Vaccine researchers are currently faced with the challenges of developing novel vaccine strategies to protect humankind from devastating infections including the long-standing foes of HIV, malaria, tuberculosis, and more emergent infections like Ebola and Zika virus. Vaccine research is dependent on monitoring immune responses in animal models and in humans participating in clinical trials, and flow cytometry is at the forefront of vaccine research. An unprecedented number of parameters can be measured by flow cytometry now, and this facilitates the monitoring of multiple immune cell subsets simultaneously[1].
Consider these protocols to include flow cytometry and vaccine development and research in your next preclinical research project or clinical trial.
1. Immunophenotyping
This technique uses a panel of fluorescent antibodies to measure the frequency of different immune cell subsets, such as CD4+ and CD8+ T cell subsets, including memory T cell subsets. Immunophenotyping has become a routine technique for monitoring immune status in HIV+ patients as well measuring the efficacy of HIV vaccine candidates in clinical trials.[2]
2. Functional Assays
Effective vaccines may induce antigen-specific immune cell subsets that can execute specific functions, such as CD8+ cytotoxic T cells that can mediate destruction of HIV+ T cells via degranulation and cytolysis. Degranulation can be measured by flow cytometry and can serve as measure of vaccine efficacy.[3] Numerous cell functions can be monitored by flow cytometry including cell proliferation, calcium flux, and reactive oxygen species production.
3. Intracellular Cytokines
Cytokines are a broad class of key effector molecules produced by immune cells that can drive immune cell differentiation, proliferation, cytolysis, and immune regulation. Vaccine and vaccine adjuvants are designed to target the activation and proliferation of discrete cell subsets that can best prevent or reduce infection by a pathogen. Cytokines are typically secreted by immune cells to exert effects locally or systemically, but measuring cytokine concentrations in peripheral blood can be meaningless unless the cellular source of the cytokine is known. Intracellular cytokine staining (ICS) protocols use reagents that prevent the secretion of cytokines so they can be stained within cells and their source can be determined. ICS has become one of the most commonly used flow cytometry techniques in vaccine development, and is used not only for infectious disease vaccines but for cancer vaccines as well.
Flow cytometry is a critical tool for vaccine development and has been critical to providing valuable insights into how the immune system responds to and defends against pathogens. Consider incorporating flow cytometry-based assays into your vaccine development research.
[1] Furman D, Davis MM. New approaches to understanding the immune response to vaccination and infection. Vaccine. 2015;33(40):5271-5281. doi:10.1016/j.vaccine.2015.06.117.
[2] Kestens L and Mandy F. Thirty-Five Years of CD4 T-Cell Counting in HIV Infection: From Flow Cytometry in the Lab to Point-of-Care Testing in the Field. Cytometry Part B. 2016. doi: 10.1002/cyto.b.21400
[3] Betts MR, Brenchley JM, Price DA, De Rosa SC, Douek DC, Roederer M, et al. Sensitive and viable identification of antigen-specific CD8+ T cells by a flow cytometric assay for degranulation. Journal of Immunological Methods. 2003;281:65–78.
