VAC2VAC is a wide-ranging collaborative research project funded by IMI2 which aims to develop and validate quality testing approaches for both human and veterinary vaccines using non-animal methods. The initiative that started on 1 March 2016 aims to provide the data to support the "Consistency Approach" for quality control of established vaccines, where current quality control approaches are often relying on in vivo methods.

VAC2VAC is a public-private consortium of twenty partners, involving experts from veterinary and human vaccine industry in a partnership with official medicines control laboratories, academia, translational research organisations, and vaccinology alliances. To achieve their goal, the project partners will develop, optimise and evaluate physico-chemical and immunochemical methods, cell-based and other assays for routine batch quality, safety and efficacy testing of vaccines. This will be done in collaboration and consultation with regulatory agencies. The ultimate goal of the project is to develop tests and approaches that will allow acceptance of the "Consistency Approach" for established vaccines by the regulatory agencies and thereby significantly reducing in the future the use of animals for batch testing in routine vaccine production.

 

Check new publications of VAC2VAC:

A cell-based in vitro assay for testing of immunological integrity of Tetanus toxoid vaccine antigen

Olga Ticha, Dido Klemm, Lukas Moos & Isabelle Bekeredjian-Ding

 npj Vaccines https://doi.org/10.1038/s41541-021-00344-1

Vaccines containing inactivated toxins confer protection by eliciting a neutralizing antibody response against bacterial toxins such as tetanus and diphtheria. At present, release of tetanus toxoid (TT) and diphtheria toxoid (DT)-containing vaccines relies on in vivo experiments showing the protective vaccine response. The aim of this study was to develop a reliable in vitro assay for TT vaccine antigen characterization with the potential of replacing in vivo potency experiments. To this end, we exploited that TT elicits a recall response in vaccinated donors: human peripheral blood mononuclear cells (PBMC) were stimulated with alum-adsorbed TT bulk antigen and low concentrations of TLR9 ligand; induction of TT-specific IgG was quantified via ELISpot after 5 days. Proof-of-concept was obtained using paired samples from donors before and after vaccination; anti-TT IgG was only detected in PBMC collected after booster vaccination; specificity was demonstrated with DT stimulation as control. Notably, when using PBMC from buffy coats, the specific response to TT was reproducible in 30% of cells; responsiveness correlated with higher numbers of switched memory B cells. Consecutive results showed that TT-specific IgG was also detectable when PBMC were stimulated with DTaP final vaccine product. Thus, the assay provides a viable means to test B-cell differentiation and induction of TT-specific IgG secretion using bulk antigen and final vaccine. However, prequalification of PBMC is required for reliable performance. Along with physicochemical and immunochemical methods, the functional assay could represent a complementary tool to replace in vivo potency assays in batch release of TT-containing vaccines. Download full article

In Vitro Characterization of the Innate Immune Pathways Engaged by Live and Inactivated Tick-Borne Encephalitis Virus

Aurora Signorazzi, Jeroen L. A. Pennings, Marilena P. Etna, Malou Noya, Eliana M. Coccia and Anke Huckriede

 Vaccines https://doi.org/10.3390/vaccines9060664

Tick-borne encephalitis virus (TBEV) infection can lead to inflammation of the central nervous system. The disease can be effectively prevented by whole inactivated virus vaccines. Here, we investigated the innate immune profile induced in vitro by the antigen component of the vaccines, inactivated TBEV (I-TBEV), to gain insights into the mechanism of action of the TBE vaccine as compared to the live virus. To this end, we exposed human peripheral blood mononuclear cells (PBMCs) to inactivated and live TBEV and assessed cellular responses by RNA sequencing. Both inactivated and live TBEV significantly induced an interferon-dominated gene signature and an increased RIG-I-like receptor (RLR) expression. Using pathway-specific inhibitors, we assessed the involvement of pattern recognition receptors in the sensing of inactivated or live TBEV. Only RLR pathway inhibition significantly suppressed the downstream cascade induced by I-TBEV, while responses to the replicating virus were impacted by the inhibition of RIG-I-like, as well as Toll-like, receptors. Our results show that inactivated and live TBEV predominantly engaged an interferon response in our in vitro PBMC platform, and indicate RLRs as the main pattern recognition receptors involved in I-TBEV sensing. Download full article

