Search

Glucocorticoids are extensively used to treat inflammatory diseases; however, their chronic intake increases the risk for mycobacterial infections. Meanwhile, the effects of glucocorticoids on innate host responses are incompletely understood. In this study, we investigated the direct effects of glucocorticoids on antimycobacterial host defense in primary human macrophages. We found that glucocorticoids triggered the expression of cathelicidin, an antimicrobial critical for antimycobacterial responses, independent of the intracellular vitamin D metabolism. Despite upregulating cathelicidin, glucocorticoids failed to promote macrophage antimycobacterial activity. Gene expression profiles of human macrophages treated with glucocorticoids and/or IFN-γ, which promotes induction of cathelicidin, as well as antimycobacterial activity, were investigated. Using weighted gene coexpression network analysis, we identified a module of highly connected genes that was strongly inversely correlated with glucocorticoid treatment and associated with IFN-γ stimulation. This module was linked to the biological functions autophagy, phagosome maturation, and lytic vacuole/lysosome, and contained the vacuolar H(+)-ATPase subunit a3, alias TCIRG1, a known antimycobacterial host defense gene, as a top hub gene. We next found that glucocorticoids, in contrast with IFN-γ, failed to trigger expression and phagolysosome recruitment of TCIRG1, as well as to promote lysosome acidification. Finally, we demonstrated that the tyrosine kinase inhibitor imatinib induces lysosome acidification and antimicrobial activity in glucocorticoid-treated macrophages without reversing the anti-inflammatory effects of glucocorticoids. Taken together, we provide evidence that the induction of cathelicidin by glucocorticoids is not sufficient for macrophage antimicrobial activity, and identify the vacuolar H(+)-ATPase as a potential target for host-directed therapy in the context of glucocorticoid therapy.

Mycobacteriophage L5 is a temperate phage with a broad host range among the fast- and slow-growing mycobacteria such as Mycobacterium smegmatis, Mycobacterium tuberculosis, Mycobacterium avium and Mycobacterium ulcerans. L5 switches off host protein synthesis during the early stage of lytic growth, as was previously shown by protein expression profiling. Also, lethal genetic elements have been identified in L5 based on the fact that transformants could not be obtained with these genes. Using an inducible mycobacterial shuttle vector, we have identified three ORFs within an early operon of mycobacteriophage L5 which encode gene products (gp) toxic to the host M. smegmatis when expressed. These ORFs, coding for gp77, gp78 and gp79, presumably function as shut-off genes during early stages of phage replication. There is evidence that cell division is affected by one of the proteins (gp79). The transcription of the cytotoxic polypeptides is directed by a promoter situated in ORF83 and transcription control is achieved through the phage repressor gp71, which is shown by co-expression of this protein. The findings presented here should provide useful tools for the molecular genetics of mycobacteria. Further analysis of these and other mycobacteriophage-derived toxic polypeptides, together with the identification of their cellular targets, might provide a tool for the rapid identification of promising drug targets in emerging and re-emerging mycobacterial pathogens.

Background Viruses can evade immune surveillance, but the underlying mechanisms are insufficiently understood. Here, we sought to understand the mechanisms by which natural killer (NK) cells recognize HIV-1-infected cells and how this virus can evade NK-cell-mediated immune pressure. Methods and Findings Two sequence mutations in p24 Gag associated with the presence of specific KIR/HLA combined genotypes were identified in HIV-1 clade C viruses from a large cohort of infected, untreated individuals in South Africa (n = 392), suggesting viral escape from KIR+ NK cells through sequence variations within HLA class I--presented epitopes. One sequence polymorphism at position 303 of p24 Gag ([T.sub.[Gag.sub.303]V]), selected for in infected individuals with both KIR2DL3 and [HLA-C.sup.*] 03:04, enabled significantly better binding of the inhibitory KIR2DL3 receptor to [HLA-C.sup.*] 03:04-expressing cells presenting this variant epitope compared to the wild-type epitope (wild-type mean 18.01 ± 10.45 standard deviation [SD] and variant mean 44.67 ± 14.42 SD, p = 0.002). Furthermore, activation of primary KIR2DL3+ NK cells from healthy donors in response to [HLA-C.sup.*] 03:04+ target cells presenting the variant epitope was significantly reduced in comparison to cells presenting the wild-type sequence (wild-type mean 0.78 [+ or -] 0.07 standard error of the mean [SEM] and variant mean 0.63 ± 0.07 SEM, p = 0.012). Structural modeling and surface plasmon resonance of KIR/ peptide/HLA interactions in the context of the different viral sequence variants studied supported these results. Future studies will be needed to assess processing and antigen presentation of the investigated HIV-1 epitope in natural infection, and the consequences for viral control. Conclusions These data provide novel insights into how viruses can evade NK cell immunity through the selection of mutations in HLA-presented epitopes that enhance binding to inhibitory NKcell receptors. Better understanding of the mechanisms by which HIV-1 evades NK-cell-mediated immune pressure and the functional validation of a structural modeling approach will facilitate the development of novel targeted immune interventions to harness the antiviral activities of NK cells., Introduction Natural killer (NK) cells are an important component of the antiviral innate immune response. They have the ability to lyse target cells without prior antigen sensitization and to regulate [...]

Purpose: The Choosing Wisely® initiative is an international campaign addressing over- and underuse of diagnostic and therapeutic measures in infectious diseases among others. Since 2016, the German Society for Infectious Diseases (DGI) has constantly designed new items in this regard. Here we report the most recent recommendations. Methods: The recommendations of the DGI are part of the "Klug entscheiden" initiative of the German Society of Internal Medicine (DGIM). Topics for the new items were suggested by members of the DGI, checked for scientific evidence and consented within the DGI and the DGIM before publication. Results: The new recommendations are: (1) individuals with immune-suppression, advanced liver cirrhosis or renal insufficiency should receive a dual pneumococcal vaccination. (2) In case of positive blood cultures with Candida spp. thorough diagnostics and treatment should be initiated. (3) In case of suspected meningitis, adult patients should receive dexamethasone and antibiotics immediately after venipuncture for blood cultures and before potential imaging. (4) In case of suspected meningitis a CT scan before lumbar puncture should not be ordered—except for symptoms indicating high CSF pressure or focal brain pathology or in cases of severe immune-suppression. (5) In patients with suspected severe infections, a minimum of two pairs of blood cultures should be drawn using separate venipunctures prior to antibiotic therapy—regardless of body temperature. There is no need of a minimum time interval in between the blood draws. Conclusion: Applying these new Choosing Wisely® recommendations will increase patient safety and the value of health care. [ABSTRACT FROM AUTHOR]

Capnocytophaga canimorsus is a Gram-negative bacterium present in the oral cavities of cats and dogs. It is known for its capability to cause life-threatening sepsis following a dog bite, especially in immunocompromised patients. We report the case of a 67-year-old man who suffered from septic shock and multiorgan failure presumably following contamination of a pre-existing minor skin lesion by canine saliva. The purpose of this report is to raise awareness of Capnocytophaga canimorsus among physicians when faced with a patient presenting with fulminant septic shock and Gram-negative bacteremia, who has been exposed to dogs. [ABSTRACT FROM AUTHOR]