Modulation of cytokine response of pneumonic foals by virulent Rhodococcus equi.
The ability of Rhodococcus equi to induce pneumonia in foals depends on the presence of an 85- to 90-kb plasmid. In this study, we evaluated whether plasmid-encoded products mediate virulence by modulating the cytokine response of foals. Foals infected intrabronchially with a virulence plasmid-containing strain of R. equi had similar gamma interferon (IFN-gamma) and interleukin-12 (IL-12) p35 but significantly higher IL-1beta, IL-10, IL-12 p40, and tumor necrosis factor alpha (TNF-alpha) mRNA expression in lung tissue compared to foals infected with the plasmid-cured derivative. IFN-gamma mRNA expression levels in CD4+ T lymphocytes isolated from bronchial lymph nodes (BLN) were similar for the two groups of R. equi-infected foals on day 3 postinfection. However, on day 14, in association with pneumonia and marked multiplication of virulent R. equi but with complete clearance of the plasmid-cured derivative, IFN-gamma mRNA expression in BLN CD4+ T lymphocytes was significantly (P < 0.001) higher in foals infected with the plasmid-cured derivative. These results suggests an immunomodulating role for R. equi virulence plasmid-encoded products in downregulating IFN-gamma mRNA expression by CD4+ T lymphocytes.
Giguère
S
S
Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Wilkie
B N
BN
Prescott
J F
JF
D000193:Actinomycetales Infections / Q000276:immunology / Q000662:veterinary*; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis* / Q000235:genetics; D006734:Horse Diseases / Q000276:immunology*; D006736:Horses; D018410:Pneumonia, Bacterial / Q000662:veterinary*; D012333:RNA, Messenger / Q000032:analysis; D016929:Rhodococcus equi / Q000472:pathogenicity; D014774:Virulence
D016207:Cytokines; D012333:RNA, Messenger