Serodiagnosis of Chlamydia pneumoniae infection using three inclusion membrane proteins

The Chlamydia pneumoniae genome-encoded open reading frames Cpn0146, Cpn0147, and Cpn0308 were expressed as recombinant proteins for detecting C. pneumoniae-specific antibodies in samples from three groups of individuals including 183 with C. pneumoniae-associated respiratory infection (group I), 60 healthy blood donors (group II), and 32 with no known respiratory infection (group III). The recombinant Cpn0146 was recognized by 71 (38.8% positive recognition rate), 15 (25%) and 1 (3.1%), Cpn0147 by 75 (40.9%), 14 (23.3%), and 2 (6.3%), and Cpn0308 by 82 (44.8%), 16 (26.7%), and 0 (0%) samples from groups I, II, and III, respectively. The positive recognition rates with any of the three antigens were significantly higher in group I than those in groups II and III, suggesting that more individuals from group I were likely infected with C. pneumoniae. This conclusion was confirmed with a commercially available whole organism-based ELISA kit (Savyon Diagnostics Ltd., Ashdod, Israel), which detected C. pneumoniae antibodies in 98 (64.1%), 26 (43.3%), and 4 (12.5%) samples from group I, II, and III, respectively. Comparing to the commercial kit, the recombinant antigen-based detection assays displayed >97% of detection specificity and >87% of sensitivity, suggesting that these recombinant antigens can be considered alternative tools for aiding in serodiagnosis of C. pneumoniae infection.