Novel Viral Vectors for Gene Therapy.

Viral vectors are gene transfer tools assembled from the backbones of naturally occurring viruses [...].

Chikungunya Virus Infections in Military Deployments in Tropical Settings-A Narrative Minireview.

Chikungunya fever is a vector-borne viral disease in subtropical and tropical areas of endemicity. Apart from the burden on local populations, chikungunya virus infection also poses a risk for travelers and, in particular, soldiers during prolonged deployment-associated outdoor activities. The absence of rapid diagnostic tests makes surveillance challenging during military deployments in war and crisis zones with restricted medical infrastructure. Consequently, both historical and up-to-date surveillance data from battlefields are scarce. From several studies and postdeployment assessments, some information on the epidemiology of chikungunya virus infections in deployed military personnel is nevertheless available. The few published data homogeneously suggest a low infection risk in the endemic setting. During outbreaks, however, the infection risk of military personnel is comparable to that of the local population. Infection clusters of soldiers without pronounced outdoor activity have been reported under such circumstances as well. In spite of efforts focusing on the development of a chikungunya virus vaccine, no licensed product is available so far.

Twelfth International Foamy Virus Conference-Meeting Report.

The 12th International Foamy Virus Conference took place on August 30⁻31, 2018 at the Technische Universität Dresden, Dresden, Germany. The meeting included presentations on current research on non-human primate and non-primate foamy viruses (FVs; also called spumaretroviruses) as well as keynote talks on related research areas in retroviruses. The taxonomy of foamy viruses was updated earlier this year to create five new genera in the subfamily, Spumaretrovirinae, based on their animal hosts. Research on viruses from different genera was presented on topics of potential relevance to human health, such as natural infections and cross-species transmission, replication, and viral-host interactions in particular with the immune system, dual retrovirus infections, virus structure and biology, and viral vectors for gene therapy. This article provides an overview of the current state-of-the-field, summarizes the meeting highlights, and presents some important questions that need to be addressed in the future.

DNp73-induced degradation of tyrosinase links depigmentation with EMT-driven melanoma progression.

Melanoma is an aggressive cancer with poor prognosis, requiring personalized management of advanced stages and establishment of molecular markers. Melanomas derive from melanocytes, which specifically express tyrosinase, the rate-limiting enzyme of melanin-synthesis. We demonstrate that melanomas with high levels of DNp73, a cancer-specific variant of the p53 family member p73 and driver of melanoma progression show, in contrast to their less-aggressive low-DNp73 counterparts, hypopigmentation in vivo. Mechanistically, reduced melanin-synthesis is mediated by a DNp73-activated IGF1R/PI3K/AKT axis leading to tyrosinase ER-arrest and proteasomal degradation. Tyrosinase loss triggers reactivation of the EMT signaling cascade, a mesenchymal-like cell phenotype and increased invasiveness. DNp73-induced depigmentation, Slug increase and changes in cell motility are recapitulated in neural crest-derived melanophores of Xenopus embryos, underscoring a previously unnoticed physiological role of tyrosinase as EMT inhibitor. This data provides a mechanism of hypopigmentation accompanying cancer progression, which can be exploited in precision diagnosis of patients with melanoma-associated hypopigmentation (MAH), currently seen as a favorable prognostic factor. The DNp73/IGF1R/Slug signature in colorless lesions might aid to clinically discriminate between patients with MAH-associated metastatic disease and those, where MAH is indeed a sign of regression.

Diagnostics as Prevention - A Rapid Testing-Based Strategy of Sex Workers against Sexual HIV Exposure.

