Production, quality control, stability, and potency of cGMP-produced Plasmodium falciparum RH5.1 protein vaccine expressed in Drosophila S2 cells

Abstract

Plasmodium falciparum reticulocyte-binding protein homolog 5 (PfRH5) is a leading asexual blood-stage vaccine candidate for malaria. In preparation for clinical trials, a full-length PfRH5 protein vaccine called “RH5.1” was produced as a soluble product under cGMP using the ExpreS2 platform (based on a Drosophila melanogaster S2 stable cell line system). Following development of a high-producing monoclonal S2 cell line, a master cell bank was produced prior to the cGMP campaign. Culture supernatants were processed using C-tag affinity chromatography followed by size exclusion chromatography and virus-reduction filtration. The overall process yielded >400 mg highly pure RH5.1 protein. QC testing showed the MCB and the RH5.1 product met all specified acceptance criteria including those for sterility, purity, and identity. The RH5.1 vaccine product was stored at −80 °C and is stable for over 18 months. Characterization of the protein following formulation in the adjuvant system AS01B showed that RH5.1 is stable in the timeframe needed for clinical vaccine administration, and that there was no discernible impact on the liposomal formulation of AS01B following addition of RH5.1. Subsequent immunization of mice confirmed the RH5.1/AS01B vaccine was immunogenic and could induce functional growth inhibitory antibodies against blood-stage P. falciparum in vitro. The RH5.1/AS01B was judged suitable for use in humans and has since progressed to phase I/IIa clinical trial. Our data support the future use of the Drosophila S2 cell and C-tag platform technologies to enable cGMP-compliant biomanufacture of other novel and “difficult-to-express” recombinant protein-based vaccines.

Malaria vaccines since 2000: progress, priorities, products

“…In addition, protection in monkeys required an estimated 200 µg/mL of anti-PfRH5 IgG 56 , a high level to achieve and sustain by vaccination. Efforts to improve RH5 vaccine candidates include presentation in virus-like particles (VLP) and production of a protein vaccine in Drosophila (Schneider 2) cells 59,60 .…”

Impact of a rapid decline in malaria transmission on antimalarial IgG subclasses and avidity

“…The P. falciparum antigens broadly fell into three categories; (i) infected red blood cell, (ii) merozoite apical organelle, and (iii) merozoite surface antigen associated proteins. The recombinant antigens were expressed in Escherichia coli either as glutathione S-transferase (GST) fusion proteins or as histidine tagged constructs (supplementary table1), with the exception of AMA1(51) which was expressed in Pichia pastoris and Rh5.1 which was expressed in HEK293 mammalian cells (52).…”

Generating and working with Drosophila cell cultures: Current challenges and opportunities

“…Other S2‐derived vaccine products against Dengue virus also made it to clinical trials (Manoff et al, ). Therefore, the prospect of using Drosophila cell cultures to produce other recombinant protein vaccines is promising (Jin et al, ). Furthermore, the ease for stably transforming Drosophila cells is also relevant for the development of biosensor‐based diagnostic for disease markers (H. C. Lau et al, ).…”