6. In-class assignment - parasitic defense mechanisms

Question 1

What is Variant surface glycoprotein (VSG)?

Answer 1

Glycoproteins that abundantly covers the plasma membrane of protozoan parasite from the Trypanosoma genus

Question 2

How does VSG work?

Answer 2

1. forms a dense cell surface coat to shield invariant surface antigen → protect from immune recognition
2. Shield the invariant surface antigen by binding to host antibody
3. Coat = can selectively remove VSG-specific antibody from cell surface → by degrade the
   VSG-antibody by endocytosis & shuttling VSG → cell surface = clear from antibody
4. Result = dampen immune response

Question 3

What are 4 mechanism of VSG switching?

Answer 3

1. Array VSG Conversion
2. Telomeric VSG Conversion
3. Segmental VSG Conversion
4. Transcriptional Switch

Question 4

Explain Molecular Mimicry of Plasmodium!

Answer 4

Expression of RIFINs protein on infected cell surfaces by the plasmodium → RIFINs bind to LILRB1 on NK cells → LILRB1 recognizes RIFINs as MHC molecules on the surface of healthy cells → infected cells not destroyed

Question 5

Schistosomes can do concealment of antigenic sites by…

Answer 5

Mimicry of host molecular antigens & Avoiding recognition by host pattern recognition receptors

Question 6

Explain Antibody Degradation of schistosomes!

Answer 6

The excretory/secretory layer covering the parasites trap the antibody →
prevents antigen-antibody shedding → parasite-derived proteases degrades
trapped antibody

Question 7

Explain mechanism of Phagocytic functions interference of macrophages by plasmodium

Answer 7

1. Plasmodium invades immune in human body → stimulate the release of IL-4 (cytokine that suppresses
   macrophage activity) → prevent the activation of phagocytosis
2. resides within vacuoles of its mammalian host cells → limit leakage of parasite-derived proteins into the host cytoplasm → no immune recognition of infected cell by cytotoxic T cells or NK cells
3. P. falciparum malaria pigment or hemozoin hinders phagocytic function of macrophages → cannot phagocyte more iRBC (infected RBC) and reduce the radical oxygen intermediates production