Immuno 6 - Immune Modulating therapies 1 Flashcards
• Clonal expansion following exposure to antigen
o T cells proliferate/differentiate into
o B cells proliferate/differentiate into
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)
T cell memory cell receptors
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)
What is a hemagglutination inhibition assay?
• 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)
TB vaccination BCG vaccine
which is more important in developing immunity - antibodies or T cells?
T cells more important than antibodies after vaccination
Mantoux test type of hypersensitivity reaction
Type IV hypersensitivity reaction
T cell mediated
Live vaccines advantages and disadvantages
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
Inactivated/component/ toxoid vaccines advantages and disadvantages
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
• Conjugate vaccines o Activated vaccines o Inactivated vaccines o Component/subunit vaccines o Toxoids (inactivated toxins)
• 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
How do conjugate vaccines work?
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
How do adjuvants stimulate activation of the innate immunity?
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)
How are the mrna vaccines produced?
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
How do dendritic cell vaccines work?
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
Indications for
HSCT
Antibody replacement
Specific immunoglobulin
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
Indications for virus specific T cell therapy
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
How does the tumour infiltrating lymphocyte T cell therapy work?
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
How does TCR and CAR T cell therapy work?
(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
Which immune checkpoints can be blocked to enhance immune response?
CTL-A4 pathway
Programmed death pathway
How does Ipilimumab work?
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)
How does Pembrolizumab and Nivolumab work?
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
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)
• 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
