A Novel Human Skin Tissue Model To Study Varicella-Zoster Virus and Human Cytomegalovirus

Commercial human 3D corneal epithelial equivalents for modeling epithelial infection in herpes keratitis

Herpes stromal keratitis is the leading cause of infectious blindness in the western world. Infection by HSV1 is most common, but VZV and hCMV also infect the cornea. Multiple models of HSV1 corneal infection exist, but none for VZV and hCMV because of their host specificity. Here, we used commercially available 3D human corneal epithelial equivalents (HCEE) to study infection by these herpesviruses. HCEE was infected by HSV-1 and hCMV without requiring scarification and resulted in spreading infections. Spread of HSV-1 infection was rapid, while that of hCMV was slow. In contrast, infections with VZV required damage to the HCEE and did not spread. Acyclovir dramatically reduced replication of HSV-1 in this model. We conclude that highly quality-controlled, readily available HCEE is a useful model to study human-restricted herpesvirus infection of the human corneal epithelium and for screening of antiviral drugs for treating HSK in an 3D model system.

CD3+ T-cell: CD14+monocyte complexes are dynamic and increased with HIV and glucose intolerance

An increased risk of cardiometabolic disease accompanies persistent systemic inflammation. Yet, the innate and adaptive immune system features in persons who develop these conditions remain poorly defined. Doublets, or cell-cell complexes, are routinely eliminated from flow cytometric and other immune phenotyping analyses, which limits our understanding of their relationship to disease states. Using well-characterized clinical cohorts, including participants with controlled HIV as a model for chronic inflammation and increased immune cell interactions, we show that circulating CD14+ monocytes complexed to CD3+ T cells are dynamic, biologically relevant, and increased in individuals with diabetes after adjusting for confounding factors. The complexes form functional immune synapses with increased expression of proinflammatory cytokines and greater glucose utilization. Furthermore, in persons with HIV, the CD3+T-cell: CD14+monocyte complexes had more HIV copies compared to matched CD14+ monocytes or CD4+ T cells alone. Our results demonstrate that circulating CD3+T-cell:CD14+monocyte pairs represent dynamic cellular interactions that may contribute to inflammation and cardiometabolic disease pathogenesis and may originate or be maintained, in part, by chronic viral infections. These findings provide a foundation for future studies investigating mechanisms linking T cellmonocyte cell-cell complexes to developing immune-mediated diseases, including HIV and diabetes.

Humanized mouse models: A valuable platform for preclinical evaluation of human cancer

Animal models are routinely employed to assess the treatments for human cancer. However, due to significant differences in genetic backgrounds, traditional animal models are unable to meet bioresearch needs. To overcome this restriction, researchers have generated and optimized immunodeficient mice, and then engrafted human genes, cells, tissues, or organs in mice so that the responses in the model mice could provide a more reliable reference for treatments. As a bridge connecting clinical application and basic research, humanized mice are increasingly used in the preclinical evaluation of cancer treatments, particularly after gene interleukin 2 receptor gamma mutant mice were generated. Human cancer models established in humanized mice support exploration of the mechanism of cancer occurrence and provide an efficient platform for drug screening. However, it is undeniable that the further application of humanized mice still faces multiple challenges. This review summarizes the construction approaches for humanized mice and their existing limitations. We also report the latest applications of humanized mice in preclinical evaluation for the treatment of cancer and point out directions for future optimization of these models.

Creating the "Dew Drop on a Rose Petal": the Molecular Pathogenesis of Varicella-Zoster Virus Skin Lesions

Varicella-zoster virus (VZV) is a human alphaherpesvirus that causes varicella (chicken pox) as the primary infection in a susceptible host. Varicella is very contagious through its transmission by direct contact with vesicular skin lesions that contain high titers of infectious virus and respiratory droplets. While the clinical manifestations of primary VZV infection are well recognized, defining the molecular mechanisms that drive VZV pathogenesis in the naive host before adaptive antiviral immunity is induced has been a challenge due to species specificity. This review focuses on advances made in identifying the differentiated human host cells targeted by VZV to cause varicella, the processes involved in viral takeover of these heterogenous cell types, and the host cell countermeasures that typically culminate in a benign illness. This work has revealed many unexpected and multifaceted mechanisms used by VZV to achieve its high prevalence and persistence in the human population.

