A directed molecular evolution approach to improved immunogenicity of the HIV-1 envelope glycoprotein.

Sean X Du,Christos J Petropoulos,Paul W H I Parren,Michael Chambers,Helen Chen,Michael B Zwick,Dennis R Burton,Rebecca I Boenig,Susan Tang,John A Ballantyne,Robert G Whalen,Ellaine B Mariano,Li Xu,Terri Wrin,Wenge Zhang,Clive M Gray

doi:10.1371/journal.pone.0020927

Abstract

A prophylactic vaccine is needed to slow the spread of HIV-1 infection. Optimization of the wild-type envelope glycoproteins to create immunogens that can elicit effective neutralizing antibodies is a high priority. Starting with ten genes encoding subtype B HIV-1 gp120 envelope glycoproteins and using in vitro homologous DNA recombination, we created chimeric gp120 variants that were screened for their ability to bind neutralizing monoclonal antibodies. Hundreds of variants were identified with novel antigenic phenotypes that exhibit considerable sequence diversity. Immunization of rabbits with these gp120 variants demonstrated that the majority can induce neutralizing antibodies to HIV-1. One novel variant, called ST-008, induced significantly improved neutralizing antibody responses when assayed against a large panel of primary HIV-1 isolates. Further study of various deletion constructs of ST-008 showed that the enhanced immunogenicity results from a combination of effective DNA priming, an enhanced V3-based response, and an improved response to the constant backbone sequences.

Highlights

A critical objective in the search for a vaccine to HIV-1 is the identification of immunogens that can elicit antibodies capable of neutralizing a broad array of clinically relevant viruses [1,2,3]
We transfected plasmids expressing each of the ten parental gp120 genes into Chinese Hamster Ovary (CHO)-K1 cells and analyzed the resulting secreted proteins on dot-blots for their ability to bind an anti-Histag monoclonal antibodies (mAbs), a polyclonal serum against gp120, and the human antigp120 mAbs 2G12, b3, b6, and b12
The b3 and b6 mAbs compete with b12 for the CD4 binding site (CD4BS) on gp120 but do not neutralize typical viral isolates

Summary

Introduction

A critical objective in the search for a vaccine to HIV-1 is the identification of immunogens that can elicit antibodies capable of neutralizing a broad array of clinically relevant viruses [1,2,3]. The viral envelope glycoprotein (Env) is central to vaccine research since it is the only target for neutralizing antibodies [1,4,5]. The combination of a viral vaccine and recombinant protein resulted in limited but significant protection from infection [18]. It is not known which immune responses are responsible for this result

Methods

Results

Conclusion