title: Identification of CT521 as a frequent target of Th1 cells in patients with urogenital Chlamydia trachomatis infection.
abstract: BACKGROUND
  The human immune response to a Chlamydia trachomatis serovar D lysate was investigated in patients with urogenital C. trachomatis infection, to identify novel T cell targets.
  
  
  METHODS
  A C. trachomatis lysate was fractionated on the basis of molecular mass, and each fraction was used to stimulate peripheral-blood mononuclear cells from patients with C. trachomatis infection. In frequently recognized fractions, proteins were identified by mass spectrometry, recombinantly expressed, and tested for T cell recognition.
  
  
  RESULTS
  T cell recognition of the fractions was highly heterogeneous in patients with C. trachomatis infection (n=16). Four patients exhibited responses that were strongly targeted to antigens of 16-20-kDa molecular mass. Three proteins were identified in this fraction: CT043, CT511, and CT521. The T cell response to the individual recombinant proteins were investigated, and CT521 was found to induce the highest level of interferon (IFN)- gamma. The recognition of CT521 was investigated in a larger study population (n=41), and a positive IFN-gamma response was measured in 83% of the patients. Several T cell epitopes were identified in CT521; in particular, peptide 5 in the central part of the protein was frequently recognized by T cells (63%).
  
  
  CONCLUSIONS
  We have identified a novel C. trachomatis antigen, CT521, that is frequently recognized in patients with urogenital C. trachomatis infection.
authors.affiliation: Chlamydia Research, Department of Infectious Disease Immunology, Statens Serum Institute, DK-2300 Copenhagen S, Denmark. Aol@ssi.dk
authors.forename: Anja Weinreich
authors.initials: AW
authors.lastname: Olsen
authors.forename: Frank
authors.initials: F
authors.lastname: Follmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Jensen
authors.forename: Peter
authors.initials: P
authors.lastname: Højrup
authors.forename: Robert
authors.initials: R
authors.lastname: Leah
authors.forename: Hanne
authors.initials: H
authors.lastname: Sørensen
authors.forename: Steen
authors.initials: S
authors.lastname: Hoffmann
authors.forename: Peter
authors.initials: P
authors.lastname: Andersen
authors.forename: Michael
authors.initials: M
authors.lastname: Theisen
mesh_terms: D000328:Adult; D000942:Antigens, Bacterial / Q000276:immunology; D002690:Chlamydia Infections / Q000276:immunology*; D002692:Chlamydia trachomatis / Q000276:immunology*; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D005260:Female; D052776:Female Urogenital Diseases / Q000382:microbiology; D006801:Humans; D008297:Male; D052801:Male Urogenital Diseases / Q000382:microbiology; D018417:Th1 Cells / Q000502:physiology*
chemical_list: D000942:Antigens, Bacterial; D018984:Epitopes, T-Lymphocyte