The Identification of an Adenovirus Receptor by Using Affinity Capture and Mass Spectrometry

Human species D adenovirus hexon capsid protein mediates cell entry through a direct interaction with CD46

Human adenovirus species D (HAdV-D) types are currently being explored as vaccine vectors for coronavirus disease 2019 (COVID-19) and other severe infectious diseases. The efficacy of such vector-based vaccines depends on functional interactions with receptors on host cells. Adenoviruses of different species are assumed to enter host cells mainly by interactions between the knob domain of the protruding fiber capsid protein and cellular receptors. Using a cell-based receptor-screening assay, we identified CD46 as a receptor for HAdV-D56. The function of CD46 was validated in infection experiments using cells lacking and overexpressing CD46, and by competition infection experiments using soluble CD46. Remarkably, unlike HAdV-B types that engage CD46 through interactions with the knob domain of the fiber protein, HAdV-D types infect host cells through a direct interaction between CD46 and the hexon protein. Soluble hexon proteins (but not fiber knob) inhibited HAdV-D56 infection, and surface plasmon analyses demonstrated that CD46 binds to HAdV-D hexon (but not fiber knob) proteins. Cryoelectron microscopy analysis of the HAdV-D56 virion-CD46 complex confirmed the interaction and showed that CD46 binds to the central cavity of hexon trimers. Finally, soluble CD46 inhibited infection by 16 out of 17 investigated HAdV-D types, suggesting that CD46 is an important receptor for a large group of adenoviruses. In conclusion, this study identifies a noncanonical entry mechanism used by human adenoviruses, which adds to the knowledge of adenovirus biology and can also be useful for development of adenovirus-based vaccine vectors.

Revisiting dengue virus-host cell interaction: new insights into molecular and cellular virology

Dengue virus (DENV) is an emerging mosquito-borne human pathogen that affects millions of individuals each year by causing severe and potentially fatal syndromes. Despite intense research efforts, no approved vaccine or antiviral therapy is yet available. Overcoming this limitation requires detailed understanding of the intimate relationship between the virus and its host cell, providing the basis to devise optimal prophylactic and therapeutic treatment options. With the advent of novel high-throughput technologies including functional genomics, transcriptomics, proteomics, and lipidomics, new important insights into the DENV replication cycle and the interaction of this virus with its host cell have been obtained. In this chapter, we provide a comprehensive overview on the current status of the DENV research field, covering every step of the viral replication cycle with a particular focus on virus-host cell interaction. We will also review specific chemical inhibitors targeting cellular factors and processes of relevance for the DENV replication cycle and their possible exploitation for the development of next generation antivirals.

Of mice and not humans: how reliable are animal models for evaluation of herpes CD8(+)-T cell-epitopes-based immunotherapeutic vaccine candidates?

Herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2)-specific CD8(+) T cells that reside in sensory ganglia, appear to control recurrent herpetic disease by aborting or reducing spontaneous and sporadic reactivations of latent virus. A reliable animal model is the ultimate key factor to test the efficacy of therapeutic vaccines that boost the level and the quality of sensory ganglia-resident CD8(+) T cells against spontaneous herpes reactivation from sensory neurons, yet its relevance has been often overlooked. Herpes vaccinologists are hesitant about using mouse as a model in pre-clinical development of therapeutic vaccines because they do not adequately mimic spontaneous viral shedding or recurrent symptomatic diseases, as occurs in human. Alternatives to mouse models are rabbits and guinea pigs in which reactivation arise spontaneously with clinical herpetic features relevant to human disease. However, while rabbits and guinea pigs develop spontaneous HSV reactivation and recurrent ocular and genital disease none of them can mount CD8(+) T cell responses specific to Human Leukocyte Antigen- (HLA-)restricted epitopes. In this review, we discuss the advantages and limitations of these animal models and describe a novel "humanized" HLA transgenic rabbit, which shows spontaneous HSV-1 reactivation, recurrent ocular disease and mounts CD8(+) T cell responses to HLA-restricted epitopes. Adequate investments are needed to develop reliable preclinical animal models, such as HLA class I and class II double transgenic rabbits and guinea pigs to balance the ethical and financial concerns associated with the rising number of unsuccessful clinical trials for therapeutic vaccine formulations tested in unreliable mouse models.

Role of annexin A2 in cellular entry of rabbit vesivirus

The mechanisms of calicivirus attachment and internalization are not well understood, mainly due to the lack of a reliable cell-culture system for most of its members. In this study, rabbit vesivirus (RaV) virions were shown to bind annexin A2 (ANXA2) in a membrane protein fraction from HEK293T cells, using a virus overlay protein-binding assay and matrix-assisted laser desorption/ionization time-of-flight analysis. A monoclonal anti-ANXA2 antibody and small interfering RNA-mediated knockdown of ANXA2 expression in HEK293T cells reduced virus infection significantly, further supporting the role of ANXA2 in RaV attachment and/or internalization.

