Humoral Antibody Response to the Antigens of Virulent Rhodococcus equi in Foals.

Expression of Virulence‐Associated Antigens of Rhodococcus equi Is Regulated by Temperature and pH

“…The 15-to 17-kDa antigens are expressed by virulent R. equi growing in vivo. Naturally infected foal sera reacted strongly with the virulence-associated antigens by immunoblotting (20,21), suggesting the antigens are recognized by infected hosts, and we directly demonstrated the expression of the antigens in phagocytic cells from pulmonary lesions of naturally infected foals using monoclonal antibodies (9). These virulence-associated antigens, which are induced by these signals, might be involved in the process of pathogenesis of R. equi infection in foals and humans.…”

Performance of Five Serological Assays for Diagnosis ofRhodococcus equiPneumonia in Foals

“…Anti-R. equi antibody concentrations were measured with four ELISAs (ELISA-6939, ELISA-33701, ELISA-VapA, and ELISA-California) as previously described (11,16,21,22). Antigens used were Tween 20 extract from a virulent plasmid-containing (ELISA-33701) or an avirulent (ELISA-6939) R. equi strain, supernatant antigen from clinical isolates (ELISA-California), and recombinant VapA (VapA-ELISA).…”

“…Antigens used were Tween 20 extract from a virulent plasmid-containing (ELISA-33701) or an avirulent (ELISA-6939) R. equi strain, supernatant antigen from clinical isolates (ELISA-California), and recombinant VapA (VapA-ELISA). Results for ELISA-6939 and ELISA-33701 are reported as optical density values (21,22). ELISA-California was performed by the California Animal Health and Food Safety Laboratory System (Davis, Calif.),and results are reported as the ratio of positive serum or test serum absorbance to the negative control absorbance value (11).…”

Evaluation of 5 serologic assays to detect Rhodococcus equi pneumonia in foals

“…An OD of 0.5 was selected as a cutoff because the ELISA-33701 is reportedly a more sensitive assay than the ELISA-6939. 7,24 The third ELISA used in the study consisted of a dilution ELISA, similar to that previously described, 25 and was performed at a commercial laboratory. a For this assay, purified recombinant VapA, prepared as described, 26 was used as the antigen.…”

“…Consequently, many foals may be exposed to virulent and avirulent strains of R equi and develop corresponding serum antibodies. 24 Foals residing at farms on which R equi infection is endemic are more likely to be exposed to high concentrations of the bacterium 7,13 ; however, the extent of exposure and immune responsiveness of exposed foals may vary.…”