Assay Development: Vaccines

As the demand for effective vaccines continues to rise, the importance of robust assay development for vaccine evaluation cannot be overstated. Accurate and reliable assays are critical for assessing vaccine efficacy, safety, and immunogenicity. In this article, we'll explore the latest advancements in assay development specifically tailored for vaccine testing and evaluation.

Assessment of Immunogenicity

Traditional methods for assessing vaccine immunogenicity, such as enzyme-linked immunosorbent assays (ELISAs) and neutralization assays, have been instrumental in vaccine development.
However, newer techniques, including multiplex immunoassays and flow cytometry-based assays, offer higher throughput and greater sensitivity for measuring immune responses to vaccines.
These advanced assays allow for the simultaneous detection of multiple antibody specificities and subclasses, providing a more comprehensive understanding of vaccine-induced immune responses.


In vitro models for immunogenicity prediction of therapeutic proteins


Evaluation of Vaccine Potency

Assays for evaluating vaccine potency are essential for ensuring consistent vaccine quality and efficacy.
In vitro potency assays, such as antigen quantification assays and in vitro neutralization assays, are commonly used to measure the functional activity of vaccine formulations.
Novel approaches, such as mass spectrometry-based quantification of vaccine antigens and cell-based assays using genetically engineered reporter cell lines, offer improved accuracy and reproducibility in assessing vaccine potency.

Safety Assessment

Vaccine safety assessment involves the detection of potential adverse effects, including systemic reactions and local injection site reactions.
Traditional safety assays, such as animal challenge studies and histopathological analysis, remain important for evaluating vaccine safety profiles.
However, in vitro assays, such as cytokine release assays and cell viability assays using human cell lines, offer alternatives to animal testing and provide valuable insights into vaccine-induced immune responses and potential adverse effects.

Emerging Technologies

Recent advancements in assay development have been driven by innovative technologies, such as microfluidics, next-generation sequencing (NGS), and single-cell analysis.
Microfluidic platforms enable high-throughput screening of vaccine candidates and facilitate the miniaturization of assays, reducing reagent consumption and assay time.
NGS-based approaches, including RNA sequencing and metagenomic analysis, offer unprecedented insights into vaccine-host interactions and immune system dynamics.
Single-cell analysis techniques, such as single-cell RNA sequencing and mass cytometry (CyTOF), enable the characterization of immune cell subsets and their functional responses to vaccination at the single-cell level.

Advancements in assay development have significantly enhanced our ability to evaluate vaccines with precision and efficiency. From assessing immunogenicity and potency to ensuring safety, the integration of innovative technologies and methodologies continues to drive progress in vaccine research and development. By harnessing the power of these advanced assays, researchers can accelerate the discovery and development of safe and effective vaccines to address global health challenges.

Vaccine development is a long and intensive process that begins with determining public health needs and priorities. Several organizations have compiled priorities for research and development, including the World Health Organization/United Nations Development Program for vaccine development. There are several stages of vaccine development and testing, starting with an exploratory stage to identify natural or synthetic antigens. Then, preclinical work begins and cell cultures and animal models are used to determine the immunogenicity and safety of a candidate vaccine.

Following approval of an Investigational New Drug Application with the United States Food and Drug Administration, clinical trials can begin. Specialized tests are developed in preclinical and early phase clinical trials, and validated in later clinical trial phases. Prior to batch release, the assays have well-characterized parameters and criteria, although the assay development process is not without challenges. The immune system is very complex; however, new technologies and techniques offer solutions. Eventually, a successful vaccine candidate will advance to phase III trials and be licensed. The entire rigorous process can take more than 15 years.

First, it is important to understand the underlying mechanism of action. “Vaccines generally aim to modulate or prime the immune response to a pathogen so that the body can quickly eliminate the pathogen and minimize disease,” says Claire Richards, PhD, senior scientist, infectious diseases, discovery services at Charles River Laboratories (Wilmington, MA).

Preclinical research on vaccines includes the development of assays, in part, for the quantification of immune response. Rafiqul Islam, MS, Executive Director of Bioanalytical Services at Celerion Inc., echoes the importance of immunogenicity testing: "Multiple tests are needed to measure immune responses to ensure that the vaccine candidate is at least capable of causing a robust immune response”.

Islam provides insight into the clinical development of vaccines, which “requires a specific set of specialized tests to demonstrate immunogenicity, efficacy, exposure and safety. The development and validation of these tests require the integration of therapeutic information, state-of-the-art technologies, customized reagents and robust quality management systems.

What tests are then used to assess the immune response? “A proper test to determine immune stimulation is usually needed with possible inhibition tests to show that the immune response can reduce the growth of the pathogen; [eg] antigen-specific ELISA, inhibition ELISA, neutralization test, [and] effective concentration to give 50% survival (EC50),” says Dr. Richards. Table 1 provides a summary of commonly used assays to support vaccine development.

The humoral, or antibody-mediated, immune response relies on the recognition of antigens by B lymphocytes and the subsequent release of antibodies. Ligand-binding techniques, such as ELISA (enzyme immunoassay), are often used to assess humoral response. Conversely, the cell-mediated immune response relies primarily on T cells and is often assessed by ELISpot (enzyme-linked immunospot) or flow cytometry.