Exopolysaccharides from Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 prevent influenza virus infection and attenuate secondary bacterial infection risk.

The present study assessed the inhibitory action of exopolysaccharides (EPS) produced by Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 against influenza virus infection followed by secondary bacterial infection. We found that the presence of 200 or 400 µg ml-1 of EPS significantly protected against influenza virus infection in a dose-dependent manner when A549 cells were treated with EPS before infection but not after it. The expression of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1), an adhesion molecule for bacteria adherence, on A549 cells was significantly enhanced during influenza virus infection compared with viral-non-infected A549 cells. However, this upregulated CEACAM-1 expression was significantly decreased by EPS treatment before viral infection in association with the reduction in the virus titre in A549 cells. In a bacterial adhesion assay using Staphylococcus aureus, the bacterial adherence to viral-infected A549 cells was significantly greater than that to viral-non-infected A549 cells, and the increased bacterial adherence induced by influenza virus infection tended to be decreased by EPS treatment before the infection. Our findings show that EPS treatment before viral infection can inhibit influenza virus infection and alleviate secondary bacterial infection through decreased CEACAM-1 expression.

Difference in cholesterol-binding and cytolytic activities between listeriolysin O and seeligeriolysin O: a possible role of alanine residue in tryptophan-rich undecapeptide.

We have constructed recombinant listeriolysin O (rLLO) and seeligeriolysin O (rLSO) from Listeria monocytogenes and Listeria seeligeri, respectively. In hemolysis and cholesterol-binding assays, the specific activity of recombinant toxin was lower for LSO as compared to LLO. To understand the molecular basis of this difference, in particular with respect to the conserved Trp-rich undecapeptide, a naturally occurring Ala to Phe substitution in LSO was introduced into rLLO. The rLLO:A488F hemolysin exhibited a reduced activity in both hemolysis and cholesterol-binding. The reverse mutation, inserted into rLSO, also increased the hemolytic activity of this mutant LSO. These results suggested that the natural replacement of Ala to Phe is involved in the weak cytolytic activity of LSO.

Listeriolysin O, a cytolysin derived from Listeria monocytogenes, inhibits generation of ovalbumin-specific Th2 immune response by skewing maturation of antigen-specific T cells into Th1 cells.

Listeriolysin O (LLO), a cholesterol-dependent cytolysin derived from Listeria monocytogenes, is a potent inducer of interleukin (IL)-12, IL-18 and interferon (IFN)-gamma. We have shown that LLO facilitates development of T cells mediating protective immunity against L. monocytogenes through the induction of IFN-gamma production at an early stage. Based on this finding, it is postulated that LLO inhibits differentiation of Th2 cells and the Th2 immune response. By using a murine model of ovalbumin (OVA)-induced allergic rhinitis, we investigated whether LLO has an ability to modulate the Th2-type immune disorder. In mice sensitized intraperitoneally with ovalbumin (OVA)/alum and challenged intranasally with OVA, a large number of eosinophils migrated into the nasal tissue, and high titres of anti-OVA IgE and IgG(1) antibodies were detected in sera. However, LLO treatment during sensitization markedly inhibited the eosinophil infiltration and production of these anti-OVA antibodies. A large number of T cells from mice sensitized and challenged with OVA produced high level of IL-4 and IL-5 but not IFN-gamma after stimulation with OVA. In contrast, OVA-specific IFN-gamma-producing T cells were preferentially induced in mice treated with LLO at the time of sensitization. In the absence of LLO administration, the expression level of GATA-3 and SOCS-3 in CD4(+) T cells was enhanced after sensitization with OVA. LLO treatment resulted in a reduction of GATA-3 and SOCS-3 expressions but induced the transcription of T-bet instead. Taken together, these data show clearly that LLO is capable of inhibiting Th2 immune response by skewing differentiation of antigen-specific T cells into Th1 cells.

Effect of verapamil on the calcium and magnesium transports of rat kidney cortex mitochondria.

The effect of verapamil on Ca2+ and Mg2+ accumulation was investigated in isolated rat kidney cortex mitochondria. For the 50% inhibition of Ca2+ accumulation, 2 x 10(-4) M verapamil concentration was required in the presence of ATP (2 mM) and phosphate (5 mM). Omission of phosphate from the medium increased the inhibitory effect of verapamil on Ca2+ accumulation. Verapamil had no effect on Ca2+ accumulation in the presence of both ATP and succinate (7.8 mM), but further addition of phosphate resulted in a significant inhibition of Ca2+ accumulation by verapamil. Mg2+ accumulation of mitochondria was similarly depressed by verapamil. The same tendency was found as for the modification of verapamil effect by acetate in mitochondrial Ca2+ and Mg2+ accumulation. Succinate oxidation of mitochondria was not affected by verapamil in the absence of phosphate, but was inhibited by verapamil in the presence of phosphate. Therefore, it seemed reasonable to assume that the depression of Ca2+ and Mg2+ transport of mitochondria by verapamil is modulated by permeant anions.