INTRODUCTION: German sex workers have illegally established a prevention strategy, which consists of testing potential sexual partners with human immunodeficiency virus (HIV)-specific rapid diagnostic tests (RDTs) prior to engaging in unprotected sexual intercourse eventually performed in case of a negative test result. Based on a recently established modeling approach, the effectiveness of this strategy regarding the risk of HIV exposure was compared with protection provided by condom use. METHODS: Based on a literature search, the following assumptions were used for the calculations: an averaged 80% exposure risk reduction with a condom used during sexual intercourse, usage of a well-characterized 4th-generation HIV RDT, and a 10 day post-infection period without any measurable viral load in peripheral blood followed by a sero-conversion period of about 3 weeks with 12.3% test sensitivity (antigen-specific) and only afterwards 97.3% (antibody-specific) test sensitivity. RESULTS: In most constellations, the HIV exposure risk in case of RDT-based prevention was lower than with condom use. Conclusions: The RDT-based HIV exposure prevention as established by sex workers is effective in most situations. A notable weakness of the strategy is the RDTs' poor sensitivity in spite of a high transmission risk during the seroconversion stage.

Pharmaceutical interactions between antiretroviral and antimalarial drugs used in chemoprophylaxis.

Human immunodeficiency virus (HIV) is the causative agent of the Acquired Immunodeficiency Syndrome (AIDS). The pandemic is believed to have originated within the Northern Congo basin covering large parts of the Democratic Republic of Congo, the Republic of Congo, the Central African Republic, Cameroon and Gabon. Although over decades, HIV-1 has spread throughout the World leaving no country unaffected, sub-Saharan Africa remains the region with more than 80% of all infected individuals. The HIV-2 epidemic has largely remained restricted to West Africa along the Upper Guinean forests. Co-incident with these regions of highest HIV distribution is a part of the malaria belt and therefore, co-infections are common. In this review we carve out the consequences of HIV transmission prevention and synchronous malaria prophylaxis during occupational or leisure travelling activities within this World region. In particular, we elaborate on considering pre-existing drug resistances of both, the malaria parasites and the immunodeficiency viruses, when determining a combination for prophylactic and, if necessary, post-expositional measures with a focus on the compatibility of both medications.

E2F1 Signalling is Predictive of Chemoresistance and Lymphogenic Metastasis in Penile Cancer: A Pilot Functional Study Reveals New Prognostic Biomarkers.

BACKGROUND: For penile cancer (PC) there are no known molecular predictors of lymphatic spread and/or chemoresistance. OBJECTIVE: To identify functional biomarkers that can predict malignant progression and treatment responsiveness. DESIGN, SETTING, AND PARTICIPANTS: We used four patient-derived PC cell lines and measured invasion and capillary tube formation, chemoresponsiveness, and mRNA and protein expression. Data were further validated in E2F1 transcription factor knockdown and overexpression experiments. We quantified E2F1 transcript levels in a set of nonmetastatic tumours (NM), metastasised primary tumours (PT), and lymph node metastases (M) from 24 patients. E2F1 immunohistochemistry was performed in another set of 13 PC biopsies. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Relationships between different parameters were analysed using Student t tests. Transcript levels in patient samples were compared using Mann-Whitney U tests. Significance was set at p<0.05. RESULTS AND LIMITATIONS: In cell lines established from lymph node metastases, E2F1 was more abundantly expressed, pRB was inactivated, and CDK2, CDK4, and cyclins D and E were elevated in comparison to cells from primary PC. Overexpression of E2F1 enhanced migratory capacity and lymphatic endothelial tubule formation, while depletion reduced invasiveness and increased chemosensitivity. VEGFR-3 and VEGF-C and mesenchymal markers were upregulated by high E2F1. E2F1 was clearly upregulated in infiltrative and metastatic primary tumours and metastases (NM vs PT, p<0.05; NM vs M, p<0.0005). E2F1 Quick scores increased from grade I to grade III tumours. A limitation of the study is the small number of patients. CONCLUSIONS: E2F1 is a driver of invasion and lymphatic dissemination and promotes chemoresistance. E2F1-related biomarkers might assist in stratifying PC patients for different treatment regimens. PATIENT SUMMARY: The availability of penile cancer cell lines allows molecular research on the mechanisms underlying metastasis and chemotherapy. A critical pathway involved in both features has been identified and may lead to better patient stratification for treatment selection.

Advances in cancer stem cell targeting: How to strike the evil at its root.

