New treatment strategies for malignant gliomas are indispensible, due to the poor prognosis for patients. Fluorescence diagnosis (FD) and photodynamic therapy (PDT) are currently under intensive investigation and seem to improve the prognosis. Especially for deep seated malignant brain lesions and in order to optimize therapy new diagnostic tools are needed.
Scanning mutagenesis is a powerful protein engineering technique used to study protein structure-function relationship, map binding sites and design more stable proteins or proteins with altered properties. One of the time-consuming tasks encountered in application of this technique is the design of primers for site-directed mutagenesis. Here we present an open-source multi-platform software AAscan developed to design primers for this task according to a set of empirical rules such as melting temperature, overall length, length of overlap regions, and presence of GC clamps at the 3 end, for any desired substitution. We also describe additional software tools which are used to analyse a large number of sequencing results for the presence of desired mutations, as well as related software to design primers for ligation independent cloning. We have used AAscan software to design primers to make over 700 mutants, with a success rate of over 80%. We hope that the open-source nature of our software and ready availability of freeware tools used for its development will facilitate its adaptation and further development. The software is distributed under GPLv3 licence and is available at http://www.psi.ch/lbr/aascan.
Malignant gliomas are diffuse infiltrative growing tumors with a poor prognosis despite treatment with a combination of surgery, radiotherapy and chemotherapy. It has been shown recently that complete tumor resection improves the survival time significantly. Hypericin, a component of St. Johns Wort, is one of the most powerful photosensitizers in nature. The aim of the present study was to investigate accumulation of hypericin in intracerebral implanted malignant glioma in vivo. Rats underwent stereotactic implantation of C6 glioma cells. After intravenous administration of hypericin (5 mg per kg body weight), accumulation of the compound was studied in tumor, the infiltration zone surrounding the tumor and healthy brain (contralateral hemisphere) by fluorescence microscopy between 0 and 48 h after injection. Results were compared by one-way analysis of variance. For post hoc pair-wise comparison the Tukey-Kramer HSD test was used. Accumulation of hypericin was significantly higher in C6 glioma as compared to normal tissue. Maximum hypericin uptake was achieved at 24 h after injection. Ratios of fluorescence intensity between tumor and normal tissue as well as infiltration zone and normal tissue of about 6.1:1 and 1.4:1 were found. Considering tissue auto-fluorescence, fluorescence ratios of about 19.8:1 and 2.5:1 were calculated, respectively. Therefore, hypericin seems to be quite an effective fluorescence marker for the detection of glioma in vivo. To the best of our knowledge, the present study demonstrates for the first time that hypericin accumulates selectively in intracerebral implanted C6 glioma in vivo after systemic (intravenous) administration.
Despite their close phylogenetic relationship, natural intertypic reassortants between influenza A (FluA) and B (FluB) viruses have not been described. Inefficient polymerase assembly of the three polymerase subunits may contribute to this incompatibility, especially because the known protein-protein interaction domains, including the PA-binding domain of PB1, are highly conserved for each virus type. Here we show that substitution of the FluA PA-binding domain (PB1-A(1-25)) with that of FluB (PB1-B(1-25)) is accompanied by reduced polymerase activity and viral growth of FluA. Consistent with these findings, surface plasmon resonance spectroscopy measurements revealed that PA of FluA exhibits impaired affinity to biotinylated PB1-B(1-25) peptides. PA of FluB showed no detectable affinity to biotinylated PB1-A(1-25) peptides. Consequently, FluB PB1 harboring the PA-binding domain of FluA (PB1-AB) failed to assemble with PA and PB2 into an active polymerase complex. To regain functionality, we used a single amino acid substitution (T6Y) known to confer binding to PA of both virus types, which restored polymerase complex formation but surprisingly not polymerase activity for FluB. Taken together, our results demonstrate that the conserved virus type-specific PA-binding domains differ in their affinity to PA and thus might contribute to intertypic exclusion of reassortants between FluA and FluB viruses.
