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114 Residues of GP120 Core Structure on the GP41 Interacting Face Contributing to the High Neutralization Resistance of Wild-Type Strains of HIV-1: Relevance to Vaccine Development
M. Leavitt*, E.-J. Park, and G. Quinnan
Uniformed Services Univ. of the Hlth. Sci., Bethesda, MD, USA
Background: Efforts to develop a vaccine against HIV-1 have been slow as a result of resistance of virus to neutralization and difficulties in preparing envelope protein in a stable conformation that expresses conserved neutralization epitopes. We have shown that the neutralization resistance (NR) phenotype is linked to high infectivity (HI). Here we report additional studies on the mechanism of this phenotype.
Methods: Clones were developed of the neutralization sensitive, T-cell line-adapted MN strain (MN-T) and the neutralization resistant, primary MN strain (MN-P). Mutations that distinguished the gp120 clones were clustered in the receptor and coreceptor binding sites and in a region hypothesized to be the gp41-binding site (gp41bs). Mutations in these regions contributed to the NR and HI phenotypes through effects that depended on interaction with sequences in the MN-P gp41 leucine zipper (LZ) domain. We have attempted to map the gp41bs through study of effects of mutations in the putative gp41bs.
Results: Our results indicated that effects of mutations in this region of gp120 are completely dependent on the presence of sequences containing 3 mutations in the extreme amino terminus of gp120 (first 92 amino acids), but that in this context a substantial contribution to phenotype was made by a sequence containing 3 mutations downstream (residues 212(278). Four of those mutations have known atomic locations and are localized to 1 pole of the hypothesized gp41bs. Further, we found that spontaneous dissociation of gp120 from gp41 was high for MN-T and low for MN-P, whereas sCD4 binding did not effect further dissociation of MN-TCLA, but did effect dissociation of MN-P glycoproteins. In the context of MN-P LZ sequences, the 6 mutations in the putative gp41bs that affected infectivity also conferred the MN-P glycoprotein dissociation phenotype.
Conclusions: Mapping of the gp41bs should have significant implications for vaccine development and for establishing strategies for designing proteins with stable conformations for induction of responses against conserved neutralization epitopes.
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