Project Details


In spite of considerable progress in recent years towards the
characterization of functional regions of HIV env proteins and in
defining critical neutralizing epitopes, available vaccination strategies
have not been effective in producing high titers of broadly crossreactive
neutralizing antibodies. HIV env proteins are among the most highly
glycosylated eucaryotic proteins, and recent studies have emphasized the
importance of glycosylation in the formation of conformational structures
necessary for proper function and immunogenicity of HIV env. We have
recently isolated a chimpanzee monoclonal antibody, C108G, that has very
potent neutralizing activity against some primary and laboratory strains
of HIV-1. This antibody does not react with sites either in the V3 loop
or the CD4-binding site, but recognizes a unique, carbohydrate-dependent
epitope that we have localized to a site in or near the V2 loop of gpl20.
Other investigators have isolated additional MAbs with similar properties
that also map to the V2 domain. In the present proposal, we will use a
novel glycopeptide expression system to express glycosylated fragments
corresponding to both conserved and variable domains of HIV env in native
forms. This expression system generates heterologous glycopeptide
fragments linked to the N-terminal domain of the murine leukemia virus
(MuLV) SU protein. The fused glycoproteins are highly expressed,
efficiently secreted and easily purified by immunoaffinity methods. In
contrast to previous studies, this system results in the production of
properly folded and fully glycosylated domains, thereby allowing the
characterization of conformational and carbohydrate-dependent epitopes.
We will use this system to precisely map the epitopes recognized by C108G
and other neutralizing MAbs directed against conformation and
glycosylation dependent epitopes in the V1/V2 domains. We will also
characterize the immunoreactivities and immunogenicities of different
glycopeptide subregions of the V1/V2 domains and analyze the functional
activities of antibodies directed against these regions that are present
in sera of infected individuals and that are induced upon immunization
with the purified fusion proteins. Similar methods will be used to
express the V3 and V4/C4 domains of HIV-1 gpl20 in their correctly folded
and glycosylated forms, and to evaluate their immunoreactivities and
immunogenicities. These studies will be performed for a number of
different viral strains, including primary and macrophage-tropic
isolates. The goal of this work is to define native epitopes important
for HIV neutralization and to identify additional domains capable of
producing conserved neutralizing responses, that may have been missed by
previous studies because of their conformational and glycan-dependent
nature. Once such sites have been identified, novel features of our
expression system can be used to produce these regions in highly
immunogenic forms suitable as effective vaccines.
Effective start/end date7/1/936/30/00


  • National Institute of Allergy and Infectious Diseases
  • National Institute of Allergy and Infectious Diseases
  • National Institute of Allergy and Infectious Diseases
  • National Institute of Allergy and Infectious Diseases
  • National Institute of Allergy and Infectious Diseases


  • Virology
  • Immunology


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