Antigenicity and immunogenicity of the V3 domain of HIV type I glycoprotein 120 expressed on the surface of Streptococcus gordonii

Five different V3 domains of HIV-1 gp120 were expressed on the surface of t he gram-positive bacterium Streptococcus gordonii, a model live vector for vaccine delivery. Sera of HIV-1-infected individuals and human monoclonal a ntibodies specifically recognized the gp120 sequences on the bacterial surf ace. Recombinant V3 from the reference HIV-1 strain MN was also shown to re tain a conformation that allowed reaction with a conformation-specific mono clonal antibody. A V3-specific serum antibody response was detected in mice immunized both by subcutaneous injection and by vaginal colonization. V3-s pecific IgG(2a) antibodies, suggestive of a Th1 response, were found in the sera of mice colonized by recombinant bacteria.