Varicella-zoster Virus Titers Research Articles

Evaluation of the Immunological Efficacy of an LNP-mRNA Vaccine Prepared from Varicella Zoster Virus Glycoprotein gE with a Double-Mutated Carboxyl Terminus in Different Untranslated Regions in Mice.

Cell-mediated immunity (CMI) plays a key role in the effectiveness of varicella zoster virus (VZV) vaccines, and mRNA vaccines have an innate advantage in inducing CMI. Glycoprotein E (gE) has been used widely as an antigen for VZV vaccines, and carboxyl-terminal mutations of gE are associated with VZV titer and infectivity. In addition, the untranslated regions (UTRs) of mRNA affect the stability and half-life of mRNA in the cell and are crucial for protein expression and antigenic translational efficiency. In this study, three UTRs were designed and connected to the nucleic acid sequence of gE-M, which is double mutated in the extracellular region of gE. Then, mRNA with different nucleic acids was encapsulated in lipid nanoparticles (LNPs), forming three LNP-mRNA VZV vaccines, named gE-M-Z, gE-M-M, and gE-M-P. The immune response elicited by these vaccines in mice was evaluated at intervals of 4 weeks, and the mice were sacrificed 2 weeks after the final immunization. In the results, the gE-M-P group, which retains the nucleic acid sequence of gE-M and is connected to Pfizer/BioNTech's BNT162b2 UTRs, induced the strongest humoral immune response and CMI. Because CMI is crucial for protection against VZV and for the design of VZV vaccines, this study provides a feasible strategy for improving the effectiveness and economy of future VZV vaccines.

Varicella-zoster virus inhibits autophagosome-lysosome fusion and the degradation stage of mTOR-mediated autophagic flux

Macroautophagy (herein referred to as autophagy) is a lysosomal degradation mechanism that is important for maintaining homeostasis and for coping with cellular stress such as nutrient deprivation. Previously, varicella-zoster virus (VZV) was reported to modulate the autophagy pathway in the host. However, how VZV affects the autophagy pathway is still unclear. In this study, we examined how wild-type rOka and attenuated vOka strains of cell-associated VZV affect autophagy in MRC-5 fibroblasts by using ratiometric flow cytometry and immunoblotting methods. While VZV does not prevent autophagosome formation, we demonstrate that, particularly when autophagy is upregulated, VZV inhibits late-stage autophagic flux, likely at the point where autophagosomes and lysosomes fuse or where vesicle contents are degraded. Importantly, inhibition of autophagy yields higher VZV titers. These results substantially contribute to the current view of the interaction between VZV and autophagy, and to a better understanding of VZV pathogenesis.

The Glycoprotein B Cytoplasmic Domain Lysine Cluster Is Critical for Varicella-Zoster Virus Cell-Cell Fusion Regulation and Infection.

Varicella-zoster virus (VZV) is a ubiquitous pathogen that causes chickenpox and shingles. Individuals afflicted with shingles risk developing the painful condition of postherpetic neuralgia (PHN), which has been difficult to treat because the underlying cause is not well understood. Additional therapies are needed, as the current vaccine is not recommended for immunocompromised individuals and its efficacy decreases with the age of the recipient. VZV is known to induce the formation of multinuclear cells in neuronal tissue, which has been proposed to be a factor contributing to PHN. This study examines the role of a lysine cluster in the cytoplasmic domain of the VZV fusion protein, gB, in the formation of VZV induced multinuclear cells and in virus replication kinetics and spread. The findings further elucidate how VZV self-regulates multinuclear cell formation and may provide insight into the development of new PHN therapies.

