vaccines work?

Answer 12

o Tumour-bearing animals and cancer patients demonstrate acquired defects in dendritic cells (DC) maturation and function

o Acquired defects in DC maturation + function associated with some malignancy suggests a rationale for using ex-vivo generated DC pulsed with tumour antigens as vaccines

o Take a patient’s dendritic cells and load them with a tumour antigen and reintroduce them to the patient to try and boost the immune response against the tumour antigens

o Requires antigens specific to the tumour and distinct from normal cells

Question 13

Indications for

HSCT
Antibody replacement
Specific immunoglobulin

Answer 13

HSCT

• Life-threatening immunodeficiency
• Haematological malignancy

Antibody replacement
Problem with B cell or ab production
- Primary antibody deficiency
• Bruton’s X-linked hypogammaglobulinemia
• X-linked hyper-IgM syndrome (pt can’t make other classes of Ig)
• Common variable immunodeficiency

• Secondary antibody deficiency

Specific immunoglobulin
- PEP

Question 14

Indications for virus specific T cell therapy

Answer 14

EBV B cell lymphoproliferative disorder

Severe persistent viral infection in immunocompromised

How? Expansion of EBV specific T cells in vitro + re-infusion back into patient

Question 15

How does the tumour infiltrating lymphocyte T cell therapy work?

Answer 15

1) Remove tumour from patient
 (2) Tumour fragments grown with IL-2  Stimulate T cells within tumour with cytokines (e.g. IL-2) so they develop a response against tumour
 (3) Select and expand the tumour infiltrating lymphocytes and reinfuse back into the patient

Question 16

How does TCR and CAR T cell therapy work?

Answer 16

 (1) T cells taken from patient and viral / non-viral vectors used to insert gene fragments into T cells coding for specific T cell receptor (targeting tumour specific antigen presented on an MHC molecule)  expand those cells + infuse them into the patient

• TCR therapy  insert a gene that encodes a specific TCR (e.g. against a tumour cell antigen)
o Recognises MHC presented peptide

• CAR therapy  receptors are chimeric (it contains both B and T cell components)
o Recognises cell surface CD markers
o This is a way to bring your B cells in contact with your T cells and then the T cells can kill the B cells
• CAR therapy is increasingly being used in ALL and NHL (not useful in solid tumours)
• Used for B cell malignancies

Question 17

Which immune checkpoints can be blocked to enhance immune response?

Answer 17

CTL-A4 pathway

Programmed death pathway

Question 18

How does Ipilimumab work?

Answer 18

Treatment against melanoma (complication- autoimmunity)

Monoclonal ab against CTL-A4 - blocks immune checkpoint

o CTLA4 and CD28 both expressed by T cells and both recognise the same antigens on APCs (CD80 and CD86)
 APC CD80 and CD86 interact with CD28  transmit a T cell stimulatory signal
 APC CD80 and CD86 interact with CTLA4  transmit an T cell inhibitory signal

o Ipilimumab will bind to CTLA4 – blocks immune checkpoint, allows T cell activation  all of the interactions of CD80 and CD86 occur through CD28  more APCs can present to T cells  thereby boosting the T cell response (you get more active T cells)

Question 19

How does Pembrolizumab and Nivolumab work?

Answer 19

Monoclonal ab against PD-1

Block PD-1 (T-regulatory cells) and therefore do not allow interaction with PDL1 or PDL2 (APC) which inactivates T cells

allow T cell activation  prevent the inhibitory effect of binding PD1 and PD1-L  activating the T cells to kill

o Indications – advanced melanoma, metastatic RCC
o Complications – autoimmunity

Question 20

Boosting the immune response with cytokines

where are the following cytokines used

• IFN-a
• IFN-β
• IFN-2a – immunomodulatory effect mediated by the cytokines which are regulating the response
• IFN-g:
• IL-2 (increases clonal expansion)

Answer 20

•	IFN-a: 
o	Antiviral effect
o	HBV
o	HCV (with ribavirin) 
o	Kaposi’s sarcoma
o	Hairy cell leukaemia
o	CML
o	Malignant melanoma 
o	ABC: Interferon Alpha for Hep B and C + CML

• IFN-β
o Relapsing MS

• IFN-2a – immunomodulatory effect mediated by the cytokines which are regulating the response
o Bechet’s
o Uveitis
o Skin disease

• IFN-g:
o Enhance macrophage function
o Chronic granulomatous disease (problems with oxidative killing within macrophages)

• IL-2 (increases clonal expansion):
o Stimulates T cell response (promote T cell responsiveness against the antigens of a renal malignancy)
o Renal cell cancer