Mimm 413: Lecture 04 Shio

Front 1

What causes malaria?

Back 1

Parasite: Plasmodium

Front 2

What Phylum, class and group does Plasmodium fall under?

Back 2

Phylum: Apicomplexa
Class: Sporozoea
Group: Protozoa

Front 3

How many clinical cases is malaria responsible for?

Back 3

300-500 million

Front 4

How many ppl are killed by malaria each year?

Back 4

1 million + ppl

Front 5

How many species of malaria infect humans?

Back 5

4

Front 6

What are the 4 species of Plasmodium that infect humans?

Back 6

P. vivax
P. falciparum
P. ovale
P. malariae

Front 7

How many hosts are involved in this parasite life cycle?

Back 7

2
Invertebrate host: determinant host, where parasite underoges its sexual cycle
Vertebrate host: parasite goes through its asexual cycle

Front 8

Describe the general life cycle of Plasmodium

Back 8

Invertebrate host (insect) bites a human
Sporozoites are injected into the body (1hr)
Sporozoites infect the liver (24-48 hrs)
Get widespread infection in the blood, under the merozoite form (1 week)
Merozoites infect RBCs where they go through their asexual cycle
Some may become gametocytes and can be transmitted back to the mosquito when bitten again

Front 9

What secretory glands do Sporozoites have?

Back 9

Rhoptries and micronemes
--> Important for entry

Front 10

What is CSP (circumsporozoite ptn)?

Back 10

Important ptn that is expressed on the surface of all Plasmodium species

Front 11

Describe CSP

Back 11

10-15 um
Has an apical complex and an apicoplast (part of the Apicomplexa phylum)

Front 12

What does CSP bind?

Back 12

Heparan sulfate proteoglycans (HSPGs) in liver sinusoids)

Front 13

What is TRAP?

Back 13

Thrombospondin related anonymous ptn (like CSP, it is a sporozoite expressed surface ptn)

Front 14

What are CSP and TRAP involved in?

Back 14

Gliding mobility of sporozoites through the hepatocytes

Front 15

Where are HSPGs expressed?

Back 15

On hepatocytes, stellate and kupffer cells (in the liver)

Front 16

What happens during the liver stage?

Back 16

Interaction between HSPGs/CS/TRAP ==> Causes arrest of sporozoites
Sporozoites cross through sinusoidal layer of the liver to the Kupffer cells
Sporozoites use their gliding motility to go across several hepatocytes until the parasitophorous vacuole is formed
Sporozoites multiply and form schizonts containing merozoite, within the hepatocytes
Merozoites escape from the PV and mix with the host cytoplasm
Form Merosomes (merozoite-filled vesicles)
Merosomes mbs have a host feature and is .: not recognized by kupffer cells and DCs

Front 17

How does plasmodium remain dormant?

Back 17

Sporozoites remain hypnozoites

Front 18

Which Plasmodium species can remain dormant?

Back 18

P. vivax
P. ovale

Front 19

What starts the erythrocytic cycle?

Back 19

Release of merezoites (smaller than sporozoites) into the bloodstream

Front 20

Describe the erythrocytic cycle

Back 20

Merozoites infect RBCs
Go into their ring stage
Develop into gametozyes or mature trophozoite
Mature trophozoite becomes a schizont
Schizont ruptures and releases the parasite

Front 21

Describe merozoites

Back 21

Smaller than sporozoite (~2.5 um)
Have an apical comples that has 3 secretory glands
Merozoites are covered by surface coat made of merozoite surface ptns (MSP) and apical mb ptn Ag (AMA-1)

Front 22

What are the 3 secretory glands of the merozoites apical complex?

Back 22

Rhoptry
Microneme
Dense granules

Front 23

What do these secretory glands do?

Back 23

release ptns involved in the invasion of the host RBC

Front 24

What are the most important ptns in the merozoite?

Back 24

Erythocyte binding Ag (EBA-175): Located on the microneme
Duff-binding Ag (on P. vivax)

Front 25

What ptns does the Dense granule have?

