Enhancement of the lethal effects of endotoxins by interferon inducers

Current Findings on Gut Microbiota Mediated Immune Modulation against Viral Diseases in Chicken

Chicken gastrointestinal tract is an important site of immune cell development that not only regulates gut microbiota but also maintains extra-intestinal immunity. Recent studies have emphasized the important roles of gut microbiota in shaping immunity against viral diseases in chicken. Microbial diversity and its integrity are the key elements for deriving immunity against invading viral pathogens. Commensal bacteria provide protection against pathogens through direct competition and by the production of antibodies and activation of different cytokines to modulate innate and adaptive immune responses. There are few economically important viral diseases of chicken that perturb the intestinal microbiota diversity. Disruption of microbial homeostasis (dysbiosis) associates with a variety of pathological states, which facilitate the establishment of acute viral infections in chickens. In this review, we summarize the calibrated interactions among the microbiota mediated immune modulation through the production of different interferons (IFNs) ILs, and virus-specific IgA and IgG, and their impact on the severity of viral infections in chickens. Here, it also shows that acute viral infection diminishes commensal bacteria such as Lactobacillus, Bifidobacterium, Firmicutes, and Blautia spp. populations and enhances the colonization of pathobionts, including E. coli, Shigella, and Clostridial spp., in infected chickens.

Inhibited hormonal induction of hepatic phosphoenolpyruvate carboxykinase in poly I: treated mice, an endotoxin-like glucocorticoid antagonism

Corticosteroid induction of mouse hepatic phosphoenolpyruvate carboxykinase was inhibited by prior injection of poly I:C. Mice challenged with a lethal dose of endotoxin 4 h after administration of poly I: C could not be protected by a concurrent injection of hydrocortisone.

Increased toxicity of double-stranded ribonucleic acid in virus-infected animals

Virus-infected mice were significantly more susceptible to the toxic effects of double-stranded ribonucleic acid (RNA) than uninfected mice. A dramatic increase in mortality was observed after injection of either synthetic (polyriboinosinic.polyribocytidylic acid) or natural (mycophage) double-stranded RNA in mice infected with Newcastle disease virus (NDV) or vesicular stomatitis virus (VSV). With the exception of endotoxin, interferon inducers other than double-stranded RNA, such as tilorone-hydrochloride and chlorite-oxidized oxyamylose, did not show this increased toxicity in virus-infected animals. The increased susceptibility of virus-infected animals to the toxic effects of double-stranded RNA appears to be related to the levels of interferon induced by the virus infection, either systemically, in the blood stream (after inoculation of NDV), or locally, in the brain (after infection with VSV).

Increased susceptibility of cells treated with interferon to the toxicity of polyriboinosinic-polyribocytidylic acid

Concentrations of the synthetic polymer polyriboinosinic.polyribocytidylic acid that produced no detectable toxicity in normal L cells produced marked cytotoxicity in L cells treated with interferon. This increase in the susceptibility of cells to the toxicity of the polymer was also observed in human cells and secondary mouse embryo cells treated with homologous interferons before exposure to the polynucleotides. The degree of enhancement of toxicity was dependent on the concentration of interferon to which the cells were exposed. The ratio of antiviral activity induced by interferon to enhancement of toxicity by interferon remained constant through about 1000-fold purification. Various interferon preparations induced by viruses or by polyriboinosinic.polyribocytidylic acid in vivo or in vitro, and international reference standard interferons all exhibited enhancement of toxicity. Both enhancement of toxicity and antiviral activity were destroyed by trypsin and by incubation at 56 degrees for 1 hr, did not act on heterologous cells, were not sedimented by ultracentrifugation, and were not inactivated by ribonuclease, deoxyribonuclease, irradiation with ultraviolet light, or exposure to a pH of 2.

Pyran and polyribonucleotides: differences in biological activities

Maleic anhydride-divinyl ether copolymer (pyran) and the polyribonucleotides are both large polyanions with potent antiviral activity. However, they are biologically quite different. Interferon levels of 100 units or more/ml were associated with antiviral activity of polyribonucleotides. Interferon induction by pyran compounds was not primarily involved in antiviral resistance because preparations that did not induce interferon possessed antiviral activity equal to that of interferoninducing preparations. Both polyriboinosinic-cytidylic acid [poly (rI.rC)] and pyran increased the immune response to sheep erythrocytes in the Jerne hemolytic plaque-forming cell (PFC) assay, but their modes of immunoadjuvant action differed. On peak day, poly (rI.rC)-treated mice demonstrated 5.1 x 10(4) PFC/spleen (557 PFC/10(6) nucleated cells) and pyran-treated mice exhibited 4.5 x 10(4) PFC/spleen (299 PFC/10(6) nucleated cells), as compared with 2.7 x 10(4) PFC/spleen (261 PFC/10(6) nucleated cells) in controls. The compounds also differed in phagocytic alteration; polyribonucleotides did not affect phagocytosis whereas pyran produced a biphasic response. Both polyanions exhibited toxic inhibition of liver microsomal enzyme metabolism of type I and type II drugs. However, whereas pyran sensitized mice 50-fold to the lethal effects of endotoxin, the polyribonucleotides did not significantly sensitize mice to endotoxin.

Enhanced toxicity for mice of combinations of antibiotics with Escherichia coli cells or Salmonella typhosa endotoxin

Enhanced lethality for BALB/c mice has been observed after the administration of Salmonella typhosa endotoxin with either actinomycin D, cycloheximide, or nogalamycin. The dose of actinomycin D required to kill half of the mice (LD(50)) was 0.8 mg/kg in normal animals, 0.35 mg/kg in mice administered 0.08 mg of endotoxin per kg, and 0.28 mg/kg in mice administered 0.2 mg of endotoxin per kg. The LD(50) of endotoxin in normal mice was 12 mg/kg and in mice given 0.4 mg of actinomycin D per kg was 0.067 mg/kg. The LD(50) of actinomycin D in mice administered 1.8 x 10(8) live Escherichia coli cells per kg or 1.8 x 10(9) heat-killed E. coli cells per kg was reduced to 0.4 mg/kg. The LD(50) of cycloheximide was 181 mg/kg in normal animals and 28 mg/kg in mice administered 4 mg of endotoxin per kg. The LD(50) of endotoxin in mice given 120 mg of cycloheximide per kg was 0.02 mg/kg. Enhanced lethality due to various combinations of cycloheximide and endotoxin was abolished by pretreatment of mice with endotoxin. The LD(50) of nogalamycin was 21 mg/kg in normal mice and 13 mg/kg in mice receiving 1 mg of endotoxin per kg.