Development of functionally relevant potency assays for monovalent and multivalent vaccines delivered by evolving technologies

Abstract

A potency or potency-indicating assay is a regulatory requirement for the release of every lot of a vaccine. Potency is a critical quality attribute that is also monitored as a stability indicator of a vaccine product. In essence, a potency measurement is a test of the functional integrity of the antigen and is intended to ensure that the antigen retains immunocompetence, i.e., the ability to stimulate the desired immune response, in its final formulation. Despite its central importance, there is incomplete clarity about the definition and expectation of a potency assay. This article provides a perspective on the purpose, value, and challenges associated with potency testing for vaccines produced by new technologies. The focus is on messenger RNA vaccines in the light of experience gained with recombinant protein-based vaccines, which offer the opportunity to directly correlate in vitro antigenicity with in vivo immunogenicity. The challenges with developing immunologically relevant in vitro assays are discussed especially for multivalent vaccine products, the importance of which has been reinforced by the ongoing emergence of SARS-CoV-2 variants of concern. Immunoassay-based release of multivalent vaccine products, such as those containing multiple antigens from different variants or serotypes of the same virus, require antibodies that are selective for each antigen and do not significantly cross-react with the others. In the absence of such exclusively specific antibodies, alternative functional assays with demonstrable correlation to immunogenicity may be acceptable. Initiatives for geographically distributed vaccine technology facilities should include establishing these assay capabilities to enable rapid delivery of vaccines globally.

Steps toward nebulization in-use studies to understand the stability of new biological entities

“…For functional assessment, the use of immunoassays, such as ELISAs or surface plasmonic resonance (SPR; e.g., Biacore™) is common for ligand binding and dissociation constants, although cell-based assays are a new option [44] . Similar trends are also associated with the characterization of mRNA vaccines (using virus-like particles in ELISAs) [45] . However, new products take a closer look at selectivity and function, as in the case of immunotherapy platforms, such as oncolytic virus [46] or chimeric antigen receptor T cells (CART-T) [47] .…”

Effects of Shock and Vibration on Product Quality during Last-Mile Transportation of Ebola Vaccine under Refrigerated Conditions1

“…Product stability can be demonstrated through a quantitative measure of potency, which is linked to vaccine safety and efficacy ( 14 ). Potency can correlate with infectious titer and transgene expression and may be negatively affected by aggregate formation ( 14 ). Aggregates can affect immunogenicity and subsequently compromise vaccine efficacy ( 14 ).…”

Development and Qualification of an Antigen Integrity Assay for a Plasmodium falciparum Malaria Transmission Blocking Vaccine Candidate, Pfs230

“…Therefore, for those purposes, an in vitro assay is preferable to an in vivo assay where possible. US and European regulatory agencies have accepted use of ELISA-based in vitro potency assays for hepatitis B and human papillomavirus vaccines [ 6 ].…”

“…Furthermore, lot-to-lot consistency and stability of drug substance or drug product must be assessed. Multiple biophysical and biochemical methods, such as western blot, high-performance liquid chromatography (HPLC), circular dichroism, static light scattering, and dynamic light scattering, are commonly used for the quality control of vaccines, but a potency assay is another key evaluation [ 5 , 6 ]. In the case of a malaria TBV, based on the mode of action, an in vivo immunization study (often in mice) that assesses antisera or induced antibodies by SMFA is an acceptable potency assay.…”

“…In the case of a malaria TBV, based on the mode of action, an in vivo immunization study (often in mice) that assesses antisera or induced antibodies by SMFA is an acceptable potency assay. However, antibody titers in animal studies can fluctuate significantly even when the same batch of vaccine is utilized for immunization [ 6 ]. For example, in the case of Diphtheria, Tetanus and acellular Pertussis (DTaP) vaccine, the coefficients of variance (CV) in antibody titers against pertussis antigen were reported as high as 131.7% in mouse immunization studies [ 7 ].…”