(1) Goals of project: - To study the activities of monoclonal antibodies (mAbs) raised against HIV-1 envelope (gp120), CD4, gp120/CD4 complexes, or the HIV-1 co-receptors, on HIV-1 fusion/infection of primary human cells. - To examine the effects of such mAbs on the normal biological functions of primary human cells. - To compare the HIV neutralization capacity of different HIVIG subclasses (2) Experimental approach: - We have collected a panel of murine mAbs specific for the HIV-1 gp 120 or for the CD4 molecules, that bind with increased avidity to the gp120/CD4 complex and may be involved in co-receptor recruitment. - These mAbs were tested for their effects on HIV-1 fusion/infection (both M-tropic and T-tropic strains), and for their activity in various assays designed to measure the formation of tri-molecular complexes between gp120,CD4, and the HIV-1 co-receptors. - HIVIG was fractionated into IGG1, IGG2, and IGG3 subclasses using preparative Protein A column. The purified subclasses were tested in a variety of binding assays ans HIV fusion inhibition and neutralization assays. (3) Major Findings: - CD4-specific mAbs (CG1,7,8) that bind with 10 fold higher avidity to preformed CD4/gp120 complexes than to CD4, were tested in multiple assays of HIV-1 co-receptor (CXCR4 or CCR5) recruitment. In three different assays these mAbs were found to stabilize the association of co-receptor, gp120, and CD4 in tri-molecular comlexes. Such antibodies may be used as tools to disect the steps leading to HIV-1 cell entry. In vivo, they may lead to an increase in viral-cell entry resulting in increased viral loads. - Using HIVIG preparations that were used in human trials, we demonstrated that the IGG3 subclass (which reperesents only 10% of the total IG in the original HIVIG preparation) is superior to other subclasses in its abilty to block HIV-1 mediated fusion and to neutralize multiple cell-free HIV-1 strains, including primary isolates. This superior biological activity may be explained by the unusually long """"""""Hinge"""""""" region, unique to IGG3 molecules.

Agency
National Institute of Health (NIH)
Institute
Center for Biologics Evaluation and Resarch - Viral Products (CBERVP)
Type
Intramural Research (Z01)
Project #
1Z01BK003002-08
Application #
6433504
Study Section
(LR)
Project Start
Project End
Budget Start
Budget End
Support Year
8
Fiscal Year
2000
Total Cost
Indirect Cost