A Novel and Secure Pseudovirus Reporter System Based Assay for Neutralizing and Enhancing Antibody Assay Against Marburg Virus

Establishment of a pseudovirus neutralization assay for TGEV

Introduction

Transmissible Gastroenteritis Virus (TGEV) is a major pathogen causing swine enteric diseases, necessitating effective control strategies. Vaccination plays a key role, but assessing vaccine efficacy remains challenging due to variations in immune response and existing detection limitations. Current antibody detection methods, such as neutralization assays and ELISA, are often subjective, labor-intensive, and time-consuming, highlighting the need for a more efficient evaluation approach.

Methods and results

The TGEV S gene was amplified and inserted into the eukaryotic vector PM2.G-ΔG-HA to construct the recombinant plasmid PM2.G-ΔG-TGEV-S-HA. Transfecting ST cells with this plasmid, followed by infection with G*VSV-GFP/LUC, successfully produced TGEV P0 pseudoviruses. Western blot and electron microscopy confirmed the presence of TGEV S and VSV N proteins and the distinct pseudovirus morphology. Optimization determined that 0.5 μg/well of plasmid, 24 h transfection, and 24 h post-infection harvest yielded a viral titer of 106-107 TCID50/mL. The pseudoviruses exhibited strong ST cell tropism and were effectively neutralized by TGEV-positive sera. A pseudovirus-based neutralization test (pNT) was established, showing 100% sensitivity, 96.6% specificity, no cross-reactivity with PEDV, PPV, PDCoV, or PRoV, and a 94% concordance with the live virus neutralization test. The method effectively tracked antibody level changes post-TGEV vaccination.

Discussion

This study successfully developed a novel pseudovirus-based detection method, overcoming traditional assay limitations. The pNT method provides a scalable, efficient, and reliable tool for TGEV antibody evaluation, with broad potential applications in pathogen detection and vaccine assessment.

Pseudoviruses, a safer toolbox for vaccine development against enveloped viruses

INTRODUCTION

Pseudoviruses are recombinant, replication-incompetent, viral particles designed to mimic the surface characteristics of native enveloped viruses. They are a safer, and cost-effective research alternative to live viruses. With the potential emergence of the next major infectious disease, more vaccine scientists must become familiar with the pseudovirus platform as a vaccine development tool to mitigate future outbreaks.

AREAS COVERED

This review aims at vaccine developers to provide a basic understanding of pseudoviruses, list their production methods, and discuss their utility to assess vaccine efficacy against enveloped viral pathogens. We further illustrate their usefulness as wet-lab simulators for emerging mutant variants, and new viruses to help prepare for current and future viral outbreaks, minimizing the need for gain-of-function experiments with highly infectious or lethal enveloped viruses.

EXPERT OPINION

With this platform, researchers can better understand the role of virus-receptor interactions and entry in infections, prepare for dangerous mutations, and develop effective vaccines.

A rabies virus-vectored vaccine expressing two copies of the Marburg virus glycoprotein gene induced neutralizing antibodies against Marburg virus in humanized mice

Marburg virus disease (MVD) is a lethal viral haemorrhagic fever caused by Marburg virus (MARV) with a case fatality rate as high as 88%. There is currently no vaccine or antiviral therapy approved for MVD. Due to high variation among MARV isolates, vaccines developed against one strain fail to protect against other strains. Here we report that three recombinant rabies virus (RABV) vector vaccines encoding two copies of GPs covering both MARV lineages induced pseudovirus neutralizing antibodies in BALB/c mice. Furthermore, high-affinity human neutralizing antibodies were isolated from a humanized mouse model. The three vaccines produced a Th1-biased serological response similar to that of human patients. Adequate sequential immunization enhanced the production of neutralizing antibodies. Virtual docking suggested that neutralizing antibodies induced by the Angola strain seemed to be able to hydrogen bond to the receptor-binding site (RBS) in the GP of the Ravn strain through hypervariable regions 2 (CDR2) and CDR3 of the VH region. These findings demonstrate that three inactivated vaccines are promising candidates against different strains of MARV, and a novel fully humanized neutralizing antibody against MARV was isolated.

Characterization of a Vesicular Stomatitis Virus-Vectored Recombinant Virus Bearing Spike Protein of SARS-CoV-2 Delta Variant

The frequent emergence of SARS-CoV-2 variants thwarts the prophylactic and therapeutic countermeasures confronting COVID-19. Among them, the Delta variant attracts widespread attention due to its high pathogenicity and fatality rate compared with other variants. However, with the emergence of new variants, studies on Delta variants have been gradually weakened and ignored. In this study, a replication-competent recombinant virus carrying the S protein of the SARS-CoV-2 Delta variant was established based on the vesicular stomatitis virus (VSV), which presented a safe alternative model for studying the Delta variant. The recombinant virus showed a replication advantage in Vero E6 cells, and the viral titers reach 10^7.3 TCID₅₀/mL at 36 h post-inoculation. In the VSV-vectored recombinant platform, the spike proteins of the Delta variant mediated higher fusion activity and syncytium formation than the wild-type strain. Notably, the recombinant virus was avirulent in BALB/c mice, Syrian hamsters, 3-day ICR suckling mice, and IFNAR/GR^-/- mice. It induced protective neutralizing antibodies in rodents, and protected the Syrian hamsters against the SARS-CoV-2 Delta variant infection. Meanwhile, the eGFP reporter of recombinant virus enabled the visual assay of neutralizing antibodies. Therefore, the recombinant virus could be a safe and convenient surrogate tool for authentic SARS-CoV-2. This efficient and reliable model has significant potential for research on viral-host interactions, epidemiological investigation of serum-neutralizing antibodies, and vaccine development.