Vitaliano Cusumano

Secondary metabolites of Aspergillus exert immunobiological effects on human monocytes.

This project focused on the effects of aflatoxin B1 (AFB1), a food-contaminating mycotoxin produced by fungi, genus Aspergillus, on the release and genetic expression of some important cytokines, i.e., (interleukin-1 alpha (IL-1 alpha), IL-6, tumor necrosis factor-alpha (TNF alpha)) by human monocytes. Monocytes, preincubated for different time periods with concentrations of AFB1 ranging from 0.01 to 1.0 pg/mL, were then activated with bacterial lipopolysaccharide. Cytokine levels were measured by immunoassay and mRNA by cDNA amplification. Pretreatment of monocytes with AFB1 resulted in a decrease in IL-1, IL-6 and TNF alpha release already at a concentration of 0.05 pg/mL. The gene expression of the cytokines considered was drastically affected by treatment with AFB1. In fact, AFB1 completely blocked the transcription of IL-1 alpha, IL-6 and TNF alpha mRNAs, while it did not affect beta-actin mRNA at the concentrations used. It therefore appears that AFB1 exerts its effect on cytokine release through selective inhibition of specific mRNA, without affecting general protein synthesis.

Immunobiological activities of mould products : functional impairment of human monocytes exposed to aflatoxin B1

In order to elucidate the effects upon the human immune system of aflatoxin B1 produced by the food-contaminating mould Aspergillus flavus, phagocytosis, microbicidal activity, superoxide production and intrinsic antiviral activity were studied in monocytes exposed to aflatoxin B1 for different times at concentrations ranging from 0.1 to 1 pg/ml. Phagocytosis and microbicidal activity were significantly impaired (p < 0.05) by aflatoxin B1 at doses as low as 0.1 pg/ml. However, pretreatment of monocytes with aflatoxin B1 did not modify intrinsic antiviral activity or superoxide production. These results confirmed data obtained from animals fed with mycotoxin-contaminated foods. The potential danger to human health of exposure to mycotoxins demonstrates the necessity for careful microbiological control of food.

Neonatal Hypersusceptibility to Endotoxin Correlates with Increased Tumor Necrosis Factor Production in Mice

Septic shock is a major cause of mortality in neonates. The hypothesis was tested that neonatal age is associated with altered sensitivity to shock-inducing bacterial products or proinflammatory cytokines (or both). Mice of different ages were inoculated with various doses of lipopolysaccharide (LPS), superantigenic staphylococcal enterotoxin B (SEB), or recombinant tumor necrosis factor-alpha (rTNF-alpha), alone or in combination with the sensitizing agent D-galactosamine. Neonatal mice were markedly more susceptible to LPS-induced lethality but more resistant to SEB than were adults (P < .05). Mice of different ages did not differ, however, in their sensitivity to lethal activities of rTNF-alpha. Neonatal susceptibility to LPS and SEB correlated directly with plasma TNF-alpha but not IFN-gamma levels, which was confirmed by TNF-alpha and IFN-gamma blockade experiments. These data document marked age-related differences in the pathophysiology of septic shock and suggest that IFN-gamma is not an obligatory mediator of either LPS- or SEB-induced lethality in neonates.

Interleukin-18 Is an Essential Element in Host Resistance to Experimental Group B Streptococcal Disease in Neonates

ABSTRACT Previous studies demonstrated that interleukin-12 (IL-12)-dependent gamma interferon (IFN-γ) responses have a major role in restricting in vivo bacterial growth during infection of mice with group B streptococci (GBS), important human pathogens. Like IL-12, IL-18 is a potent IFN-γ inducer. The role of IL-18 in experimental GBS infection was investigated here. Significant elevations of IL-18 levels over baseline values were detected in plasma samples from neonatal mice rendered septic with GBS. Neutralization of IL-18 significantly increased mortality and bacterial burden (P < 0.05). In contrast, administration of recombinant IL-18 (rIL-18) before or after GBS challenge remarkably improved survival and decreased blood colony counts, in association with increased IFN-γ production by spleen cells. The beneficial effects of rIL-18 were counteracted by administration of neutralizing anti-IFN-γ monoclonal antibodies, indicating that the effects of IL-18 were mediated by IFN-γ. Finally, low rIL-18 doses that had no effect of their own on bacterial burden could act in synergy with rIL-12 to protect neonatal mice during GBS infection. Collectively, our data indicate that IL-18 responses have an important role in host defenses against GBS and that rIL-18 may be useful in alternative strategies to treat neonatal GBS disease.

Bactericidal activity of lansoprazole and three macrolides against Helicobacter pylori strains tested by the time-kill kinetic method

The bactericidal activities of macrolides (clarithromycin, roxithromycin and azithromicyn) and lansoprazole, alone and in combination, against Helicobacter pylori strains were evaluated. It was found that the association of lansoprazole and clarithromycin resulted in a marked synergism, while the combination of roxithromycin or azithromycin with lansoprazole had synergistic and additive effects.

Age-related sensitivity of neonatal mice to toxicity induced by heat-killed group B streptococci.

Newborns are highly susceptible to infections by group B streptococci (GBS), a relatively infrequent cause of serious disease in adults. Several immunological defects, including decreased opsono-phagocytosis, can, at least partially, account for the increased susceptibility of neonates to GBS infections. We have previously demonstrated that tumor necrosis factor alpha (TNF-α) plays an important pathophysiologic role in neonatal models of GBS disease1. This study was undertaken to test the hypothesis that neonatal age is associated with altered sensitivity to TNF-α-dependent toxic activities of GBS products.

Effects of Taxol on TNF-α and IL-6 Production by Human Peripheral Blood Cells

Taxol, a new drug isolated from the bark of the Pacific yew tree, is being used in treating patients with breast, ovary, lung, neck, and brain cancer.’.* The therapeutic mechanisms of taxol are not yet completely known. Taxol binds to p-tubulin, stabilizes microtubules against dep~lymerization,~ and interferes with microtubules during the cell divisions, blocking the cell through me tapha~e .~ Probably, microtubules are not the only targets of this drug. On murine macrophages, taxol appears to have an action similar to that of bacterial lipopolysaccharide (LPS). There is some evidence that the drug binds to receptors proximal to those of LPS.’ LPS activates antitumor mechanisms such as biosynthesis of tumor necrosis factor alpha (TNF-cY)~,~ and direct macrophage tumoricidal activity.8 Thus, the antitumor activities of taxol may be in part related to its ability to stimulate macrophages. The objective of this study was to determine if cells from the peripheral blood of healthy donors or tumor patients can be stimulated with taxol to produce TNF-a or IL-6 directly or in the presence of “priming” signals, such as those provided by interferon-gamma (IFN-y).