A novel recombinant ORF7-siRNA delivered by flexible nano-liposomes inhibits varicella zoster virus infection

BACKGROUND

Varicella zoster virus (VZV), which is a human restricted alpha-herpesvirus, causes varicella (chickenpox) and zoster (shingles). The subsequent post-herpetic neuralgia (PHN) due to VZV infection is excruciating for most patients. Thus, developing specific therapeutics against VZV infection is imperative. RNA interference (RNAi) represents an effective approach for alternative antiviral therapy. This study aimed to develop a novel anti-VZV therapeutics based on RNAi.

RESULTS

In this study, we screened and found the open reading frame 7 (ORF7) of the VZV genome was an ideal antiviral target based on RNAi. Therefore, a novel siRNA targeting ORF7 (si-ORF7) was designed to explore the potential of RNAi antiviral treatment strategy toward VZV. We used a bio-engineering approach to manufacture recombinant siRNA agents with high yield in E. coli. Then, the efficacy of recombinant ORF7-siRNA (r/si-ORF7) in inhibiting VZV infection both in cellular level and 3D human epidermal skin model was evaluated. The r/si-ORF7 was proved to inhibit the VZV replication and reduce the virus copy numbers significantly in vitro. Furthermore, flexible nano-liposomes were established to deliver r/si-ORF7 to 3D human epidermal skin model and found r/si-ORF7 also could inhibit the VZV infection, thus maintaining normal skin morphology.

CONCLUSIONS

Taken together, our results highlighted that transdermal administration of antiviral r/si-ORF7 was a promising therapeutic strategy for functional cure of VZV infection.

Blank Spots in the Map of Human Skin: The Challenge for Xenotransplantation

Most of the knowledge about human skin homeostasis, development, wound healing, and diseases has been accumulated from human skin biopsy analysis by transferring from animal models and using different culture systems. Human-to-mouse xenografting is one of the fundamental approaches that allows the skin to be studied in vivo and evaluate the ongoing physiological processes in real time. Humanized animals permit the actual techniques for tracing cell fate, clonal analysis, genetic modifications, and drug discovery that could never be employed in humans. This review recapitulates the novel facts about mouse skin self-renewing, regeneration, and pathology, raises issues regarding the gaps in our understanding of the same options in human skin, and postulates the challenges for human skin xenografting.

Mouse Models for Human Herpesviruses

More than one hundred herpesviruses have been isolated from different species so far, with nine infecting humans. Infections with herpesviruses are characterized by life-long latency and represent a significant challenge for human health. To investigate the consequences of infections and identify novel treatment options, in vivo models are of particular relevance. The mouse has emerged as an economical small animal model to investigate herpesvirus infections. However, except for herpes simplex viruses (HSV-1, HSV-2), human herpesviruses cannot infect mice. Three natural herpesviruses have been identified in mice: mouse-derived cytomegalovirus (MCMV), mouse herpesvirus 68 (MHV-68), and mouse roseolovirus (MRV). These orthologues are broadly used to investigate herpesvirus infections within the natural host. In the last few decades, immunocompromised mouse models have been developed, allowing the functional engraftment of various human cells and tissues. These xenograft mice represent valuable model systems to investigate human-restricted viruses, making them particularly relevant for herpesvirus research. In this review, we describe the various mouse models used to study human herpesviruses, thereby highlighting their potential and limitations. Emphasis is laid on xenograft mouse models, covering the development and refinement of immune-compromised mice and their application in herpesvirus research.