[Effect of 1 alpha-hydroxycholecalciferol on cellular calcium metabolism of kidney cortex (author's transl)].

Rats were provided a normal laboratory diet or a low Ca.vitamin D-deficient diet. After the administration of 1 alpha-hydroxycholecalciferol, mitochondria, microsomes and slices were prepared from kidney cortex of both control and treated rats. When 1 alpha-hydroxycholecalciferol was given to normal and low Ca.vitamin D-deficient rats, Ca accumulation in mitochondria was stimulated during 30 minutes and the high calcium content was maintained at the subsequent incubation. There was a significant decrease of mitochondrial Ca2+-ATPase and Mg2+-ATPase activities with low Ca.vitamin D depletion, but both enzyme activities were restored by 1 alpha-hydroxycholecalciferol treatment of the depleted rats. Ca2+-ATPase and Mg2+-ATPase activities of microsomes were not altered with the administration of 1 alha-hydroxycholecalciferol. In contrast to results of mitochondrial Ca transport, changes in Ca influx and efflux of slices were not significant in response to the treatment of low Ca.vitamin D-deficient rats with 1 alpha-hydroxycholecalciferol. The results of the present study suggest that 1 alpha-hydroxycholecalciferol plays a role in the process of Ca accumulation and ATP hydrolysis of mitochondria in kidney cortex.

Cloning of cDNAs and the molecular evolution of a bovine MHC class II DRA gene.

Two overlapping cDNA clones coding for bovine major histocompatibility complex (MHC) class II antigen DRA chain were isolated and characterized. The full-length cDNA clone, MR1, encoded a primary translated product of 253 amino acids, 24 of which were deduced to be a signal peptide and 229 which formed a mature polypeptide. The amino acid sequences deduced from this clone resembled those of class II A molecules from other species in both size and structure, but no potential consensus site of N-linked glycosylation comparable to those in the human, mouse, rat and swine proteins was found in the alpha 2 domain, as well as ovine and equine DRA molecules. Comparison of amino acid sequences encoded by class II A genes among several species and a dendrogram constructed from these data places the DRA gene and the DQA/DYA genes on two distinct branches of a phylogenetic tree, with bovine DRA and ovine DRA being most similar on the DRA branch.

Essential role of domain 4 of pneumolysin from Streptococcus pneumoniae in cytolytic activity as determined by truncated proteins.

Pneumolysin (PLY), an important virulence factor of Streptococcus pneumoniae, is one of the members of thiol-activated cytolysins (TACYs) consisting of four domains. TACYs commonly bind to membrane cholesterol and oligomerize to form transmembrane pore. We have constructed full-length and various truncated PLYs to study the role of domains of PLY in the cytolytic activity. Full-length PLY had binding ability to both cell membrane and immobilized cholesterol. A truncated PLY which comprised only domain 4 molecule, the C-terminal domain of PLY, sustained the binding ability to cell membrane and cholesterol, whereas domain 1-3 molecule had no binding ability to them. Furthermore, the domain 4 molecule inhibited both the membrane binding and the hemolytic activity of full-length PLY. Accordingly, the present results provided the direct evidence that domain 4 was essential for the initial binding to membrane cholesterol and the interaction led to the subsequent membrane damage process.

Nucleotide sequence and the molecular evolution of a new A2 gene in the DQ subregion of the bovine major histocompatibility complex.

cDNA clones encoding the bovine major histocompatibility complex (MHC) class II DQ alpha chain were isolated. One clone, MQ9, encoded a primary translated product of 255 amino acids, with a signal peptide of 23 amino acids and a mature polypeptide of 232 amino acids. A new A2 gene in the DQ subregion of the bovine genome was identified from a comparison of amino acid sequences encoded by class II A genes among several species and the construction of a phylogenetic tree. It was revealed that MQ9 is most closely related to the ovine DQA2 genes among sequences from various mammalian species. By contrast, the BoLA-DQA genes previously isolated are more closely related to ovine DQA1 than to the BoLA-DQA2 gene, and they represent BoLA-DQA1 genes. Thus, the presence of two BoLA A genes, which may be expressed and functional in the bovine, as well as in sheep was confirmed. A large number of amino acids unique to products of DQA2 genes of bovine and ovine origin were identified when the predicted amino acid sequences for both species were compared, and most of the DQA2-specific residues were located in the alpha 1 domain and were conserved with respect to products of DQA1 genes of ruminants. Thus, several characteristics of the bovine DQA genes were found to differ from those of human and rodent genes, despite similarities in gene structure and in nucleotide sequence.