A clinically validated Drosophila S2 based vaccine platform for production of malaria vaccines

Drosophila S2 insect cell expression is less known than the extensively used Spodoptera or Trichoplusia ni (Hi-5) insect cell based Baculovirus expression system (BEVS). Nevertheless it has been used in research for almost 40 years. The cell line was derived from late stage Drosophila melanogaster (Fruit fly) embryos by Schneider in the 1970s, who named the cell line Drosophila Schneider line 2 (synonyms: S2, SL2, D.mel. 2). The system has been widely applied to fundamental research, where the availability of the whole genome sequence of Drosophila melanogaster (1, 2) and the S2 cells’ susceptibility to RNA interference methods (3, 4) have enabled genome wide RNAi screening and whole genome expression analysis techniques to be used to great effect. S2 cells have proved to be highly effective for the production of proteins from a great variety of protein classes (5), such as: viral proteins, toxins, membrane proteins, enzyme, etc. Recent publications have also shown the strength of the S2 system in expression of Virus Like Particles (VLPs) (6). ExpreS2ion has developed the ExpreS2, Drosophila S2 platform to achieve improved yields for difficult to express proteins. Furthermore, several technologies have been developed to improve the ease of use of the system, as well as enable fast and efficient screening of multiple constructs. S2 based production processes for two malaria vaccine clinical trails with The Jenner Institute, Oxford University (Rh5 (7,8), blood-stage malaria) and Copenhagen University (VAR2CSA (9) pregnancy associated malaria) have been developed. The placental malaria vaccine is currently in a phase Ia trail in Germany, and a Phase Ib trial in Benin. The blood-stage malaria vaccine is currently in Phase IIa trial and is expecting results by the end of 2018. Several transmission-blocking candidates have been identified over the years with some of the most prominent being pfs48/45, Pfs230C and Pfs25(10). Other vaccine targets focus on blood-stage malaria such as Rh5, PfRIPR and CyrPA. We will present data on the development of a high producing Pfs25 monoclonal cell line and the purification from said cell line,as well as expression data on a range of other malaria vaccine targets. This present the clinically validated ExpreS2 platform as a complete system for a wide range of malaria targeting vaccines. (1) Adams M.D. et al. Science 2000 287:2185-2195 (2) Ashburner M, et al. Genome Res. 2005 Dec;15(12):1661-7 (3) Neumüller RA, et al. Wiley Interdiscip Rev Syst Biol Med. 2011 Jul-Aug; 3(4):471-8 (4) D’Ambrosio M.V. et al. J. Cell Biol. Vol. 191 No. 3 471–478 (5) Schetz J.A. et al. Protein Expression in the Drosophila Schneider 2 Cell System, Current Protocols in Neuroscience, 2004 (6) Yang L. et al. J Virol. 2012, Jul;86(14):7662-76. (7) Wright K.E. et al. Nature, 2014 Nov 20;515(7527):427-30 (8) Hjerrild K.A. et al. Sci Rep. 2016 Jul 26;6:30357 (9) Nielsen M.A. et al. PLoS One. 2015 Sep 1;10(9):e0135406 (10) Chaturvedi N et al. Indian J Med Res. 2016 Jun;143(6):696-71

HER2 cancer vaccine optimization by combining Drosophila S2 insect cell manufacturing with a novel VLP-display technology

Breast cancer is a widespread oncology indication affecting more than 1.3 million people worldwide annually, 20%-30% of which are HER2 positive. HER2 is a tyrosine kinase receptor that is frequently overexpressed in several solid-tumor cancers (incl. breast, prostate, gastric, esophageal and osteosarcoma) where it denotes an aggressive phenotype, high metastatic rate, and poor prognosis. In a human context, passive HER2-targeted immunotherapy using monoclonal antibodies (mAb, e.g. Trastuzumab and Pertuzumab) has proven to be an effective treatment modality, which has dramatically improved clinical outcomes. Unfortunately, mAb therapy is very expensive and the repeated injections of high doses can be associated with severe side-effects that reduce efficacy. Vaccines are highly cost-effective, but overall progress in development of anti-cancer vaccines based on cancer-associated antigens (e.g. HER2) has been hampered by inherent immune-tolerogenic mechanisms rendering the immune system incapable of reacting against the body’s own cells/proteins (i.e. self-antigens). Consequently, many attempts to develop anti-cancer vaccines have failed in clinical trials due to insufficient immunogenicity. To circumvent this central issue, we have developed a proprietary virus-like particle (VLP)-based vaccine delivery platform. Notably, the VLP-platform is currently the only available technology to effectively facilitate multivalent “virus-like” display of large/complex vaccine antigens. This is key to overcome immune-tolerance and enable induction of therapeutically potent antibody responses directed against cancer-associated self-antigens. In this talk I will discuss the non-viral Drosophila S2 insect cell production system and how it was applied to the production of hHer2/neu antigen, including using advanced production methods such as perfusion for clinical material manufacture. Furthermore, I will present our data from a transgenic mouse model for spontaneous breast cancer development, where high-density display of the HER2 extracellular domain on the surface of virus-like particles (VLPs) enables induction of therapeutically potent anti-HER2 responses. Split-protein tag/catcher conjugation was used to facilitate directional covalent attachment of HER2 to the surface of icosahedral bacteriophage-derived VLPs, thereby harnessing the VLP platform to effectively overcome B-cell tolerance. Vaccine efficacy was demonstrated both in prevention and therapy of mammary carcinomas in HER2 transgenic mice. Thus, the HER2-VLP vaccine shows promise as a new strategy for treatment of HER2-positive cancer. The modular VLP system may also represent an effective tool for development of self-antigen based vaccines against other non-communicable diseases

