There is little doubt that antibodies to the major surface glycoprotein of HIV, the envelope protein gp160, will form part of an effective vaccine response. However, while it is known that broad ranging neutralizing antibodies can be elicited by gpl60 (Env), the frequency with which they arise has been low following immunization with many of the sources of recombinant Env used to date. This has been attributed to the failure of most recombinant Env preparations to faithfully represent the oligomeric source of Env present on the surface of primary isolates of HIV. In addition, although there have been many immunization trials using Env antigen in various soluble forms, attached to membrane carriers or as virus-like-particles, there have been no attempts to combine the oligomeric structure of primary isolate Envs with purposeful attempts to enhance immunogenicity by altering Env presentation. Here, a new form of recombinant envelope protein is proposed in which primary isolate Env is expressed in oligomeric form on the surface of baculoviruses. Specific surface expression is achieved by fusion of the full extracellular portion of Env with gp64, an integral membrane glycoprotein of baculovirus. The Env-gp64 fusion protein enters and completes the secretory pathway with attendant glycosylation, folding and oligomerization before being incorporated into the emerging baculovirus particle. As a result of the fusion to gp64, Env protein, while oligomeric and functional, is projected away from the virion membrane in a form which offers a more flexible target to the immune system. A variety of modifications to Env are also possible in this system: cleavage at the gpl20/gp41 junction, reaction with the primary ligand CD4, altered glycoprotein structure, and chaperone assisted folding. This application seeks support for the expression and characterization of these sources of Env, their use in immunization, and the analysis of the serum responses obtained by both traditional and recombinant methods.
