AEGiS-07IAC: A non-immunoglobulin, normal serum protein binds specifically to the gp41 binding domain of HIV gp120.

7th International AIDS Conference

Florence, Italy — June 16-21, 1991

A non-immunoglobulin, normal serum protein binds specifically to the gp41 binding domain of HIV gp120.

Int Conf AIDS 1991 Jun 16-21; 7:95 (abstract no. M.A.1014)
Pinter C, Siccardi AG, Clivio A; Dipartimento di Biologia e Genetica per le Scienze Mediche, University of Milan, Italy

OBJECTIVE: To search, in normal human sera, HIV binding proteins possibly involved in HIV spreading strategies such as dissemination, alternative tropism or masking of functionally relevant epitopes at the virion surface.

METHODS: Normal human sera were pooled and fractionated by high resolution anion exchange HPLC (High Performance Liquid Chromatography). The fractions were monitored for HIV binding with ELISA assays on HIV-coated plates using an antiserum raised against total serum proteins as a tracer. The active fractions were labelled and incubated with HIV in solution. Molecules actively involved in HIV binding were recognized using an HPLC retardation assay and SDS-PAGE. ELISA radiobinding assays with free and coupled synthetic peptides were used to assess binding specificity.

RESULTS: A single active fraction was found by monitoring the anion exchange column elution. This contains a 42kd protein which is responsible for binding to HIV virions in solution. Attempts to demonstrate binding to specific HIV proteins in Western blots failed, but the binding to intact virions is strongly and specifically competed by the synthetic peptide SA2 (HEDIISLWDQSLKDC), a gp120 domain shown to be involved in the binding of gp41 (McPhee, personal communication).

DISCUSSION AND CONCLUSIONS: A HIV binding protein with unknown function was found in normal human serum pools and was partially characterized. It binds to the intact virion even in the presence of high titres of anti-HIV antibodies and the binding is specific for the gp41-binding domain of native HIV gp120. Future research should involve 1) investigation on a possible role of this protein (CP-1) in HIV infection and 2) studies on binding of CP-1 to specific cell types and its possible role either in alternative tropism or in virus dissemination throughout the body.

Keywords: AEGIS, HIV Antibodies, Immunoglobulins, Blood Proteins, HIV Infections, Blotting, Western, Epitopes, Enzyme-Linked Immunosorbent Assay, Virion, Peptides, Human, pharmacokinetics, ICA7
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