Endothelial targeting of cowpea mosaic virus (CPMV) via surface vimentin

Cowpea mosaic virus (CPMV) is a plant comovirus in the picornavirus superfamily, and is used for a wide variety of biomedical and material science applications. Although its replication is restricted to plants, CPMV binds to and enters mammalian cells, including endothelial cells and particularly tumor neovascular endothelium in vivo. This natural capacity has lead to the use of CPMV as a sensor for intravital imaging of vascular development. Binding of CPMV to endothelial cells occurs via interaction with a 54 kD cell-surface protein, but this protein has not previously been identified. Here we identify the CPMV binding protein as a cell-surface form of the intermediate filament vimentin. The CPMV-vimentin interaction was established using proteomic screens and confirmed by direct interaction of CPMV with purified vimentin, as well as inhibition in a vimentin-knockout cell line. Vimentin and CPMV were also co-localized in vascular endothelium of mouse and rat in vivo. Together these studies indicate that surface vimentin mediates binding and may lead to internalization of CPMV in vivo, establishing surface vimentin as an important vascular endothelial ligand for nanoparticle targeting to tumors. These results also establish vimentin as a ligand for picornaviruses in both the plant and animal kingdoms of life. Since bacterial pathogens and several other classes of viruses also bind to surface vimentin, these studies suggest a common role for surface vimentin in pathogen transmission.

Novel vectors forin vivogene delivery to vascular tissue

Although some success has been achieved with gene delivery in animal models of vascular disorders, the results from some clinical trials have been less promising, possibly due, in part, to the use of suboptimal vectors for in vivo gene transfer. Non-viral vectors have a very low transfection efficiency so are largely unsuitable for most in vivo applications, and the relatively broad tropism of many of the commonly used viral vectors can limit efficient gene delivery specifically to target vascular tissues. However, characterisation of novel virus serotypes and advances in techniques that enable vectors to be targeted to the required tissue have led to progress in the development of novel vectors that could be utilised for gene delivery for vascular disorders.

Interaction between a 54-kilodalton mammalian cell surface protein and cowpea mosaic virus

Cowpea mosaic virus (CPMV), a plant virus that is a member of the picornavirus superfamily, is increasingly being used for nanotechnology applications, including material science, vascular imaging, vaccine development, and targeted drug delivery. For these applications, it is critical to understand the in vivo interactions of CPMV within the mammalian system. Although the bioavailability of CPMV in the mouse has been demonstrated, the specific interactions between CPMV and mammalian cells need to be characterized further. Here we demonstrate that although the host range for replication of CPMV is confined to plants, mammalian cells nevertheless bind and internalize CPMV in significant amounts. This binding is mediated by a conserved 54-kDa protein found on the plasma membranes of both human and murine cell lines. Studies using a deficient cell line, deglycosidases, and glycosylation inhibitors showed that the CPMV binding protein (CPMV-BP) is not glycosylated. A possible 47-kDa isoform of the CPMV-BP was also detected in the organelle and nuclear subcellular fraction prepared from murine fibroblasts. Further characterization of CPMV-BP is important to understand how CPMV is trafficked through the mammalian system and may shed light on how picornaviruses may have evolved between plant and animal hosts.

Proteomic Analysis of Human Immunodeficiency Virus Using Liquid Chromatography/Tandem Mass Spectrometry Effectively Distinguishes Specific Incorporated Host Proteins

A major challenge to studying virus-incorporated host proteins is the fact that they are not encoded by the viral genome. We used Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS) on whole virions to obtain a snapshot of the HIV-1 proteome. We identified known viral and host-cellular proteins and also identified novel components of HIV-1 and confirm these by traditional biochemical methods. Our comparison of wild-type and mutant viruses demonstrates that LC-MS/MS has the specificity to distinguish the presence/absence of a single host protein in intact virions.

The influence of adenovirus fiber structure and function on vector development for gene therapy

The collective attributes of adenoviruses (Ads), including ease of accomplishing replication deficiency, readily achievable high titers, encoding of large expression cassettes, efficiency of gene delivery to most cell types, and well-characterized biology, have made Ads, particularly Ad serotype 5 (Ad 5), some of the most utilized vectors for gene delivery. In recent years, however, it has become apparent that additional aspects of basic Ad virology must be uncovered for this vector system to succeed in the clinic. While local gene delivery is generally efficient, the broad tropism of Ad 5 and its tendency to home to the liver after systemic administration have proved to be limitations for other therapeutic applications, such as the treatment of disseminated cancers and cardiovascular disease. This has refocused research into the biology of Ad capsid components, particularly the main tropism determinant, the fiber/penton base complex, and their influence on transduction of selected cell types in vivo.