Effects of conidia of various Aspergillus species on apoptosis of human pneumocytes and bronchial epithelial cells

Aspergillus species can cause mycoses in human and animals. Previously, we demonstrated that A. fumigatus conidia from a human isolate inhibited apoptosis in human pneumocytes and bronchial epithelial cells. In the current study, we studied the effects of A. fumigatus conidia non-human origin and A. flavus, A. nidulans, A. niger and A. oryzae conidia on human cells apoptosis. Human pneumocytes or bronchial epithelial cells were simultaneously exposed to apoptotic inductors and aspergilli conidia. The cell cultures were analyzed by flow cytometry, immunoblotting, and examination of nuclear morphology. Similar to A. fumigatus conidia, A. flavus conidia inhibited cellular apoptosis while A. nidulans, A. niger and A. oryzae conidia did not affect apoptosis. We further studied the species specificity of conidia: there were no differences in the inhibition of apoptosis by A. fumigatus conidia from either human or bird isolates. In order to determine whether the inhibition of apoptosis by conidia is limited to certain strains, the effect on human cell apoptosis of different A. fumigatus human clinical isolates and A. fumigatus of environmental origin was evaluated. All A. fumigatus isolates inhibited apoptosis; an anti-apoptotic factor was released by conidia. For TNF-induced apoptosis, the anti-apoptotic effect of conidia of all isolates was found to be associated with a reduction of caspase-3 in human cells. The results suggest that suppression of apoptosis may play a role in reducing the efficacy of host defense mechanisms during infection with Aspergillus species.

Tumor necrosis factor mutants with selective cytotoxic activity

Tumor necrosis factor (TNF-alpha) has a cytotoxic or cytostatic effect when tested with various malignant cell lines. Clinical trials in cancer patients, however, revealed high systemic toxicity of TNF-alpha. The existence of two types of receptor may partially explain the pleiotropic activity of TNF-alpha. The purpose of this study was to characterize the relative cytotoxic activity of TNF-alpha and TNF mutants on the mouse fibrosarcoma L929 cells in a standard cytotoxicity test, on human larynx carcinoma HEp-2 cells, and on human monoblastoid leukemic cells U937. TNF mutants were obtained by site-directed mutagenesis. The purity of TNF-alpha was established by capillary electrophoresis. TNF-alpha and TNF mutants were analysed by Western blot analysis using monoclonal antibodies against TNF-alpha. The results show that TNF mutants can recognize the different TNF-receptors (TNF-R) selectivity. It is generally believed that activation of TNF-R75 is responsible for the systemic toxicity of TNF-alpha. Hence, the development of TNF mutants, binding selectively to TNF-R55, could lead to new option for an anticancer treatment that would be devoid of the deleterious effect of TNF-alpha.

Development of an enzyme immunoassay for the measurement of human tumour necrosis factor-alpha (hTNF-alpha) using bispecific antibodies to hTNF-alpha and horseradish peroxidase

The cytokine tumour necrosis factor-alpha (TNF-alpha) is involved in several pathological processes, and human recombinant TNF-alpha (hrTNF-alpha) is available for testing in preclinical and clinical research. The purpose of this work was the creation of tetradomas producing bispecific anti-hTNF-alpha/anti-HRP (horseradish peroxidase) antibodies and the development of a rapid and sensitive solid-phase enzyme immunoassay. Monoclonal antibodies obtained against hrTNF-alpha could recognize both natural and recombinant hTNF-alpha. The four chosen hybridomas produced IgG1 with an affinity constant of the order of 10(-9) M. Three of them recognized different epitopes. The clone selected for fusion with the hybridoma producing anti-HRP antibodies secreted antibodies against portion 30-50 of the hTNF-alpha N-terminal amino acid residues as found by Western-blot analysis with mutant and chimaeric proteins. The tetradoma producing bispecific anti-hTNF-alpha/anti-HRP antibodies was identified using a fluorescence-activated cell sorter. Bispecific antibodies were isolated by hydroxyapatite chromatography. A sandwich ELISA was developed: one of the monoclonal anti-TNF-alpha antibodies was absorbed to the solid phase as the catcher and was detected by a bispecific anti-hTNF-alpha/anti-HRP antibody. The detection limit of the assay was 1 ng/ml. With such ELISA, the level of hTNF-alpha could be conveniently estimated in different samples containing either natural or recombinant hTNF-alpha in an experimental environment or in clinical trials.