The Antigenic Structure of the Rabies Virus Glycoprotein

Summary

The rabies virus glycoprotein is the virion component responsible for induction of virus-neutralizing antibody and protection of animals against challenge. To determine its antigenic structure, a limited number of fragments were obtained by chemical cleavage and isolated by SDS-polyacrylamide gel electrophoresis. Eight large peptides, ranging in size from 32 to 77 amino acid residues, were mapped within the predicted amino acid sequence of the glycoprotein by determining the N-terminal sequence of each fragment. The antigenicity and immunogenicity of these peptides were then evaluated. Following inoculation of mice, all peptides induced significant levels of antibodies capable of binding to virus or purified viral glycoprotein in a solid-phase immunoassay. Fragments Cr1, Cr3, and Cr4, also induced significant levels of virus-neutralizing and complement-dependent lytic antibodies. Fragments Cr3 and Cr4 were immunoprecipitated by hyperimmune rabbit antirabies serum. To locate domains of the glycoprotein responsible for the stimulation of T helper cells, the peptides were tested for their capacity to stimulate proliferation of nylon wool-purified T cells obtained from spleens of rabies-immune mice. Peptides Cr1, Cr2, and Cr3 stimulated antigen-specific proliferation. Proliferation required the addition of syngeneic irradiated antigen-presenting cells and the proliferating cells were Lyt1-positive, Lyt2-negative. In addition, stimulation was obtained using a 36 amino acid synthetic peptide comprised of almost the entire sequence of Crl. Cytotoxic T cells are postulated to play a major role in protection against rabies infection. In vitro, glycoprotein and mixtures of glycoprotein fragments stimulated a secondary cytotoxic response (mediated by Lyt2-positive cells) comparable in magnitude with that stimulated by virus. In the presence of added T cell growth factors, fragment Cr4 also stimulated cytotoxic activity. The immunologic analysis of rabies virus glycoprotein fragments showed that specific immunologic functions are associated with different regions of the molecule. This finding should be a major consideration in the designing of a synthetic rabies vaccine.

This work was supported by Research Grants AI-09706 and AI-18883 from the National Institutes of Allergy and Infectious Diseases