Genomic screening for Chlamydophila pneumoniae-specific antigens using serum samples from patients with primary infection.

Chlamydophila pneumoniae, an obligate intracellular human pathogen, causes respiratory tract infections. The most common techniques used for the serological diagnosis of C. pneumoniae infections are microimmunofluorescence tests and commercial serological ELISA tests; these are based on the detection of antibodies against whole chlamydial elementary bodies and lipopolysaccharide/outer membrane protein, respectively. Identification of more specific and highly immunodominant antigens is essential for the development of new serodiagnostic assays. To identify novel specific antigens from C. pneumoniae, we screened 455 genes with unknown function in the genome of C. pneumoniae J138. Extracts of Saccharomyces cerevisiae cells expressing GFP-tagged C. pneumoniae proteins were subjected to Western blot analysis using serum samples from C. pneumoniae-infected patients as the primary antibodies. From this comprehensive analysis, 58 clones expressing C. pneumoniae open reading frames, including hypothetical proteins, were identified as antigens. These results have provided useful information for the development of new serological tools for the diagnosis for C. pneumoniae infections and for the development of vaccines in future.