ELISA for Legionnaires' Disease - Antibody and Antigen Detection Systems: An Interim Report 



ml ethanol). Stock does not deteriorate if stored in the dari<. for up to 1 wk. Working 

 substrate is composed of 1 ml of stock plus 99 ml of distilled water containing 0.1 ml of 3% 

 hydrogen peroxide. 



1 2. Cover plates and incubate in the dark at 37° C for 30 min to 1 h, depending upon the 

 color reaction desired. 



13. Remove plates from the incubator; add 1 drop of 8 N Ho SO4 to each well to temiinate 

 the reaction and deepen the color. 



C. Interpretation 



Place the plate on a white background or on a reading mirror, and grade the color of each 

 well against that of the partically colorless negative control. The end point is defined as the 

 highest dilution of serum which is distinctly different in color from the first dilution of the 

 negative control. Report titer as the reciprocal of the end point. 



D. Limitations 



Because the sensitivity and specificity of this developmental procedure are not adequately 

 defined, sera for which positive or doubtful or equivocal results are obtained should be 

 referred to the state health department for confimiatory testing with the indirect IF proce- 

 dure. 



ELISA FOR ANTIGEN 



This ELISA is a "sandwich" technique with four layers (Figure 2) and uses the alkaline 

 phosphatase enzyme detection system. The ELISA can detect antigen representing as little as 3 

 pg of protein in a purified lipopolysaccharide protein complex which is a major antigenic consti- 

 tuent of serogroup 1 LDB (S). Further antigen-detection studies with respiratory secretions and 

 with acute-phase sera, as well as efforts to incorporate other serogroups into the test system, are 

 clearly warranted. In addition, sensitivity and specificity must be determined. Until these parame- 

 ters are defined a detailed procedure cannot be recommended. 



SUMMARY 



Although still in the developmental stages, ELISA for both antibody and antigen detection 

 appear to offer promise as aids in the diagnosis of Legionnaires' disease. 



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