Virus-infected cells secrete a broad range of interferons (IFN) which confer resistance to yet uninfected cells by triggering the synthesis of antiviral factors. The relative contributions of the various IFN subtypes to innate immunity against virus infections remain elusive. IFN-alpha, IFN-beta, and other type I IFN molecules signal through a common, universally expressed cell surface receptor, whereas type III IFN (IFN-lambda) uses a distinct cell-type-specific receptor complex for signaling. Using mice lacking functional receptors for type I IFN, type III IFN, or both, we found that IFN-lambda plays an important role in the defense against several human pathogens that infect the respiratory tract, such as influenza A virus, influenza B virus, respiratory syncytial virus, human metapneumovirus, and severe acute respiratory syndrome (SARS) coronavirus. These viruses were more pathogenic and replicated to higher titers in the lungs of mice lacking both IFN receptors than in mice with single IFN receptor defects. In contrast, Lassa fever virus, which infects via the respiratory tract but primarily replicates in the liver, was not influenced by the IFN-lambda receptor defect. Careful analysis revealed that expression of functional IFN-lambda receptor complexes in the lung and intestinal tract is restricted to epithelial cells and a few other, undefined cell types. Interestingly, we found that SARS coronavirus was present in feces from infected mice lacking receptors for both type I and type III IFN but not in those from mice lacking single receptors, supporting the view that IFN-lambda contributes to the control of viral infections in epithelial cells of both respiratory and gastrointestinal tracts.
There is an urgent need for new drugs against influenza type A and B viruses due to incomplete protection by vaccines and the emergence of resistance to current antivirals. The influenza virus polymerase complex, consisting of the PB1, PB2 and PA subunits, represents a promising target for the development of new drugs. We have previously demonstrated the feasibility of targeting the protein-protein interaction domain between the PB1 and PA subunits of the polymerase complex of influenza A virus using a small peptide derived from the PA-binding domain of PB1. However, this influenza A virus-derived peptide did not affect influenza B virus polymerase activity. Here we report that the PA-binding domain of the polymerase subunit PB1 of influenza A and B viruses is highly conserved and that mutual amino acid exchange shows that they cannot be functionally exchanged with each other. Based on phylogenetic analysis and a novel biochemical ELISA-based screening approach, we were able to identify an influenza A-derived peptide with a single influenza B-specific amino acid substitution which efficiently binds to PA of both virus types. This dual-binding peptide blocked the viral polymerase activity and growth of both virus types. Our findings provide proof of principle that protein-protein interaction inhibitors can be generated against influenza A and B viruses. Furthermore, this dual-binding peptide, combined with our novel screening method, is a promising platform to identify new antiviral lead compounds.
Gene expression of nonsegmented negative-strand RNA viruses is regulated at the transcriptional level and relies on the canonical 5-end-dependent translation of capped viral mRNAs. Here, we have used internal ribosome entry sites (IRES) from picornaviruses to control the expression level of the phosphoprotein P of the neurotropic rabies virus (RV; Rhabdoviridae), which is critically required for both viral replication and escape from the host interferon response. In a dual luciferase reporter RV, the IRES elements of poliovirus (PV) and human rhinovirus type 2 (HRV2) were active in a variety of cell lines from different host species. While a generally lower activity of the HRV2 IRES was apparent compared to the PV IRES, specific deficits of the HRV2 IRES in neuronal cell lines were not observed. Recombinant RVs expressing P exclusively from a bicistronic nucleoprotein (N)-IRES-P mRNA showed IRES-specific reduction of replication in cell culture and in neurons of organotypic brain slice cultures, an increased activation of the beta interferon (IFN-beta) promoter, and increased sensitivity to IFN. Intracerebral infection revealed a complete loss of virulence of both PV- and HRV2 IRES-controlled RV for wild-type mice and for transgenic mice lacking a functional IFN-alpha receptor (IFNAR(-/-)). The virulence of HRV2 IRES-controlled RV was most severely attenuated and could be demonstrated only in newborn IFNAR(-/-) mice. Translational control of individual genes is a promising strategy to attenuate replication and virulence of live nonsegmented negative-strand RNA viruses and vectors and to study the function of IRES elements in detail.
Low oxygen tension is a metabolic hallmark of chronic infection. To investigate the influence of hypoxia on macrophage biology, we analyzed the interaction between the intracellular pathogen Mycobacterium tuberculosis and primary human macrophages. Although the metabolic activity of extracellular M. tuberculosis was reduced at oxygen levels between 0.5 and 10%, the bacilli remained viable throughout the 4 d of culture. Phagocytosis of virulent M. tuberculosis and the pathogen-induced release of inflammatory cytokines by macrophages were not affected by oxygen levels as low as 1%. However, we detected the upregulation of an antimicrobial effector pathway mediated by the vitamin D receptor and human ? defensin 2. This finding was functionally relevant, because intracellular mycobacterial growth was inhibited by 58 ± 8% at 1% O(2). We conclude that a hypoxic microenvironment, which is characteristic of infected tissue, supports the efficacy of antimicrobial immunity, in part by the upregulation of the antimicrobial peptide human ? defensin 2.
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