The ability of poliovirus to propagate in neuronal cells can be reduced by introducing appropriate nucleotide substitutions into the viral genome. Specific mutations scattered throughout the poliovirus genome yielded the live attenuated vaccine strains of poliovirus. Neuron-specific propagation deficits of the Sabin strains are partially encrypted within a confined region of the internal ribosomal entry site (IRES), which carries attenuating point mutations in all three serotypes. Recently, high levels of neurovirulence attenuation were achieved with genetically engineered polioviruses containing heterologous IRES elements. This is exemplified with poliovirus recombinants replicating under control of a human rhinovirus type 2 (HRV2) IRES element. We have carried out experiments delineating the genetic basis for neuronal IRES function. Neuronal dysfunction of the HRV2 IRES is determined mainly by IRES stem-loop domain V, the locus for attenuating point mutations within the Sabin strains. Neuronal incompetence associated with HRV2 IRES domain V is substantially more pronounced than that observed with the attenuating IRES point mutation of the Sabin serotype 1 vaccine strain. Mix-and-match recombination of polio and HRV2 IRES domain V suggests that the attenuation phenotype correlates with overall structural features rather than primary sequence. Our experiments have identified HEK 293 cells as a novel system for the study of neuron-specific replication phenotypes of poliovirus. This cell line, originally derived from embryonic human kidney, has recently been described to display neuronal characteristics. We report propagation properties in HEK 293 cells for poliovirus recombinants with attenuated neurovirulence in experimental animals that corroborate this observation.Poliovirus (PV), a positive-strand RNA virus of approximately 7,500 nucleotides (nt), is the prototypic member of the genus Enterovirus in the family Picornaviridae. PV is the causative agent of poliomyelitis, a paralytic condition complicating ϳ1% of all PV infections. The incidence of poliomyelitis has been drastically reduced since the introduction of two effective vaccines-the live attenuated (Sabin) strains and the formalininactivated (Salk) vaccine. Serial passage of wild-type (wt) PV in various culture systems yielded the serotype 1 and 3 Sabin strains, while serotype 2 is a naturally occurring variant with inherently reduced neurovirulence (48).It is generally assumed that the excellent safety record of the Sabin strains (the rate of vaccine-associated paralytic poliomyelitis [VAPP] is estimated at 0.14 per 1,000,000 doses) (60) is a direct reflection of tissue type-specific deficiencies that affect their propagation in the human central nervous system (CNS). Nevertheless, despite over 40 years of successful application, the molecular basis for neuroattenuation of the Sabin strains is not completely understood (16).Elucidation of the genomic sequences of PV type 1 (Sabin) [PV1(S)] (38) and PV3(S) (53, 58) and comparison to their wt progenitor...

Purpose: The toxicity and antitumor activity of regional intrathecal delivery of an oncolytic recombinant poliovirus, PVS-RIPO, was evaluated in rodent models of glioblastoma multiforme neoplastic meningitis. Experimental Design: To evaluate for toxicity, PVS-RIPO was administered into the spinal cord of transgenic mice that express the human poliovirus receptor, CD155, and into the intrathecal space of athymic rats without tumor. To evaluate efficacy, two different doses of PVS-RIPO were administered intrathecally 3 days after athymic rats were inoculated intrathecally with an aggressive human glioblastoma multiforme xenograft. Results: No clinical or histologic evidence of toxicity was found. In efficacy studies, median survival was increased by 174.47% from 8.5 days in the group treated with UV light-inactivated virus to 15 days in the rats treated with 1.0 Â 10 7 plaque-forming units (pfu) of PVS-RIPO (P < 0.0001).A similar increase in median survival was seen in the group receiving 1.0 Â 10 9 pfu PVS-RIPO (P < 0.0001); however, there was no statistically significant dose-response relationship (P = 0.345). In addition, 1 of 10 rats in lower-dose PVS-RIPO^treated group and 3 of 10 rats in higher-dose PVS-RIPO^treated group survived >60 days after tumor cell inoculation and had no evidence of residual tumor at autopsy. Conclusion: These results suggest that intrathecal treatment with PVS-RIPO may be useful for treatment of neoplastic meningitis in patients with glioblastoma multiforme and provides a rationale for clinical trials in this area.

Background:The mechanism whereby CCT is auto-inhibited by its membrane-induced amphipathic helix (m-AH) is unknown. Results: m-AH regions sharing an amphipathic 22-mer element can be interchanged between CCTs with retention of catalytic silencing and activation by lipids. Conclusion:The 22-mer element is the principal auto-inhibitory motif. Significance: Multi-tasking and conformationally malleable motifs are widely used to regulate protein function; the CCT m-AH is a novel example of this.

