Immunoblot Analysis of Legionella pneumophila Serogroup 1 Antigens Using In-House Polyclonal and Monoclonal Antibodies.

Introduction: Legionella pneumaphila is a fastidious organism and difficult to grow in culture medium. Diagnosis by antibody detection is not helpful in the acute stage due to a delay in seroconversion. Therefore, newer techniques including antigen detection in serum and urine have been developed to improve the diagnosis. In-house polyclonal and monoclonal antibodies: against L. pneumophila serogroup 1 antigen have been produced. Objective: The aim of the present study is to determine the antigenic fractions of L.pneumophila serogroup 1 that are recognized by the antibodies and to study the specificity of the in-house polyclonal and monoclonal antibodies. Materials and Methods: Profiling of the antigens and detection of reactivity to the polyclonal and monoclonal antibodies were performed using SDS-PAGE followed by immunoblotting technique. Results: SDS-PAGE revealed the presence of approximately 13 bands, 4 of which were prominent with approximate size of 17K, 24K, 33K and 42K. Immunoblot analysis using the rabbit polyclonal antibodies showed that at least 7 antigenic fractions with the prominent fractions at I4K, I7K, 22K and 24 K. Monoclonal antibody 1F4.10E reacted with antigenic fraction of approximately 33K of the L.pneumophila serogroup 1, reference strain Knoxvillel and local isolate L30, 1.18 and L29. Then was no cross-reaction observed between the monoclonal antibody with the other bacterial antigens. Conclusion: This study revealed that the immunogenic fractions of the Legionella pneumophila serogroup I antigens were mainly of the lower molecular weight sizes. Monoclonal antibody 1F4.10E which specifically detected antigenic fraction of 33 h has potential to be used for serodiagnosis of L.pneumophila serogroup 1 infection. [ABSTRACT FROM AUTHOR]