Production of HIV virus-like particles by transient transfection of CAP-T cells at bioreactor scale avoiding medium replacement

How promising are HIV-1-based virus-like particles for medical applications

New approaches aimed at identifying patient-specific drug targets and addressing unmet clinical needs in the framework of precision medicine are a strong motivation for researchers worldwide. As scientists learn more about proteins that drive known diseases, they are better able to design promising therapeutic approaches to target those proteins. The field of nanotechnology has been extensively explored in the past years, and nanoparticles (NPs) have emerged as promising systems for target-specific delivery of drugs. Virus-like particles (VLPs) arise as auspicious NPs due to their intrinsic properties. The lack of viral genetic material and the inability to replicate, together with tropism conservation and antigenicity characteristic of the native virus prompted extensive interest in their use as vaccines or as delivery systems for therapeutic and/or imaging agents. Owing to its simplicity and non-complex structure, one of the viruses currently under study for the construction of VLPs is the human immunodeficiency virus type 1 (HIV-1). Typically, HIV-1-based VLPs are used for antibody discovery, vaccines, diagnostic reagent development and protein-based assays. This review will be centered on the use of HIV-1-based VLPs and their potential biomedical applications.

Adaptive laboratory evolution of stable insect cell lines for improved HIV-Gag VLPs production

Adaptive laboratory evolution (ALE) has been extensively used to modulate the phenotype of industrial model organisms (e.g. Escherichia. coli and Saccharomyces cerevisae) towards a specific trait. Nevertheless, its application to animal cells, and in particular to insect cell lines, has been very limited. In this study, we describe employing an ALE method to improve the production of HIV-Gag virus-like particles (VLPs) in stable Sf-9 and High Five cell lines. Serial batch transfer was used for evolution experiments. During the ALE process, cells were cultured under controlled hypothermic conditions (22 °C instead of standard 27 °C) for a prolonged period of time (over 3 months), which allowed the selection of a population of cells with improved phenotype. Adapted cells expressed up to 26-fold (Sf-9 cells) and 10-fold (High Five cells) more Gag-VLPs than non-adapted cells cultured at standard conditions. The production of HIV Gag-VLPs in adapted, stable insect Sf-9 cell lines was successfully demonstrated at bioreactor scale. The Gag-VLPs produced at 22 °C and 27 °C were comparable, both in size and morphology, thus confirming the null impact of adaptation process and hypothermic culture conditions on VLP's quality. This work demonstrates the suitability of ALE as a powerful method for improving yields in stable insect cell lines producing VLPs.

Intracellular Delivery of HCV NS3p gene using vectored particles

Viral hepatitis caused by the hepatitis C virus (HCV) affects millions of people worldwide. The non-structural protein 3 (NS3), one of the most conserved proteins in HCV, is the target of many therapeutic studies. The NS3 protease domain (NS3p) has a range of cytotoxic T lymphocyte (CTL) epitopes, and synthesizing the protein inside the cells is the most appropriate way to present it to the immune system. We developed a tool to study this kind of presentation, using two vectored particle (VP) systems, one based on the Semliki Forest virus (SFV) and the other on HCV pseudoparticles (HCVpp), both carrying the protease domain of the NS3 gene. In addition to producing the particles, we developed a method to quantify these VPs using qRT-PCR. We produced batches of approximately 2.4 × 10⁴ SFV-NS3p/μL and 4.0 × 10² HCVpp-NS3p/μL. BHK-21 and HuH-7 cells treated with the VPs expressed the NS3 protein, thus showing the functionality of this system.