Effect of Aspergillus terreus mycotoxins on nitric oxide synthase activity in human erythroid K-562 cells

A Protective Mechanism in Lungs of Rats Experimentally Infected with Aspergillus fumigatus

Aspergillus fumigatus is associated with invasive disease aspergillosis in immunocompromised individuals. The major aim of this study was to investigate the biochemical and immunological responses of male Wistar rats against A. fumigatus experimentally-induced pulmonary fungal infection. Nostril experimental exposure of male Wistar rats to a high dose of A. fumigatus freeze-dried preparation for only 24 hr resulted in a significant increase in levels of catalase, nitric oxide and lipid peroxide in lung homogenates, compared to those of the control animals. However, the oxidative status of the lungs of rats challenged with killed fungus did not change significantly, except for the stimulation in the level of lipid peroxide. IgG level was significantly elevated only in rats that received two low doses of fungus, compared to unexposed animals (p<0.005). Examining the lung of rats exposed to A. fumigatus revealed no abnormal changes, except for pus in bronchial lumen spaces and per bronchial inflammation. Histologically, large numbers of granuloma cells were evident in the lungs of challenged rats, while no granuloma formation was evident in the lungs of rats exposed to killed fungus.

Effect of Mycotoxins on Some Activities of Isolated Human Neutrophils

Activities of mycotoxins--citrinin, ochratoxin B, rubratoxin B, and zearalenol beta--that affected superoxide anion (O2-) production were studied on human neutrophils with regard to hypochlorous acid (HOCl) generation, nitric oxide (NO) formation, and chemotaxis of isolated cells. At the doses of 10(-8), 10(-6), 10(-4), or 10(-2) mg/mL, in stimulated cells the mycotoxins inhibited HOCl production proportionally to that of O2- because HOCl production is directly dependent on O2- generation. But unlike the others, zearalenol beta decreased HOCl production much more than one of O2-, indicating an effect also on myeloperoxidase secretion. All mycotoxins inhibited NO generation but only at the dose of 10(-2) mg/mL. Formyl-met-leu-phe-induced chemotaxis of neutrophils was deeply affected as well, as all mycotoxins at all doses used decreased it. All considered effects were not dose-dependent, likely connected to high variability of individual sensitivity to these compounds and because they already are present in blood introduced with foods. These activities of neutrophils confirm and extend the danger for immune systems by mycotoxins also in very small quantities, since the smaller concentrations we used are easily reachable in blood.

The contribution of animal models of aspergillosis to understanding pathogenesis, therapy and virulence

Animal models of aspergillosis have been used extensively to study various aspects of pathogenesis, innate and acquired host-response, disease transmission and therapy. Several different animal models of aspergillosis have been developed. Because aspergillosis is an important pulmonary disease in birds, avian models have been used successfully to study preventative vaccines. Studies done to emulate human disease have relied on models using common laboratory animal species. Guinea pig models have primarily been used in therapy studies of invasive pulmonary aspergillosis (IPA). Rabbits have been used to study IPA and systemic disease, as well as fungal keratitis. Rodent, particularly mouse, models of aspergillosis predominate as the choice for most investigators. The availability of genetically defined strains of mice, immunological reagents, cost and ease of handling are factors. Both normal and immunosuppressed animals are used routinely. These models have been used to determine efficacy of experimental therapeutics, comparative virulence of different isolates of Aspergillus, genes involved in virulence, and susceptibility to infection with Aspergillus. Mice with genetic immunological deficiency and cytokine gene-specific knockout mice facilitate studies of the roles cells, and cytokines and chemokines, play in host-resistance to Aspergillus. Overall, these models have been critical to the advancement of therapy, and our current understanding of pathogenesis and host-resistance.

Investigation of cellular and humoral immune responses to whole cell and acellular pertussis vaccines

New generation acellular pertussis vaccines were compared with the established whole cell pertussis vaccine for the induction of humoral and cellular immune-responses in mice. At the same time, the in vivo protective effect of these two types of vaccine was also compared in both intracerebral (ic) and aerosol challenge models. In general, whole cell vaccine induced lower antibody titres to pertussis toxin, filamentous haemagglutinin and pertactin than the acellular vaccine. Nitric oxide concentration in macrophage cultures was used as a marker for macrophage activation. The nitric oxide concentrations in the macrophage cultures from mice following immunisation with the whole cell vaccine were higher than those from mice immunised with the acellular vaccine, which indicated that the whole cell vaccine was more effective than the acellular vaccine in activating macrophages. This was associated with better protection in vivo after challenge. After ic challenge of mice following immunisation with whole cell or acellular vaccine, 90% of the whole cell vaccine group survived compared with 40% of the acellular vaccine group at the vaccine dose selected. Following aerosol challenge, mice in the whole cell vaccine group showed faster clearance of bacteria from the lungs than those in the acellular vaccine group. Our findings suggest that the different types of pertussis vaccines may achieve protection in different ways and that CMI may play an important role in eliminating bacteria which escape humoral defence mechanisms.