Antigenic lipopolysaccharide components of Legionella pneumophila recognized by monoclonal antibodies: possibilities and limitations for division of the species into serogroups

Abstract

Legionella pneumophila accounts for the majority of cases of Legionnaires' disease. By using rabbit antisera, the species has been divided into 14 numbered and 1 unnumbered serogroups. To recognize the antigenic diversity of the lipopolysaccharide (LPS) responsible for this classification, the Dresden Legionella LPS MAb panel, containing 98 monoclonal antibodies (MAbs), was created. Each serogroup reference strain possesses at least one specific epitope not found on any other reference strain and therefore designated the serogroupspecific epitope. When the appropriate MAbs were used for serotyping of 1,064 human and environmental isolates, 1,045 (98%) could be placed into the known serogroups. In most cases (97%), this was in agreement with the polyclonal typing. Of the 29 isolates that showed strong cross-reactivities with the rabbit antiserum panel, 11 could be typed easily by MAbs; for the remaining 18, however, only serogroup-cross-reactive epitopes could be determined. Below the serogroup level, monoclonal subtypes were found for 11 serogroups. Altogether, the Dresden Legionella LPS MAb panel was able to divide the 1,064 isolates tested into 64 phenons, indicating its usefulness for both serogrouping and subgrouping of L. pneumophila strains. In order to compare the identities of patient and environmental isolates, testing their reactivity with MAbs should be the first step, especially if large numbers of colonies are to be typed. Only in cases of identical patterns are the more time consuming and expensive genetic fingerprints necessary. Moreover, the MAbs can also be used for specific antigen detection in respiratory specimens on the serogroup or subgroup level.

Identification and serotyping of atypical Legionella pneumophila strains isolated from human and environmental sources

“…Analysis of LPS epitope pattern by serogroupcross-reactive mAbs Legionella pneumophila isolates were tested by ELISA using five serogroup-cross-reactive mAbs as described elsewhere (Helbig et al 1997). These mAbs showed different reaction patterns with the serogroup reference type strains ( Table 2), but did not react adequately with all strains belonging to the individual serogroups.…”

“…The environmental isolate 16453-92, which was obtained in Spain, reacted with only one serogroup-cross-reactive mAb (mAb 32/3). This strain was used as an immunogen for the production of rabbit immune sera according to Cherry and McKinney (1979) and for the production of mAbs according to Helbig et al (1997). mAbs were also raised against strain D4954, which was isolated from a clinical specimen in the USA.…”

“…Serological testing of L. pneumophila has resulted in the designation of 15 serogroups (Brenner et al 1988), and testing with monoclonal antibodies (mAbs) has shown that serogroups 1 (Joly et al 1986), 4, 5 and 6 consist of numerous subtypes (Helbig et al 1997). In recent years, molecular genotyping methods have been increasingly used in epidemiological investigations of L. pneumophila serogroup 1 infections (Fry et al 1999;Gaia et al 2005).…”

Legionella pneumophila: an aquatic microbe goes astray

“…Lipopolysaccharide (LPS) produced by L. pneumophila is a major immunogenic cell surface determinant that can activate both classical and alternative complement pathways [64,65]. Recently phase variable expression of a LPS epitope in L. pneumophila serogroup 1 strains has been reported to be associated with changes in virulence properties in the human macrophage-like cell line HL60 and in A. castellanii [66,67].…”

Epitope mapping of the O‐chain polysaccharide of Legionella pneumophila serogroup 1 lipopolysaccharide by saturation‐transfer‐difference NMR spectroscopy

“…In the human lung L. pneumophila invades and replicates within alveolar macrophages [3]. The serogroup-speci®c antigens of the Gram-negative legionellae reside in the lipopolysaccharide (LPS) of the outer membrane [4,5].…”