ELISA for Legionnaires' Disease - 



Antibody and Antigen 



Detection Systems: An Interim Report 



Carol E. Farshy and John C. Feeley 



INTRODUCTION 



In many cases, laboratory confimiation of Legionnaires' disease (LD) is accomplished retro- 

 spectively either by indirect immunotluorescence (IF) tests of acute- and convalescent-phase sera 

 (7), or by direct IF tests of postmortem lung tissue {2). Previously we reported a micro enzyme- 

 linked immunosorbent assay (ELISA) for the detection of antibodies against serogroup 1 LDB 

 soluble antigens (i), using the horseradish peroxidase enzyme. Although the test appears promis- 

 ing, its sensitivity and specificity need further refinement and evaluation. The primary disadvan- 

 tage of using antibody detection tests is the delay involved in seroconversion (appro.ximately 3 

 weeks) and, therefore, in diagnosis. 



Earlier diagnosis of LD is needed so that specific therapy can be instituted during the acute 

 stage of illness. Accordingly, we have investigated the use of ELISA for the detection of sero- 

 group 1 antigen in urine (/). 



In a preliminary evaluation of the ELISA. antigen was detected in the urine of all six guinea 

 pigs tested within 4 h and for at least 1 wk after they were inoculated with nonviable LDB 

 serogroup 1 (Philadelphia 1 and 2 and Knoxville 1). Urine specimens from animals inoculated 

 with the serogroup 2 strain (Togus 1) were negative in the serogroup 1 ELISA, as would be 

 expected because of the antigenic dissimilarity of these serogroups (5, 7). Urine specimens from 

 control animals were negative. 



Urine specimens from 20 human subjects with no recent history of respiratory disease were 

 also negative. Antigen was detected, however, in urine which had been collected in 1*^76 from 

 three of four LD patients during the Philadelphia outbreak (4). Urine from a fifth patient with a 

 chnically compatible illness but equivocal serological test results was negative in the ELISA. Since 

 this work was completed, investigators conducting an independent Imiited study have used 

 ELISA to detect antigen in sputum and urine from two LD patients (ft). 



ELISA FOR ANTIBODY 



The micro-ELISA for detecting antibodies to the Legionnaires" disease bacterium (LDB) 

 involves a soluble antigen prepared from heat-killed organisms. Comparison testing of this proce- 

 dure and the indirect IF test has not been completed. ELISA appears to be a promising labora- 

 tory tool which continues to be improved with research on other enzyme systems and immuno- 

 purified conjugates. The instructions for perfomiing the micro-ELISA for antibody titration are 

 shown below: 



A. Antigen Preparation 



I. Grow the LDB on Mueller-Hinton agar plates supplemented with 1% IsoVitaleX (BBL) 

 and \% hemoglobin for 72 h at 37° C in a candle jar. 



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