Cancer progression to metastatic stages is still unmanageable and the promise of effective anti-metastatic therapy remains largely unmet, emphasizing the need to develop novel therapeutics. The special focus here is on cancer stem cells (CSC) as the seed of tumor initiation, epithelial-mesenchymal transition, chemoresistance and, as a consequence, drivers of metastatic dissemination. We report on targeted therapies gearing towards the CSC's internal and membrane-anchored markers using agents such as antibody derivatives, nucleic therapeutics, small molecules and genetic payloads. Another emphasis lies on novel proceedings envisaged to deliver current and prospective therapies to the target sites using newest viral and non-viral vector technologies. In this review, we summarize recent progress and remaining challenges in therapeutic strategies to combat CSC.

Non-canonical pathway induced by Wnt3a regulates ß-catenin via Pyk2 in differentiating human neural progenitor cells.

Wnt/ß-catenin and Wnt/Ca2+ pathways are involved in cellular processes during embryonic development and the interaction between them in the same cell decides the outcome of cellular functions. In this study, we showed that Wnt3a triggers the Wnt/Ca2+ signaling pathway, indicated by an increase of cytosolic free calcium ([Ca2+]i) and activation of calmodulin dependent kinase II (CaMKII) during the differentiation of human neuronal progenitor cells (hNPCs). Wnt3a via the increase of [Ca2+]i activates proline-rich tyrosine kinase 2 (Pyk2), which subsequently regulates phosphorylation of glycogen synthase kinase 3ß (GSK3ß) and ß-catenin stabilization. Our findings suggest that Pyk2 plays an important role in the coordination of stabilization of ß-catenin in the crosstalk between Wnt/ß-catenin and Wnt/Ca2+ signaling pathways upon Wnt3a stimulation in differentiating hNPCs.

Novel subventricular zone early progenitor cell-specific adenovirus for in vivo therapy of central nervous system disorders reinforces brain stem cell heterogeneity.

Neural stem/progenitor cells (NSPCs) have the potential to self-renew and to generate all neural lineages as well as to repopulate damaged areas in the brain. Our previous targeting strategies have indicated precursor cell heterogeneity between different brain regions that warrants the development of NSPC-specific delivery vehicles. Here, we demonstrate a target-specific adenoviral vector system for the in vivo manipulation of progenitor cells in the subventricular zone of the adult mouse brain. For this purpose, we identified a series of peptide ligands via phage display. The peptide with the highest affinity, SNQLPQQ, was expressed in conjunction with a bispecific adaptor molecule. To verify the targeting potential of the specific peptide, green fluorescent protein-expressing Ad vectors were coupled with the adaptor molecule and injected into the subventricular region of adult mice by stereotaxic surgery. An efficient and selective transduction of NSPCs in the SVZ was achieved, whereas hippocampal NSPCs were negative. Our results offer an expeditious and simple tool to produce retargeted viral vectors for a specific and direct in vivo manipulation of these progenitor cells. This powerful technique provides an opportunity to develop innovative strategies and express therapeutic genes in specific types of neural progenitor cells to allow success in treatment of brain disorders.

Eradication of metastatic melanoma through cooperative expression of RNA-based HDAC1 inhibitor and p73 by oncolytic adenovirus.

Malignant melanoma is a highly aggressive cancer that retains functional p53 and p73, and drug unresponsiveness largely depends on defects in death pathways after epigenetic gene silencing in conjunction with an imbalanced p73/DNp73 ratio. We constructed oncolytic viruses armed with an inhibitor of deacetylation and/or p73 to specifically target metastatic cancer. Arming of the viruses is aimed at lifting epigenetic blockage and re-opening apoptotic programs in a staggered manner enabling both, efficient virus replication and balanced destruction of target cells through apoptosis. Our results showed that cooperative expression of shHDAC1 and p73 efficiently enhances apoptosis induction and autophagy of infected cells which reinforces progeny production. In vitro analyses revealed 100% cytotoxicity after infecting cells with OV.shHDAC1.p73 at a lower virus dose compared to control viruses. Intriguingly, OV.shHDAC1.p73 acts as a potent inhibitor of highly metastatic xenograft tumors in vivo. Tumor expansion was significantly reduced after intratumoral injection of 3 x 108 PFU of either OV.shHDAC1 or OV.p73 and, most important, complete regression could be achieved in 100 % of tumors treated with OV.shHDAC1.p73. Our results point out that the combination of high replication capacity and simultaneous restoration of cell death routes significantly enhance antitumor activity.

