Pseudotyped Viruses

Receptor-binding proteins from animal viruses are broadly compatible with human cell entry factors

Cross-species transmission of animal viruses poses a threat to human health. However, systematic experimental assessments of these risks remain scarce. A critical step in viral infection is cellular internalization mediated by viral receptor-binding proteins (RBPs). Here we constructed viral pseudotypes bearing the RBPs of 102 enveloped RNA viruses and assayed their infectivity across 5,202 RBP-cell combinations. This showed that most of the tested viruses have the potential to enter human cells. Pseudotype infectivity varied widely among the 14 viral families examined and was influenced by RBP characteristics, host of origin and target cell type. Cellular gene expression data revealed that the availability of specific cell-surface receptors is not necessarily the main factor limiting viral entry and that additional host factors must be considered. Altogether, these results suggest weak interspecies barriers in the early stages of infection and advance our understanding of the molecular interactions driving viral zoonosis.

SARS-CoV-2 Neutralizing Antibodies 2.0

As the SARS-CoV-2 mutates, especially into those variants causing immune escape, COVID-19 continues to wreak havoc [...].

A validated and standardized pseudotyped microneutralization assay as a safe and powerful tool to measure LASSA virus neutralising antibodies for vaccine development and comparison

Background

Over the past few decades, World Health Organization (WHO) has made massive efforts to promote the development of a vaccine against Lassa virus (LASV), one of the top ten priority pathogens for research and development under the WHO R&D Blueprint for Emerging Infections. To date, several vaccines are at different stages of development. In this scenario, a validated and standardised assay to measure LASV neutralising antibodies is urgently needed for vaccine development and comparison.

Methods

The neutralisation assay remains the gold standard for determining antibody efficacy. Here we have proposed a safe and validated pseudotyped neutralisation assay for LASV, taking advantage of the development of the first WHO International Standard and Reference Panel for Anti-Lassa Fever (NIBSC code 21/332).

Results and Conclusions

The proposed results demonstrate that the pseudotyped luciferase neutralisation assay is a specific serological test for the measurement of LASV neutralising antibodies without cross-reacting with standard sera specific for heterologous viral infections. In addition, the assay is accurate, precise, and linear according to criteria and statistical analyses defined and accepted by international guidelines.

Development of a SARS-CoV-2 neutralization assay based on a pseudotyped virus using a HIV system

Regarding the extensive global attention to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that constitutes an international public health emergency, pseudovirus neutralization assays have been widely applied due to their advantages of being able to be conducted in biosafety level 2 laboratories and having a high safety factor. In this study, by adding a blue fluorescent protein (AmCyan) gene to the HIV system pSG3-△env backbone plasmid HpaI and truncating the C-terminal 21 amino acids of the SARS-CoV-2 spike protein (S), high-titer SARS-CoV-2-Sdel21-AmCyan fluorescent pseudovirus was successfully packaged. The fluorescent pseudovirus was used to establish a neutralization assay in a 96-well plate using 293T cells stably transfected with the AF cells. Then, parameters such as the ratio of backbone and membrane plasmid, sensitive cells, inoculation of cells and virus, as well as incubation and detection time were optimized. The pseudovirus neutralization assay demonstrated high accuracy, sensitivity, repeatability, and a strong correlation with the luminescent pseudovirus neutralization assay. Additionally, we scaled up the neutralizing antibody determination method by increasing the plate size from 96 wells to 384 wells. We have established a robust fluorescent pseudotyped virus neutralization assay for SARS-CoV-2 using the HIV system, providing a foundation for serum neutralization antibody detection, monoclonal antibody screening, and vaccine development.

Transduction Efficiency of Zika Virus E Protein Pseudotyped HIV-1gfp and Its Oncolytic Activity Tested in Primary Glioblastoma Cell Cultures

The development of new tools against glioblastoma multiforme (GBM), the most aggressive and common cancer originating in the brain, remains of utmost importance. Lentiviral vectors (LVs) are among the tools of future concepts, and pseudotyping offers the possibility of tailoring LVs to efficiently transduce and inactivate GBM tumor cells. Zika virus (ZIKV) has a specificity for GBM cells, leaving healthy brain cells unharmed, which makes it a prime candidate for the development of LVs with a ZIKV coat. Here, primary GBM cell cultures were transduced with different LVs encased with ZIKV envelope variants. LVs were generated by using the pNLgfpAM plasmid, which produces the lentiviral, HIV-1-based, core particle with GFP (green fluorescent protein) as a reporter (HIVgfp). Using five different GBM primary cell cultures and three laboratory-adapted GBM cell lines, we showed that ZIKV/HIVgfp achieved a 4-6 times higher transduction efficiency compared to the commonly used VSV/HIVgfp. Transduced GBM cell cultures were monitored over a period of 9 days to identify GFP+ cells to study the oncolytic effect due to ZIKV/HIVgfp entry. Tests of GBM tumor specificity by transduction of GBM tumor and normal brain cells showed a high specificity for GBM cells.

Pseudotyped zoonotic thogotoviruses exhibit broad entry range in mammalian cells

Viruses in the thogotovirus genus of the family Orthomyxoviridae are much less well-understood than influenza viruses despite documented zoonotic transmission and association with human disease. This study therefore developed a cell-cell fusion assay and three pseudotyping tools and used them to assess envelope function and cell tropism. Envelope glycoproteins of Dhori (DHOV), Thogoto (THOV), Bourbon, and Sinu viruses were all revealed to exhibit pH-dependent triggering of membrane fusion. Lentivirus vectors were robustly pseudotyped with these glycoproteins while influenza virus vectors showed pseudotyping compatibility, albeit at lower efficiencies. Replication-competent vesicular stomatitis virus expressing DHOV or THOV glycoproteins were also successfully generated. These pseudotyped viruses mediated entry into a wide range of mammalian cell lines, including human primary cells. The promiscuousness of these viruses suggests the use of a relatively ubiquitous receptor and their entry into numerous mammalian cells emphasize their high potential as veterinary and zoonotic diseases.