Immunogenicity of cytopathic and noncytopathic viral vectors

The impact of cytolytic versus noncytolytic viral infections on host responses is not well understood, due to limitations of the systems that have been used to address this issue. Using paired cytopathic and noncytopathic rabies viruses that differ by only two amino acids, we investigated several fundamental aspects of the immune response to these viral vectors. Greater cytopathic capacity translated into a greater degree of cross-priming to CD8(+) T cells (T(CD8)(+)) and more-robust short-term humoral and cellular responses. However, long-term responses to the two viruses were similar, suggesting that direct priming drives the bulk of the T(CD8)(+) antirabies response and that enhanced acute responses associated with greater virally mediated cellular destruction were balanced by other factors, such as prolonged antigen expression associated with noncytopathic virus. Such compensatory mechanisms may be in place to ensure comparable immunologic memories to various pathogens.     

Combining Regulatory T Cell Depletion and Inhibitory Receptor Blockade Improves Reactivation of Exhausted Virus-Specific CD8+ T Cells and Efficiently Reduces Chronic Retroviral Loads

Chronic infections with human viruses, such as HIV and HCV, or mouse viruses, such as LCMV or Friend Virus (FV), result in functional exhaustion of CD8⁺ T cells. Two main mechanisms have been described that mediate this exhaustion: expression of inhibitory receptors on CD8⁺ T cells and expansion of regulatory T cells (Tregs) that suppress CD8⁺ T cell activity. Several studies show that blockage of one of these pathways results in reactivation of CD8⁺ T cells and partial reduction in chronic viral loads. Using blocking antibodies against PD-1 ligand and Tim-3 and transgenic mice in which Tregs can be selectively ablated, we compared these two treatment strategies and combined them for the first time in a model of chronic retrovirus infection. Blocking inhibitory receptors was more efficient than transient depletion of Tregs in reactivating exhausted CD8⁺ T cells and reducing viral set points. However, a combination therapy was superior to any single treatment and further augmented CD8⁺ T cell responses and resulted in a sustained reduction in chronic viral loads. These results demonstrate that Tregs and inhibitory receptors are non-overlapping factors in the maintenance of chronic viral infections and that immunotherapies targeting both pathways may be a promising strategy to treat chronic infectious diseases.     

A persistent virus vector confers superior anti-tumor immunity, compared with a non-persistent vector

Active vaccination strategies using viral vectors often give disappointing protection from tumor development, and usually require multiple immunizations. These approaches normally use viruses that cause acute infections, as they provoke potent CD8 T cell responses. Persistent virus vectors have not been used in this setting due to the perception that exhaustion of the T cell response occurs and would lead to poor anti-tumor protection. However, such exhaustion generally only occurs in high-load virus infections, whereas T cell function is intact in lower-load persistent infections. In fact, CD8 T cell responses in these infections, which are adapted for long-term immune surveillance, have properties that may make them more desirable for long-term anti-tumor immunity. In this report, we show that a persistent gammaherpesvirus vector provides superior protection against melanoma, relative to a non-persistent mutant of the same virus. These data suggest that vaccine vectors derived from persistent viruses may perform better than those from acute viruses at mediating anti-tumor protection.     

MicroRNA-like antivirals

Employing engineered DNA templates to express antiviral microRNA (miRNA) sequences has considerable therapeutic potential. The durable silencing that may be achieved with these RNAi activators is valuable to counter chronic viral infections, such as those caused by HIV-1, hepatitis B, hepatitis C and dengue viruses. Early use of expressed antiviral miRNAs entailed generation of cassettes containing Pol III promoters (e.g. U6 and H1) that transcribe virus-targeting short hairpin RNA mimics of precursor miRNAs. Virus escape from single gene silencing elements prompted later development of combinatorial antiviral miRNA expression cassettes that form multitargeting siRNAs from transcribed long hairpin RNA and polycistronic primary miRNA sequences. Weaker Pol III and Pol II promoters have also been employed to control production of antiviral miRNA mimics, improve dose regulation and address concerns about toxicity caused by saturation of the endogenous miRNA pathway. Efficient delivery of expressed antiviral sequences remains challenging and utilizing viral vectors, which include recombinant adenoviruses, adeno-associated viruses and lentiviruses, has been favored. Investigations using recombinant lentiviruses to transduce CD34+ hematological precursor cells with expressed HIV-1 gene silencers are at advanced stages and show promise in preclinical and clinical trials. Although the use of expressed antiviral miRNA sequences to treat viral infections is encouraging, eventual therapeutic application will be dependent on rigorously proving their safety, efficient delivery to target tissues and uncomplicated large scale preparation of vector formulations. This article is part of a special issue entitled: MicroRNAs in viral gene regulation.     

Relevancia de la anfotericina B liposomal en el tratamiento de las infecciones fúngicas invasoras en pacientes oncohematológicos

Liposomal amphotericin B (L-AmB) has been a key cornerstone for the management of invasive fungal infections (IFI) caused by a wide array of molds and yeasts during the last three decades. Multiple studies performed over this period have generated a large body of evidence on its efficacy and safety, becoming the main antifungal agent in the management of IFI in patients with hematologic malignancies in several not mutually exclusive clinical settings. First, L-AmB is the most commonly used antifungal agent in patients undergoing intensive chemotherapy for acute leukemia and high-risk myelodysplastic syndrome, as well as in hematopoietic stem cell transplant recipients. Additionally, due to the administration of newer targeted therapies (such as monoclonal antibodies or small molecule inhibitors), opportunistic mold infections are increasingly being reported in patients with hematologic malignancies usually considered low-risk for IFI. These agents usually have a high drug-drug interaction potential, being triazoles, commonly used for antifungal prophylaxis, included. Finally, patients developing breakthrough IFI because of either subtherapeutic concentrations of antifungal prophylactic drugs in blood or selection of resistant strains, require broad spectrum antifungal therapy, usually with an antifungal of a different class. In both situations, L-AmB remains as the best option for early antifungal therapy.     

New roles for large and small viral RNAs in evading host defences

It has been known for decades that some clinically important viruses encode abundant amounts of non-coding RNAs (ncRNAs) during infection. Until recently, the number of viral ncRNAs identified was few and their functions were mostly unknown. Although our understanding is still in its infancy, several recent reports have identified new functions for viral microRNAs and larger ncRNAs. These results so far show that different classes of viral ncRNAs act to autoregulate viral gene expression and evade host antiviral defences such as apoptosis and the immune response.     

Improving immune reconstitution while preventing GvHD in allogeneic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is the treatment of choice for many hematologic malignancies and inherited disorders of the hematopoietic system. Ex vivo T-cell depletion (TCD) of the graft and post-transplantation immunosuppression efficiently prevents the development of GvHD in no- MHC-identical settings. However, the consequence of these non-specific strategies is a long-lasting immunodeficiency associated with increased incidence of disease relapse, graft rejection and reactivation of viral infections. Donor lymphocyte infusion, which is used for treating leukemic relapse after allogeneic HSCT, can result in severe GvHD. Several strategies are being optimized specifically to inactivate anti-host T cells while preserving anti-leukemic or anti-microbial immunocompetence. Based on the ex vivo or in vivo elimination of anti-host T cells, or on the modulation of their anti-host activity, these approaches, which have been explored extensively in pre-clinical studies and tested in some preliminary clinical trials, are discussed in this paper.     

Reverse genetics of negative-stranded RNA viruses: a global perspective

The advent of reverse genetics technology has revolutionized the field of RNA viruses. It is now possible to manipulate even negative-stranded RNA viruses at will, and evaluate the effects of these changes on the biology and pathogenesis of these viruses. The fundamental insights gleaned from the reverse genetics-based studies over the last several years have provided a new momentum for the development of designed therapies for the control and prevention of these viral pathogens. The recombinant viruses have been exploited also as vectors for devising targeted therapies for non-viral diseases such as malignancies, and in gene therapy for inherited disorders. This review provides a brief summary of the stumbling blocks and the successes in the development of the technology for the negative-stranded RNA viruses. The many and varied applications of the recombinant vectors are also outlined.     

Effects of schistosomes on host anti-viral immune response and the acquisition,virulence, and prevention of viral infections: A systematic review

Although a growing number of studies suggest interactions between Schistosoma parasites and viral infections, the effects of schistosome infections on the host response to viruses have not been evaluated comprehensively. In this systematic review, we investigated how schistosomes impact incidence, virulence, and prevention of viral infections in humans and animals. We also evaluated immune effects of schistosomes in those coinfected with viruses. We screened 4,730 studies and included 103. Schistosomes may increase susceptibility to some viruses, including HIV and Kaposi’s sarcoma-associated herpesvirus, and virulence of hepatitis B and C viruses. In contrast, schistosome infection may be protective in chronic HIV, Human T-cell Lymphotropic Virus-Type 1, and respiratory viruses, though further research is needed. Schistosome infections were consistently reported to impair immune responses to hepatitis B and possibly measles vaccines. Understanding the interplay between schistosomes and viruses has ramifications for anti-viral vaccination strategies and global control of viral infections.     

RNA‐Directed rna polymerases of plants

The report in 1971 by Comuet and Astier‐Manifacier that Chinese cabbage contains an active RNA‐dependent RNA polymerase has been extended to all plants studied. This has met with much opposition because the central dogma of molecular biology requires no replication mechanism for RNA. Only upon RNA virus infection are such enzymes needed, and it was generally believed that these were always and only virus‐coded. The purification and characterization of several of these plant viruses will be reviewed, with particular reference to the fact that while their amount in plant tissue is variably increased by various RNA virus infections their nature is unaffected by the viral genome and is strictly host‐specific. It will be noted, however, that in a specific instance viral infection has been shown to affect an important property of the enzyme. Also, it has become evident that certain plant viruses resemble animal picorna viruses (e.g., polio virus) and that these viruses carry an RNA polymerase gene. The same may be true, but has not been proven, for a small group of plant viruses that shows resemblances to the prokaryotic RNA phages in which a viral gene product together with host proteins form the RNA polymerase. An important question that remains to be solved in future work is the role of RNA polymerases in normal plant cell biology. Also, the mechanism by which viral infection causes the enzyme to become largely membrane or organelle bound and possibly conformationally changed in the process remains to be elucidated.     

Diagnosis and treatment of viral diseases in recipients of allogeneic hematopoietic stem cell transplantation

Viral infections are important causes of morbidity and mortality after allogeneic stem cell hematopoietic transplantation (allo-HSCT). Although most viral infections present with asymptomatic or subclinical manifestations, viruses may result in fatal complications in severe immunocompromised recipients. Reactivation of latent viruses, such as herpesviruses, is frequent during the immunosuppression that occurs with allo-HSCT. Viruses acquired from community, such as the respiratory and gastrointestinal viruses, are also important pathogens of post-transplant viral diseases. Currently, molecular diagnostic methods have replaced or supplemented traditional methods, such as viral culture and antigen detection, in diagnosis of viral infections. The utilization of polymerase chain reaction facilitates the early diagnosis. In view of lacking efficacious agents for treatment of viral diseases, prevention of viral infections is extremely valuable. Application of prophylactic strategies including preemptive therapy reduces viral infections and diseases. Adoptive cellular therapy for restoring virus-specific immunity is a promising method in the treatment of viral diseases.     

Current status of genetic modification of T cells for cancer treatment

Clinical studies of adoptive immunotherapy with T cells have shown activity directed at hematologic and solid malignancies and viral infections. Genetic modification of infused T cells offers the prospect of improving such therapies and has already been used to track infused T cells, insert suicide genes and redirect the immune response towards specific Ag. Pre-clinical studies are evaluating novel approaches to genetically modify T cells to confer resistance to tumor evasion mechanisms. There is also increasing interest in developing suicide gene strategies as a failsafe mechanism to eradicate genetically modified cells should adverse effects occur.     

Viral RNA Intermediates as Targets for Detection and Discovery of Novel and Emerging Mosquito-Borne Viruses

Mosquito-borne viruses encompass a range of virus families, comprising a number of significant human pathogens (e.g., dengue viruses, West Nile virus, Chikungunya virus). Virulent strains of these viruses are continually evolving and expanding their geographic range, thus rapid and sensitive screening assays are required to detect emerging viruses and monitor their prevalence and spread in mosquito populations. Double-stranded RNA (dsRNA) is produced during the replication of many of these viruses as either an intermediate in RNA replication (e.g., flaviviruses, togaviruses) or the double-stranded RNA genome (e.g., reoviruses). Detection and discovery of novel viruses from field and clinical samples usually relies on recognition of antigens or nucleotide sequences conserved within a virus genus or family. However, due to the wide antigenic and genetic variation within and between viral families, many novel or divergent species can be overlooked by these approaches. We have developed two monoclonal antibodies (mAbs) which show co-localised staining with proteins involved in viral RNA replication in immunofluorescence assay (IFA), suggesting specific reactivity to viral dsRNA. By assessing binding against a panel of synthetic dsRNA molecules, we have shown that these mAbs recognise dsRNA greater than 30 base pairs in length in a sequence-independent manner. IFA and enzyme-linked immunosorbent assay (ELISA) were employed to demonstrate detection of a panel of RNA viruses from several families, in a range of cell types. These mAbs, termed monoclonal antibodies to viral RNA intermediates in cells (MAVRIC), have now been incorporated into a high-throughput, economical ELISA-based screening system for the detection and discovery of viruses from mosquito populations. Our results have demonstrated that this simple system enables the efficient detection and isolation of a range of known and novel viruses in cells inoculated with field-caught mosquito samples, and represents a rapid, sequence-independent, and cost-effective approach to virus discovery.     

TRAIL/TRAIL‐R in hematologic malignancies

Defects in apoptosis are observed in many cancer cell types and contribute in a relevant way to tumorigenesis. Apoptosis is a complex and well‐regulated cell death program that plays a key role in the control of cell homeostasis, particularly at the level of the hematopoietic system. Apoptosis can be initiated through two different mechanisms involving either activation of the death receptors (extrinsic pathway) or activation of a mitochondrial apoptotic process (intrinsic pathway). Among the various death receptors a peculiar role is played by TNF‐related apoptosis‐inducing ligand (TRAIL)‐receptors (TRAIL‐Rs) and their ligand TRAIL. TRAIL recently received considerable interest for its potent anti‐tumor killing activity, sparing normal cells. Here, we will review the expression and the abnormalities of TRAIL/TRAIL‐R system in hematologic malignancies. The large majority of primary hematologic tumors are resistant to TRAIL‐mediated apoptosis, basically due to the activation of anti‐apoptotic signaling pathway (such as NF‐κB), overexpression of anti‐apoptotic proteins (such as FLIP, Bcl‐2, XIAP) or expression of TRAIL decoy receptors or reduced TRAIL‐R1/‐R2 expression. Strategies have been developed to bypass this TRAIL resistance and are based on the combination of TRAIL with chemotherapy or radiotherapy, or with proteasome or histone deacetylase or NF‐κB inhibitors. The agents used in combination with TRAIL either enhance TRAIL‐R1/‐R2 expression or decrease expression of anti‐apoptotic proteins (c‐FLIP, XIAP, Bcl‐2). Many of these combinatorial therapies hold promise for future developments in treatment of hematologic malignancies. J. Cell. Biochem. 110: 21–34, 2010. © 2010 Wiley‐Liss, Inc.     

Cytokine-induced viral purging--role in viral pathogenesis.

The control of viral infections was previously thought to rely exclusive ly on the antigen-specific destruction of infected cells by the antigen-specific destruction of infected cells by the immune system; however, recent studies have shown that several viral infections can be primarily controlled by noncytopathic, cytokine- dependent 'curative' mechanisms (i.e. viral purging). The relative sensitivity of viruses to such curative mechanisms depends not only on the virus but also on the capacity of the specific infected cell to produce the appropriate intracellular antiviral factors.     

