Immunoglobulin G Subisotype Responses of Pneumonic and Healthy, Exposed Foals and Adult Horses toRhodococcus equiVirulence-Associated Proteins
Open Access
- 1 May 2003
- journal article
- research article
- Published by American Society for Microbiology in Clinical and Vaccine Immunology
- Vol. 10 (3), 345-351
- https://doi.org/10.1128/cdli.10.3.345-351.2003
Abstract
Rhodococcus equicauses severe pyogranulomatous pneumonia in foals and in immunocompromised humans. Replication of virulent isolates within macrophages correlates with the presence of a large plasmid which encodes a family of seven virulence-associated proteins (VapA and VapC to VapH), whose functions are unknown. Although cell-mediated immunity is thought to be crucial in eliminatingR. equiinfection, antibody partially protects foals. The antibody response to both VapA and VapC was similar in six adult horses and six naturally exposed but healthy foals, as well as in eight foals withR. equipneumonia. The immunoglobulin G (IgG) subisotype response of pneumonic foals to Vap proteins was significantly IgGb biased and also had a trend toward higher IgGT association compared to the isotype association of antibody in adult horses and healthy exposed foals. This suggests that in horses, IgGb and IgGT are Th2 isotypes and IgGa is a Th1 isotype. Furthermore, it suggests that foals which developR. equipneumonia have a Th2-biased, ineffective immune response whereas foals which become immune develop a Th1-biased immune response. Pneumonic foals had significantly more antibody to VapD and VapE than did healthy exposed foals. This may indicate a difference in the expression of these two Vap proteins during persistent infection. Alternatively, in pneumonic foals the deviation of the immune response toward VapD and VapE may reflect a bias unfavorable toR. equiresistance. These data indicate possible age-related differences in the equine immune response affecting Th1-Th2 bias as well as antibody specificity bias, which together favor the susceptibility of foals toR. equipneumonia.Keywords
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