Epitope Mapping and Topology of Baculovirus-Expressed HIV-1 gp160 Determined with a Panel of Murine Monoclonal Antibodies

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Abstract
To define protein folding patterns of HIV-1 Env subunit vaccines, we have isolated a set of 30 monoclonal antibodies (MAbs) from BALB/c mice immunized with a recombinant gp160 vaccine (rgp160) expressed in a baculovirus system. This article describes epitope mapping for the MAb panel and topology of the epitopes for rgp160 and a recombinant gp120 (rgp120) also expressed in a baculovirus system. The following results are reported: (1) rgp160 harbors a minimum of 4 antigenic domains, 3 mapping to the C1, C2, and C3/V4 regions of gp120 and 1 mapping to the cytoplasmic tail of gp41; (2) there are at least 3 adjacent or overlapping epitopes in each antigenic domain; (3) a minimum of 14 independent epitopes were mapped, all of which are continuous sites; (4) each of the epitopes is exposed on rgp160 without prior manipulation of the protein; and (5) by contrast, 6 of the 8 epitopes mapping to the C1, C2, and C3/V4 regions arenot exposed on rgp120, but become exposed when the protein is denatured. Taken together, these results show that rgp160 and rgp120 are folded differently, illustrating the use of this MAb panel to compare epitope topographies of recombination HIV-1 Env proteins. This MAb panel may aid in the refinement of HIV-1 Env subunit vaccines.