1. I guess you think you know this story. You don’t. The real one’s much more gory. The phoney one, the one you know Was cooked up years and years ago.” Roald Dahl “Revolting Rhymes”

2. http://www.avert.org/his81_86.htm Reverse transcriptase inhibitors were a Major breakthrough in treating AIDS

3. http://www.avert.org/his81_86.htm Even as new uses for AZT were reported… January 1993 A study, ACTG 076, showed that AZT reduced by two thirds the risk of HIV transmission from infected mothers to their babies. Connor E.D. et al. (1994) 'Reduction of maternal-infant transmission of Human Immunodeficiency Virus type 1 with zidovudine treatment', The New England Journal of Medicine, Vol. 331:1173-1180, November 3, No. 18

4. http://www.avert.org/his81_86.htm And AZT and other RT inhibitors started to level off the rise in AIDS cases

5. New RT inhibitors bought some time but by the mid 1990s resistance to AZT and other RT inhibitors was a serious problem some people with AIDS already had resistance to AZT even though they themselves had never taken the drug. We needed a new approach--what can TB treatment teach us about how we might approach things?

6. We need a new drug target

7. Enzymes make good drug targets what other enzymes does HIV use?

8. Let’s look here!

9. The Gag protein gets cleaved into pieces by an enzyme called a protease

10. Gag Capsid Matrix The Gag protein gets cleaved into pieces by an enzyme called a protease

11. You want a drug that fits into the “active site” Where the enzyme does its work Copyright ©2006 by the National Academy of Sciences Das, Amit et al. (2006) Proc. Natl. Acad. Sci. USA 103, 18464-18469

12. Retroviruses. CSHL Press Fig. 13-15 You start with its natural substrate: a polypeptide backbone and the site of protease cleavage (arrow)

13. Retroviruses. CSHL Press Fig. 13-15 You look for things with a similar shape In part of the molecule

14. www.clubbiotech.at/ blundell.htm These can fit into the “active site” and stop up the works preventing the enzyme from doing its work

15. The “protease inhibitors” that pass further tests become drugs! December 1995 The FDA approved the first of a potent new family of anti-AIDS medications. The drug saquinavir belonged to a class of drugs called protease inhibitors.

16. December 1995 The FDA approved the first of a potent new family of anti-AIDS medications. The drug saquinavir belonged to a class of drugs called protease inhibitors. Do you want to use “protease inhibitors” alone?

17. Retroviruses. CSHL Press Fig. 13-18, Modified from Gulick et al. 1997 Combination therapy worked well The baseline median viral RNA level in this study was 41,000 copies/ml. Indinavir = protease inhibitor AZT + 3TC = RT inhibitors

18. Retroviruses. CSHL Press Fig. 13-18, Modified from Gulick et al. 1997 In some patients it worked exceptionally well assay's limit of detection = 50 copies/ml

19. Retroviruses. CSHL Press Fig. 13-18, Modified from Gulick et al. 1997 The median initial cell count was 142 cells/μl (compared to a normal value of 1000). With viral load reduced T cells and thus the immune system rebounded

20. With the addition of these new drugs The fight against AIDS in the US Took a dramatic turn for the better

21. FDA-Approved Drugs to Treat HIV Infection

22. Mutations associated with resistance to protease inhibitors http://atc.atccu.chula.ac.th/biosci_PR.htm Of course we can’t halt evolution by natural selection

23. Combination treatment takes time to reduce viral load

24. And it’s required for a lifetime Why? What about the viral life cycle makes this virus so difficult to eradicate?

25. Remember that the virus integrates into our own DNA? One infected cell can re-start the infection Which cells in your body might harbor HIV for a long time?

26. Picture courtesy of Frank Church What does the future hold in terms of HIV drugs?

27. Go back to what happens when virus enters T cells

28. What if we could block this step?

29. Could we target Viral fusion with host cells??

30. A: Trimer of gp41/gp120 heterodimers B: CD4 interaction with gp120 induces conformational change C: Interaction with CCR5 or CXCR4 co-receptor induces gp41 conformational change to insert fusion peptide into plasma membrane D: Formation of a fusion pore through which viral core passes HIV entry into a CD4+ T cell THE BIOLOGY OF HIV, SIV, AND OTHER LENTIVIRUSES: Harrington and Swanstrom

31. A: Trimer of gp41/gp120 heterodimers B: CD4 interaction with gp120 induces conformational change C: Interaction with CCR5 or CXCR4 co-receptor induces gp41 conformational change to insert fusion peptide into plasma membrane D: Formation of a fusion pore through which viral core passes A 36 amino acid “peptide” resembling gp41 blocks fusion THE BIOLOGY OF HIV, SIV, AND OTHER LENTIVIRUSES: Harrington and Swanstrom

32. FDA-Approved Drugs to Treat HIV Infection

33. Or as the drug company sees it….

34. But guess what happens?

36. More inhibitors are in the pipeline

37. Drug designers are also targeting integrase Merck's Isentress (raltegravir) was approved by the FDA in October 2007. A second integrase inhibitor, Gilead's elvitegravir (GS-9137), is in advanced clinical trials.

38. FDA-Approved Drugs to Treat HIV Infection

39. Our understanding of the biology of HIV also has given us insights into other aspects of the disease

40. Our understanding of the biology of HIV also has given us insights into other aspects of the disease For example, clinicians noticed that a small fraction of people engaged in “high-risk” behaviors did not develop AIDS

41. Our understanding of the biology of HIV also has given us insights into other aspects of the disease For example, clinicians noticed that a small fraction of people engaged in “high-risk” behaviors did not develop AIDS WHY NOT?

42. Let’s do an experiment Isolate CD4+ T cells from these people and add HIV

43. They do not get infected!

44. WHY NOT?

45. Remember how the virus enters T cells?

46. These people are mutants!

47. Both copies of the gene encoding the co-receptor CCR5 had deletion mutations and thus they did not express a functional co-receptor

48. Even individuals carrying one good copy of the gene and one bad copy of the gene have delayed progression from infection to AIDS

49. Other “long-term non-progressors” generate antibodies against conserved regions of gp120 and gp41 Or have a vigorous response of killer T cells to HIV

50. Finally, some Long-term non-progressors are infected with a mutant HIV virus lacking the accessory gene Nef Nef function: 1.Down regulate CD4 so virus can escape 2.Modulates expression of other immune effector molecules

51. Potential Therapies- Life Cycle of HIV-1 Picture courtesy of Frank Church