Back 25

Ring-infected erythrocyte surface Ag (RESA)

Front 26

What kind of ptns do the Rhoptries have?

Back 26

AMA
RAP
Rhop

Front 27

Describe the merozoite-RBC interaction

Back 27

Initial attachment and reorientation\Irreversible attachment and jct formation\Parasitophorous vacuole (PV) formation and invasion

Front 28

What does step 1, initial attachment and reorientation, involve?

Back 28

Use coat ptns on the merozoite
--> Need MSP and AMA-1 on the surface
Surface ptns on merozoite deposited in a gradient

Front 29

What happens in step 2 (irreversible attachment and jct formation)?

Back 29

Requires 2 ptns: Pf EBA-175 (P. falciparum) and Duff-binding ptn (P. vivax)
-Get the secretion of microneme ptns
-High-affinity adhesion

Front 30

What does EBA-175 bind? (for P. falciparum)

Back 30

Glycophorin A

Front 31

What does Duff binding ptn (for P. vivax) bind?

Back 31

Duffy ptn on the RBC

Front 32

What happens during the 3rd step of merozoite-RBC interaction (PV formation and invasion)?

Back 32

Secretion of rhoptry ptns and lipids
Inwards motion driven by actomyosin motor
Proteolytic processing/cleavage of parasite surface ptns (MSP & AMA-1)
Localized reorganization of host cell mb and cytoskeleton

Front 33

Describe the erythrocyte cycle of P. falciparum

Back 33

~5 minutes for merozoite to enter RBC
After ~12 hours, have ring formation, start seeing clefts
~24 hours: Trophozoite
-> see cleft and loop structures and knobs with the parasite adhesin Pf-EMP1 (makes RBCs stick more to the blood vessel).
--> Also see food vacuole with hemozoin in it.
-->Has a larger cytoplasm
~36 hours: start formaing merozoites
~40 hours: develop schizont
~48 hours: Schizont ruptures and RBCs release merozoites

Front 34

Describe gametocytes

Back 34

Formed from merozoites (not entirely sure how)
Takes a dew days to appear in broad circulation
can be taken up by mosquito
-->Goes into the invertebrate cycle

Front 35

Describe the plasmodium life cycle in invertebrates (Anophole mosquitoes)

Back 35

Insect ingests the gametocytes
Female and male gametes combine and fertilization takes place (in the stomach)
Ookinete can penetrate the stomach lining
Oocysts end up below the stomahc lining
Sporogeny takes place
Sporozoites develop into oocysts and migrate to the salivary glands of the insect (from there, they can be injected into the human host when the bug takes a blood meal)

Front 36

Which Plasmodium species infect the most?

Back 36

P. falciparum (50%) > P. vivax (43%) >>> P malariae (7%) >> P. ovale (rare)

Front 37

What kind of paroxysm does P. vivax cause?

Back 37

Benign tertian

Front 38

What kind of paroxysm does P. falciparum cause?

Back 38

Malignant tertian

Front 39

What kind of paroxysm does P. ovale cause?

Back 39

Bening tertian

Front 40

What kind of paroxysm does P. malariae cause?

Back 40

Benign quartan

Front 41

What's the difference between being benign and malignant?

Back 41

Benign: not complicated, host doesn't die
Malignant: host dies

Front 42

For P. vivax, describe the
Periodicity
Hepatic cycle
Prepatent (amt of merozoites)
Relapse or Recrudescense

Back 42

Periodicy: 48 hrs
Hepatic cycle: 8-27 days
Prepatent: 10, 000 mz
Relapse up to 8 years
(have hypnozoites)

Front 43

For P. falciparum describe the
Periodicity
Hepatic cycle
Prepatent (amt of merozoites)
Relapse or Recrudescense

Back 43

Periodicity: 36- 48 hours
Hepatic cycle: 8-25 days
Prepatent: 30, 000 mz**
Recrudescence 1 yr
RBC

