All ETDs from UAB

Advisory Committee Chair

George M Shaw

Advisory Committee Members

John F Kearney

Olaf Kutsch

Robinna G Lorenz

Ming Luo

Document Type

Dissertation

Date of Award

2008

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Defining the epitope specificities of the neutralizing antibody response to the HIV-1 envelope protein (Env) during natural human infection and in response to vaccination by HIV-1 immunogens could provide insight into the mechanisms of virus immune containment and facilitate vaccine design. Transplantation of discrete HIV-1 neutralizing epitopes into HIV-2 Env scaffolds may provide a sensitive, biologically functional context in which to quantify specific antibody reactivities in complex sera. Here we describe the development of a novel HIV-2 proviral scaffold (pHIV-2KR.X7) into which we have substituted the env V3 region of several laboratory and primary HIV-1 strains to yield a panel of chimeric viruses. The HIV-2KR.X7HIV-1 V3 chimeric viruses were found to be infectious and replication competent, and each maintained receptor engagement, coreceptor selection, and virus-cell membrane fusion kinetics typical of primary viruses. The HIV-2KR.X7HIV-1 V3 chimeras and parental viruses, HIV-2KR.X4 and HIV-2KR.X7, were each found to be resistant to neutralization by anti-HIV-1 monoclonal antibodies (mAbs) directed at the CD4 binding site, CD4 induced (CD4i) epitopes, and the membrane proximal external region (MPER). Notably, the HIV- 2KR.X7HIV-1 V3 chimeras were exquisitely sensitive to neutralization by the HIV-1 V3 specific mAbs 447-52D and F425 B4e8 (IC50 < 0.005 μg/ml for each), while the parental viruses remained resistant. Evaluation of V3-specific reactivities in plasma specimens from clade B and clade C HIV-1 infected individuals and from subjects vaccinated with iv HIV-1 immunogens indicated that potent, broadly reactive V3-specific antibodies are elicited early during natural HIV-1 infection and after vaccination with HIV-1 immunogens, prior to the development of antibodies targeting CD4i epitopes, the MPER, or epitopes that mediate autologous or heterologous neutralization. However, V3- specific antibodies exhibited low potency against autologous or heterologous primary HIV-1 strains because V3 epitopes are effectively masked within the trimeric Env spike. We conclude that V3-specific antibodies possess potent and broad neutralizing potential and constrain the HIV-1 Env to structure(s) in which the V3 is occluded prior to CD4 engagement. Otherwise, V3 antibodies fail to contribute to neutralization breadth or potency against primary viruses including in the setting of vaccination.

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