Prodrug Strategies for the Development of β-l-5-((E)-2-Bromovinyl)-1-((2S,4S)-2-(hydroxymethyl)-1,3-(dioxolane-4-yl))uracil (l-BHDU) against Varicella Zoster Virus (VZV)

Varicella zoster virus (VZV) establishes lifelong infection after primary disease and can reactivate. Several drugs are approved to treat VZV diseases, but new antivirals with greater potency are needed. Previously, we identified β-l-5-((E)-2-bromovinyl)-1-((2S,4S)-2-(hydroxymethyl)-1,3-(dioxolane-4-yl))uracil (l-BHDU, 1), which had significant anti-VZV activity. In this communication, we report the synthesis and evaluation of numerous l-BHDU prodrugs: amino acid esters (14-26), phosphoramidates (33-34), long-chain lipids (ODE-l-BHDU-MP, 38, and HDP-l-BHDU-MP, 39), and phosphate ester prodrugs (POM-l-BHDU-MP, 41, and POC-l-BHDU-MP, 47). The amino acid ester l-BHDU prodrugs (l-phenylalanine, 16, and l-valine, 17) had a potent antiviral activity with EC₅₀ values of 0.028 and 0.030 μM, respectively. The phosphate ester prodrugs POM-l-BHDU-MP and POC-l-BHDU-MP had a significant anti-VZV activity with EC₅₀ values of 0.035 and 0.034 μM, respectively, and no cellular toxicity (CC₅₀ > 100 μM) was detected. Out of these prodrugs, ODE-l-BHDU-MP (38) and POM-l-BHDU-MP (41) were selected for further evaluation in future studies.

A Variant Allele in Varicella-Zoster Virus Glycoprotein B Selected during Production of the Varicella Vaccine Contributes to Its Attenuation

Attenuation of the live varicella Oka vaccine (vOka) has been attributed to mutations in the genome acquired during cell culture passage of pOka (parent strain); however, the precise mechanisms of attenuation remain unknown. Comparative sequence analyses of several vaccine batches showed that over 100 single-nucleotide polymorphisms (SNPs) are conserved across all vaccine batches; 6 SNPs are nearly fixed, suggesting that these SNPs are responsible for attenuation. By contrast, prior analysis of chimeric vOka and pOka recombinants indicates that loci other than these six SNPs contribute to attenuation. Here, we report that pOka consists of a heterogenous population of virus sequences with two nearly equally represented bases, guanine (G) or adenine (A), at nucleotide 2096 of the ORF31 coding sequence, which encodes glycoprotein B (gB) resulting in arginine (R) or glutamine (Q), respectively, at amino acid 699 of gB. By contrast, 2096A/699Q is dominant in vOka (>99.98%). gB699Q/gH/gL showed significantly less fusion activity than gB699R/gH/gL in a cell-based fusion assay. Recombinant pOka with gB669Q (rpOka_gB699Q) had a similar growth phenotype as vOka during lytic infection in cell culture including human primary skin cells; however, rpOka_gB699R showed a growth phenotype similar to pOka. rpOka_gB699R entered neurons from axonal terminals more efficiently than rpOka_gB699Q in the presence of cell membrane-derived vesicles containing gB. Strikingly, when a mixture of pOka with both alleles equally represented was used to infect human neurons from axon terminals, pOka with gB699R was dominant for virus entry. These results identify a variant allele in gB that contributes to attenuation of vOka. IMPORTANCE The live-attenuated varicella vaccine has reduced the burden of chickenpox. Despite its development in 1974, the molecular basis for its attenuation is still not well understood. Since the live-attenuated varicella vaccine is the only licensed human herpesvirus vaccine that prevents primary disease, it is important to understand the mechanism for its attenuation. Here we identify that a variant allele in glycoprotein B (gB) selected during generation of the varicella vaccine contributes to its attenuation. This variant is impaired for fusion, virus entry into neurons from nerve terminals, and replication in human skin cells. Identification of a variant allele in gB, one of the essential herpesvirus core genes, that contributes to its attenuation may provide insights that assist in the development of other herpesvirus vaccines.