Front 44

For P. ovale, describe the
Periodicity
Hepatic cycle
Prepatent (amt of merozoites)
Relapse or Recrudescense

Back 44

Periodicity: 48 hours
Hepatic cycle: 9-17 days
Prepatnet: 15, 000 mz
Relapse up to 8 years, hypnozoites

Front 45

For P. malariae, describe the
Periodicity
Hepatic cycle
Prepatent (amt of merozoites)
Relapse or Recrudescense

Back 45

Periodicity: 72 hrs **
Hepatic cycle: 15-30 dyass
Prepatent: 2,000 mz
Recrudescence up to 53 years
iRNC without symptoms

Front 46

Why is the relapse of a disease important?

Back 46

Some parasites develop into hypnozoites (P. ovale and P. vivax)
These parasites might come back years later

Front 47

What is recrudescence?

Back 47

After treatment, there are no more symptomsm but the parasite is still subdividing
Parasite is still there in RBCs, but they can't be seen
This can increase the incidence of transmission (i.i through blood donor)
These ppl still have the disease, but it cannot be observed

Front 48

What are the 3 pathognomonic cardinal signs of malarial paroxysm?

Back 48

Chills and vigorous shivering (host and parasite-derived factors)
Pyrexia or spiking high fever
Profuse sweating

Front 49

What are some other non-specific symptoms of malarial paroxysm?

Back 49

Headache
Muscle aches
Tiredness
Nausea
Vomiting
Diarrhea
Flu may be included

Front 50

What do malarial paroxysm episodes vary with?

Back 50

Dpeneds on the Plasmodium species

Front 51

Describe the malarial paroxysm (MP) according to P. vivax/ovale

Back 51

Benign tertian
Schizont ruptures the first day: corresponds to MP
Schizonts rupture again on the 3rd day
Fever and other MP symptoms decrease after the spike on the 1st and 3rd days

Front 52

Describe the malarial paroxysm (MP) according to P. falciparum

Back 52

Malignant tertian
Schizont ruptures on the 1st day but fever stays high until end of 2nd day, then goes down and spikes up again on the 3rd day
(also a 48 hour cycle)

Front 53

Describe the malarial paroxysm (MP) according to P. malariae

Back 53

Benign quatern
Schizont ruptures day 1 and get spike of fever
Symptoms of MP decrease and stay low until day 4**, when fever peaks again
=>3 day cycle

Front 54

How does paroxysm occur?

Back 54

Starts with rupture of the schizont, release of merozoites, cellular devris and metabolic waste (hemozoin)

Front 55

What hapens when a merozoite infects and RBC?

Back 55

Merozoite surface coat ptns are cleaved
MSP or GPI-MSP are cleaved and shed continuously into the blood

Front 56

How many domains does MSP-1 have?

Back 56

5

Front 57

How is MSP1 anchored?

Back 57

through GPI (glycosylphosphatidylinositols)

Front 58

How can the parasite Ag be detected?

Back 58

By ELISA

Front 59

What is the role of hemozoin in the paroxysm?

Back 59

Hemozoin interacts with many cells of the immune system and induces proinflammatory mediators (IL-1, TNF)

Front 60

What is the role of MSP in paroxysm?

Back 60

MSP-2 can stimulate macs to make cytokines (TNF, IL-1a/B, IL-6)
When MSP is in the presence of GPI, production of these cytokines is increased

Front 61

Through which receptors does GPI stimulate macrophages?

Back 61

TLR2/1 or 6

GPI, MSP and Hemozoin cause an increase in the produciton of inflammatory cytokines

Front 62

What is the evidence that TNF-a is a critical mediator of MP?

Back 62

1) TNF changes correspond with changes in body T and MP in P. vivax infecte children (in Gambia)
2) Peak TNF level preceded fever peak (30-60 min)
3) Passive transfer of anti-TNF Ab decreases fever

Front 63

Summary of malarial paroxysm

Back 63

Rupture of RBC-schizonts/merozoites infection
Release of malarial toxin (Hz/GPI-exogenous pyrogen)
Activation of RE cells, such as macrophages
Release of TNF, IL-1α, IL-1, IL-6 (endogenous pyrogens-EP)
EP interaction with hypothalamic endothelial vessels
Increased level of prostaglandin E2 in hypothalamus
Elevation in core temperature set point

Front 64

What are factors affecting the course and severity of malaria?

