Formalin-killed versus heat-killed Legionella pneumophila serogroup 1 antigen in the indirect immunofluorescence assay for legionellosis

Abstract

Indirect immunofluorescence assay titers of human sera obtained against the Legionella pneumophila serogroup 1 antigen (Philadelphia 1 strain) killed with 10% Formalin showed a tendency to be lower than those obtained against the reference heat-killed antigen (geometric mean titer of 194 and 370, respectively) when all other variables in the test were held constant. Test results were interpreted the same for 96% of 60 paired sera if the cutoff level used to interpret a positive test result for the formalinized antigen was lowered by one twofold dilution factor.

The Legionnaires' disease bacterium (Legionella pneumophila) inhibits phagosome-lysosome fusion in human monocytes.

“…However, formalin treatment does not eliminate L. pneumophila's capacity to induce proliferation and production of monocyte activating cytokines by lymphocytes from patients recovered from Legionnaires' disease (25). Also, formalin-treated L. pneumophila are recognized about as well as heat-killed L. pneumophila by anti-L, pneumophila antibody in immune human serum (26). As with formalin-killed L. pneumophila, glutaraidehyde-fixed T. gondii (2) and heat-killed C. psittaci (6) fail to inhibit phagosome-lysosome fusion.…”

Legionella pneumophilain aerosols from shower baths

“…The two concerned had titres of < 16 against a formalin-killed yolk sac antigen and 32 against a heat-killed locally isolated strain. The difference in titre may have been due to strain differences, but Wilkinson & Brake (1982) have drawn attention to the fact that formalin-killed antigens tend to have lower titres than heat-killed. Titres of 32 are not considered significant and were found in 20 of 2023 normal individuals in the Nottingham area using the Colindale antigen (Macrae, Appleton & Laverick, 1979).…”

Antigenic and genetic characterization of Leaionella Proteins: Contribution to taxonomy, diagnosis and pathogenesis

“…This technique has been thoroughly evaluated for L. pneumophila SG1 using epidemic sera (Wilkinson et al 1983), showing a specificity of 99 %. Comparisons of different antigen preparations (ether-, formolized or heat-killed) seem to favor the use of formolized antigens which yield the highest specificity (Taylor et al 1979, Wilkinson & Brake 1982, since several unspecific cross-reactions have been reported for the heat-killed antigen , Wang et al 1987. Interestingly, apparent LPS-associated cross-reactivity has been reported between Legionella spp.…”