Lecture 13 - Life Cycle Of Sporozoites

Question 1

Where are sporozoites present?

Answer 1

They are present on mosquito salivary glands

Question 2

Where to the sporozoites travel?

Answer 2

They travel to the liver and invade hepatocytes by binding to HS proteoglycans

Question 3

What do sporozoites become?

Answer 3

Exocrythrocytic and multiply and burst from liver cells and go into the blood as merozoites

Question 4

What happens when sporozoites enter the blood?

Answer 4

They mature, divide and rupture the cell and infect new erythrocytes

Question 5

What are the symptoms of malaria?

Answer 5

The loss of RBCs as they are destroying RBCs

Question 6

What type of cycle is the erythrocytes symptoms of malaria?

Answer 6

It is an asexual cycle

Question 7

What do some merozoites differentiate into?

Answer 7

Gametocytes which enter the gut of the mosquito and fertilisation occurs producing a zygote

Question 8

What does the zygote differentiate into?

Answer 8

An ookinete and crosses the midgut wall and sits extracellularly between the basal lamina and the midgut

Question 9

What does the ookinete differentiate into?

Answer 9

Into a Oocyst and sporozoites develop inside it

Question 10

Where do the sporozoites mature?

Answer 10

They mature and invade the hemocoel of the mosquito and then travel to the salivary glands

Question 11

What happens when the sporozoites travel to the salivary glands?

Answer 11

The mosquito bites a new host and the cycle repeats

Question 12

How do sporozoites bind when they reach the liver?

Answer 12

They bind via circumsprozoite protein (CSP) which is positively charged to Heparan sulphate proteoglycan on the hepatocyte cell surface

Question 13

The liver heparan sulphate (HS) is ….

Answer 13

Highly sulphated - more than other cells

Question 14

What is the interaction between CSP on HS with liver cell surface?

Answer 14

It is a charged:charged interaction

Question 15

How do the sporozoites identify the liver HS?

Answer 15

Because it is highly sulphated

Question 16

What are the different forms of HS?

Answer 16

Unsulphated form - GlcNac-1-4 iduronic acid and an over sulphated form - GlcNS6S-14IdoA2S-1-4 (which has 3 sulphates)

Question 17

What of HS do the mosquitos recognise the most?

Answer 17

The over sulphated form

Question 18

What is the other function of the liver?

Answer 18

To remove the glycoprotein reminence - circlulating glycoprotein complexes that are present in the blood

Question 19

What binds to HS proteoglycan to take up the glycoprotein remanents?

Answer 19

ApoE binds to HS proteoglycan via its highly sulphated surface

Question 20

What competes with ApoE?

Answer 20

CSP competes for the same binding site hijacking the system, if you have lots of remanents being taken up by the liver (ApoE) then the uptake of the parasite (CSP) will be low

Question 21

What does the mosquito do when the mosquito lands on you?

Answer 21

It spits and makes a hole, they have an anticoagulant so the blood doesn’t clot when they suck it up

Question 22

What is present in mosquitos?

Answer 22

Syndecan is presnet

Question 23

What does CSP bind to?

Answer 23

It binds to salivary glands not other cells

Question 24

How could you extract GAGs from the PGs of the mosquitoes?

Answer 24

By SDS which leads to beta elimination - chop the GAG of the protein core

Question 25

What would you use to get a better analysis?

Answer 25

Chop up HS to look for the trisulphated bit - use heparin lyase

Question 26

What was found in peak 6 - the trisulphated entity?

Answer 26

No difference between the whole mosquito, salivary glands m midgut and ovary

Question 27

What does surface plasmon resonance allow?

Answer 27

It allows for measurements of interactions

Question 28

What is the comparison between HS and CSP with porcine liver HS?

Answer 28

The binding of HS and CSP has a slow association and slow dissociation, in porcine it is very rapid, comes to a plateau and then dissociates slowly

Question 29

What do plasmodium sporozoites use to target their organs in human and mosquito?

Answer 29

They used HS proteoglycans

Question 30

What is the most abundant transcripts in mosquito salivary glands?

Answer 30

Syndecan

Question 31

What was found that the mosquito contains?

Answer 31

Trisulphated disaccharide that binds to ApoE on liver cells

Question 32

Why does the sporozoite bind to liver cells if there is the same amount of trisulphate in the midgut?

Answer 32

When looking at the levels of chondroitin sulphates there was a much lower level in the gut than in the salivary glands. Binding in the salivary glands may require both GAGs (HS and Cs), CPS has been showed to bind to Cs

Question 33

What will future studies show?

Answer 33

SPR with HS on specific organs instead of the whole fly

Question 34

What is a receptor essential for erythrocyte invasion by plasmodium?

Answer 34

Basigin

Question 35

What is the major infective agent in malaria?

Answer 35

Plasmodium falciparum (Pf)

Question 36

What does the merozoite have on its surface?

Answer 36

PfRh5 which has been shown to be essential for parasite growth so it is a good candidate as a ligand for a receptor on red blood cells

Question 37

What does soluble Basigin do?

Answer 37

Reduces the invasion efficiency of CSP

Question 38

Basigin =

Answer 38

An OK blood group antigen

Question 39

What happens if you don’t express highly level of Basigin?

Answer 39

You have a better chance of avoiding the problems of malaria

Question 40

What is Basigin also known as?

Answer 40

CD147

Question 41

What id needed for binding?

Answer 41

Ig domains 1 and 2 not carbohydrates

Question 42

What is a new treatment for malaria?

Answer 42

Naturalising antibodies instead of injections

Question 43

What is a problem with neutralising antibodies?

Answer 43

They don’t last long in circulation so you have to modify them to increase their life time circulation