Immunoevasion and Immunotherapy in Infectious Disease Flashcards
(173 cards)
1
Q
after more than 70 years of widespread use, evolution of disease-causing microbes has resulted in…
A
… many antimicriobials losing their effectiveness
2
Q
As microbes evolve, they adapt to
A
their environment
3
Q
If something stops them growing (e.g. antimicrobial), it introduces
A
a selection pressure
4
Q
Genetic mutations which counter the selection pressure will be reproduced in
A
offspring and fixed in the population.
5
Q
New mechanisms to resist the antimicrobials will
A
evolve.
6
Q
in the 1970s Hungary was highly dependent on
A
penicillin for treating infections.
7
Q
in the 1970s Hungary was highly dependent on penicillin for treating infections.
Quickly this led to
A
half of the strains of Streptococcus pneumoniae being resistant
- Things improved only when penicillin usage dropped
8
Q
Antibiotic resistance is a global problem;
increasing numbers of bacteria are
A
becoming resistant to antibiotics
9
Q
It is predicted that by 2050
A
AMR infections will be leading ahead of cancer as causes of death.
And we have been being given cautionary notes ever since 1945, even by the discoverer of penicillin himself…
10
Q
what is PBP?
A
penicillin binding protein (transpeptidase involved in peptidoglycan cell wall synthesis)
11
Q
what kind of antibiotic is methicillin?
A
a β-lactam antibiotic (penicillin class)
12
Q
β-lactam antibiotics are effective against
A
gram +ve bacteria because they inhibit the trans-peptidase involved in cell wall synthesis
13
Q
Bacteria develop resistance through
A
acquisition of β-lactamase gene
14
Q
β-lactamase hydrolyses
A
the β-lactam ring – drug becomes ineffective
15
Q
Staphylococcus aureus
A gram +ve commensal bacteria, part of skin and
nasopharangeal flora – normally causes
A
no harm
16
Q
Infections can occur when
A
barriers are breached (skin and mucosal barriers)
17
Q
Staphylococcus aureus
A gram +ve commensal bacteria, part of skin and
nasopharangeal flora – normally causes no harm
Infections can occur when barriers are breached
(skin and mucosal barriers)
can treat with
A
β-lactam antibiotics (methicillin)
- methicillin resistant strains (MRSA)
18
Q
MRSA stands for…..
A
… methicillin-resistant staphylococcus aureus. This type of bacteria causes staph infections that are resistant to treatment with usual antibiotics.
19
Q
mrsa occurs most frequently…
A
… among patients who undergo invasive medical proceuures or who have weakned immune systems and are being treated in hospitals and healthcare fcacilities such as nursing homes and dialysis centers
20
Q
mrsa in healthcare settings commonly causes
A
serious and potentially life threatening infections such as bloodstream infections, surgical site infections, or pneumonia.
21
Q
Disease incidence caused by MRSA in UK and Europe has been on a steady increase since
A
1993
22
Q
Recent years has seen a fall in nosocomial MRSA infections in the UK, due to
A
the introduction of 60% isopropylalcohol gels in wards (spread has been limited)
23
Q
However MRSA is still there and remains a global problem with strains now
A
carrying additional vancomycin resistant genes (multi-drug resistant MRSA strains)
24
Q
Vancomycin is an antibiotic of
A
the glycopeptide class
25
Like the β-lactams, glycopeptide antibiotics target
cell wall synthesis and are thus most effective against gram +ve – bind to; D-Ala-D-Ala in peptidoglycan
26
Vancomycin is used to treat MRSA – but
vancomycin resistance is becoming a problem
27
mid-1980’s was an area which
saw the greatest development of new antibiotics
28
during the 2008 - 2012 period only
2 new antibiotics were developed
(running out of targets??)