The Biology of Varicella-Zoster Virus Replication in the Skin

The replication of varicella-zoster virus (VZV) in skin is critical to its pathogenesis and spread. Primary infection causes chickenpox, which is characterised by centrally distributed skin blistering lesions that are rich in infectious virus. Cell-free virus in the cutaneous blistering lesions not only spreads to cause further cases, but infects sensory nerve endings, leading to the establishment of lifelong latency in sensory and autonomic ganglia. The reactivation of virus to cause herpes zoster is again characterised by localised painful skin blistering rash containing infectious virus. The development of in vitro and in vivo models of VZV skin replication has revealed aspects of VZV replication and pathogenesis in this important target organ and improved our understanding of the vaccine strain vOKa attenuation. In this review, we outline the current knowledge on VZV interaction with host signalling pathways, the viral association with proteins associated with epidermal terminal differentiation, and how these interconnect with the VZV life cycle to facilitate viral replication and shedding.

Development of Robust Varicella Zoster Virus Luciferase Reporter Viruses for In Vivo Monitoring of Virus Growth and Its Antiviral Inhibition in Culture, Skin, and Humanized Mice

There is a continued need to understand varicella-zoster virus (VZV) pathogenesis and to develop more effective antivirals, as it causes chickenpox and zoster. As a human-restricted alphaherpesvirus, the use of human skin in culture and mice is critical in order to reveal the important VZV genes that are required for pathogenesis but that are not necessarily observed in the cell culture. We previously used VZV-expressing firefly luciferase (fLuc), under the control of the constitutively active SV40 promoter (VZV-BAC-Luc), to measure the VZV spread in the same sample. However, the fLuc expression was independent of viral gene expression and viral DNA replication programs. Here, we developed robust reporter VZV viruses by using bacterial artificial chromosome (BAC) technology, expressing luciferase from VZV-specific promoters. We also identified two spurious mutations in VZV-BAC that were corrected for maximum pathogenesis. VZV with fLuc driven by ORF57 showed superior growth in cells, human skin explants, and skin xenografts in mice. The ORF57-driven luciferase activity had a short half-life in the presence of foscarnet. This background was then used to investigate the roles for ORF36 (thymidine kinase (TK)) and ORF13 (thymidylate synthase (TS)) in skin. The studies reveal that VZV-∆TS had increased sensitivity to brivudine and was highly impaired for skin replication. This is the first report of a phenotype that is associated with the loss of TS.

The Role of Nervous System and Immune System in Herpes Zoster Ophthalmicus Dissemination and Laterality - Current Views

PURPOSE

Herpes zoster ophthalmicus (HZO) is a sight-threatening condition that is defined as HZ involving the ophthalmic division of the trigeminal nerve. Cases of bilateral HZO in recent literature question the notion of HZO being a strictly unilateral disease. Its pathogenesis is a topic of debate and current literature on VZV dissemination lacks insight into the underlying immunology. This review focuses on novel research in immunology of HZO and aims to formulate hypotheses of spread of lesions through the CNS.

METHODS

A literature search was conducted on Entrez PubMed using the search terms "bilateral" and "herpes zoster ophthalmicus". Articles on ("Immunology" or "immune cells") and "herpes zoster ophthalmicus" were also searched for. Articles published from January 1942 to April 2020 that were in English language were included.

RESULTS

Our findings revealed that hypothesised mechanisms of dissemination causing bilateral ocular disease include transmission from nerves to vessel walls, the synergistic action of the immune and nervous systems through the action of substance P and the von Szily reaction.

CONCLUSIONS

These mechanisms may be investigated using newer models of animal experimentation. It is imperative to define the molecular mechanisms behind VZV transmission to improve methods of identification, treatment, and prevention of HZO.

A Human Skin Model for Assessing Arboviral Infections

Arboviruses such as flaviviruses and alphaviruses cause a significant human healthcare burden on a global scale. Transmission of these viruses occurs during human blood feeding at the mosquito-skin interface. Not only do pathogen immune evasion strategies influence the initial infection and replication of pathogens delivered, but arthropod salivary factors also influence transmission foci. In vitro cell cultures do not provide an adequate environment to study complex interactions between viral, mosquito, and host factors. To address this need for a whole tissue system, we describe a proof of concept model for arbovirus infection using adult human skin ex vivo with Zika virus (flavivirus) and Mayaro virus (alphavirus). Replication of these viruses in human skin was observed up to 4 days after infection. Egressed viruses could be detected in the culture media as well. Antiviral and proinflammatory genes, including chemoattractant chemokines, were expressed in infected tissue. Immunohistochemical analysis showed the presence of virus in the skin tissue 4 days after infection. This model will be useful to further investigate: (i) the immediate molecular mechanisms of arbovirus infection in human skin, and (ii) the influence of arthropod salivary molecules during initial infection of arboviruses in a more physiologically relevant system.

