vi. Malaria I and II Flashcards
1
Q
Malaria I and II=
History:
A
History: Ancient disease that co-evolved w Homo sapiens
2
Q
1880 Laveran discovered malaria parasite in Algeria —> 1897 Ross discovered _____ _____ in India —> 1972 Tu Youyou isolated artemisinin in China
A
mosquito vector
3
Q
Global Disease burden:
- 85 malaria ______ countries; 2020 - estimated 241 million cases globally
- WHO African region - 2020 estimated malaria cases 228 million accounts for ____% global burden; ___% deaths in this region = children under 5yrs
- Since 2000 malaria case incidence reduced from 368 to 222 cases per 1000 pop @ risk in 2019 before _______ to 233 in 2020 owing to disruptions during Covid-19 pandemic
A
endemic
95%; 80%
increasing
4
Q
The Parasite and the vector
Parasite =
Vector =
A
Plasmodium species: P. Falciparum; P. Ovals; P. Vivax; P. Malariae; P. Knowlesi
Female Anopheles mosquito
5
Q
*Apical prominence =
A
*Apical prominence = place where merozoite attaches to RBC
6
Q
Process of Parasite Invasion Proteins: (4)
A
- Attachment to RBCs = Merozoite surface protein MSP-1
- Junction formation = proteins secreted from micro eyes and rhoptries + erythrocyte binding antigen EBA-175
- Complex regulation of sequential release of invasion proteins
- Molecular interaction w host RBC receptors = glycosylated membrane proteins
7
Q
Host RBC Membrane Receptors
P. Vivax —
P. Falciparum —
A
- P. Vivax — Duffy blood group antigen / IL8 which is only present on young RBCs therefore only invades young RBC
- P. Falciparum — several receptor pathways; Shalicious acid dep and indep (glycoproteins, Band 3, Basigin); P. Falciparum invades RBC of all ages
8
Q
What is the process of remodelling of Host RBC? (4)
A
- New transport pathways: nutrient entry and waste prod disposal; movement across 3 membranes; parasitophorous duct
- Exports several hundred proteins into RBC
- Modification of host RBC proteins
- Insertion of parasite proteins into RBC membrane
9
Q
Haemoglobin Degradation
- 95% of soluble RBC protein is haemoglobin; 25-75% haemoglobin = ____ ____ ______; 25% utilized for AAs; rest exported for volume control
- Haemoglobin ingested by parasite via ______ — fusion w acidic digestive vacuole — digestion by parasite specific protease — Release of _______ haemoglobin from globin —
auto-oxidation to toxic ferriprotoporphyrin — ________________ into inert haemoglobin
A
degraded by parasite
cystoscome
ferrous
bicrystallisation
10
Q
How does the malaria parasite evade the host immune system? (3)
A
- Parasite growth alters pRBC surface — triggers an immune response
- Decreased deformability of parasitized RBC causes splenic trapping and destruction
- P. Falciparum parasites evade host immune system and spleen
- sequestration/ cytoadherence
- variation of exposed antigens
11
Q
Cytoadherence: adhesion of pRBC to vascular endothelium
- Mature asexual P. Falciparum ________
- Immature P. Falciparum _______
A
parasites
gametocytes
11
Q
What is Autoagglutination?
A
Adhesion of pRBC to other pRBC
12
Q
What is Resetting?
A
Adhesion of pRBC to uninflected RBC
13
Q
Parasite Cytoadherence Ligands:
Knobs:
A
protrusions on RBC membrane surface; host RBC spectrum, actin, protein 4.1 and 4.9; PfKAHRP; PfEMP 1,2 and 3
13
Q
Parasite Cytoadherence Ligands:
Parasite ligands:
A
PfEMP1; Modified host band 3
14
Q
Host Receptors for Cytoadherence: (5)
A
15
Q
Parasite Antigenic Variation:
PfEMP 1 - most NB determinant; Encoded by fam of var genes; 50-150 copies of var gene per genome; Each parasite expresses a single var gene Invasion proteins: ______; ______
A
MSP 1; EBA 175
16
Q
Release of Merozoites:
2 step mechanism:
A
parasitophorous vacuole membrane ruptures — parasite liberates proteases into RBC — proteolytic cleavage of RBC membrane — pressure driven explosion of RBC — rapid
discharge of merozoites
17
Q
What is Gametocytogenesis? (8)
A
18
Q
Gametocytogenesis
In mosquito:
- rapid gamete formation to avoid ______ detection
- rapid fertilization and ______ formation
- limited invasion of ookinetes in mosquito midgut
- limited number of ________ in the salivary glands
- Infected mosquitoes bite more
- Trade off btw rapid optimal transmission to human host and killing the _______ host
A
immune
ookinete
sporozoites
mosquito
19
Q
Parasite Survival Strategies: Within human RBC = (4)
A
- metabolism adapted to host RBC environment
- Detoxifies haemoglobin
- regulates vol of RBC
- Induces alterations of RBC membrane
20
Q
Parasite Survival Strategies:
Immune Evasion = (3)
A
- cytoadherence to escape destruction in spleen
- Antigenic variation to escape immune response
- Minimum time outside RBC to evade detection
21
Q
Parasite Survival Strategies:
Other:
- gametocyte formation to ensure _______
- Regulates ________ to protect human host-apoptosis
- Drug resistance
A
transmission
parasitaemia
22
Q
Survival stategies of human host
Malaria hypothesis Haldan 1949:
A
to explain the high incidence of hereditary Angelia in regions where malaria was endemic
23
Survival stategies of human host
Balanced polymorphism -
Balanced polymorphism - selection of a deletorious gene by survival advantage for another disease
24
Survival stategies of human host
Inherited genetic defects or polymorphisms:
haemoglobinopathies; enzymopathies; RBC membrane protein defects; blood groups and antigens
25
Haemoglobinopathies:
1. Sickle cell haemoglobin: (7)
25
What are the Haemoglobinopathies?