Peptide-based technologies to alter adenoviral vector tropism: ways and means for systemic treatment of cancer.

Due to the fundamental progress in elucidating the molecular mechanisms of human diseases and the arrival of the post-genomic era, increasing numbers of therapeutic genes and cellular targets are available for gene therapy. Meanwhile, the most important challenge is to develop gene delivery vectors with high efficiency through target cell selectivity, in particular under in situ conditions. The most widely used vector system to transduce cells is based on adenovirus (Ad). Recent endeavors in the development of selective Ad vectors that target cells or tissues of interest and spare the alteration of all others have focused on the modification of the virus broad natural tropism. A popular way of Ad targeting is achieved by directing the vector towards distinct cellular receptors. Redirecting can be accomplished by linking custom-made peptides with specific affinity to cellular surface proteins via genetic integration, chemical coupling or bridging with dual-specific adapter molecules. Ideally, targeted vectors are incapable of entering cells via their native receptors. Such altered vectors offer new opportunities to delineate functional genomics in a natural environment and may enable efficient systemic therapeutic approaches. This review provides a summary of current state-of-the-art techniques to specifically target adenovirus-based gene delivery vectors.

Chikungunya virus capsid protein contains nuclear import and export signals.

BACKGROUND: Chikungunya virus (CHIKV) is an alphavirus of the Togaviridae family. After autoproteolytic cleavage, the CHIKV capsid protein (CP) is involved in RNA binding and assembly of the viral particle. The monomeric CP is approximately 30 kDa in size and is small enough for passive transport through nuclear pores. Some alphaviruses are found to harbor nuclear localization signals (NLS) and transport of these proteins between cellular compartments was shown to be energy dependent. The active nuclear import of cytoplasmic proteins is mediated by karyopherins and their export by exportins. As nuclear and cytoplasmic trafficking may play a role in the life cycle of CHIKV, we have sought to identify nuclear localization and nuclear export signals in CHIKV CP in a virus-free system. METHODS: EGFP-fusion proteins of CHIKV CP and mutants thereof were created and used to monitor their intracellular localization. Binding of cellular proteins was confirmed in pull-down assays with purified CP using co-immuoprecipitation. Nuclear localization was demonstrated in a virus-free system using fluorescence microscopy. RESULTS: Here we show that CHIKV CP is a nuclear-cytoplasmic shuttling protein with an active NLS that binds to karyopherin α (Karα) for its nuclear translocation. We also found that the Karα4 C-terminal NLS binding site is sufficient for this interaction. We further demonstrate that CHIKV CP interacts directly with the export receptor CRM1 to transport this viral protein out of the nucleus via a nuclear export signal (NES). The CHIKV CP NES was mapped between amino acids 143 and 155 of CP. Deduced from in silico analyses we found that the NES has a mode of binding similar to the snurportin-1 CRM1 complex. CONCLUSIONS: We were able to show that in a virus-free system that the CHIKV capsid protein contains both, a NLS and a NES, and that it is actively transported between the cytoplasma and the nucleus. We conclude that CHIKV CP has the ability to shuttle via interaction with karyopherins for its nuclear import and, vice versa, by CRM1-dependent nuclear export.

Development of Adenoviral Delivery Systems to Target Hepatic Stellate Cells In Vivo.