Antiviral Targeting of Varicella Zoster Virus Replication and Neuronal Reactivation Using CRISPR/Cas9 Cleavage of the Duplicated Open Reading Frames 62/71

Varicella Zoster Virus (VZV) causes Herpes Zoster (HZ), a common debilitating and complicated disease affecting up to a third of unvaccinated populations. Novel antiviral treatments for VZV reactivation and HZ are still in need. Here, we evaluated the potential of targeting the replicating and reactivating VZV genome using Clustered Regularly Interspaced Short Palindromic Repeat-Cas9 nucleases (CRISPR/Cas9) delivered by adeno-associated virus (AAV) vectors. After AAV serotype and guide RNA (gRNA) optimization, we report that a single treatment with AAV2-expressing Staphylococcus aureus CRISPR/Cas9 (saCas9) with gRNA to the duplicated and essential VZV genes ORF62/71 (AAV2-62gRsaCas9) greatly reduced VZV progeny yield and cell-to-cell spread in representative epithelial cells and in lytically infected human embryonic stem cell (hESC)-derived neurons. In contrast, AAV2-62gRsaCas9 did not reduce the replication of a recombinant virus mutated in the ORF62 targeted sequence, establishing that antiviral effects were a consequence of VZV-genome targeting. Delivery to latently infected and reactivation-induced neuron cultures also greatly reduced infectious-virus production. These results demonstrate the potential of AAV-delivered genome editors to limit VZV productive replication in epithelial cells, infected human neurons, and upon reactivation. The approach could be developed into a strategy for the treatment of VZV disease and virus spread in HZ.

The important role of non-covalent drug-protein interactions in drug hypersensitivity reactions

Drug hypersensitivity reactions (DHR) are heterogeneous and unusual immune reactions with rather unique clinical presentations. Accumulating evidence indicates that certain non‐covalent drug‐protein interactions are able to elicit exclusively effector functions of antibody reactions or complete T‐cell reactions which contribute substantially to DHR. Here, we discuss three key interactions; (a) mimicry: whereby soluble, non‐covalent drug‐protein complexes (“fake antigens”) mimic covalent drug‐protein adducts; (b) increased antibody affinity: for example, in quinine‐type immune thrombocytopenia where the drug gets trapped between antibody and membrane‐bound glycoprotein; and (c) p‐i‐stimulation: where naïve and memory T cells are activated by direct binding of drugs to the human leukocyte antigen and/or T‐cell receptors. This transient drug‐immune receptor interaction initiates a polyclonal T‐cell response with mild‐to‐severe DHR symptoms. Notable complications arising from p‐i DHR can include viral reactivations, autoimmunity, and multiple drug hypersensitivity. In conclusion, DHR is characterized by abnormal immune stimulation driven by non‐covalent drug‐protein interactions. This contrasts DHR from “normal” immunity, which relies on antigen‐formation by covalent hapten‐protein adducts and predominantly results in asymptomatic immunity.

H84T BanLec has broad spectrum antiviral activity against human herpesviruses in cells, skin, and mice

