Development of a Moloney murine leukemia virus-based pseudotype anti-HIV assay suitable for accurate and rapid evaluation of HIV entry inhibitors

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.

Correlation between pseudotyped virus and authentic virus neutralisation assays, a systematic review and meta-analysis of the literature

Background

The virus neutralization assay is a principal method to assess the efficacy of antibodies in blocking viral entry. Due to biosafety handling requirements of viruses classified as hazard group 3 or 4, pseudotyped viruses can be used as a safer alternative. However, it is often queried how well the results derived from pseudotyped viruses correlate with authentic virus. This systematic review and meta-analysis was designed to comprehensively evaluate the correlation between the two assays.

Methods

Using PubMed and Google Scholar, reports that incorporated neutralisation assays with both pseudotyped virus, authentic virus, and the application of a mathematical formula to assess the relationship between the results, were selected for review. Our searches identified 67 reports, of which 22 underwent a three-level meta-analysis.

Results

The three-level meta-analysis revealed a high level of correlation between pseudotyped viruses and authentic viruses when used in an neutralisation assay. Reports that were not included in the meta-analysis also showed a high degree of correlation, with the exception of lentiviral-based pseudotyped Ebola viruses.

Conclusion

Pseudotyped viruses identified in this report can be used as a surrogate for authentic virus, though care must be taken in considering which pseudotype core to use when generating new uncharacterised pseudotyped viruses.

Efficient Gene Transfer to Kidney Using a Lentiviral Vector Pseudotyped with Zika Virus Envelope Glycoprotein

Gene therapy's entrance into clinical settings has made it an ever more attractive field of study for various diseases. However, relatively little progress has been made in targeting kidney diseases due to poor gene delivery efficiency in renal cells. The development of novel gene therapy vectors for medical intervention to treat kidney diseases is needed. In this study, we designed and produced a pseudotyped lentiviral vector with envelope glycoproteins of Zika virus (ZIKV), and evaluated its potential use in viral vector entry, neutralization assay, and gene delivery especially in the renal context. The lentiviral vector, simplified as ZIKV-E, is pseudotyped with Env/G-TC representing the transmembrane (TM) and cytoplasmic (CY) domains of Env replaced with the TM and CY domains of the glycoprotein (G) of the vesicular stomatitis virus. In vivo results show that ZIKV-E induced efficient transduction in tubular epithelial cells in mouse kidneys, demonstrating >100-fold higher expression of exogenous green fluorescent protein gene compared with that achieved by vesicular stomatitis virus G (VSV-G) protein pseudotyped lentiviral vector. The results also showed that the vector ZIKV-E transduced cells in a pH-independent manner and the transduction was inhibited by anti-ZIKV Env domain III antibodies. Results also show that ZIKV-E can be used as a surrogate for studies of ZIKV entry mechanisms and neutralization antibody assay. In all, this study successfully demonstrated a novel pseudotyped lentiviral vector ZIKV-E for inducing high transduction efficiency in renal tubular epithelial cells that could serve as a foundation for gene therapy for the treatment of inherited renal diseases in humans.

AutoPlate: Rapid Dose-Response Curve Analysis for Biological Assays

The emergence of COVID-19 has emphasised that biological assay data must be analysed quickly to develop safe, effective and timely vaccines/therapeutics. For viruses such as SARS-CoV-2, the primary way of measuring immune correlates of protection is through assays such as the pseudotype microneutralisation (pMN) assay, thanks to its safety and versatility. However, despite the presence of existing tools for data analysis such as PRISM and R the analysis of these assays remains cumbersome and time-consuming. We introduce an open-source R Shiny web application and R library (AutoPlate) to accelerate data analysis of dose-response curve immunoassays. Using example data from influenza studies, we show that AutoPlate improves on available analysis software in terms of ease of use, flexibility and speed. AutoPlate (https://philpalmer.shinyapps.io/AutoPlate/) is a tool for the use of laboratories and wider scientific community to accelerate the analysis of biological assays in the development of viral vaccines and therapeutics.

Construction and applications of SARS-CoV-2 pseudoviruses: a mini review

The ongoing coronavirus disease 2019 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has posed a serious threat to global public health and social stability. There is an urgent need for understanding the nature and infection mechanism of the virus. Owing to its high infectivity and pathogenicity and lack of effective treatments, live SARS-CoV-2 has to be handled in biosafety level 3 laboratories, which has impeded research into SARS-CoV-2 and the development of vaccines and therapeutics. Pseudotyped viruses that lack certain gene sequences of the virulent virus are safer and can be investigated in biosafety level 2 laboratories, providing a useful virological tool for the study of SARS-CoV-2. In this review, we will discuss the construction of SARS-CoV-2 pseudoviruses based on different packaging systems, current applications, limitations, and further explorations.

Current status on the development of pseudoviruses for enveloped viruses

Emerging and reemerging infectious diseases have a strong negative impact on public health. However, because many of these pathogens must be handled in biosafety level, 3 or 4 containment laboratories, research and development of antivirals or vaccines against these diseases are often impeded. Alternative approaches to address this issue have been vigorously pursued, particularly the use of pseudoviruses in place of wild-type viruses. As pseudoviruses have been deprived of certain gene sequences of the virulent virus, they can be handled in biosafety level 2 laboratories. Importantly, the envelopes of these viral particles may have similar conformational structures to those of the wild-type viruses, making it feasible to conduct mechanistic investigation on viral entry and to evaluate potential neutralizing antibodies. However, a variety of challenging issues remain, including the production of a sufficient pseudovirus yield and the inability to produce an appropriate pseudotype of certain viruses. This review discusses current progress in the development of pseudoviruses and dissects the factors that contribute to low viral yields.

