Preparation and evaluation of monoclonal antibodies against chlamydial protease-like activity factor to detect Chlamydia pneumoniae antigen in early pediatric pneumonia.

Chlamydia pneumoniae causes diseases in humans, including community-acquired pneumonia, bronchitis, and sinusitis. It is also associated with atherosclerosis, coronary heart disease, and hyperlipidemia. In this study, we investigated novel materials with which to develop a sensitive and specific method to identify early C. pneumoniae infection, to allow more effective clinical treatment and prevention. We prepared novel monoclonal antibodies (mAbs) against a recombinant protein equivalent to the immunodominant region of chlamydial protease-like activity factor (CPAF) from C. pneumoniae. The mAbs specifically reacted with the endogenous CPAF antigen of the C. pneumoniae type strain in immunoblotting and indirect immunofluorescence (IIF) assays, but did not react with C. trachomatis type strains or genital secretions from patients with acute C. trachomatis infection. The mAb with the highest titer was used to develop a new IIF assay and enzyme-linked immunosorbent assay (ELISA) to detect the C. pneumoniae antigen in clinical specimens from child patients suspected of pneumonia. The sensitivity, specificity, and concordance rate of the mAb-based IIF and ELISA tests were compared with those of polymerase chain reaction (PCR). Our results show that these mAbs have excellent specificity and may be used to develop new screening tools for the diagnosis of early pediatric pneumonia.