CD4+-T-cell responses generated during murine Salmonella enterica serovar Typhimurium infection are directed towards multiple epitopes within the natural antigen FliC.
The flagellar filament protein FliC is a natural antigen recognized by memory CD4+ T cells recovered from Salmonella enterica serovar Typhimurium-infected humans and mice. To further investigate T-cell responses to FliC, we derived FliC-specific CD4+-T-cell clones from mice of two different haplotypes following oral S. enterica serovar Typhimurium infection. Using C-terminal truncations of MalE-FliC recombinant fusion proteins, we mapped antigenic activity to four different regions of FliC; three of the four epitope-containing regions were present in both FliC and the alternate flagellin subunit FljB. We determined that two novel FliC epitopes were also present in flagellins from several gram-negative enteric bacterial species: E(k)-restricted FliC 80-94 (amino acids 80 to 94) and A(b)-restricted FliC 455-469. Further mapping confirmed the presence of two previously identified FliC epitopes: A(k)-restricted FliC 339-350 and A(b)-restricted FliC 428-442. Therefore, like the recognition site of the innate immune receptor Toll-like receptor 5, three of four FliC epitopes recognized by CD4+ T cells colocalize in the D0/D1 domains of FliC. Salmonella-infected macrophages and dendritic cells stimulated epitope-specific CD4+-T-cell proliferation; infected dendritic cells also activated T cells to produce gamma interferon. These data demonstrate that Salmonella infection generates murine CD4+-T-cell responses to multiple epitopes in the natural antigen FliC and that recognition of infected phagocytes by FliC-specific CD4+ T cells triggers effector functions known to be essential for protective immunity. Together, these data suggest that FliC-specific CD4+ T cells may contribute to cell-mediated host defenses against Salmonella.
Bergman
Molly A
MA
Department of Microbiology, University of Washington Medical Center, Box 357110, 1959 NE Pacific Street, Seattle, WA 98195, USA.
Cummings
Lisa A
LA
Alaniz
Robert C
RC
Mayeda
Laura
L
Fellnerova
Ivana
I
Cookson
Brad T
BT
D000595:Amino Acid Sequence; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D000939:Epitopes / Q000737:chemistry* / Q000276:immunology*; D005260:Female; D005408:Flagellin / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D007371:Interferon-gamma / Q000276:immunology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010586:Phagocytes / Q000276:immunology; D017434:Protein Structure, Tertiary; D012481:Salmonella Infections, Animal / Q000276:immunology*; D012486:Salmonella typhimurium / Q000276:immunology*; D017386:Sequence Homology, Amino Acid
D000939:Epitopes; D005408:Flagellin; D007371:Interferon-gamma