The ELISpot assay stands out as a robust and reliable tool in the realm of cancer research, particularly in evaluating T cell responses to novel cancer vaccines. Its ability to detect rare, antigen-specific T cells makes it a valuable immune monitoring tool in the assessment of new therapeutic strategies. Let’s take a closer look at how the researchers at Memorial Sloan Kettering Cancer Center utilized ELISpot in their groundbreaking study.
Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer death worldwide with a survival rate of only 12%. Surgery is the only curative treatment for the cancer, but almost 90% of patients have disease recurrence and the 5-year survival rate is only 8-10%. With the limited success of radiation and targeted therapies, new treatments are needed for PDAC.
Recently it was found that primary tumors from PDAC patients had high densities of activated CD8+ T cells which correlated with delayed disease recurrence and longer patient survival. With this knowledge, the researchers at Memorial Sloan Kettering Cancer Center in New York set out to develop a new strategy to stimulate T cells against neoantigens from PDAC in hopes of delaying or preventing disease recurrence. They tested whether adjuvant individualized mRNA neoantigen vaccines could stimulate neoantigen-specific T cells and have a clinical benefit to the patients. Individualized mRNA vaccines encoding for up to 20 neoantigens were developed for each patient enrolled in the phase I clinical trial. Patients were immunized with multiple priming doses of the personalized vaccines and they also received chemotherapy followed by a booster dose of the vaccine. Blood samples were taken before and after priming immunizations as well as after chemotherapy and booster doses to assess T cell responses.
Figure 1 from the article summarizes the study design including neoantigen vaccine design, administration, and assessment of T cell responses using Mabtech’s ELISpot Pro: Human IFN-γ kits.
Using Mabtech’s ELISpot Pro: Human IFN-γ kits, the researchers found that 50% of the patients had detectable neoantigen-specific T cells following vaccination. Furthermore, they tested each specific neoantigen separately and found that 11% of them induced a sufficient, high-magnitude T cell response. ELISpot proved to be an effective tool in screening for responding T cells towards the 230 neoantigens. With this data, the researchers gained valuable insights that could prove beneficial in future vaccine design.
In addition to determining which neoantigens induced T cell responses, the researchers were also able to measure polytopic responses (responses to >1 neoantigen) in the donors that had detectable neoantigen-specific T cells. Intra-patient variation in the magnitude of polytopic responses was observed with responses ranging from 100 spot-forming units (SFU) per million PBMCs to >2,000 SFU per million PBMCs.
The ELISpot assay can be an extremely sensitive and helpful technique in assessing antigen-specific immune responses. One can rather easily screen a large number of antigens and detect rare, responding cells making it an excellent screening tool. The information gained from ELISpot can guide future vaccine design as well as direct the study design for an even more in-depth analysis of the responding T cells.
All of us at Mabtech were thoroughly impressed by the design and application of the ELISpot assay in this study. We believe the researchers harnessed the assay's capabilities effectively and are excited to see the advancements in personalized vaccines that emerge from this innovative work.
Learn more about why ELISpot and FluoroSpot are key immunoassays to use in other cell and gene therapy evaluations and get inspired!