Regulatory workshop on challenge strain development and GMP manufacture - A stakeholder meeting report

Within the Innovative Health Initiative (IHI) Inno4Vac CHIMICHURRI project, a regulatory workshop was organised on the development and manufacture of challenge agent strains for Controlled Human Infection Model (CHIM) studies. Developers are often uncertain about which GMP requirements or regulatory guidelines apply but should be guided by the 2022 technical white paper "Considerations on the Principles of Development and Manufacturing Qualities of Challenge Agents for Use in Human Infection Models" (published by hVIVO, Wellcome Trust, HIC-Vac consortium members). Where those recommendations cannot be met, regulators advise following the "Principles of GMP" until definitive guidelines are available. Sourcing wild-type virus isolates is a significant challenge for developers. Still, it is preferred over reverse genetics challenge strains for several reasons, including implications and regulations around genetically modified organisms (GMOs). Official informed consent guidelines for collecting isolates are needed, and the characterisation of these isolates still presents risks and uncertainty. Workshop topics included ethics, liability, standardised clinical endpoints, selection criteria, sharing of challenge agents, and addressing population heterogeneity concerning vaccine response and clinical course. The organisers are confident that the workshop discussions will contribute to advancing ethical, safe, and high-quality CHIM studies of influenza, RSV and C. difficile, including adequate regulatory frameworks.

Controlled Human Infection Studies: Proposals for guidance on how to design, develop and produce a challenge strain

There is an increasing need to establish quality principles for designing, developing and manufacturing challenge agents as currently these agents are classified differently by various jurisdictions. Indeed, considerations for challenge agent manufacturing vary between countries due to differences in regulatory oversight, the categorization of the challenge agent and incorporation into medicinal/vaccine development processes. To this end, a whitepaper on the guidance has been produced and disseminated for consultation to researchers, regulatory experts and regulatory or advisory bodies. This document is intended to discuss fundamental principles of selection, characterization, manufacture, quality control and storage of challenge agents for international reference. In the development phase, CMC documentation is needed for a candidate challenge agent, while standard operating procedure documentation is needed to monitor and control the manufacturing process, followed by use of qualified methods to test critical steps in the manufacturing process, or the final product itself. These activities are complementary: GMP rules, which intervene only at the time of the routine manufacturing of batches, do not contribute to the proper development and qualification of the candidate product. Some considerations regarding suitability of premises for challenge manufacturing was discussed in the presentation dedicated to "routine manufacturing".

Assessment of aloe vera for qualitative fit testing of particulate respirators: a logistic regression approach

Fit testing procedure is required for filtering facepiece respirators (FFRs) to ascertain an acceptable fit between the skin and facepiece sealing surface. The present study seeks to compare the efficacy of Aloe vera (A. vera) and commercial BitrexTM as challenge agents of qualitative fit testing of particulate respirators. An herbal solution consisting of A. vera at seven different concentrations was developed. Threshold Screening Tests (TSTs) of A. vera solutions were compared to BitrexTM. To do so, solutions were administered randomly on a total of 62 participants. A placebo was also tested to ensure the taste response being valid. Statistical analysis was performed using R 3.2.5.0 software. There were no statistically significant differences between the A. vera (41.7, 58.3, 75, and 91.7 mg/ml) and BitrexTM threshold tests. Therefore, the minimum concentration of A. vera to develop the threshold solution was considered to be 41.7 mg/ml. When commercial products are expensive and unavailable, a cost-effective technique would be to replace A. vera solution with a commercial product as a challenge agent of qualitative fit testing of respirators.

Feasibility of replacing homemade solutions by commercial products for qualitative fit testing of particulate respirators: a mixed effect logistic regression study

Qualitative fit testing is mandatory for tight-fitting respirators to ensure that the wearer fitted properly before entering a contaminated workplace. The purpose of this study was to evaluate the homemade solutions as substitution of commercial products for qualitative fit testing of particulate respirators. Two homemade solutions of Bitrex™ and saccharin were made according to the Occupational Safety and Health Administration (OSHA) regulation 29 CFR 1910.134. Threshold Screening Tests (TSTs) of commercial solutions, as well as homemade ones, were conducted on 62 participants in a random order. A placebo was also tested to assure the participants could distinguish its flavorless from other taste of solutions. There were no statistically significant differences between the commercial and homemade solutions representing that participants detected the bitter taste of the Bitrex™ and sweet taste of the saccharin solutions (96.8% vs. 91.9% and 93.5% vs. 83.9%, respectively). Homemade solutions that were stable and haven't been contained microbial contaminations, could be substituted for commercial products in qualitative fit testing of filtering face-piece respirators (FFRs). Overall, this protocol presents a practical and cost-benefit technique to assess the fit testing of FFRs.