790 Immunology of Infectious Disease 3/7/2013 Bieneke Bron

1. Sailing on the cell surface 790 Immunology of Infectious Disease3/7/2013 Bieneke Bron

2. Outline • Background • Trypanosoma • Antigenic variation • Hydrodynamics • Paper • Figures • Summary • Discussion

3. Trypanosomabruceii http://www.ilri.org/InfoServ/Webpub/fulldocs/Ilrad88/Trypanosomiasis.htm • Unicellular hemoflaggelate • Vector: tsetse fly • Disease: sleeping sikcness • Human & livestock • Africa, Asia, South America

4. Trypanosoma life cycle 1960 almost disappeared Surveillance relaxed 40.000 – 300.000 cases/year 1990 new efforts to control the disease started 2009 <10.000 No vaccine

5. Trypanosoma survival strategies Antigenic variation of surface coat Clearance of surface bound antibodies Immune suppression

6. Cyclus: Antigenic variation Nature Reviews Microbiology10, 431-438

7. Hydrodynamics the branch of science concerned with the mechanical properties of fluids http://www.no.adeptnordic.com/products/dataanal/tecplot/showcase/studies/2005/gwu.htm

8. Paper – main question How are antibody – VSG complexes sorted on the cell surface? How are they cleared from the cell surface? Thus this give immunological protection?

9. Figure 1 A

10. Figure 1 B

11. Figure 2 37C 24 C ☐ 18 C 12 C 6 C

12. Figure S1 VSG IgG

13. Conclusion: Figure 1 & 2 Direction movement of cell surface IgG-VSG toward the posterior end of the cell and the subsequent rapid endocytosis provides a very efficient mechanism to clear immune complexes from the surface.

14. Table 1 Clearance on population = Clearance on single cell

15. Figure 3

16. Figure 4

17. Figure 5 Forward swimming Reversed swimming

18. Take home figure 3,4,5 • Immune complex redistribution: • Provides resistance to complement* • Dependent on directional motility of the trypanosoma • Independent of • Endocytosis • Actin skeleton • Do we agree?

19. Figure 6: Hydrodynamic drag force

20. Hydrodynamics for dummies r = radius of the IgG 7.5 nm R = mean diameter of tryp. 3 um v = mean velocity of the IgG TBD vt = mean velocity of tryp. 20 um/s n = viscosity of bloodstream 0.03 kg/(s*m) Assuming no slip conditions and a cylinder shaped trypanosoma v = r vt/ R v = 7.5*10-3 * 20 / 3 = 0.05 um/s v = 15*10-3 * 20 / 3 = 0.1 um/s

21. Hydrodynamics for dummies Mean velocity of IgG in no slip conditions = 0.05 um/s Average length of trypanosoma = 20 um Estimate of T ½ IgG = (0.5 * 20) / 0,05 = 200 seconds Estimate of T ½ +/-IgM = (0.5 * 20) / 0.1 = 100 seconds Not even close..

22. Table 1 Larger structures  Shorter half-life

23. Figure 6: Hydrodynamic drag force

24. Summary • Direction movement of cell surface IgG-VSG toward the posterior end of the cell and the subsequent rapid endocytosis provides a very efficient mechanism to clear immune complexes from the surface. • Immune complex redistribution: • Provides resistance to complement* • Dependent on directional motility of the trypanosoma • Independent of • Endocytosis • Actin skeleton • Hydrodynamic drag force is a good model for the complex movement over the cell (sailing on the cell surface). • Thus: T. brucei evolved another subtle defense strategy besides antigenic variation, in which directional cell motility and plasma membrane recycling function cooperatively in the removal of host antibodies from the cells surface.

25. Discussion • Why would the endocytosis of stumpy cells increase? • What could be an explanation for just having one location for endocytosis?

26. Discussion • If you were a bloodborne parasite, what immune evading strategy would you use of this repertoire or what would you add to make it more efficient? • What could be the next step of this research? • For medicine development • For academic curiosity

27. Thank you

28. Thank you 2

29. S2

30. Table S1

31. Figure S3

32. Table S2