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Rhodococcus equi: equine neutrophil chemiluminescent and bactericidal responses to opsonizing antibody
R J Martens1, J G Martens, H W Renshaw
1Department of Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A & M University, College Station 77843.
Veterinary Microbiology
|August 1, 1987
Summary
Serum from foals infected with Rhodococcus equi (R. equi) contains specific antibodies that significantly enhance the ability of neutrophils to kill bacteria. This indicates effective opsonic activity in infected foal serum.
Area of Science:
- Veterinary Immunology
- Equine Infectious Diseases
- Microbial Pathogenesis
Background:
- Rhodococcus equi (R. equi) is a significant cause of pneumonia in foals.
- Opsonic capacity of serum is crucial for effective phagocytosis and bacterial clearance by immune cells.
- The role of specific antibodies in R. equi opsonization and subsequent neutrophil function in foals requires further elucidation.
Purpose of the Study:
- To compare the opsonic capacity of serum from foals infected with R. equi against antibody-deficient control sera.
- To evaluate the biological effectiveness of R. equi-specific antibodies in enhancing neutrophil-mediated bacterial killing.
- To investigate the functional activity of complement-inactivated sera in the context of R. equi infection.
Main Methods:
- Utilized luminol-dependent chemiluminescence (LDCL) and bactericidal assays to assess neutrophil function.
- Opsonized R. equi bacteria with either control (neonatal equine pre-colostral) or principal (infected foal) complement-inactivated sera.
- Quantified R. equi-specific antibody levels using Enzyme-Linked Immunosorbent Assay (ELISA).
Main Results:
- Significantly higher mean peak LDCL was observed with principal sera (2.4 X 10(5) cpm) compared to control sera (0.018 X 10(5) cpm) (P < 0.01).
- Neutrophils exhibited significantly higher mean peak R. equi kill percentage with principal sera (95.2%) than with control sera (54.6%) (P < 0.01).
- Mean ELISA values for R. equi-specific antibody were significantly higher in principal sera (71.8) versus control sera (0.0) (P < 0.01).
Conclusions:
- Complement-inactivated sera from foals with R. equi infections possess significant opsonic activity.
- R. equi-specific antibodies in infected foal serum are biologically effective in enhancing neutrophil-mediated bacterial killing.
- This study confirms the presence and functional importance of opsonic antibodies in equine R. equi infections.