29
during the 2008 - 2012 period only 2 new antibiotics were developed
(running out of targets??)
this accounts for the apocalypse hysteria
so what is being done?
immunotherapy is one avenue that is being explored
30
multidrug resistant Tuberculosis (MDR-TB) – first new antibiotic to be discovered for
30 years (2015)
31
when is immunotherapy important?
particularly important for viral, chronic or difficult to treat infections such as; methicillin resistant Staphylococcus aureus (MRSA)
32
MRSA can enter the blood causing...
...septicaemia or sepsis (ultimately death)- systemic inflammation
33
post antibiotic era looking to establish
new ways to treat antibiotic resistant bacteria; including MRSA
34
Immunotherapeutic strategies examples:
-immunise (some epitopes identified); preventative
-cytokine treatment, to boost immune response
-adoptive immunoglobulin's, pathogen specific antibody therapy
-adoptive T cell transfer (donor/self pathogen specific T cells)
35
what provides the first line of defence?
Anatomical barriers SKIN and MUCOSA provide the first line of defence against microbial infection (innate)
36
Biochemical secretions have
an ‘antimicrobial’ activity
37
Human 1-defensin is a
polypeptide with positively charged and hydrophobic regions, that creates pores in the membrane
38
positive domain is attracted to
negative phospholipid
39
hydrophobic domains group
together - creating pore
40
lysozyme hydrolyses
NAG-NAM glycosidic bonds (gram +ve bacteria)
41
go look at 34
42
how do lysozymes break down bacteria?
1) rupture of peptidoglycan by lysozyme action
2) inflow of water
3) lysis
43
A newly synthesized PG monomer consists of a
disaccharide, NAG linked to NAM with an
attached peptide stem, and the NAM is anchored to the membrane via a lipid carrier
44
Lysozyme hydrolyzes the
β-1,4 glycosidic bond between the NAG of 1 monomer and the NAM of the adjacent monomer
45
Lysozyme hydrolysis of PG leads to...
...cell wall instability and bacterial cell death.
46
Lysozyme can also kill bacteria independently of
PG hydrolysis
47
Lysozyme can also kill bacteria independently of PG hydrolysis - mechanism involving its
cationic nature
48
Cationic killing of bacteria may involve
the formation of pores by lysozyme
(red cylinders) on the bacterial cell membrane.
49
Oat-A promotes
acetylation at the N-muramic acid of peptidoglycan
50
describe the inflammatory response driven by leucocytes?
tissue macrophages become activated and send chemotactic signals (cytokines) to recruit neutrophils (phagocytic leukocytes)
51
cytokines are important...
... mediators
52
Cytokines are important mediators in the inflammatory response and neutrophils (50 – 70% of total leukocyte count) are...
... important cells for recognising and killing bacteria (phagocytosis, cytotoxicity and cytokine secretion)
53
neutrophils make up
50 to 70% of all leukocytes
54
Neutrophils: 50 to 70% of all leukocytes, important for
bacterial and fungal infections, last only hours to a few days in circulation
55
function of neutrophils
Phagocytic function (engulf and digest bacteria)
56
how do neutrophils identify bacteria?
Identify bacteria through Pathogen Associated Molecular Pattern (PAMP) receptors – toll-like receptors (TLRs)
57
neutrophils are [...] in functioin?
These cells are innate in function (see all that is foreign ‘non-self’ and kill)
58
How many TLRs are identified?
12
59
what does TLR2 do?
recognises peptidoglycan of gram +ve bacteria cell wall (e.g. MRSA)
60
what does TLR4 do?
recognises lipopolysaccharide of gram -ve bacteria (e.g. Salmonella)
61
Cytokines are chemical (peptides) that bind
cognate receptors on immune cells
62
Proinflammatory cytokines activate
immune cells and mediate inflammation by targeting vessel endothelial cells
63
what are 4 types of cytokine?
interleukin-1B (IL-1B)
IL-18
Interferon-a (IFNa)
Tumour necrosis factor-a (TNFa)
64
interleukin-1B (IL-1B) immune target cell ?