1. Sickle cell haemoglobin
2. HaemoglobinC
3. Other haemoglobinopathies
26
Haemoglobinopathies:
2. HaemoglobinC: (2)
27
Haemoglobinopathies:
3. Other haemoglobinopathies: (3)
HBE and HbF:
- decreased parasite growth
- Increased immune clearance by phagocytosis
- Stable HbF tetramer is poor substrate
28
What are Thalassemias? (4)
- Imbalance of globin chain synthesis
- Decreased parasite growth
- Increased phagocytosis and oxidative damage
- Impaired rosetting
29
What are Enzymopathies? (2)
1. G6PD Deficiency
2. Pyruvate Kinase (PK) Deficiency
29
Enzymopathies
1. G6PD Deficiency: (4)
30
Enzymopathies
2. Pyruvate Kinase (PK) Deficiency: (3)
- PK catalyses an essential step in anaerobic glycolysis
- critical for ATP production in erythrocytes which lack mitochondria
- PK deficient red cells show marked in vitro resistance to P. Falciparum invasion and growth
31
RBC Membrane Protein Defects:
1. South East Asian Ovalocytosis
- V high ______ in South East Asia
- Homozygote = ______
- 9 AA deletion in band 3
- Inhibits parasite invasion
- Decreases ________
- protects against ______ malaria
prevalence
lethal
cytoadherence
cerebral
32
Blood group Antigens:
P Falciparum -
P Vivax -
- P Falciparum - absence oof glycophorins/ hybrid glycophorins; decreased invasion/ growth of parasites; protection not complete, can use multiple receptors
- P Vivax - Duffy antigen receptor; 100% Duffy negative in parts of west Africa; absence of P. Vivax
33
ABO blood groups:
- current ABO distribution due to ______ ______ from malaria
- Blood group O protects against _____ P. Falciparum malaria
- Reduced cytoadherence/ resetting of group O _____
- O>A in endemic malaria areas; A>O in non-malaria areas
selective pressure
severe
pRBC
34
Blood group Antigens:
2. Hereditary Spherocytosis (HS)
3. Hereditary Elliptocytosis (HE)
- Decreased parasite growth ____ ______
in vitro
35
Symptoms of P. Falciparum Malaria:
What is Acute Febrile Illnesses?
Can rapidly progress to severe disease and death; initial symptoms non specific: fever, chills, perspiration, headache, myalgia, tiredness, loss of appetite, poor feeding (young children), nausea, vomiting, diarrhoea, abdominal discomfort; spleen omega lay (areas of high transmission)
36
Symptoms of P. Falciparum Malaria
Severe Malaria:
- Impaired consciousness; prostration (unable to sit/ stand/ walk w/o assistance; multiple convulsions (more than 2 in 24hrs); respiratory distress; acidotic breathing; acute pulmonary edema; auria; jaundice; abnormal bleeding
37
Pathogenesis of P. Falciparum Malaria:
Fever and chills =
- haemolysis of infected RBCs every __ hrs
- release of ______ which infect new RBCs
- Release of haemoglobin an _____
- Endothelial cell injury and _______ damage
- _____ release, inflammatory response, fever
48
merozoites
toxins
oxidative
Cytokine
38
Severe Anaemia:
- Haemolysis of infected RBCs every 48hrs and of _______ bystander RBCs
- Destruction of infected RBCs in ____
- Impaired _________
uninflected
spleen
erythropoietin’s
39
What is Pathogenesis of P. Falciparum Malaria?