Effects of long-term cryopreservation of PBMC on recovery of B Cell subpopulations

Olga Ticha, Lukas Moos, Isabelle Bekeredjian-Ding

 J. Immunol. Methods https://doi.org/10.1016/j.jim.2021.113081

Cryopreservation of human peripheral blood mononuclear cells (PBMC) is used in many clinical and research applications to avoid direct and on-site analysis of samples. Storage of PBMC further allows prequalification of donor cells for routine laboratory methods involving the evaluation of immune responses. Previous studies re[1]ported changes in cellular composition and phenotype of PBMC following the freezing procedure. In our 12- month follow-up study, we focused on B cells and proportional representation of B cell subpopulations during long-term storage at − 80 ◦C. Over the 12-month period, we observed a gradual decline in B cell viability and recovery. Notably, no changes in the proportional representation of human B cell subpopulations occurred in this period and the functional response elicited by antigen and TLR9 ligand CpG remained comparable to that observed after short-term storage for one month. Download full article

Characterisation of tetanus monoclonal antibodies as a first step towards the development of an in vitro vaccine potency immunoassay

Rebecca Riches-Duit, Laura Hassall, Amy Kogelman, Janny Westdijk, Shalini Rajagopal, Bazbek Davletov, Ciara Doran, Alexandre Dobly, Antoine Francotte, Paul Stickings

 Biologicals https://doi.org/10.1016/j.biologicals.2021.04.002

Batch release testing for human and veterinary tetanus vaccines still relies heavily on methods that involve animals, particularly for potency testing. The quantity and quality of tetanus antigen present in these products is of utmost importance for product safety and clinical effect. Immunochemical methods that measure consistency of antigen content and quality, potentially as an indicator of potency, could be a better choice and negate the need for an in vivo potency test. These immunochemical methods require at least one well characterised monoclonal antibody (mAb) that is specific for the target antigen. In this paper we report the results of the comprehensive characterisation of a panel of mAbs against tetanus with a view to select antibodies that can be used for development of an in vitro potency immunoassay. We have assessed binding of the antibodies to native antigen (toxin), detoxified antigen (toxoid), adsorbed antigen and heat-altered antigen. Antibody function was determined using an in-house cell-based neutralisation assay to support prior in vivo potency data that was available for some, but not all, of the antibodies. In addition, antibody affinity was measured, and epitope competition analysis was performed to identify pairs of antibodies that could be deployed in a sandwich immunoassay format. Not all characterisation tests provided evidence of “superiority” of one mAb over another, but together the results from all characterisation studies allowed for selection of an antibody pair to be taken forward to assay development. Download full article

Common Reference-Based Tandem Mass Tag Multiplexing for the Relative Quantification of Peptides: Design and Application to Degradome Analysis of Diphtheria Toxoid

Thomas J. M. Michiels, Madelief A. van Veen, Hugo D. Meiring, Wim Jiskoot, Gideon F. A. Kersten and Bernard Metz

 J. Am. Soc. Mass Spectrom. https://doi.org/10.1021/jasms.1c00070

Currently, animal tests are being used to confirm the potency and lack of toxicity of toxoid vaccines. In a consistency approach, animal tests could be replaced if production consistency (compared to known good products) can be proven in a panel of in vitro assays. By mimicking the in vivo antigen processing in a simplified in vitro approach, it may be possible to distinguish aberrant products from good products. To demonstrate this, heatexposed diphtheria toxoid was subjected to partial digestion by cathepsin S (an endoprotease involved in antigen processing), and the peptide formation/degradation kinetics were mapped for various heated toxoids. To overcome the limitations associated

with the very large number of samples, we used common referencebased tandem mass tag (TMT) labeling. Instead of using one label per condition with direct comparison between the set of labels, we compared multiple labeled samples to a common reference (a pooled sample containing an aliquot of each condition). In this method, the number of samples is not limited by the number of unique TMT labels. This TMT multiplexing strategy allows for a 15-fold reduction of analysis time while retaining the reliability advantage of TMT labeling over label-free quantification. The formation of the most important peptides could be followed over time and compared among several conditions. The changes in enzymatic degradation kinetics of diphtheria toxoid revealed several suitable candidate peptides for use in a quality control assay that can distinguish structurally aberrant diphtheria toxoid from compliant toxoids. Download full article

 

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