Cytokine appearance and effects of anti-tumor necrosis factor alpha antibodies in a neonatal rat model of group B streptococcal infection.
Cytokines are suspected of playing an important role in the pathophysiology of septic shock. This study was undertaken to determine whether tumor necrosis factor alpha (TNF-alpha) induces the production of other cytokines and mediates mortality in a neonatal rat model of sepsis caused by group B streptococci (GBS). We have measured TNF-alpha, interleukin-1 alpha (IL-1 alpha), interleukin-6 (IL-6), and gamma interferon (IFN-gamma) levels in neonatal rats infected with different strains (H738, 259, and 90) and doses (1 50% lethal dose [LD50] and 5 90% lethal doses [LD90]) of type III GBS. TNF-alpha and IL-6 were detected by the L929 cytotoxicity and the B9 proliferation assays, respectively, in serial plasma samples. IL-1 alpha and IFN-gamma were measured in spleen homogenates by enzyme-linked immunosorbent assay kits by using antibodies raised against the corresponding mouse cytokines. Plasma TNF-alpha levels significantly rose above baseline values within 12 h after intraperitoneal challenge with 5 LD90 of GBS strain H738, corresponding to 3 x 10(3) CFU. A mean peak TNF-alpha concentration of 232 +/- 124 U/ml was reached at 20 h. Peak IL-1 alpha and IL-6 levels of 766 +/- 404 U/g and 1,033 +/- 520 U/ml, respectively, were reached at 24 h after bacterial challenge. Maximal spleen concentrations of IFN-gamma (449 +/- 283 U/g) were measured at 36 h. Concentrations of TNF-alpha, but not other cytokines, remained significantly elevated at 72 h, a time when mortality approached 100%. Significant correlations were found between concentrations of each of the cytokines tested and the logs of CFU concentrations in the blood. In order to ascertain whether TNF-alpha influenced the production of other cytokines, rat pups received two injections of anti-murine TNF-alpha or normal rabbit serum at 2 h before and at 26 h after challenge with live GBS. Plasma TNF-alpha bioactivity was undetectable in anti-TNF-alpha-treated animals, while IL-6 and IFN-gamma, but not IL-1 alpha, levels were significantly reduced, compared with normal serum controls. Rat pups pretreated with anti-TNF-alpha serum and infected with 1 and 5 LD90 of strains H738 and 259 showed enhanced early (48 to 72 h) survival. However, by 96 h this protection was no longer apparent.
Teti
G
G
Istituto di Microbiologia, Facoltà di Medicina e Chirurgia, Università degli Studi di Messina, Italy.
Mancuso
G
G
Tomasello
F
F
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D003114:Colony-Forming Units Assay; D016207:Cytokines / Q000096:biosynthesis*; D004195:Disease Models, Animal; D004306:Dose-Response Relationship, Immunologic; D004797:Enzyme-Linked Immunosorbent Assay; D007371:Interferon-gamma / Q000096:biosynthesis; D007378:Interleukins / Q000096:biosynthesis; D051381:Rats; D012772:Shock, Septic / Q000276:immunology; D013290:Streptococcal Infections / Q000276:immunology* / Q000401:mortality; D013292:Streptococcus agalactiae; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D016207:Cytokines; D007378:Interleukins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma