Recovery of humoral immunity is critical for successful antiviral therapy in disseminated mouse adenovirus type 1 infection

The RGD-binding integrins αvβ6 and αvβ8 are receptors for mouse adenovirus-1 and -3 infection

Mammalian adenoviruses (AdVs) comprise more than ~350 types including over 100 human (HAdVs) and just three mouse AdVs (MAdVs). While most HAdVs initiate infection by high affinity/avidity binding of their fiber knob (FK) protein to either coxsackievirus AdV receptor (CAR), CD46 or desmoglein (DSG)-2, MAdV-1 (M1) infection requires arginine-glycine-aspartate (RGD) binding integrins. To identify the receptors mediating MAdV infection we generated five novel reporter viruses for MAdV-1/-2/-3 (M1, M2, M3) transducing permissive murine (m) CMT-93 cells, but not B16 mouse melanoma cells expressing mCAR, human (h) CD46 or hDSG-2. Recombinant M1 or M3 FKs cross-blocked M1 and M3 but not M2 infections. Profiling of murine and human cells expressing RGD-binding integrins suggested that αvβ6 and αvβ8 heterodimers are associated with M1 and M3 infections. Ectopic expression of mβ6 in B16 cells strongly enhanced M1 and M3 binding, infection, and progeny production comparable with mαvβ6-positive CMT-93 cells, whereas mβ8 expressing cells were more permissive to M1 than M3. Anti-integrin antibodies potently blocked M1 and M3 binding and infection of CMT-93 cells and hαvβ8-positive M000216 cells. Soluble integrin αvβ6, and synthetic peptides containing the RGDLXXL sequence derived from FK-M1, FK-M3 and foot and mouth disease virus coat protein strongly interfered with M1/M3 infections, in agreement with high affinity interactions of FK-M1/FK-M3 with αvβ6/αvβ8, determined by surface plasmon resonance measurements. Molecular docking simulations of ternary complexes revealed a bent conformation of RGDLXXL-containing FK-M3 peptides on the subunit interface of αvβ6/β8, where the distal leucine residue dips into a hydrophobic pocket of β6/8, the arginine residue ionically engages αv aspartate215, and the aspartate residue coordinates a divalent cation in αvβ6/β8. Together, the RGDLXXL-bearing FKs are part of an essential mechanism for M1/M3 infection engaging murine and human αvβ6/8 integrins. These integrins are highly conserved in other mammals, and may favour cross-species virus transmission.

A synthetic stigmastane displays antiadenoviral activity and reduces the inflammatory response to viral infection

Although human adenovirus (ADV) infections are mild and self-limited in immunocompetent individuals, they can be severe and life-threatening in immunocompromised patients. Despite their significant clinical impact, there are not currently approved antiviral therapies for ADV infections. On the other hand, in some cases, the immune response induced by ADV infection can cause tissue damage. Even more, in the case of adenovirus vectors used in gene therapy, host immunity generally antagonize viral efficacy. Therefore, the need for searching an effective and safe therapy is increasing. In this work, we describe the antiadenoviral activity of the synthetic stigmastane (22S, 23S)-22,23-dihydroxystigmast-4-en-3-one (Compound 1) with already reported antiviral and antiinflammatory activities against other viruses of clinical importance. Compound 1 displayed no virucidal activity and did not affect ADV entry to the cells. The compound inhibited viral replication and it also reduced cytokine secretion in epithelial and inflammatory infected cells. Thus, Compound 1 would be a promissory drug potentially useful against adenoviral infections as well as an adjuvant of adenoviral vectors in gene therapy.

In vitro co-infection by cytomegalovirus improves the antiviral activity of ganciclovir against human adenovirus

Human adenovirus (HAdV) infection has an important clinical impact in the immunosuppressed population and is associated with high morbidity and mortality rates. The lack of a specific, safe and effective antiviral treatment against HAdV makes necessary the search for new therapeutic options. The aim of this study was to evaluate the in vitro activity of ganciclovir (GCV) against HAdV in co-infection by human cytomegalovirus (HCMV) and HAdV in cellular cultures. Quantitative real-time polymerase chain reaction (qPCR) was used to measure HAdV and HCMV DNA replication efficiency in monocultures and in co-infection situations in the presence of both cidofovir (CDV) and GCV. The effects of GCV and CDV were also evaluated in a burst assay (used to measure the production of virus particles) for both viruses, alone and in combination. GCV decreased by 1-log the HAdV DNA replication efficiency in co-infection with HCMV compared with its activity in HAdV monoculture. The burst assay showed that the reductions in virus yield in the presence of GCV were higher for HCMV and co-infection than for HAdV in monoculture (145.2±35.5- vs. 116.4±27.3- vs. 23.0±10.0-fold, respectively, P<0.05). The improved anti-HAdV activity of GCV during co-infection may be because of the more efficient phosphorylation of GCV by the HCMV protein kinase, UL97. Patients treated with GCV as pre-emptive therapy for HCMV infection may be considered as low-risk for developing HAdV infections; however, further evaluations are required to confirm these results.

Murine adenoviruses: tools for studying adenovirus pathogenesis in a natural host

Small laboratory animals are powerful models for investigating in vivo viral pathogenesis of a number of viruses. For adenoviruses (AdVs), however, species-specificity poses limitations to studying human adenoviruses (HAdVs) in mice and other small laboratory animals. Thus, this review covers work on naturally occurring mouse AdVs, primarily mouse adenovirus type 1 (MAdV-1), a member of the species Murine mastadenovirus A. Molecular genetics, virus life cycle, cell and tissue tropism, interactions with the host immune response, persistence, and host genetics of susceptibility are described. A brief discussion of MAdV-2 (member of species Murine mastadenovirus B) and MAdV-3 (member of species Murine mastadenovirus C) is included. We report the use of MAdVs in the development of vectors and vaccines.

Small-size recombinant adenoviral hexon protein fragments for the production of virus-type specific antibodies

Background

Adenoviruses are common pathogens infecting animals and humans. They are classified based on serology, or genome sequence information. These methods have limitations due to lengthy procedures or lack of infectivity data. Adenoviruses are easy to produce and amenable to genetic and biochemical modifications, which makes them a powerful tool for biological studies, and clinical gene-delivery and vaccine applications. Antibodies directed against adenoviral proteins are important diagnostic tools for virus identification in vivo and in vitro, and are used to elucidate infection mechanisms, often in combination with genomic sequencing and type specific information from hyper-variable regions of structural proteins.

Results

Here we describe a novel and readily useable method for cloning, expressing and purifying small fragments of hyper-variable regions 1-6 of the adenoviral hexon protein. We used these polypeptides as antigens for generating polyclonal rabbit antibodies against human adenovirus 3 (HAdV-B3), mouse adenovirus 1 (MAdV-1) and MAdV-2 hexon. In Western immunoblots with lysates from cells infected from thirteen human and three mouse viruses, these antibodies bound to homologous full-length hexon protein and revealed variable levels of cross-reactivity to heterologous hexons. Results from immuno-fluorescence and electron microscopy studies indicated that HAdV-B3 and MAdV-2 hexon antibodies recognized native forms of hexon.

Conclusions

The procedure described here can in principle be applied to any adenovirus for which genome sequence information is available. It provides a basis for generating novel type-specific tools in diagnostics and research, and extends beyond the commonly used anti-viral antibodies raised against purified viruses or subviral components.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0822-5) contains supplementary material, which is available to authorized users.

Large-Scale Analysis of Drug Side Effects via Complex Regulatory Modules Composed of microRNAs, Transcription Factors and Gene Sets

Identifying the occurrence mechanism of drug-induced side effects (SEs) is critical for design of drug target and new drug development. The expression of genes in biological processes is regulated by transcription factors(TFs) and/or microRNAs. Most of previous studies were focused on a single level of gene or gene sets, while studies about regulatory relationships of TFs, miRNAs and biological processes are very rare. Discovering the complex regulating relations among TFs, gene sets and miRNAs will be helpful for researchers to get a more comprehensive understanding about the mechanism of side reaction. In this study, a framework was proposed to construct the relationship network of gene sets, miRNAs and TFs involved in side effects. Through the construction of this network, the potential complex regulatory relationship in the occurrence process of the side effects was reproduced. The SE-gene set network was employed to characterize the significant regulatory SE-gene set interaction and molecular basis of accompanied side effects. A total of 117 side effects complex modules including four types of regulating patterns were obtained from the SE-gene sets-miRNA/TF complex regulatory network. In addition, two cases were used to validate the complex regulatory modules which could more comprehensively interpret occurrence mechanism of side effects.

Valganciclovir inhibits human adenovirus replication and pathology in permissive immunosuppressed female and male Syrian hamsters

Adenovirus infections of immunocompromised pediatric hematopoietic stem cell transplant patients can develop into serious and often deadly multi-organ disease. There are no drugs approved for adenovirus infections. Cidofovir (an analog of 2-deoxycytidine monophosphate) is used at times but it can be nephrotoxic and its efficacy has not been proven in clinical trials. Brincidofovir, a promising lipid-linked derivative of cidofovir, is in clinical trials. Ganciclovir, an analog of 2-deoxyguanosine, has been employed occasionally but with unknown efficacy in the clinic. In this study, we evaluated valganciclovir against disseminated adenovirus type 5 (Ad5) infection in our permissive immunosuppressed Syrian hamster model. We administered valganciclovir prophylactically, beginning 12 h pre-infection or therapeutically starting at Day 1, 2, 3, or 4 post-infection. Valganciclovir significantly increased survival, reduced viral replication in the liver, and mitigated the pathology associated with Ad5 infection. In cultured cells, valganciclovir inhibited Ad5 DNA replication and blocked the transition from early to late stage of infection. Valganciclovir directly inhibited Ad5 DNA polymerase in vitro, which may explain, at least in part, its mechanism of action. Ganciclovir and valganciclovir are approved to treat infections by certain herpesviruses. Our results support the use of valganciclovir to treat disseminated adenovirus infections in immunosuppressed patients.

Ganciclovir inhibits human adenovirus replication and pathogenicity in permissive immunosuppressed Syrian hamsters

Adenovirus infections of immunocompromised patients can develop into deadly multiorgan or systemic disease. The virus is especially threatening for pediatric allogeneic hematopoietic stem cell transplant recipients; according to some studies, 10% or more of these patients succumb to disease resulting from adenovirus infection. At present, there is no drug approved for the treatment or prevention of adenovirus infections. Compounds that are approved to treat other virus infections are used off-label to combat adenovirus, but only anecdotal evidence of the efficacy of these drugs exists. Ganciclovir, a drug approved for the treatment of herpesvirus infection, was previously reported to be effective against human adenoviruses in vitro. To model adenovirus infections in immunocompromised humans, we examined ganciclovir's efficacy in immunosuppressed Syrian hamsters intravenously infected with type 5 human adenovirus (Ad5). This animal model is permissive for Ad5 replication, and the animals develop symptoms similar to those seen in humans. We demonstrate that ganciclovir suppresses Ad5 replication in the liver of infected hamsters and that it mitigates the consequences of Ad5 infections in these animals when administered prophylactically or therapeutically. We show that ganciclovir inhibits Ad5 DNA synthesis and late gene expression. The mechanism of action for the drug is not clear; preliminary data suggest that it exerts its antiadenoviral effect by directly inhibiting the adenoviral DNA polymerase. While more extensive studies are required, we believe that ganciclovir is a promising drug candidate to treat adenovirus infections. Brincidofovir, a drug with proven activity against Ad5, was used as a positive control in the prophylactic experiment.

Intracellular antibody-mediated immunity and the role of TRIM21

Protection against bacterial and viral pathogens by antibodies has always been thought to end at the cell surface. Once inside the cell, a pathogen was understood to be safe from humoral immunity. However, it has now been found that antibodies can routinely enter cells attached to viral particles and mediate an intracellular immune response. Antibody-coated virions are detected inside the cell by means of an intracellular antibody receptor, TRIM21, which directs their degradation by recruitment of the ubiquitin-proteasome system. In this article we assess how this discovery alters our view of the way in which antibodies neutralise viral infection. We also consider the antiviral function of TRIM21 in the context of its other reported roles in immune signalling and autoimmunity. Finally, we discuss the conceptual implications of intracellular antibody immunity and how it alters our view of the discrete separation of extracellular and intracellular environments.

Immunotherapy of viral infections

Among the microorganisms that cause diseases of medical or veterinary importance, the only group that is entirely dependent on the host, and hence not easily amenable to therapy via pharmaceuticals, is the viruses. Since viruses are obligate intracellular pathogens, and therefore depend a great deal on cellular processes, direct therapy of viral infections is difficult. Thus, modifying or targeting nonspecific or specific immune responses is an important aspect of intervention of ongoing viral infections. However, as a result of the unavailability of effective vaccines and the extended duration of manifestation, chronic viral infections are the most suitable for immunotherapies. We present an overview of various immunological strategies that have been applied for treating viral infections after exposure to the infectious agent.

Clinical features and treatment of adenovirus infections

Adenoviruses (Ads) are common opportunistic pathogens that are rarely associated with severe clinical symptoms in healthy individuals. In contrast, in patients with compromised immunity, Ad infections often result in disseminated and potentially life-threatening disease. Among these are AIDS patients, individuals with hereditary immunodeficiencies and recipients of solid organ or haematopoietic stem cell transplants (HSCT) who receive immunosuppressive therapy. The latter account for the largest number of severe Ad infections. There is currently no formally approved antiviral therapy for the treatment of severe Ad keratoconjunctivitis and life-threatening Ad infections in immunocompromised patients. Here we update current knowledge on Ad biology, the clinical features observed in different patient groups and specific immune responses towards Ad infections. In addition, we review current and future treatment options, including: (i) the antiviral drugs cidofovir, ribavirin and new investigational compounds, as evaluated in the clinic or in relevant animal models, as well as (ii) novel immunotherapeutic strategies.