2'-5'-Oligoadenylate synthetase-like protein inhibits intracellular M. tuberculosis replication and promotes proinflammatory cytokine secretion

Host cytoplasmic surveillance pathways are known to elicit type I interferon (IFN) responses which are crucial to antimicrobial defense mechanisms. Oligoadenylate synthetase-like (OASL) protein has been extensively characterized as a part of the anti-viral mechanism, however a number of transcriptomic studies reveal its upregulation in response to infection with a wide variety of intracellular bacterial pathogens. To date, there is no evidence documenting the role (if any) of OASL during mycobacterium tuberculosis infection. Using two pathogenic strains differing in virulence only, as well as the non-pathogenic M. bovis BCG strain, we observed that pathogenicity and virulence strongly induced OASL expression after 24 h of infection. Further, we observed that OASL knock down led to a significant increase in M. tb CFU counts 96 h post-infection in comparison to the respective controls. Luminex revealed that OASL silencing significantly decreased IL-1β, TNF-α and MCP-1 secretion in THP-1 cells and had no effect on IL-10 secretion. We therefore postulate that OASL regulates pro-inflammatory mediators such as cytokines and chemokines which suppress intracellular mycobacterial growth and survival.

Role of biocontrol yeasts Debaryomyces hansenii and Wickerhamomyces anomalus in plants' defence mechanisms against Monilinia fructicola in apple fruits

The role of killer yeasts of the species Debaryomyces hansenii and Wickerhamomyces anomalus in biocontrol of Monilinia fructicola, and their involvement in plant defence mechanisms against brown rot in apple fruits, were investigated. D. hansenii KI2a and W. anomalus BS91 strains showed the highest in vitro biocontrol activity, inhibiting mycelium growth by 69.53% and 66.08% respectively, as compared to control fungal cultures. Brown rot on apple fruits was significantly reduced by BS91 and two strains of D. hansenii KI2a and AII4b by 92.46%, 85.10% and 70.02%, respectively, in comparison to infected fruits, which did not receive any pre-treatment. In enzymatic tests, the most significant changes in peroxidase (POD) and catalase (CAT) activities were observed in fruits inoculated either with BS91 followed by M. fructicola infection or with AII4b yeast strain alone, where POD activities were significantly higher by 67% and 54%, respectively, and CAT activities were significantly lower by 65% and 68%, respectively, than in untreated control fruits. These results confirmed the ability of killer yeasts to influence host-defence related enzyme activities in apple fruit tissue and may suggest that AII4b killer strain has a potential as biocontrol agent prior to infection by triggering immune response mechanisms in plant tissue, whereas BS91 strain is the most effective during pathogen infection and could be used as biocontrol agent in postharvest disease onset. Accordingly, the antagonistic strains of W. anomalus BS91 and D. hansenii KI2a and AII4b could be proposed as active ingredients for the development of biofungicide against M. fructicola.

OAS1, OAS2 and OAS3 restrict intracellular M. tb replication and enhance cytokine secretion

The 2',5' (OASs) are known as mediators of the antiviral response system through activation of the RNA cleavage pathway. Interestingly, we observe OAS1, OAS2 and OAS3 upregulation in a number of gene expression signatures which discriminate active TB from latent TB infection, however their biological role during bacterial infection has not yet been elucidated. We observed that the expression of these genes was associated with pathogenicity and virulence of mycobacteria as infection with Mycobacterium bovis BCG failed to significantly induce OAS expression. Further, we observed that after silencing of these genes, M. tb CFU counts increased significantly 96h post-infection in comparison to the respective controls. Luminex revealed that OAS silencing significantly decreased IL-1β, TNF-α and MCP-1 and had no effect of IL-10 secretion. We show for the first time that OAS1, 2 and 3 restrict intracellular pathogenic mycobacterial replication and enhance pro-inflammatory cytokine secretion.

Impaired intracellular signaling, myeloperoxidase release and bactericidal activity of neutrophils from patients with alcoholic cirrhosis

BACKGROUND & AIMS

Myeloperoxidase exocytosis and production of hydrogen peroxide via the neutrophil superoxide-generating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase contribute to efficient elimination of bacteria. Cirrhosis impairs immune functions and increases susceptibility to bacterial infection. We recently showed that neutrophils from patients with decompensated alcoholic cirrhosis exhibit a severe impairment of formylpeptide receptor (fPR)-mediated intracellular signaling and superoxide production. Here, we performed ex vivo studies with these patients' neutrophils to further investigate myeloperoxidase release, bactericidal capacity and signaling events following fPR stimulation by the formylpeptide formyl-met-leu-phe (fMLP).

METHODS

Myeloperoxidase release was studied by measuring extracellular myeloperoxidase activity. Activation of signaling effectors was studied by Western blot and their respective contribution to myeloperoxidase release studied using pharmacological antagonists.

RESULTS

fMLP-induced myeloperoxidase release was strongly impaired in patients' neutrophils whereas the intracellular myeloperoxidase stock was unaltered. The fMLP-induced phosphorylation of major signaling effectors, AKT, ERK1/2 and p38-MAP-Kinases, was also strongly deficient despite a similar expression of signaling effectors or fPR. However, based on effector inhibition in healthy neutrophils, AKT and p38-MAPK but not ERK1/2 upregulated fMLP-induced myeloperoxidase exocytosis. Interestingly, patients' neutrophils exhibited a defective bactericidal capacity that was reversed ex vivo by the TLR7/8 agonist CL097, through potentiation of the fMLP-induced AKT/p38-MAPK signaling axis and myeloperoxidase release.

CONCLUSIONS

We provide first evidence that neutrophils from patients with decompensated alcoholic cirrhosis exhibit a deficient AKT/p38-MAPK signaling, myeloperoxidase release and bactericidal activity, which can be reversed via TLR7/8 activation. These defects, together with the previously described severe deficient superoxide production, may increase cirrhotic patients' susceptibility to bacterial infections.

The diversity and evolution of anuran skin peptides

Amphibians exhibit various, characteristic adaptations related to their "incomplete" shift from the aquatic to the terrestrial habitat. In particular, the integument was subject to a number of specialized modifications during the evolution of these animals. In this review, we place special emphasis on endogenous host-defence skin peptides from the cuteanous granular glands anuran amphibians (frogs and toads). The overview on the two broad groups of neuroactive and antimicrobial peptides (AMPs) goes beyond a simple itemization in that we provide a new perspective into the evolution and function of anuran AMPs. Briefly, these cationic, amphipathic and α-helical peptides are traditionally viewed as being part of the innate immune system, protecting the moist skin against invading microorganisms through their cytolytic action. However, the complete record of anuran species investigated to date suggests that AMPs are distributed sporadically (i.e., non-universally) across Anura. Together with the intriguing observation that virtually all anurans known to produce neuropeptides in their granular glands also co-secrete cytolytic peptides, we call the traditional role for AMPs as being purely antimicrobial into question and present an alternative scenario. We hypothesize AMPs to assist neuroactive peptides in their antipredator role through their cytolytic action increasing the delivery of the latter to the endocrine and nervous system of the predator. Thus, AMPs are more accurately viewed as cytolysins and their contribution to the immune system is better regarded as an accessory benefit.