Macrophage, monocyte & neutrophil
65
interleukin-1B (IL-1B) major actions?
Activates cells, stimulates inflammatory cytokine release
66
interleukin-1B (IL-1B) major outcomes?
Acute phase response, fever, wound healing & pain
67
IL-18 immune cell target?
Macrophage & neutrophil
68
IL-18 Major actions?
T cell maturation, stimulates IFN production
69
IL-18 major outcomes?
Regulates homeostasis
70
Interferon-α (IFNα) immune cell target?
Macrophage and NK cells
71
Interferon-α (IFNα) major actions?
Activates macrophages and NK cells
72
Interferon-α (IFNα) major outcomes?
Fever (flu-like symptoms)
73
Tumour necrosis factor-α (TNFα) immune cell target?
Macrophage, Th1 cells and NK cells
74
Tumour necrosis factor-α (TNFα) major actions?
Potent immune cell activator
75
Tumour necrosis factor-α (TNFα) major outcomes?
Acute phase response, fever & sepsis
76
Cytokine therapy potential for
treating antibiotic resistant infection
77
Cytokines have a central role in
driving the immune response
78
Cytokines have a central role in driving the immune response, thus administering certain cytokines has the potential to ...
... improve the host immune response during MRSA infection
79
in this study IL-18 (important in inflammatory immune response), protected from...
... MRSA induced death, following burn injury
80
IL-18 was found to induce
significantly neutrophil number and function (doubled)
81
IL-18 administration correlated with
a decrease in blood associated MRSA sepsis
82
what does antibody therapy involve?
involves the generation of ‘humanised’ monoclonal antibodies (anti-bodies that recognise specific bacterial epitopes)
83
in antibody therapy, spleen cells are harvested from
mice challenged with the epitope
84
Spleen cells harvested from mice challenged with the epitope are used to form
hybridoma culture with myeloma cells (plasma cell cancer)
85
Bacteria epitope specific antibodies are
harvested from the culture medium
86
The antibodies are then transfused into
a patient who has been diagnosed with bacteria infection (e.g. MRSA)
87
describe antibody structure?
‘Y’ shaped proteins that consist of two heavy chains and two light chains held together by intermolecular disulphide bonds
88
what are the variable domains (V) of antibodies for?
antibody specificity
89
what are the constant domains (C) of antibodies for?
biological activity
90
FAB (variable end) binds to
the antigen (bacteria or foreign invader)
91
describe antibody bacteria binding
1) Antibody binds to bacterium
2) Antibody-coated bacterium binds to Fc receptors on cell surface
3) Macrophage membrane surrounds bacterium
4) Macrophage membranes fuse, creating a membrane bounded vesicle, the phagosome
5) Lysosome fuse with the phagosome, creating the phagolysosome.
