Immune monitoring of functional responses is a fundamental parameter to establish correlates of protection in clinical trials evaluating vaccines and therapies to boost antigen-specific responses. The IFNγ ELISPOT assay is a well-standardized and validated method for the determination of functional IFNγ-producing T-cells in peripheral blood mononuclear cells (PBMC); however, its performance greatly depends on the quality and integrity of the cryopreserved PBMC. Here, we investigate the effect of overnight (ON) resting of the PBMC on the detection of CD8-restricted peptide-specific responses by IFNγ ELISPOT. The study used PBMC from healthy donors to evaluate the CD8 T-cell response to five pooled or individual HLA-A2 viral peptides. The results were analyzed using a modification of the existing distribution free resampling (DFR) recommended for the analysis of ELISPOT data to ensure the most rigorous possible standard of significance. The results of the study demonstrate that ON resting of PBMC samples prior to IFNγ ELISPOT increases both the magnitude and the statistical significance of the responses. In addition, a comparison of the results with a 13-day preculture of PBMC with the peptides before testing demonstrates that ON resting is sufficient for the efficient evaluation of immune functioning.
The discovery of T cell epitopes is essential not only for gaining knowledge about host response to infectious disease but also for the development of immune-intervention strategies. In Chagas disease, given the size and complexity of the Trypanosoma cruzi proteome and its interaction with the host’s immune system, the fine specificity of T cells has not been extensively studied yet, and this is particularly true for the CD4+ T cell compartment. The aim of the present work was to optimize a protocol for the generation of parasite-specific memory T cell lines, representative of their in vivo precursor populations and capable of responding to parasite antigens after long-term culture. Accordingly, peripheral blood mononuclear cells (PBMC) from both chronic asymptomatic and cardiac patients, and from non-infected individuals, underwent different in vitro culture and stimulation conditions. Subsequently, cells were tested for their capacity to respond against T. cruzi lysate by measuring [3H]-thymidine incorporation and interferon-γ and GM-CSF secretion. Results allowed us to adjust initial T. cruzi lysate incubation time as well as the number of expansions with phytohemagglutinin (PHA) and irradiated allogeneic PBMC prior to specificity evaluation. Moreover, our data demonstrated that parasite specific T cells displayed a clear and strong activation by using T. cruzi lysate pulsed, Epstein-Barr virus (EBV)-transformed human B lymphocytes (B-LCL), as autologous antigen presenting cells. Under these culture conditions, we generated a clone from an asymptomatic patient’s memory CD4+ T cells which responded against epimastigote and trypomastigote protein lysate. Our results describe a culture method for isolating T. cruzi specific T cell clones from patients with Chagas disease, which enable the acquisition of information on functionality and specificity of individual T cells.
T cell receptor (TCR) signaling pathway regulates T cell homeostasis and adaptive immune responses. Clinically, the activation of TCR is indispensable to the success of T cell-based immunotherapy. The engagement of TCR phosphorylates immunoreceptor tyrosine-based activation motifs (ITAM) on CD3, which is followed by a protein phosphorylation cascade. Protein phosphorylation, regulated by kinases and phosphatases, changes protein conformation and determines protein function. A better understanding of TCR signaling phosphorylation events is crucial to both decipher the T cell regulation mechanism and boost the efficacy of T cell immunotherapy. Here, we developed a panel of monoclonal antibodies that target several of the TCR signaling regulators and are applicable for both intracellular flow cytometry (ICFC) and western blot (WB). Using these antibodies, we performed a kinetic analysis of the TCR signaling pathway. Jurkat T cells were cross-linked by soluble anti-CD3 and anti-CD28 antibodies, and the phosphorylation kinetics of the key TCR signaling regulators, such as phospho-ZAP-70 and phospho-PLCg1, were evaluated by ICFC and WB. We show that TCR signaling activation induced by cross-linking CD3 and CD28 is a relatively transient event and the optimal activation of the key TCR signaling regulators varies from 1 to 15 minutes. Our data profiled the phosphorylation kinetics of the key regulators in TCR signaling pathway.
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