The pros and cons of autophagic flux among herpesviruses

Autophagy has been intensively studied in herpes simplex virus type 1 (HSV-1), a human alphaherpesvirus. The HSV-1 genome encodes a well-known neurovirulence protein called ICP34.5. When the gene encoding this protein is deleted from the genome, the virus is markedly less virulent when injected into the brains of animal models. Subsequent characterization of ICP34.5 established that the neurovirulence protein interacts with BECN1, thereby inhibiting autophagy and facilitating viral replication in the brain. However, an ortholog of the ICP34.5 gene is lacking in the genomes of other closely related alphaherpesviruses, such as varicella-zoster virus (VZV). Further, autophagosomes are easily identified in the exanthem (rash) that is the hallmark of both VZV diseases—varicella and herpes zoster. Inhibition of autophagy leads to diminished VZV titers. Finally, no block is detected in studies of autophagic flux following VZV infection. Thus autophagy appears to be proviral during VZV infection while antiviral during HSV-1 infection. Because divergence to this degree is extremely unusual for 2 closely related herpesviruses, we postulate that VZV has accommodated its infectious cycle to benefit from autophagic flux, whereas HSV-1 has captured cellular immunomodulatory genes to inhibit autophagy.

Vaccine-related varicella-zoster rash in a hospitalized immunocompetent patient

An immunocompetent health care worker with no known history of varicella-zoster virus (VZV) disease was exposed to a patient with herpes zoster and was immunized 2 days later. Twenty-seven days after receiving the varicella vaccine, while hospitalized, she developed a disseminated rash. This exposure and subsequent development of symptoms posed infection control challenges. A polymerase chain reaction analysis of her vesicular fluid was positive for vaccine-type VZV, and a blood specimen collected before vaccination demonstrated a positive VZV titer by the fluorescent antibody to membrane antigen test. To the best of our knowledge, there have been no previous reports of an immunocompetent seropositive person developing vaccine-type VZV after receiving the vaccine.

Tropism of varicella-zoster virus for human CD4+ and CD8+ T lymphocytes and epidermal cells in SCID-hu mice

To investigate the cell tropism and pathogenicity of varicella-zoster virus (VZV) strains, we analyzed VZV replication by using SCID-hu mice that carry human fetal thymus/liver implants under the kidney capsule or as subcutaneous fetal skin implants. MRC-5 cells infected with wild-type VZV or the Oka strain, used in the live attenuated varicella vaccine, were injected into the implants. The implants were surgically removed 2, 7, 14, and 21 days postinfection. The VZV titer from infected thymus/liver implants peaked on day 7 for the wild-type strain and on day 14 for the Oka strain. Histological analysis showed necrotic areas characterized by thymocyte depletion and fibrosis. VZV protein synthesis was detectable by immunohistochemical staining in the necrotic areas and in distant regions that did not show cytopathic changes, and VZV DNA was detected by in situ hybridization in the same distribution. Fluorescence-activated cell sorting analysis of thymocytes harvested at day 7 postinfection showed that VZV proteins were expressed in CD4+, CD8+, and CD4+ CD8+ T cells; VZV was cultured from each T-cell subpopulation. The Oka strain had tropism for human cell types similar to that of wild-type VZV. T lymphocytes released infectious VZV, which is a novel and important observation about the replication of this otherwise highly cell associated virus. VZV-infected skin implants exhibited microscopic epidermal lesions that were indistinguishable histologically from the characteristic lesions of varicella. These experiments demonstrate a unique tropism of VZV for human T lymphocytes, explaining its capacity to cause viremia in natural disease, and demonstrate the value of the SCID-hu model for studies of VZV pathogenesis.

Factors influencing quantitative isolation of varicella-zoster virus.

Optimal conditions are described for the recovery of cell culture-derived varicella-zoster virus (VZV). Of the cells tested, human embryonic lung fibroblasts were the most sensitive. Storage and handling procedures were examined to determine the stability of VZV in viral transport medium. When the initial VZV titer was high (2 X 10(4) PFU/ml) 40% of the VZV survived room temperature for 24 h and 75% of the VZV remained viable for this long at 4 degrees C. Recovery was 5- to 10-fold less at lower initial VZV titers (less than 2 X 10(3) PFU/ml). Other factors which influenced VZV recovery included freezing at -20 degrees C, the use of cotton or calcium alginate swabs, and filtration to remove bacterial contaminants. The tissue culture methods described were used in a reconstruction experiment to demonstrate that VZV could be recovered from a laboratory coat or human skin (0.1 to 0.3% of input VZV) or from a stethoscope (19% of input VZV) as late as 30 min after inoculation. During a clinical trial using optimal VZV recovery procedures, 76% of the patients with herpes zoster yielded VZV when first cultured, and 60% remained culture positive for an additional 48 h.