92
Antibodies also activate the
complement system
93
Antibodies also activate the complement system; specialised proteins that collectively form the
‘membrane attack complex’ – produce holes in bacteria cell membrane
94
Antibodies specific to the pathogen bind at
the FAB region
95
The protruding FC region contains
complement binding sites
96
The protruding FC region contains complement binding sites that
bind and activate the complement system sequentially (C1 to C9)
97
complement proteins arrange in
a specific way (and order) to create pores in the pathogen membrane
98
complement proteins arrange in a specific way (and order) to create pores in the pathogen membrane - a process known as
the complement cascade
99
Unlike neutrophils (innate cells that are activated towards foreign antigen indiscriminately) B cells (a type of lymphocyte) are
activated to specific regions of the antigen (foreign invader) ‘epitopes’ – ADAPTIVE IMMUNE CELLS
100
Each B cell has a
unique receptor
101
Each B cell has a unique receptor – once activated
differentiates into plasma cell that secretes antibody (same shape as receptor)
102
Create transgenic humanised B cells toward a
specific bacterial epitope
103
Isolate cells and create
hybridomas (immortalised antibody secreting cells)
104
Purify antibodies from
supernatant and transfuse
105
the antibodies are then transfused into a patient who
has been diagnosed with bacteria infection (e.g. MRSA)
106
Antibodies can be designed to target
bacterial ‘epitopes’ at numerous levels
107
Potential bacterial epitope targets:
Target 1 - antibodies directed to surface increasing phagocytosis (opsonising)
Target 2 - antibodies directed to virulence factors such as toxins (neutralising)
Target 3 - antibodies directed to virulence factors such as quorum sensing peptides (sequestering)
108
describe opsonising
Opsonises specific antibiotic resistant bacteria; tagging them for phagocytic destruction
109
different antibiotic resistant bacteria epitopes are under investigation; including
the bacteria cell surface polysaccharide poly-β-(1-6)-N-acetyl-glucosamine (PNAG)
110
promising results highlighted the efficacy of these antibodies to kill
various multidrug resistant bacteria, via opsonophagocytosis
111
antibodies were able to prevent death by
peritonitis in pre-clinical models, even when co-infected with MRSA
112
enterotoxin-B is a
virulence factor produced by some MRSA strains
113
enterotoxin-B is a virulence factor produced by some MRSA strains
antibodies have been designed to recognise this pathogen and have been shown to
improve survival in pre-clinical MRSA-sepsis models
114
vaccination with enterotoxin-B epitope provided
immunity to infection
115
antibody treatment also reduced
the amount of MRSA present in skin lesions
116
antibody treatment also reduced the amount of MRSA present in skin lesions
thus treatment could have wider implications for
topical MRSA infections (such as post-operative infections).
117
MRSA establishes virulence though
quorum sensing
118
since MRSA establishes virulence though quorum sensing, antibodies have been designed to
target this process
119
antibodies have been designed to target
quorum sensing peptides
120
antibodies have been designed to target quorum sensing peptides; such as
AIP-4
121
the sequestering (mopping-up) of AIP-4 by antibodies, inhibits
quorum sensing-mediated gene expression changes
122
the sequestering (mopping-up) of AIP-4 by antibodies, inhibits quorum sensing-mediated gene expression changes -> what does this cause?
decreases MRSA virulence -> protects pre-clinical models from a lethal S. aureus dose
123
Like B cells, T cells are
adaptive (Specific)
124
Like B cells, T cells are adaptive (specific) and activated through
unique cell surface receptors
125
T cells are
lymphocytes (like B cells)
126
T cells are lymphocytes (like B cells) but do not
secrete antibodies
127
Two types of T cell:
1) Cytotoxic T cells (or Tc cells) - viral infections
2) Helper T cells (or TH cells)
128
how does adoptive t cell therapy work?
take autologous or HLA matched donor t cells, before expanding the pathogen specfic cells in vitro and infusing back into the patient
129
adoptive t cell therapy has the potential to...
... genetically engineer t cells before infusion.
130
adoptive t cell therapy is excellent for
viral infections, where viral specific cytotoxic t cells can be generated
131
Hepatitis B virus causes
causes infection of the liver
132
Hepatitis B virus causes infection of the liver and is associated with the onset of
cirrhosis (liver scarring) and hepatocellular carcinoma
133
Adoptive transfer of HBV specific donor t cells neutralised
infection in patients with chronic HBV infection
134
Epstein-barr virus (EBV) is associated with
lymphoproliferative disorders and malignancies, such as; lymphoma and chronic lymphocytic leukaemia (CLL)
135
EBV infected B cells can become
malignant
136
EBV infected B cells can become malignant, with affected cells expressing
EBV specific mRNA and viral proteins – viral antigen
137
Numerous studies show that adoptive transfer of EBV specific T cells can enhance
anti-tumour response and improve survival in pre-clinical disease models
138
Adoptive transfer in conjunction with cytokine (IL-15), may enhance
the effects by relieving immune suppression (combination immune therapy)
139
L. monocytogenes is one of the most
virulent food born pathogens, with death resulting in up to 30% clinical infections
140
L. monocytogenes specific cytotoxic t cells neutralise
infection
141
various L. monocytogenes epitopes have
been investigated
142
combining more than 1 epitope specific cytotoxic t cell clone in mixed culture assays improved
the efficacy of L. mono-cytogenes killing
143
Bacteria have evolved several mechanisms to
‘evade’ the immune response
Viruses present another challenge:
144
All immune cells ignore
self antigen (some immune cells like T and B cells are educated to ignore self)
145
But viruses replicate inside
our cells (hide away from neutrophils)
146
How does our immune system deal with viral infected cells?