Climate change effects on physiology and population processes of hosts and vectors that influence the spread of hemipteran-borne plant viruses

Plant virus diseases constitute one of the limiting factors to the productivity of agriculture. Changes in host plants and insect vector populations that might result from climate change (their geographical distribution range, their densities, migration potential and phenology) could affect the spread of plant viruses. At the individual level, alterations in plant physiological processes that are relevant to their molecular interactions with viruses, like changes in metabolism, leaf temperature, and their effects on some processes, like the temperature-sensitive antiviral resistance based in RNA silencing, can also influence the ability of individual plants to control viral infections. In order to assess the impact that climate change may have on the incidence and spread of hemipteran-borne plant viruses, its potential effects on virus/plant interactions and hemipteran insect vectors, as well as other operating processes, which could exacerbate or mitigate them, are identified and analyzed in this review.     

Understanding Interferon Subtype Therapy for Viral Infections: Harnessing the Power of the Innate Immune System.

Type I and III interferons (IFNs) of the innate immune system belong to a polygenic family, however the individual subtype mediators of the antiviral response in viral infections have been hindered by a lack of reagents. Evaluation studies using different IFN subtypes have distinguished distinct protein properties with different efficacies towards different viruses, opening promising avenues for immunotherapy. This review largely focuses on the application of IFN-α/β and IFN-λ therapies for viral infections, influenza, herpes, HIV and hepatitis. Such IFN subtype therapies may help to cure patients with virus infections where no vaccine exists. The ability of cell types to secrete a number of IFN subtypes from a multi-gene family may be an intuitive counterattack on viruses that evade IFN subtype responses. Hence, clinical use of virus-targeted IFN subtypes may restore antiviral immunity in viral infections. Accumulating evidence suggests that individual IFN subtypes have differential efficacies in selectively activating immune cell subsets to enhance antiviral immune responses leading to production of sustained B and T cell memory. Cytokine therapy can augment innate immunity leading to clearance of acute virus infections but such treatments may have limited effects on chronic virus infections that establish lifelong latency. Therefore, exploiting individual IFN subtypes to select those with the ability to sculpt protective responses as well as reinstating those targeted by viral evasion mechanisms may inform development of improved antiviral therapy.     

Nuclear remodelling during viral infections

Because of their limited coding capacity, viruses are not able to encode all proteins that are required for their replication. Therefore, they depend on a wide variety of cellular functions and structures, such as the host cell nucleus. It has been shown that DNA, as well as RNA viruses, exploit the nucleus because it provides essential machinery for viral replication. On the other hand, the nucleus undergoes significant remodelling during viral usurpation or exploitation. Moreover, it is becoming increasingly clear that some subnuclear structures, such as promyelocytic leukaemia nuclear bodies, act as an antiviral defence mechanism, and several viruses antagonize this intracellular defence by modifying subnuclear structures. This article reviews the main alterations that take place in nucleus during viral infections.     

Prevention and control of emerging infections: a challenge for the 3rd millennium

In the last 30 years, several emerging infections due to novel viruses have been identified, from haemorrhagic fever viruses to HIV, from the SARS-Coronavirus to Avian influenza viruses. Ecological and genetic changes are important determinants of the emergence of new viral infections, driving to an increase of R0 (the basic reproductive number) through increasing the probability of transmission. The current H5N1 epidemic may be considered a prepandemic paradigm that needs thorough investigation.     

Oncoviruses: How do they hijack their host and current treatment regimes

Viruses have the ability to modulate the cellular machinery of their host to ensure their survival. While humans encounter numerous viruses daily, only a select few can lead to disease progression. Some of these viruses can amplify cancer-related traits, particularly when coupled with factors like immunosuppression and co-carcinogens. The global burden of cancer development resulting from viral infections is approximately 12%, and it arises as an unfortunate consequence of persistent infections that cause chronic inflammation, genomic instability from viral genome integration, and dysregulation of tumor suppressor genes and host oncogenes involved in normal cell growth. This review provides an in-depth discussion of oncoviruses and their strategies for hijacking the host's cellular machinery to induce cancer. It delves into how viral oncogenes drive tumorigenesis by targeting key cell signaling pathways. Additionally, the review discusses current therapeutic approaches that have been approved or are undergoing clinical trials to combat malignancies induced by oncoviruses. Understanding the intricate interactions between viruses and host cells can lead to the development of more effective treatments for virus-induced cancers.