title: Enhancement of gp120-specific immune responses by genetic vaccination with the human immunodeficiency virus type 1 envelope gene fused to the gene coding for soluble CTLA4.
abstract: DNA vaccines exploit the inherent abilities of professional antigen-presenting cells to prime the immune system and to elicit immunity against diverse pathogens. In this study, we explored the possibility of augmenting human immunodeficiency virus type 1 gp120-specific immune responses by a DNA vaccine coding for a fusion protein, CTLA4:gp120, in mice. In vitro binding studies revealed that secreted CTLA4:gp120 protein induced a mean florescence intensity shift, when incubated with Raji B cells, indicating its binding to B7 proteins on Raji B cells. Importantly, we instituted three different vaccination regimens to test the efficacy of DNA vaccines encoding gp120 and CTLA4:gp120 in the induction of both cellular (CD8(+)) and antibody responses. Each of the vaccination regimens incorporated a single intramuscular (i.m.) injection of the DNA vaccines to prime the immune system, followed by two booster injections. The i.m.-i.m.-i.m. regimen induced only modest levels of gp120-specific CD8(+) T cells, but the antibody response by CTLA4:gp120 DNA was nearly 16-fold higher than that induced by gp120 DNA. In contrast, using the i.m.-subcutaneous (s.c.)-i.m. regimen, it was found that gp120 and CTLA4:gp120 DNAs were capable of inducing significant levels of gp120-specific CD8(+) T cells (3.5 and 11%), with antibody titers showing a modest twofold increase for CTLA4:gp120 DNA. In the i.m.-gene gun (g.g.)-g.g. regimen, the mice immunized with gp120 and CTLA4:gp120 harbored gp120-specific CD8(+) T cells at frequencies of 0.9 and 2.9%, with the latter showing an eightfold increase in antibody titers. Thus, covalent antigen modification and the routes of genetic vaccination have the potential to modulate antigen-specific immune responses in mice.
mesh_terms: D016915:AIDS Vaccines / Q000008:administration & dosage / Q000276:immunology*; D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D000943:Antigens, Differentiation / Q000235:genetics / Q000276:immunology*; D018122:B7-1 Antigen / Q000032:analysis; D051940:B7-2 Antigen; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D060908:CTLA-4 Antigen; D005260:Female; D015483:HIV Antibodies / Q000097:blood; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D007117:Immunization, Secondary; D008562:Membrane Glycoproteins / Q000032:analysis; D051379:Mice; D008807:Mice, Inbred BALB C; D011993:Recombinant Fusion Proteins / Q000276:immunology*; D014611:Vaccination; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000276:immunology*
chemical_list: D016915:AIDS Vaccines; D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; C497965:Cd86 protein, mouse; C556707:Ctla4 protein, mouse; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D019444:Vaccines, DNA