major histocompatibility complex (MHC) molecules present vial peptide on cell surface
147
MHC-I is expressed on
all nucleated cells and presents antigen (viral peptides, cancer peptides) to cytotoxic T cells (Tc cells)
148
If a Tc cell has a receptor complementary to the viral antigen it will become
activated
149
If a Tc cell has a receptor complementary to the viral antigen it will become activated
Tc cells will then
destroy the viral infected cell (not by phagocytosis) but through the release of cytotoxic granules.
150
Like bacteria, certain viral strains have
evolved / acquired genes
151
Like bacteria, certain viral strains have evolved / acquired genes that when translated into protein, ...
... help the viral evade Tc cells during the intracellular replication phase
152
what are two strategies used by viral strains to evade Tc cells ?
1) Viral homologues to human cell surface immunosuppressive molecules
2) Viral homologues to human immunosuppressive cytokines
153
It is important to prevent immune responses in certain parts of the body in order to...
... protect certain vital organs from immune destruction (immune privileged sites
154
what proteins protect cells from immune attack in immune privileged sites?
Cell surface proteins (e.g. CD200, PD-1), protect these cells from immune attack
155
what is CD200 ?
CD200 is a cell surface immunoprotective glycoprotein – expression high in immune privileged sites
156
Downregulation of CD200 is linked with
the development of neurodegeneration (multiple sclerosis)
157
cancer cells that up-regulate CD200 are
protected from immune attack
158
Study found that herpesvirus K14 protein (40% homology) mimics
the effects of CD200 by interacting with the CD200 receptor (CD200R), supressing immune cell activity and the release of proinflammatory cytokines
159
Study found that herpesvirus K14 protein (40% homology) mimics the effects of CD200 by interacting with the CD200 receptor (CD200R), supressing immune cell activity and the release of proinflammatory cytokines
This virus is linked to ...
... the development of Kaposi’s sarcoma
160
Viral homologues for CD200 found in
poxviruses and cytomegalovirus (CMV)
161
Viral K14 protein binds to
CD200R with similar affinity and kinetics as CD200
162
K14 mediates
immunosuppression in immortalised cells
163
As well a lifting the immuno-suppression mediated by CD200 through the receptor, certain antibody clones have been shown to
promote Antibody Dependent Cell Cytotoxicity (ADCC) – improve Tc cell activity (tags cells for destruction)
164
Proinflammatory cytokine production is a vicious cycle, which must be
attenuated (homeostatic feedback)
165
Production of immunosuppressive cytokines can provide
feedback control – e.g. interleukin-10 (IL-10)
166
what is IL-10 ?
IL-10 is a peptide secreted by special immunosuppressive cells known as regulatory T cells (Treg)
167
IL-10 is a potent
immunosuppressive cytokine
168
IL-10 is a potent immunosuppressive cytokine:
- supress inflammation
- supress activation
- supress proliferation
- supress chemotaxis
- anti-pyrogenic
169
Human herpes virus-4 (aka EBV) IL-10 homologue induces
immune suppression
170
Viral homologues of IL-10 are
old news
171
Epstein-Barr virus (EBV IL-10) homologue further
characterised
172
EBV linked to
lymphoma and other cancers
173
