title: Human T-helper cell recognition of an immunodominant epitope of HIV-1 gp120 expressed on the surface of Streptococcus gordonii.
abstract: Our genetic system for expression of heterologous proteins on the surface of the Gram-positive bacterium Streptococcus gordonii was used to express a human T-helper epitope of HIV-1 envelope glycoprotein gp120. In previous work on the naive repertoire of human T-helper cells, it was shown that a 15-amino acid synthetic peptide of the HIV-1 gp120 sequence contained an immunodominant T-helper epitope. Synthetic DNA coding for this peptide was cloned in frame within the gene for the streptococcal surface protein M6, and the gene fusion was integrated by transformation into the chromosome of S. gordonii. The expected M6-gp120 fusion protein was found to be expressed on the surface of the recombinant streptococci. To test whether the T epitope could be recognized by T cells when expressed on the bacterial surface within the context of M6, recombinant bacteria were used as antigen in proliferation assays to stimulate the 15-amino acid-specific human T-helper clone, in the presence of autologous antigen-presenting cells. Bacteria expressing the T epitope were efficiently recognized by the T cells in culture. In proliferation assays, 10(6)-10(7) bacteria induced responses comparable to those obtained by standard amounts of synthetic peptide (0.02-0.2 micrograms). Recombinant S. gordonii, a candidate for a live vaccine vector, appeared suitable for delivering T epitopes to the immune system.
authors.affiliation: Department of Molecular Biology, University of Siena, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Pozzi
authors.forename: M R
authors.initials: MR
authors.lastname: Oggioni
authors.forename: R
authors.initials: R
authors.lastname: Manganelli
authors.forename: D
authors.initials: D
authors.lastname: Medaglini
authors.forename: V A
authors.initials: VA
authors.lastname: Fischetti
authors.forename: D
authors.initials: D
authors.lastname: Fenoglio
authors.forename: M T
authors.initials: MT
authors.lastname: Valle
authors.forename: A
authors.initials: A
authors.lastname: Kunkl
authors.forename: F
authors.initials: F
authors.lastname: Manca
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D001483:Base Sequence; D015139:Blotting, Southern; D015153:Blotting, Western; D016466:CHO Cells; D002352:Carrier Proteins; D002460:Cell Line; D003001:Cloning, Molecular; D006224:Cricetinae; D004279:DNA, Viral / Q000235:genetics; D005455:Fluorescent Antibody Technique; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D015699:HIV Envelope Protein gp120 / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D006801:Humans; D016056:Immunodominant Epitopes / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000276:immunology; D013291:Streptococcus / Q000235:genetics* / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D014169:Transformation, Bacterial
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004279:DNA, Viral; D015699:HIV Envelope Protein gp120; D016056:Immunodominant Epitopes; D011993:Recombinant Fusion Proteins; C014689:streptococcal M protein