Neutralising antibodies block the function of Rh5/Ripr/CyRPA complex during invasion of <i>Plasmodium falciparum</i> into human erythrocytes

An effective vaccine is a priority for malaria control and elimination. The leading candidate in the Plasmodium falciparum blood stage is PfRh5. PfRh5 assembles into trimeric complex with PfRipr and PfCyRPA in the parasite, and this complex is essential for erythrocyte invasion. In this study, we show that antibodies specific for PfRh5 and PfCyRPA prevent trimeric complex formation. We identify the EGF-7 domain on PfRipr as a neutralising epitope and demonstrate that antibodies against this region act downstream of complex formation to prevent merozoite invasion. Antibodies against the C-terminal region of PfRipr were more inhibitory than those against either PfRh5 or PfCyRPA alone, and a combination of antibodies against PfCyRPA and PfRipr acted synergistically to reduce invasion. This study supports prioritisation of PfRipr for development as part of a next-generation antimalarial vaccine

An 8-gene mRNA expression profile in circulating tumor cells predicts response to aromatase inhibitors in metastatic breast cancer patients

Background: Molecular characterization of circulating tumor cells (CTC) is promising for personalized medicine. We aimed to identify a CTC gene expression profile predicting outcome to first-line aromatase inhibitors in metastatic breast cancer (MBC) patients. Methods: CTCs were isolated from 78 MBC patients before treatment start. mRNA expression levels of 96 genes were measured by quantitative reverse transcriptase polymerase chain reaction. After applying predefined exclusion criteria based on lack of sufficient RNA quality and/or quantity, the data from 45 patients were used to construct a gene expression profile to predict poor responding patients, defined as disease progression or death <9 months, by a leave-one-out cross validation. Results: Of the 45 patients, 19 were clinically classified as poor responders. To identify them, the 75 % most variable genes were used to select genes differentially expressed between good and poor responders. An 8-gene CTC predictor was significantly associated with outcome (Hazard Ratio [HR] 4.40, 95 % Confidence Interval [CI]: 2.17-8.92, P < 0.001). This predictor identified poor responding patients with a sensitivity of 63 % and a positive predictive value of 75 %, while good responding patients were correctly predicted in 85 % of the cases. In multivariate Cox regression analysis, including CTC count at baseline, the 8-gene CTC predictor was the only factor independently associated with outcome (HR 4.59 [95 % CI: 2.11-9.56], P < 0.001). This 8-gene signature was not associated with outcome in a group of 71 MBC patients treated with systemic treatments other than AI. Conclusions: An 8-gene CTC predictor was identified which discriminates good and poor outcome to first-line aromatase inhibitors in MBC patients. Although results need to be validated, this study underscores the potential of molecular characterization of CTCs

Particle Size Effects of Carbon Supported Nickel Nanoparticles for High Pressure CO2 Methanation

Supported nickel nanoparticles are promising catalysts for the methanation of CO2. The role of nickel particle size on activity and selectivity in this reaction is a matter of debate. We present a study of metal particle size effects on catalytic stability, activity and selectivity, using nickel on graphitic carbon catalysts. Increasing the Ni particle size from 4 to 8 nm led to a higher catalytic activity, both per gram of nickel and normalized surface area. However, the apparent activation energy remained the same (∼105 kJ mol−1). Comparing experiments at atmospheric to 30 bar pressure demonstrates the importance of testing under industrially relevant pressures; the highest selectivity is obtained at high CO2 conversions and pressures. Finally, the selectivity was particle size-dependent. The largest particles were not only most active but also most selective to methane. With this work we contribute to the ongoing debate about Ni particle size effects in CO2 methanation

Human Antibodies that Slow Erythrocyte Invasion Potentiate Malaria-Neutralizing Antibodies.

The Plasmodium falciparum reticulocyte-binding protein homolog 5 (PfRH5) is the leading target for next-generation vaccines against the disease-causing blood-stage of malaria. However, little is known about how human antibodies confer functional immunity against this antigen. We isolated a panel of human monoclonal antibodies (mAbs) against PfRH5 from peripheral blood B cells from vaccinees in the first clinical trial of a PfRH5-based vaccine. We identified a subset of mAbs with neutralizing activity that bind to three distinct sites and another subset of mAbs that are non-functional, or even antagonistic to neutralizing antibodies. We also identify the epitope of a novel group of non-neutralizing antibodies that significantly reduce the speed of red blood cell invasion by the merozoite, thereby potentiating the effect of all neutralizing PfRH5 antibodies as well as synergizing with antibodies targeting other malaria invasion proteins. Our results provide a roadmap for structure-guided vaccine development to maximize antibody efficacy against blood-stage malaria. Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved

Transient Marker System for Iterative Gene Targeting of a Prototrophic Fungus▿

Auxotrophic microorganisms are often used for genetic engineering, because their biosynthetic deficiency can be complemented by the transforming DNA and allows selection for transformants that have become prototrophic. However, when complementation is obtained by ectopic expression this may lead to unpredictable side effects on the phenotype and, consequently, misinterpretation of experimental data. There are various ways to overcome the problem of auxotrophy, but the most reliable is to restore the function of the defective biosynthetic gene at the native genomic locus. This can be done by either sexual crossing or further genetic engineering. For fungal species lacking a perfect state or situations in which gene targeting is generally cumbersome we have developed a concept that allows transient disruption of pyrG. When the gene is in the disrupted state, multiple rounds of gene targeting can be performed with the strain. Once the desired genome engineering is completed, pyrG function can be rapidly returned to wild type by a simple selection scheme