Usage of standardized antigen-presenting cells improves ELISpot performance for complex protein antigens

Improved ELISPOT protocol for monitoring Th1/Th17 T-cell response following T.gondii infection

In the monitoring of human Toxoplasma gondii infection, it is crucial to confirm the development of a specific Th1/Th17 immune response memory. The use of a simple, specific, and sensitive assay to follow the T-cell activation is thus required. Current protocols are not always specific as stimulation with peptides is Human Leukocyte Antigen (HLA)-dependent, while stimulation with total-lysis antigens tends to stimulate seronegative donors resulting to false positives. Here, an improved ELISPOT protocol is reported, using peripheral blood mononuclear cells (PBMC) of T.gondii-infected donors, incubated with the inactivated parasite. The results showed that, contrary to standard protocols, a pre-incubation step at high cell density in presence of the inactivated parasite allowed a specific Th1/Th17 response with the secretion of IFN-γ, IL-2, IL-12 and IL-17 cytokines. This protocol allows to evaluate precisely the immune response after a T.gondii infection.

Preclinical risk assessment strategy to mitigate the T-cell dependent immunogenicity of protein biotherapeutics: State of the art, challenges and future perspectives

Protein therapeutics hold a prominent role and have brought significant diversity in efficacious medicinal products. Not just monoclonal antibodies and different antibody formats (pegylated antigen-binding fragments, bispecifics, antibody-drug conjugates, single chain variable fragments, nanobodies, dia-, tria- and tetrabodies), but also purified blood products, growth factors, recombinant cytokines, enzyme replacement factors, fusion proteins are all good instances of therapeutic proteins that have been developed in the past decades and approved for their value in oncology, immune-oncology, and autoimmune diseases discovery programs. Although there was an ingrained belief that fully humanized proteins were expected to have limited immunogenicity, adverse effects associated with immune responses to biological therapies raised some concern in biotech companies. Consequently, drug developers are designing strategies to assess potential immune responses to protein therapeutics during both the preclinical and clinical phases of development. Despite the many factors that can contribute to protein immunogenicity, T cell- (thymus-) dependent (Td) immunogenicity seems to play a crucial role in the development of anti-drug antibodies (ADAs) to biologics. A broad range of methodologies to predict and rationally assess Td immune responses to protein drugs has been developed. This review aims to briefly summarize the preclinical immunogenicity risk assessment strategy to mitigate the risk of potential immunogenic candidates coming towards clinical phases, discussing the advantages and limitations of these technologies, and suggesting a rational approach for assessing and mitigating Td immunogenicity.

Assay format diversity in pre-clinical immunogenicity risk assessment: Toward a possible harmonization of antigenicity assays

A major impediment to successful use of therapeutic protein drugs is their ability to induce anti-drug antibodies (ADA) that can alter treatment efficacy and safety in a significant number of patients. To this aim, in silico, in vitro, and in vivo tools have been developed to assess sequence and other liabilities contributing to ADA development at different stages of the immune response. However, variability exists between similar assays developed by different investigators due to the complexity of assays, a degree of uncertainty about the underlying science, and their intended use. The impact of protocol variations on the outcome of the assays, i.e., on the immunogenicity risk assigned to a given drug candidate, cannot always be precisely assessed. Here, the Non-Clinical Immunogenicity Risk Assessment working group of the European Immunogenicity Platform (EIP) reviews currently used assays and protocols and discusses feasibility and next steps toward harmonization and standardization.

Identification of Novel Mycobacterial Targets for Murine CD4+ T-Cells by IFNγ ELISPOT

Enzyme-linked immunospot (ELISPOT) is an assay used to detect secretion of cytokines from immune cells. The resolution and sensitivity of ELISPOT allow for the detection of rare T cell specificities and small quantities of molecules produced by individual cells. In this chapter, we describe an epitope screening method that uses CD4⁺ T cell ELISPOT assays to identify specific novel mycobacterial antigens as potential vaccine candidates. In order to screen a large number of candidate epitopes simultaneously, pools of predicted MHC class II peptides were used to identify mycobacterial specific CD4⁺ T cells. Using this method, we identified novel mycobacterial antigens as vaccine candidates.

ELISpot and DC-ELISpot Assay to Measure Frequency of Antigen-Specific IFNγ-Secreting Cells

ELISpot is a highly sensitive method in immunology to enumerate cells producing a given cytokine. Cells are stimulated in a microtiter plate pre-coated with a specific anti-analyte antibody. In response to the stimulation, cells release cytokines that are bound to the anti-analyte antibody. After a washing step, which removes the cells from the wells, the location of the cytokine-releasing cell is visualized by an enzyme-labeled detection antibody and its corresponding chromogenic substrate. The end result is a set of colored spots, each of which represents an area where a cell secreting the cytokine had been located. Here we describe the standard ELISpot protocol and a variation denominated dendritic cell (DC)-ELISpot for the detection of IFNγ-secreting cells upon stimulation with oligopeptides and protein antigens, respectively.