1. Fever and chills
2. Severe Anaemia
3. Hypoglycemia and metabolic acidosis
4. Organ damage and cerebral malaria
40
Pathogenesis of P. Falciparum Malaria:
Hypoglycemia and metabolic acidosis =
- Increased anaerobic glycolysis in infected ____
- ________ and increased lactic acid prod
- metabolic _____
RBCs
Hypoglycemia
acidosis
41
Organ damage and cerebral malaria:
- cytoadherence/ agglutination/ resetting _____ RBCs
- Obstruction of capillaries and small blood vessels
- Reduced blood flow and _____
- Endothelial cell injury and _______ damage
- Decreased nitric oxide, impaired _______
- cytokine storm and inflammatory response
infected
hypoxia
oxidant
vasoregulation
42
Diagnosis of Malaria: (4)
1. Microscopy of blood smears
2. Rapid diagnostic tests (RDT)
3. PCR
4. Automated diagnosis
[Clinician has to request malaria test, clinical suspicion or travel history required]
43
Diagnosis of Malaria:
1. Microscopy:
What are the differences between a thin blood smear and a thick blood smear?
(3 x 3)
44
Diagnosis of Malaria:
1. Microscopy
Advantages or Disadvantages: (5 x 4)
45
Diagnosis of Malaria:
2. RDT - rapid antibody-based dipstick tests/ lateral flow immunoassay; malaria antigens pHRP/ pLDH
Advantages or Disadvantages: (3 x 6)
46
Diagnosis of Malaria:
3. PCR - molecular test
Advantages or Disadvantages: (4 x 6)
47
What test is used to calculate percentage parasitaemia?
SYSMEX Analyser:
Number of infected RBC (MI-RBC 103/ul) % parasitaemia (MI-RBC %)
Full blood count
48
Automated Diagnosis of Malaria:
- Haematology analysers; __________ based on cell size and complexity
- Indirect measurement of WBCs w haemoglobin; laser light differentiates btw diff WBCs Intraerythrocytic parasites produce ________
Monocytes ingest parasitized erythrocytes; monocytes scattered abnormally Haemozoin is _________ and depolarizes laser light
- Direct measurement of parasites in RBCs
- ________ can also be detected
scattergrams
haemozoin
birefringent
Gametocyte
49
What are the anti-malaria drugs? (10)
50
Pharmacological Therapy:
Uncomplicated P.
Falciparum malaria in non-pregnant patients:
- Fixed dose artemisinin-based combination therapy (ACT), artemether-lumefantrine (Coartem) 6 doses + low dose primaquine
- When artemether-lumefantrine is not available or is contraindicated (history of allergy to artemisinins/lumefantrine), uncomplicated malaria can be treated w/ oral quinine plus either doxycycline or clindamycin
51
Pharmacological Therapy:
Complicated/Severe malaria:
Intravenous artesunate at 0.12 and 24 hours, then daily until Pt s able to tolerate oral treatment (Coartem)
52
Pharmacological Therapy:
Non falciparum malaria: (2)
- Artemether-lumefantrine (Coartem)
- For P. Vivax or P. Ovale, a follow-on treatment course on primaquinine is essential to eradicate residual hepatic phase to prevent relapse
53
Artemisinin Resistance:
54
What are the Prophylactic Measures?
ABCDE
A: Awareness and assessment of malaria risk
B: Avoidance of bites (insecticide treated bed nets, mosquito repellants, long sleeve clothes at night etc.)
C: Chemoprophylaxis
D: Early detection and diagnosis
E: Effective treatment
Other strategies: Indoor residual spraying (IRS), larvicides
55
Vaccines:
Challenges w/ vaccine dev & admin:
dif parasite stages express dif antigens, incredible antigenic variation of parasite proteins, parasites can establish asymptomatic chronic infection in an immune-competent host
56
Vaccines:
Vaccine approaches:
Anti-infection vaccine (target sporozoites or liver stages eg. CSP), anti disease/mortality vaccine (target asexual RBC stage eg. MSP 1), Anti-transmission/
mosquito vaccine (target gametocytes/gametes/ookinetes)
57
Vaccines:
Strategies for Vaccine Design: (2)
1. Antigens must be accessible to immune system, induce a protective immune response
Vaccines should combine antigens from dif parasite stages, combine several antigens from single parasite stage, elicit correct type of immune
2. Response for stage of parasite, elicit antibody & cell-mediated immune response, simple & inexpensive
58
What is the GSK RTS,S AS01 Vaccine?
59
Molecular Research Advances:
Genome sequences:
- Human: Homo Sapiens around 3 billion bp, ______ genes
- Parasite: P. Falciparum with 23 million bp, around _____ genes
- Mosquito: Anopheles gambiae, 280 million bp, ___-_______ genes
25 000
5300
13-14 000
60
Molecular Research Advances:
P. Falciparum can be cultured __ _____, protein biochem and cell biology
- Advanced molecular biology tech: gene transfection, gene knockout, ____-________ genome editing, RNAi - controversial, Microarrays, transcriptome sequencing, proteomics
- Enhances our knowledge of biology of _____, enables rational design of new drugs and vaccines
in vitro
CRISPR-Cas9
parasite
61
