AEGiS-07IAC: Human monoclonal antibodies against the putative CD4 binding site and the V3 loop of HIV gp120 act in concert to neutralize virus.

7th International AIDS Conference


Florence, Italy — June 16-21, 1991

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Human monoclonal antibodies against the putative CD4 binding site and the V3 loop of HIV gp120 act in concert to neutralize virus.

Int Conf AIDS 1991 Jun 16-21; 7:39 (abstract no. M.A.70)
Tilley SA, Honnen WJ, Racho ME, Hilgartner M, Pinter A; Public Health Research Institute, New York, NY

OBJECTIVE: To develop human monoclonal antibodies (HuMAbs) against HIV with potent neutralizing and/or other anti-viral activities.

METHODS: HuMAbs were derived by EBV transformation of PBMC from asymtomatic, seropositive hemophiliacs. The specificity of HuMAbs was determined by ELISAs, Western blot and RIPA analyses, and immunofluorescence (IF) assays. Neutralization of virus was assessed 24 hours after infection by an IF focus assay.

RESULTS: At least 2 of our anti- env HuMAbs have potent neutralizing activity against HIV. One of these HuMAbs, 1125H (gamma1, kappa), is inhibited in its binding to gp120 by CD4, probably indicating that its epitope is in or near the CD4 binding site. The epitope of 1125H is destroyed by reduction, but not by removal of N-linked sugars under conditions that do not disrupt disulfide bonds. Thus, the epitope is conformationally determined and does not appear to involve carbohydrate. HuMAb 1125H has potent neutralizing activity against all of the HIV-1 strains which we have tested thus far: MN, RF, SF-2, and IIIB. Our other neutralizing HuMAb, 4117C (gamma1, lambda), is against the V3 loop and is reactive with V3 peptides from the MN, SF-2, and NY-5 isolates, in increasing order of preference. 4117C has been tested for neutralizing activity against the MN strain and has potent activity against it. Recently, we have compared the neutralizing activity against MN strain of the two HuMAbs combined to that of each HuMAb alone. Preliminary experiments indicate that, whereas approximately 10 mug/ml of each HuMAb alone is required to effect greater than 90% neutralization of 5 x 10(4) infectious units of virus added to 5 x 10(5) H9 cells, only 1.25 mug/ml of an equimolar mixture of the two HuMAbs is required to obtain this level of neutralization. A fine analysis of this phenomenon will delineate whether the two HuMAbs are actually acting synergistically.

CONCLUSIONS: HuMAbs against different neutralizing epitopes of HIV gp120, specifically the putative CD4 binding site and V3 loop, may act in concert, either synergistically or additively, to neutralize HIV. This indicates that combinations of such HuMAbs may be superior for passive immunotherapy to single HuMAbs and implies that a vaccine ideally should elicit Abs against more than one neutralizing epitope.

Keywords: AEGIS, Antigens, CD4, Antibodies, Monoclonal, HIV-1, Epitopes, Binding Sites, Blotting, Western, Enzyme-Linked Immunosorbent Assay, Radioimmunoprecipitation Assay, Human, ICA7KWDaegis,antigens,cd4,antibodies,monoclonal,hiv-1,epitopes,bindingsites,blotting,western,enzyme-linkedimmunosorbentassay,radioimmunoprecipitationassay,human,ica7
910616
MA70

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