Details

Autor(en) / Beteiligte

• Welch, Brett D

Titel

Targeted inhibition of HIV-1 entry via the GP41 N -trimer

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2008

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Approximately 33 million people are infected with human immunodeficiency virus type 1 (HIV), the causative agent of acquired immunodeficiency syndrome (AIDS). Infection begins with fusion of viral and target cell membranes (viral entry), mediated by the HIV envelope (Env) protein. During entry, Env transiently exposes a critical trimeric domain (N-trimer) that is vulnerable to inhibition. HIV entry is a promising inhibitory target because blocking this first event prevents infection, and entry is a uniquely extracellular process that is vulnerable to peptide inhibitors and antibodies. The N-trimer is a particularly ideal vaccine target because of its critical role in membrane fusion, it is highly conserved, and its structure is well characterized and informative for antigen design. However, attempts to develop potent and broadly neutralizing anti-N-trimer antibodies have, thus far, failed. Chapter 2 describes our discovery of a steric shield surrounding the N-trimer, which protects it from antibody neutralization. We find that bulky cargo proteins attached to a small inhibitor of the N-trimer have similar in vitro target affinities, but that potency dramatically decreases with increasing cargo size. We conclude that large molecules, such as antibodies, cannot access the N-trimer in vivo. Based on these data, we propose strategies to overcome this defense mechanism in the design of future vaccines. Fuzeon, a drug that binds the N-trimer and prevents entry, is the only approved HIV fusion inhibitor. However, as a natural L-peptide it is sensitive to protease degradation resulting in: (1) high dosing requirements, (2) twice daily delivery by injection, and (3) high cost (∼$25,000/year/patient). These problems restrict its use to "salvage therapy" for patients with multidrug-resistant HIV. Chapters 3 and 4 describe our use of phage display and structure-assisted design to discover and optimize protease-resistant D-peptides (peptides made of D-amino acids) that target a highly conserved N-trimer hydrophobic pocket. The best of these inhibitors is ∼105-fold more potent than the best previously described D-peptides. We have designed our best inhibitors with a reserve of binding energy to minimize stepwise accumulation of subtle resistance mutations (i.e., "resistance capacitor"). These promising inhibitors are in preclinical trials for therapeutic and preventative (microbicide) applications.