Hepatic stellate cells (HSCs) are known as initiator cells that induce liver fibrosis upon intoxication or other noxes. Deactivation of this ongoing remodeling process of liver parenchyma into fibrotic tissue induced by HSCs is an interesting goal to be achieved by targeted genetic modification of HSCs. The most widely applied approach in gene therapy is the utilization of specifically targeted vectors based on Adenovirus (Ad) serotype 5. To narrow down the otherwise ubiquitous tropism of parental Ad, two modifications are required: a) ablating the native tropism and b) redirecting the vector particles towards a specific entity solely present on the cells of interest. Therefore, we designed a peptide of the nerve growth factor (NGFp) with specific affinity for the p75 neurotrophin receptor (p75NTR) present on HSCs. Coupling of this NGFp to vector particles was done either via chemical conjugation using bifunctional polyethylene glycol (PEG) or, alternatively, by molecular bridging with a fusion protein specific for viral fiber knob and p75NTR. Both Ad vectors transmit the gene for the green fluorescent protein (GFP). GFP expression was monitored in vitro on primary murine HSCs as well as after systemic administration in mice with healthy and fibrotic livers using intravital fluorescence microscopy. Coupling of NGFp to Ad via S11 and/or PEGylation resulted in markedly reduced liver tropism and an enhanced adenoviral-mediated gene transfer to HSCs. Transduction efficiency of both specific Ads was uniformly higher in fibrotic livers, whereas Ad.GFP-S11-NGFp transduce activated HSCs better than Ad.GFP-PEG-NGFp. These experiments contribute to the development of a targeted gene transfer system to specifically deliver antifibrotic compounds into activated HSCs by systemically applied adenoviral vector modified with NGFp.

Effect of natural polymorphisms in the HIV-1 CRF02_AG protease on protease inhibitor hypersusceptibility.

Hypersusceptibility (HS) to inhibition by different antiretroviral drugs (ARVs) among diverse HIV-infected individuals may be a misnomer because clinical response to treatment is evaluated in relation to subtype B infections while drug susceptibility of the infecting virus, regardless of subtype, is compared to a subtype B HIV-1 laboratory strain (NL4-3 or IIIB). Mounting evidence suggests that HS to different ARVs may result in better treatment outcome just as drug resistance leads to treatment failure. We have identified key amino acid polymorphisms in the protease coding region of a non-B HIV-1 subtype linked to protease inhibitor HS, namely, 17E and 64M in CRF02_AG. These HS-linked polymorphisms were introduced in the BD6-15 CRF02_AG molecular clone and tested for inhibition using a panel of protease inhibitors. In general, suspected HS-linked polymorphisms did increase susceptibility to specific protease inhibitors such as amprenavir and atazanavir, but the combination of the 17E/64M polymorphisms showed greater HS. These two mutations were found at low frequencies but linked in a sequence database of over 700 protease sequences of CRF02_AG. In direct head-to-head virus competitions, CRF02_AG harboring the 17E/64M polymorphisms also had higher replicative fitness than did the 17E or the 64M polymorphism in the CFR02_AG clone. These findings suggest that subtype-specific, linked polymorphisms can result in hypersusceptibility to ARVs. Considering the potential benefit of HS to treatment outcome, screening for potential HS-linked polymorphisms as well as preexisting drug resistance mutations in treatment-naïve patients may guide the choice of ARVs for the best treatment outcome.

Hepatitis E virus ORF2 protein activates the pro-apoptotic gene CHOP and anti-apoptotic heat shock proteins.

BACKGROUND: Hepatitis E virus (HEV) is a non-enveloped plus-strand RNA virus that causes acute hepatitis. The capsid protein open reading frame 2 (ORF2) is known to induce endoplasmic reticulum stress in ORF2 expressing cells. METHODOLOGY/PRINCIPAL FINDINGS: In this study we found that HEV ORF2 activates the expression of the pro-apoptotic gene C/EBP homologous protein (CHOP). ORF2 stimulates the CHOP promoter mainly through AARE (amino acid response elements) and to a minor extent the ERSE (endoplasmic reticulum stress response elements). Activating transcription factor 4 (ATF4) protein binds and activates the AARE regulatory sites of the CHOP promoter. ORF2 expression also leads to increased phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α) that in turn initiates the translation of ATF4 mRNA. The pro-apoptotic gene CHOP is an important trigger to initiate endoplasmic reticulum stress induced apoptosis. However, the activation of CHOP by ORF2 in this study did not induce apoptosis, nor did BCL2-associated X protein (Bax) translocate to mitochondria. Microarray analysis revealed an ORF2 specific increased expression of chaperones Hsp72, Hsp70B', and co-chaperone Hsp40. Co-immunoprecipitation (Co-IP) and in silico molecular docking analysis suggests that HEV ORF2 interacts with Hsp72. In addition, Hsp72 shows nuclear accumulation in ORF2 expressing cells. CONCLUSIONS/SIGNIFICANCE: These data provide new insight into simultaneously occurring counter-acting effects of HEV ORF2 that may be part of a strategy to prevent host suicide before completion of the viral replication cycle.