Back 64

1) Species of plasmodium infection (P. falciparum is the most virulent)
2) Immature/incompetent immune mechanisms
3) Host genetic factors
4) Frequency of infected mosquito bites

Front 65

What are the immature/incompetent immune mechanisms due to?

Back 65

Age: children under 5 have 80% mortality rate in sub-Saharan Africa
Primigravida (1st preganancy) and nutritional states --> malnutrition

Front 66

How do the host genetic factors influence the severity of the disease?

Back 66

Renders refractory to infection or if infected, develop mild disease
1) Duffy blood gp: expressed because of alleles Fy-a/b that are codominant, which produce a ptn rec'z by P. vivax
Ppl who don't have these allese are protected vs P. vivax malaria
2) G6P-dehydrogenase deficiency: these ppl protected vs malaria
3) Rigid RBCs (sickle cell trait or HgAS): protected vs malaria

Front 67

What does repeated exposure to malaria, due to the frequency of infected mosquito bites, lead to?

Back 67

Premunition

Front 68

What is premunition?

Back 68

Takes place in hyperendemic areas because the ppl have been continuously exposed to infection
Takes years to develop
Very easy to lose (1 year without infection)
Not a sterilizing type of immunity because infected RBCs persist at subclinical level

Front 69

What are the mechanisms of premunition?

Back 69

1) Ag polymorphism: Pf-EMP-1 present in knob structure encoded by gene Var, ~150 genes that provide ~2.4% rate switching/generation
2) Lower response to malarial Ags (higher CD8+ cells and suppressor T cells)

Front 70

What mediates the premunition response?

Back 70

IgG/IgM
-->Ab dependent cellular inhibition (ADCI)

Front 71

Where is premunition seen?

Back 71

Pre-adults/Adults (not seen in children under the age of 5)

Front 72

Who does premunition benefit?

Back 72

Both partners\Parasite can still be transmitted and host doesn't get as badly hurt

Front 73

What kind of a disease is malaria?

Back 73

Tropical disease (caused by 4 plasmodium species that infect humans)

Front 74

Which P. species have worldwide distribution?

Back 74

PV and PF

Front 75

Which species is responsible for 90% of malaria caused deaths?

Back 75

PF (can cause serious complications)

Front 76

What insect is responsible for malaria transmission?

Back 76

Anopheles species mosquito

Front 77

What happens when sporozoites are injected into the blood from the mosquito?

Back 77

Sporozoites migrate to the liver (HSPG/CS/TRAM iunteraction)
Cross via Kuppfer cells\Infect hepatocytes
Merozoites are released from liver schizont via merosome formation

Front 78

How do hepatocyte-derived merozoites infect RBCs?

Back 78

Use MSP/AMA-1 dependent reorientation, tight jct (through EBA and Duff-binding Ag) and the Parasitophorus vacuole)

Front 79

What happens once merozoites enter the RBC?

Back 79

Differentiate into:
Ring stage
Trophozoite stage
Schizont stage
Merozoites than released into the blood and infect new RBCs

Front 80

What is paroxysm ass't with?

Back 80

Rupture of the schizont stage

Front 81

What happens when the schizont is ruptured?

Back 81

Hemozoin and GPI are released, which stimulated monocytoid cells to release endogenous pyrogen (IL-1, TNF-a)
This affects the T receptors in the hypothalamus, initiating MP

Front 82

What does the course and severity of malaria depend on?

Back 82

Plasmodium species
Immature/incompetent immune system
Host genetic factors
Development of premunition

Front 83

How can malaria be diagnosed?

Back 83

Microscopic examination of Giemsa stained blood film