Identification of a Highly Conserved Surface on Tat Variants

Sonia Mediouni,Albert Darque,Isabelle Ravaux,Gilbert Baillat,Christian Devaux,Erwann P Loret

doi:10.1074/jbc.m113.466011

Abstract

Extracellular Tat is suspected to protect HIV-1-infected cells from cellular immunity. Seropositive patients are unable to produce neutralizing antibodies against Tat, and Tat is still secreted under antiviral treatment. In mice, the Tat OYI vaccine candidate generates neutralizing antibodies such as the mAb 7G12. A peptide called MIMOOX was designed from fragments of Tat OYI identified as the possible binding site for mAb 7G12. MIMOOX was chemically synthesized, and its structure was stabilized with a disulfide bridge. Circular dichroism spectra showed that MIMOOX had mainly β turns but no α helix as Tat OYI. MIMOOX was recognized by mAb 7G12 in ELISA only in reduced conditions. Moreover, a competitive recognition assay with mAb 7G12 between MIMOOX and Tat variants showed that MIMOOX mimics a highly conserved surface in Tat variants. Rat immunizations with MIMOOX induce antibodies recognizing Tat variants from the main HIV-1 subtypes and confirm the Tat OYI vaccine approach.

Highlights

The Tat OYI vaccine might reduce HIV-1-infected cells due to neutralizing antibodies targeting extracellular Tat
The mAb 7G12 did not recognize denatured MIMO or denatured MIMOOX, whereas mAb 6E7 was able to recognize denatured MIMOOX. These results showed that mAb 7G12 recognizes a conformation of MIMOOX and not a sequence corresponding to a linear epitope as mAb 6E7
An effective therapeutic vaccine against AIDS should maintain an undetectable viremia without antiretroviral treatments (ART), but none have been reported so far with or without Tat protein [42]

Summary

Introduction

The Tat OYI vaccine might reduce HIV-1-infected cells due to neutralizing antibodies targeting extracellular Tat. Results: MIMOOX is a peptide designed to mimic a three-dimensional epitope of Tat OYI-inducing neutralizing antibodies against Tat variants. Conclusion: There is a highly conserved surface on Tat variants that the Tat OYI vaccine helps to recognize. Extracellular Tat is suspected to protect HIV-1-infected cells from cellular immunity. Seropositive patients are unable to produce neutralizing antibodies against Tat, and Tat is still secreted under antiviral treatment. The Tat OYI vaccine candidate generates neutralizing antibodies such as the mAb 7G12. A competitive recognition assay with mAb 7G12 between MIMOOX and Tat variants showed that MIMOOX mimics a highly conserved surface in Tat variants. Rat immunizations with MIMOOX induce antibodies recognizing Tat variants from the main HIV-1 subtypes and confirm the Tat OYI vaccine approach

Objectives

Results

Conclusion