Agonist-induced internalization of CC chemokine receptor 5 as a mechanism to inhibit HIV replication

The chemokine G protein-coupled receptor CC chemokine receptor 5 (CCR5) is used as an entry gate by CCR5-tropic and dual- or CCR5/CXC chemokine receptor 4-tropic strains of HIV to enter the human host cells. Thus, CCR5 antagonists (i.e., maraviroc) have been proven to be clinically effective by preventing the interaction between viral glycoprotein 120 and CCR5 and thus impeding viral entry into host cells. However, the emergence of HIV strains resistant to CCR5 antagonists has been reported in vitro and in vivo, where the virus has adapted to enter the cells via antagonist-bound CCR5. An alternative strategy that should obviate this mode of viral resistance would entail the ablation of the CCR5 portal for HIV entry from the cell surface through agonist-induced receptor internalization. Although this protective effect has been demonstrated clearly with natural CCR5 ligands, the chemoattractant properties of these chemokines have precluded them from further consideration in terms of drug development. Thus, we sought to explore the possibility of developing novel small molecules and selective CCR5 agonists devoid of eliciting chemotaxis. Indeed, the CCR5 agonists described herein were found to induce profound down-modulation of CCR5 (and not CXC chemokine receptor 4) from the cell surface and its sustained sequestration in the intracellular compartment without inducing chemotaxis in vitro. The bioactivity profile of these novel CCR5 agonists is exemplified by the compound (R)-2-(4-cyanophenyl)-N-(1-(1-(N,1-diphenylmethylsulfonamido)propan-2-yl)piperidin-4-yl)acetamide (ESN-196) that potently inhibits HIV-1 infection in human peripheral blood mononuclear cells and macrophages in vitro with potencies comparable to that of maraviroc and moreover demonstrates full activity against a maraviroc-resistant HIV-1 RU570 strain.

Characterization of Chikungunya pseudotyped viruses: Identification of refractory cell lines and demonstration of cellular tropism differences mediated by mutations in E1 glycoprotein

Chikungunya virus (CHIKV) is an alphavirus responsible for a number of large outbreaks. Here we describe the efficient incorporation of CHIKV envelope glycoproteins into lentiviral and rhabdoviral particles. Vectors pseudotyped with CHIKV envelope proteins efficiently transduced many cell types from different species. However, hematopoietic cell types were either partially or completely refractory. A mutation in E1 (A226V) has been linked with expansion of tropism for mosquito species, although differences in in vitro infection of mosquito cell lines have not been noted. However, pseudovirion infectivity assays detected subtle differences in infection of mosquito cells, suggesting an explanation for the changes in mosquito tropism. The presence of C-type lectins increased CHIKV pseudotyped vector infectivity, but not infection of refractory cells, suggesting that they act as attachment factors rather than primary receptors. CHIKV pseudotypes will serve as an important tool for the study of neutralizing antibodies and the analysis of envelope glycoprotein functions.

High-throughput screening using pseudotyped lentiviral particles: a strategy for the identification of HIV-1 inhibitors in a cell-based assay

Two decades after its discovery the human immunodeficiency virus (HIV) is still spreading worldwide and killing millions. There are 25 drugs formally approved for HIV currently on the market, but side effects as well as the emergence of HIV strains showing single or multiple resistances to current drug-therapy are causes for concern. Furthermore, these drugs target only 4 steps of the viral cycle, hence the urgent need for new drugs and also new targets. In order to tackle this problem, we have devised a cell-based assay using lentiviral particles to look for post-entry inhibitors of HIV-1. We report here the assay development, validation as well as confirmation of the hits using both wild-type and drug-resistant HIV-1 viruses. The screening was performed on an original library, rich in natural compounds and pure molecules from Traditional Chinese Medicine pharmacopoeia, which had never been screened for anti-HIV activity. The identified hits belong to four chemical sub-families that appear to be all non-nucleoside reverse transcriptase inhibitors (NNRTIs). Secondary tests with live viruses showed that there was good agreement with pseudotyped particles, confirming the validity of this approach for high-throughput drug screens. This assay will be a useful tool that can be easily adapted to screen for inhibitors of viral entry.

Problems and emerging approaches in HIV/AIDS vaccine development

According to recent estimates, 39.5 million people have been infected with HIV and 2.9 million have already died. The effect of HIV infection on individuals and communities is socially and economically devastating. Although antiretroviral drugs have had a dramatically beneficial impact on HIV-infected individuals who have access to treatment, it has had a negligible impact on the global epidemic. Therefore, the need for an efficacious HIV/AIDS vaccine remains the highest priority of the world HIV/AIDS agenda. The generation of a vaccine against HIV/AIDS has turned out to be extremely challenging, as indicated by > 20 years of unsuccessful attempts. This review discusses the major challenges in the field and key experimental evidence providing a rationale for the use of non-structural HIV proteins, such as Rev, Tat and Nef, either in the native form or expressed by viral vectors such as a replicating adeno-vector. These non-structural proteins alone or in combination with modified structural HIV-1 Env proteins represent a novel strategy for both preventative and therapeutic HIV/AIDS vaccine development.