Strategies to enhance immunogenicity of cDNA vaccine encoded antigens by modulation of antigen processing.
Most vaccines are based on protective humoral responses while for intracellular pathogens CD8(+) T cells are regularly needed to provide protection. However, poor processing efficiency of antigens is often a limiting factor in CD8(+) T cell priming, hampering vaccine efficacy. The multistage cDNA vaccine H56, encoding three secreted Mycobacterium tuberculosis antigens, was used to test a complete strategy to enhance vaccine' immunogenicity. Potential CD8(+) T cell epitopes in H56 were predicted using the NetMHC3.4/ANN program. Mice were immunized with H56 cDNA using dermal DNA tattoo immunization and epitope candidates were tested for recognition by responding CD8(+) T cells in ex vivo assays. Seven novel CD8(+) T cell epitopes were identified. H56 immunogenicity could be substantially enhanced by two strategies: (i) fusion of the H56 sequence to cDNA of proteins that modify intracellular antigen processing or provide CD4(+) T cell help, (ii) by substitution of the epitope's hydrophobic C-terminal flanking residues for polar glutamic acid, which facilitated their proteasome-mediated generation. We conclude that this whole strategy of in silico prediction of potential CD8(+) T cell epitopes in novel antigens, followed by fusion to sequences with immunogenicity-enhancing properties or modification of epitope flanking sequences to improve proteasome-mediated processing, may be exploited to design novel vaccines against emerging or 'hard to treat' intracellular pathogens.
Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
Anouk C M
ACM
Platteel
Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
A
A
Marit de Groot
Institut für Biochemie, Charité - Universitätsmedizin Berlin, Berlin, Germany; Berlin Institute of Health, Berlin, Germany.
Christin
C
Keller
Department of Infectious Disease Immunology, Statens Serum Institut, Copenhagen, Denmark.
Peter
P
Andersen
Department of Chemical Immunology, Leiden University Medical Center, Leiden, The Netherlands.
Huib
H
Ovaa
Institut für Biochemie, Charité - Universitätsmedizin Berlin, Berlin, Germany; Berlin Institute of Health, Berlin, Germany.
Peter M
PM
Kloetzel
Institut für Biochemie, Charité - Universitätsmedizin Berlin, Berlin, Germany; Berlin Institute of Health, Berlin, Germany.
Michele
M
Mishto
Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands. Electronic address: e.j.a.m.sijts@uu.nl.
Alice J A M
AJAM
Sijts
D000818:Animals; D017951:Antigen Presentation; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003198:Computer Simulation; D018076:DNA, Complementary; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D007114:Immunization; D000071497:Immunogenicity, Vaccine; D051379:Mice; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D032581:Tuberculosis Vaccines / Q000276:immunology*; D019444:Vaccines, DNA / Q000276:immunology*
D000942:Antigens, Bacterial; D018076:DNA, Complementary; D018984:Epitopes, T-Lymphocyte; D015395:Histocompatibility Antigens Class I; D032581:Tuberculosis Vaccines; D019444:Vaccines, DNA; C072681:Mycobacterium tuberculosis antigens; D046988:Proteasome Endopeptidase Complex
Antigen presentation; CD8 T cell; Dermal DNA tattoo immunization; Flanking residue optimization; MHC class I-restricted epitopes; Proteasome