Macrophages are the primary lung phagocyte and are instrumental in maintenance of a sterile, noninflamed microenvironment. IFNs are produced in response to bacterial and viral infection, and activate the macrophage to efficiently counteract and remove pathogenic invaders. Respiratory syncytial virus (RSV) inhibits IFN-mediated signaling mechanisms in epithelial cells; however, the effects on IFN signaling in the macrophage are currently unknown. We investigated the effect of RSV infection on IFN-mediated signaling in macrophages. RSV infection inhibited IFN-b-and IFN-g-activated transcriptional mechanisms in primary alveolar macrophages and macrophage cell lines, including the transactivation of important Nod-like receptor family genes, Nod1 and class II transactivator. RSV inhibited IFN-b-and IFN-g-mediated transcriptional activation by two distinct mechanisms. RSV impaired IFN-b-mediated signal transducer and activator of transcription (STAT)-1 phosphorylation through a mechanism that involves inhibition of tyrosine kinase 2 phosphorylation. In contrast, RSV-impaired transcriptional activation after IFN-g stimulation resulted from a reduction in the nuclear STAT1 interaction with the transcriptional coactivator, CBP, and was correlated with increased phosphorylation of STAT1b, a dominantnegative STAT1 splice variant, in response to IFN-g. In support of this concept, overexpression of STAT1b was sufficient to repress the IFNg-mediated expression of class II transactivator. These results demonstrate that RSV inhibits IFN-mediated transcriptional activation in macrophages, and suggests that paramyxoviruses modulate an important regulatory mechanism that is critical in linking innate and adaptive immune mechanisms after infection. Keywords: macrophages; IFN; signal transduction; transcriptional activationRespiratory syncytial virus (RSV) is an important causative agent of severe respiratory tract infections in pediatric, immunocompromised, and elderly populations (1-5). RSV infection elicits a poor adaptive immune response; therefore, infections occur repeatedly throughout life (6, 7). This common paramyxovirus has also been associated with secondary bacterial infections of the lung (3, 8-10); however, as with other viralinduced secondary bacterial infections, the underlying mechanisms are not well understood.IFN-a and IFN-b (type I) and IFN-g (type II) are produced in the lung in response to microbial infection, and are potent activators of macrophage innate antimicrobial immunity; they also induce pathways that promote efficient antigen processing and presentation to cells of the adaptive immune system (11, 12). The requirement of IFN for the efficient clearance of pathogens is evident in IFN-b 2/2 , IFN-g 2/2 , IFN-a receptor 2/2 , and IFN-g receptor 2/2 mice, as these mice, lacking IFN signaling, display severe impairment in natural resistance to a variety of viral, bacterial, and parasitic infections (13-20). IFN-a or IFN-b ligation of the IFN-a/b receptor results in the phosphorylation and activation of the ...

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Appropriate regulation of genes that coordinate pancreas progenitor proliferation and differentiation is required for pancreas development. Here, we explore the role of H3K4 methylation and the Trithorax group (TrxG) complexes in mediating gene expression during pancreas development. Disruption of TrxG complex assembly, but not catalytic activity, prevented endocrine cell differentiation in pancreas progenitor spheroids. In vivo loss of TrxG catalytic activity in PDX1 + cells increased apoptosis and the fraction of progenitors in the G1 phase of the cell cycle. Pancreas progenitors were reallocated to the acinar lineage, primarily at the expense of NEUROG3 + endocrine progenitors. Later in development, acinar and endocrine cell numbers were decreased, and increased gene expression variance and reduced terminal marker activation in acinar cells led to their incomplete differentiation. These findings demonstrate that TrxG co-activator activity is required for gene induction, whereas TrxG catalytic activity and H3K4 methylation help maintain transcriptional stability.

Liver development is controlled by key signals and transcription factors that drive cell proliferation, migration, differentiation and functional maturation. In the adult liver, cell maturity can be perturbed by genetic and environmental factors that disrupt hepatic identity and function. Developmental signals and fetal genetic programmes are often dysregulated or reactivated, leading to dedifferentiation and disease. Here, we highlight signalling pathways and transcriptional regulators that drive liver cell development and primary liver cancers. We also discuss emerging models derived from pluripotent stem cells, 3D organoids and bioengineering for improved studies of signalling pathways in liver cancer and regenerative medicine.

After being recognized for their anti-neoplastic properties at the beginning of the last century, viruses are again being considered for use as therapeutic agents against cancer. Certain virus species have a propensity to replicate within transformed cells, which are commonly rendered vulnerable due to tumor-specific defects in their defense against viral infection. Other viruses have been modified to subject them to tumor-specific growth conditions. Oncolytic viruses carry the promise to efficiently target cancer cells for destruction and spread throughout tumor tissue to reach distant neoplastic loci without causing collateral damage to healthy tissues. In contrast to conventional cancer chemotherapy, viral anti-neoplastic agents require complex interactions with the host organism to reach their target and to unfold their oncolytic activity. Recent progress in the elucidation of the molecular mechanisms of viral pathogenesis has opened up new opportunities to manipulate virus-host interactions, generating effective anti-tumor strategies. On the other hand, significant obstacles towards the application of safe and efficacious viral therapies have become apparent. These frequently relate to the lack of cell culture and animal tumor models that accurately reflect the characteristics of cancerous tissues in patients. Throughout the past century, viral therapeutics against cancer have evolved into a new class of treatment strategies characterized by unique opportunities and challenges. A growing number of oncolytic viruses has entered clinical investigation or is scheduled to do so in the near future. Great efforts are being undertaken to rekindle an old idea and, with the help of new technologies, to realize its promise of new treatment facilities for cancer.