HIV receptor and co-receptor interactions

mteintzemontana.edu

Design of an effective vaccine against HIV must take into account the high degree of variability in the sequence of the envelope proteins that has been observed in clinical isolates, and the high mutation rate of the virus. Vaccines based on the envelope glycoprotein gp120 have been ineffective in protecting against clinical isolates of HIV. Most of the antibodies that are elicited are directed against variable portions of the sequence. Some HIV-infected patients, however, develop neutralizing antibodies with broader strain specificity, many of which appear to be directed at the three- dimensional shape of the CD4 binding site on gp120. This part of the molecule is conserved in structure, because all HIV use the CD4 receptor to gain entry into the cell. Our hypothesis is that this part of gp120 will make a more effective vaccine antigen than the whole protein. We are therefore constructing recombinant or synthetic molecules that display this conformation-dependent structure. We have identified peptide structures that can mimic the sites recognized by some of the neutralizing antibodies using phage-display technology and are displaying these peptides on the surface of other viruses or nanoparticles, and using them to immunize mice and rabbits. We are also taking the synthetic peptide sequences and determining their three-dimensional structures when bound to the antibodies. The information obtained from X-ray crystallography of the peptide-antibody complexes will be used to design better antigens that can elicit a more effective immune response to the virus. Comparing the structures of different antibodies to the CD4 binding site that vary significantly in their ability to neutralize primary HIV strains will also shed light on what determines their potency (see figure).

Selected Publications

Wilkinson, R.A., Evans, J.R., Jacobs, J.M., Slunaker, D., Pincus, S.H., Pinter, A., Parkos, C.A., Burritt, J.B., and Teintze, M.:
Peptides selected from a phage display library with an HIV-neutralizing antibody elicit antibodies to HIV gp120 in rabbits, but not to the same epitope.
Aids Res. Hum. Retroviruses 23: 1416-1427 (2007)

Wilkinson RA, Piscitelli C, Teintze M, Cavacini LA, Posner MR, Lawrence CM :
The Structure of Fab F105; A Broadly Reactive Anti-HIV Antibody That Recognizes the CD4 Binding Site of gp120.
J. Virol, 79:13060-13069 (2005)

Jacobs JM, Bailey BW, Burritt JB, Morrison SG, Morrison RP, Dratz EA, Jesaitis AJ, Teintze M :
The QSYP Peptide Sequence is Selected from Phage Display Libraries by Bovine IgG Contaminants in Monoclonal Antibody Preparations.
Biotechniques, 34:132-141. (2003)

Keywords:
Biochemistry

This project aims to determine the structure of the CCR5 chemokine receptor structure at its ligand binding site and its interaction with agonist and antagonist molecules. CCR5 is the major co-receptor required for infection by primary isolates of HIV (the M-tropic/R5 strains predominantly transmitted between people). The goals of the project are to: (1) Synthesize photo-activatable analogs of non-peptide antagonists that block HIV infection. (2) Photo-crosslink bioactive analogs to CCR5, and locate crosslinking sites using mass spectrometry (LC/MS/MS) to map the antagonist binding pocket in CCR5. (3) Map the structure of the HIV/chemokine binding pocket of CCR5 by scanning photoactivatable amino acid analogs over chemokine peptide agonist sequences, photocrosslinking the bioactive analogs to CCR5, and using MS to determine residues lining the binding sites. (4) Analyze the conformation of CCR5 with bound antagonist vs. agonist by mapping discontinuous epitopes of antibodies that discriminate between these conformations of CCR5, using random peptide libraries displayed on phage. (5) Determine the structures of these peptide epitopes bound to the antibodies using x-ray crystallography. The ultimate goal is to provide a foundation for more effective structure-based design of HIV entry inhibitors. A similar approach is being used with antagonists of the other main HIV co-receptor CXCR4.

Keywords:
Biochemistry

· View All Publications