Characterization of a lipoprotein common to Legionella species as a urinary broad-spectrum antigen for diagnosis of Legionnaires' disease.
We have previously identified the Legionella 19-kDa peptidoglycan-associated lipoprotein (PAL) as a species-common immunodominant antigen. We describe here for the first time the excretion and detection of the PAL antigen in infected urine specimens, which is useful for the diagnosis of Legionnaires' disease. Rabbit anti-PAL immunoglobulin G (IgG) antibody was produced by immunization with the purified, recombinant PAL of Legionella pneumophila serogroup 1 and used in the PAL antigen capture enzyme-linked immunosorbent assay (ELISA) to detect urinary PAL antigen. A soluble-antigen capture ELISA using rabbit IgG antibodies against Legionella soluble antigens was prepared independently and used as a broad-spectrum standard test to detect soluble antigens of several Legionella species. Urine samples were obtained from guinea pigs experimentally infected with each of L. pneumophila serogroups 1, 3, and 6, and other Legionella species. The absorbance values of the PAL antigen ELISA highly correlated with those of the soluble-antigen ELISA in infected urine samples, with a correlation coefficient of 0.84 (P < 0.01). When applied to 17 infected urine samples and 67 negative controls from guinea pigs, the sensitivity and specificity of the PAL antigen capture ELISA were 88.2 and 95.5%, respectively. Compared to the commercial Biotest enzyme immunoassay, the PAL antigen ELISA was more efficient for detecting pneumophila non-serogroup 1 and nonpneumophila species. None of the 161 control human urine specimens obtained from healthy adults and patients with either non-Legionella pneumonia or urinary tract infections tested positive in the PAL antigen ELISA. The present study shows that the Legionella PAL is a very useful broad-spectrum antigen for urinary diagnostic testing. Moreover, since recombinant PAL antigen can be produced more efficiently than the soluble antigens, the development of a broad-spectrum diagnostic immunoassay based on the detection of the PAL antigen appears to be warranted.
Kim
Min Ja
MJ
Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, Korea University, Seoul 136-705, Republic of Korea. macropha@chollian.net
Sohn
Jang Wook
JW
Park
Dae Won
DW
Park
Seung Chul
SC
Chun
Byung Chul
BC
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001425:Bacterial Outer Membrane Proteins; D004797:Enzyme-Linked Immunosorbent Assay; D029968:Escherichia coli Proteins; D006168:Guinea Pigs; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D016952:Legionella pneumophila / Q000276:immunology*; D007877:Legionnaires' Disease / Q000175:diagnosis* / Q000382:microbiology; D008074:Lipoproteins / Q000276:immunology* / Q000652:urine*; D008297:Male; D010457:Peptidoglycan / Q000276:immunology* / Q000652:urine*; D011509:Proteoglycans; D012680:Sensitivity and Specificity
D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; C031163:ExcC protein, E coli; D007074:Immunoglobulin G; D008074:Lipoproteins; D010457:Peptidoglycan; D011509:Proteoglycans; C069988:PplA protein, Legionella pneumophila