H84T BanLec is a molecularly engineered lectin cloned from bananas with broad-spectrum antiviral activity against several RNA viruses. H84T BanLec dimers bind glycoproteins containing high-mannose N-glycans on the virion envelope, blocking attachment, entry, uncoating, and spread. It was unknown whether H84T BanLec is effective against human herpesviruses varicella-zoster virus (VZV), human cytomegalovirus (HCMV), and herpes simplex virus 1 (HSV-1), which express high-mannose N-linked glycoproteins on their envelopes. We evaluated H84T BanLec against VZV-ORF57-Luc, TB40/E HCMV-fLuc-eGFP, and HSV-1 R8411 in cells, skin organ culture, and mice. The H84T BanLec EC50 was 0.025 µM for VZV (SI50 = 4000) in human foreskin fibroblasts (HFFs), 0.23 µM for HCMV (SI50 = 441) in HFFs, and 0.33 µM for HSV-1 (SI50 = 308) in Vero cells. Human skin was obtained from reduction mammoplasties and prepared for culture. Skin was infected and cultured up to 14 days. H84T BanLec prevented VZV, HCMV and HSV-1 spread in skin at 10 µM in the culture medium, and also exhibited dose-dependent antiviral effects. Additionally, H84T BanLec arrested virus spread when treatment was delayed. Histopathology of HCMV-infected skin showed no overt toxicity when H84T BanLec was present in the media. In athymic nude mice with human skin xenografts (NuSkin mice), H84T BanLec reduced VZV spread when administered subcutaneously prior to intraxenograft virus inoculation. This is the first demonstration of H84T BanLec effectiveness against DNA viruses. H84T BanLec may have additional unexplored activity against other, clinically relevant, glycosylated viruses.

Mutagenesis of the Varicella-Zoster Virus Genome Demonstrates That VLT and VLT-ORF63 Proteins Are Dispensable for Lytic Infection

Primary varicella-zoster virus (VZV) infection leads to varicella and the establishment of lifelong latency in sensory ganglion neurons. Reactivation of latent VZV causes herpes zoster, which is frequently associated with chronic pain. Latent viral gene expression is restricted to the VZV latency-associated transcript (VLT) and VLT-ORF63 (VLT63) fusion transcripts. Since VLT and VLT63 encode proteins that are expressed during lytic infection, we investigated whether pVLT and pVLT-ORF63 are essential for VZV replication by performing VZV genome mutagenesis using CRISPR/Cas9 and BAC technologies. We first established that CRISPR/Cas9 can efficiently mutate VZV genomes in lytically VZV-infected cells through targeting non-essential genes ORF8 and ORF11 and subsequently show recovery of viable mutant viruses. By contrast, the VLT region was markedly resistant to CRISPR/Cas9 editing. Whereas most mutants expressed wild-type or N-terminally altered versions of pVLT and pVLT-ORF63, only a minority of the resulting mutant viruses lacked pVLT and pVLT-ORF63 coding potential. Growth curve analysis showed that pVLT/pVLT-ORF63 negative viruses were viable, but impaired in growth in epithelial cells. We confirmed this phenotype independently using BAC-derived pVLT/pVLT-ORF63 negative and repaired viruses. Collectively, these data demonstrate that pVLT and/or pVLT-ORF63 are dispensable for lytic VZV replication but promote efficient VZV infection in epithelial cells.

Locked-nucleotide antagonists to varicella zoster virus small non-coding RNA block viral growth and have potential as an anti-viral therapy

Herpes zoster (HZ) remains a significant health burden with millions of cases in North America and Europe annually. HZ is frequently followed by long-term pain or post-herpetic neuralgia (PHN). Although effective vaccines for HZ are available, currently used nucleotide analogues often have limited effectiveness against HZ and especially PHN, so there remains a need for additional antiviral therapies for HZ. We recently identified a population of small non-coding RNA (sncRNA) encoded by Varicella Zoster Virus (VZV) and showed that single locked-nucleic acid antagonists (LNAA) to some sncRNA can modulate VZV replication in cell culture. In this work, we explored the antiviral effects of combinations of LNAA oligonucleotides targeting VZVsncRNA. Combinations of LNAA targeting three VZVsncRNA encoded in and near a critical viral regulatory gene were additive, achieving 96 % reduction in virus growth in a cell line. VZV growth was also inhibited by more than 90 % in primary human skin fibroblast cultures by individual and combinations of LNAA to VZVsncRNA. The inhibition by VZVsncRNA was specific and not a consequence of innate immune responses since LNAA to a different VZVsncRNA enhanced VZV growth. Targeted VZVsncRNA lack homologous sequences in the human transcriptome suggesting that LNAA to them would have reduced cytotoxicity if used as therapeutics. These results support further development of oligonucleotides targeting VZVsncRNA as a novel treatment for HZ.