bi0003691_si_001.pdf (244.44 kB)
A Structure-Based Approach to a Synthetic Vaccine for HIV-1†
journal contribution
posted on 2000-11-01, 00:00 authored by Edelmira Cabezas, Meng Wang, Paul W. H. I. Parren, Robyn L. Stanfield, Arnold C. SatterthwaitThe generation of neutralizing antibodies by peptide immunization is dependent on achieving
conformational compatibility between antibodies and native protein. Consequently, approaches are needed
for developing conformational mimics of protein neutralization sites. We replace putative main-chain
hydrogen bonds (NH → OCRNH) with a hydrazone link (N−NCH−CH2CH2) and scan constrained
peptides for fit with neutralizing monoclonal antibodies (MAbs). To explore this approach, a V3 MAb
58.2 that potently neutralizes T-cell lab-adapted HIV-1MN was used to identify a cyclic peptide, [JHIGPGR(Aib)F(d-Ala)GZ]G-NH2 (loop 5), that binds with >1000-fold higher affinity than the unconstrained peptide.
NMR structural studies suggested that loop 5 stabilized β-turns at GPGR and R(Aib)F(d-Ala) in aqueous
solvent implying considerable conformational mimicry of a Fab 58.2 bound V3 peptide determined by
X-ray crystallography [Stanfield, R. L. et al. (1999) Structure 142, 131−142]. Rabbit polyclonal antibodies
(PAbs) generated to loop 5 but not to the corresponding uncyclized peptide bound the HIV-1MN envelope
glycoprotein, gp120. When individual rabbit antisera were scanned with linear and cyclic peptides, further
animal-to-animal differences in antibody populations were characterized. Loop 5 PAbs that most closely
mimicked MAb 58.2 neutralized HIV-1MN with similar potency. These results demonstrate the remarkable
effect that conformation can have on peptide affinity and immunogenicity and identify an approach that
can be used to achieve these results. The implications for synthetic vaccine and HIV-1 vaccine research
are discussed.