Divergent evolution in reverse transcriptase (RT) of HIV-1 group O and M lineages: impact on structure, fitness, and sensitivity to nonnucleoside RT inhibitors.

Natural evolution in primate lentiviral reverse transcriptase (RT) appears to have been constrained by the necessity to maintain function within an asymmetric protein composed of two identical primary amino acid sequences (66 kDa), of which one is cleaved (51 kDa). In this study, a detailed phylogenetic analysis now segregates groups O and M into clusters based on a cysteine or tyrosine residue located at position 181 of RT and linked to other signature residues. Divergent evolution of two group O (C181 or Y181) and the main (Y181 only) HIV-1 lineages did not appreciably impact RT activity or function. Group O RT structural models, based on group M subtype B RT crystal structures, revealed that most evolutionarily linked amino acids appear on a surface-exposed region of one subunit while in a noncatalytic RT pocket of the other subunit. This pocket binds nonnucleoside RT inhibitors (NNRTI); therefore, NNRTI sensitivity was used to probe enzyme differences in these group O and M lineages. In contrast to observations showing acquired drug resistance associated with fitness loss, the C181Y mutation in the C181 group O lineage resulted in a loss of intrinsic NNRTI resistance and was accompanied by fitness loss. Other mutations linked to the NNRTI-resistant C181 lineage also resulted in altered NNRTI sensitivity and a net fitness cost. Based on RT asymmetry and conservation of the intricate reverse transcription process, millions of years of divergent primate lentivirus evolution may be constrained to discrete mutations that appear primarily in the nonfunctional, solvent-accessible NNRTI binding pocket.

AZT-resistant foamy virus.

Azidothymidine (AZT) is a reverse transcriptase (RT) inhibitor that efficiently blocks the replication of spumaretroviruses or foamy viruses (FVs). To more precisely elucidate the mechanism of action of the FV RT enzyme, we generated an AZT-resistant FV in cell culture. Biologically resistant virus was obtained for simian foamy virus from macaque (SFVmac), which was insensitive to AZT concentrations of 1 mM, but not for FVs derived from chimpanzees. Nucleotide sequencing revealed four non-silent mutations in the pol gene. Introduction of these mutations into an infectious molecular clone identified all changes to be required for the fully AZT-resistant phenotype of SFVmac. The alteration of individual sites showed that AZT resistance in SFVmac was likely acquired by consecutive acquisition of pol mutations in a defined order, because some alterations on their own did not result in an efficiently replicating virus, neither in the presence nor in the absence of AZT. The introduction of the mutations into the RT of the closely related prototypic FV (PFV) did not yield an AZT-resistant virus, instead they significantly impaired the viral fitness.

N-terminal Gag domain required for foamy virus particle assembly and export.

Among the Retroviridae, foamy viruses (FVs) exhibit an unusual way of particle assembly and a highly specific incorporation of envelope protein into progeny virions. We have analyzed deletions and point mutants of the prototypic FV gag gene for capsid assembly and egress, envelope protein incorporation, infectivity, and ultrastructure. Deletions introduced at the 3' end of gag revealed the first 297 amino acids (aa) to be sufficient for specific Env incorporation and export of particulate material. Deletions introduced at the 5' end showed the region between aa 6 and 200 to be dispensable for virus capsid assembly but required for the incorporation of Env and particle egress. Point mutations were introduced in the 5' region of gag to target residues conserved among FVs from different species. Alanine substitutions of residues in a region between aa 40 and 60 resulted in severe alterations in particle morphology. Furthermore, at position 50, this region harbors the conserved arginine that is presumably at the center of a signal sequence directing FV Gag proteins to a cytoplasmic assembly site.