More Than Just Gene Therapy Vectors: Lentiviral Vector Pseudotypes for Serological Investigation

Abstract

Serological assays detecting neutralising antibodies are important for determining the immune responses following infection or vaccination and are also often considered a correlate of protection. The target of neutralising antibodies is usually located in the Envelope protein on the viral surface, which mediates cell entry. As such, presentation of the Envelope protein on a lentiviral particle represents a convenient alternative to handling of a potentially high containment virus or for those viruses with no established cell culture system. The flexibility, relative safety and, in most cases, ease of production of lentiviral pseudotypes, have led to their use in serological assays for many applications such as the evaluation of candidate vaccines, screening and characterization of anti-viral therapeutics, and sero-surveillance. Above all, the speed of production of the lentiviral pseudotypes, once the envelope sequence is published, makes them important tools in the response to viral outbreaks, as shown during the COVID-19 pandemic in 2020. In this review, we provide an overview of the landscape of the serological applications of pseudotyped lentiviral vectors, with a brief discussion on their production and batch quality analysis. Finally, we evaluate their role as surrogates for the real virus and possible alternatives.

Keywords: lentivirus; pseudotype; serology; vector.

Figure 1

Application of pseudotyped lentiviral vectors (LVs) to neutralisation assays. Pseudotyped lentiviral particles are generated by transfection of a permissive cell line (e.g., HEK293T) with a mix of plasmids coding for HIV-1 structural and enzymatic proteins (HIV gagpol), the lentiviral vector with a transgene of interest, e.g., luciferase, GFP, contained within the HIV long terminal repeats (LTR) and an expression plasmid coding the Env of the virus of interest. Particles are collected in the supernatant of the transfected cells usually 48–72 h post-transfection (A). In a neutralisation assay, the pseudotyped LV particles are incubated with the serological sample to test before adding to the target cells. If no neutralising antibody is present, the pseudotyped LV will enter the target cells, and the transgene will be expressed, and infection can be monitored by the signal produced. Neutralising antibody in the sample will inhibit LV entry and no signal will be visible (B).