CD28 and inducible costimulator (ICOS) signalling can sustain CD154 expression on activated T cells

Assessment of antigen immunogenicity formulated in minigenes transfected into antigen-presenting cells

Tumor cells exhibit deficient antigen presentation to T cells, significantly contributing to immune evasion and tumor genesis. Peptide pulsed Antigen-presenting cells (APCs) are commonly used in cancer immunotherapy to circumvent the defects of tumor cells in processing and presenting antigens to T lymphocytes. However, peptides do not always represent epitopes naturally processed by tumor cells, which might reduce the identification of actual immunogenic antigens. Minigenes encoding concatenated immunogenic tumor epitope sequences offer a promising alternative to select tumor antigens naturally processed and presented to T cells. Hence, using APCs transfected with minigenes might contribute to immunotherapy's effectiveness, avoiding non-naturally processed epitopes as vaccine candidates. This study evaluates APCs transfected with a minigene construct encoding HLA-A0201-restricted immunogenic antigens to stimulate antigen-specific CD8+ T lymphocytes in vitro. Artificial APCs (aAPCs) were also designed by co-transfecting the HEK293 cell line with plasmids encoding co-stimulatory molecules (CD80, CD83, CD137L) to assess CD8+ T cell activation efficiency, intracellular cytokine production, cytotoxic activity, activation and exhaustion marker expression. In this study, we successfully implemented a transfection methodology of HEK293 cells with a minigene encoding viral and tumor HLA-A * 0201 epitopes. These cells, used as aAPCs, allow studying the expansion and the phenotype of antigen-specific CD8+ T cells. However, our results indicate that epitope presentation alone is sufficient to activate CD8+ T cells, suggesting that the presence of co-stimulatory molecules may not be necessary for effective T cell activation. Considering that the use of HEK293 cells as aAPCs has yet to be explored and due to their high transfection efficiency with minigenes, the methodology implemented in this work enables their use to identify naturally processed immunogenic neoantigens. We believe our findings can contribute to selecting and designing personalized vaccines based on tumor neoantigens that are useful for cancer immunotherapy.

Allosteric inhibition of SHP2 rescues functional T-cell abnormalities in SAP deficiency

BACKGROUND

X-linked lymphoproliferative disease (XLP) is a primary immunodeficiency arising from SH2D1A mutations leading to loss of SLAM-associated protein (SAP). SAP is an intracellular adaptor protein that binds to SLAM family receptors and is expressed in specific lymphoid lineages. In T cells, SAP relays activatory signals from the T-cell receptor but in its absence SH2 containing protein tyrosine phosphase-1 (SHP1), SH2 containing protein tyrosine phosphase-2 (SHP2), and SH2 containing inositol 5'-phosphatase proteins (SHIP) induce T-cell inhibitory signals leading to abnormal T-cell responses. This results in severe clinical manifestations including immune dysregulation, dysgammaglobulinemia, lymphoma, and hemophagocytic lymphohistiocytosis. Current treatment relies on supportive therapies including immunoglobulin replacement and symptom-directed therapy, with hematopoietic stem cell transplant offering the only curative option.

OBJECTIVES

As most XLP symptoms are due to defective T-cell function, this study investigated whether inhibition of SHP2 can restore cellular function in the absence of SAP.

METHODS

Healthy donor and XLP patient T cells were activated with anti-CD3/CD28 in T-cell media supplemented with a SHP2 inhibitor (RMC-4550 in vitro for 24 hours) and functional assays were performed to assess follicular T_H (T_FH) cell function, CD8 cytotoxicity, and sensitivity to restimulation-induced cell death. Additionally, SAP-deficient (SAP^y/-) mice were treated with RMC-4550 before T-cell mediated challenge with 4-hydroxy-3-nitrophenylacetly conjugated chicken gammaglobulin and subsequent assessment of humoral immunity analyzing T_FH cell population, germinal center formation, and antigen-dependent immunoglobulin secretion.

RESULTS

This study shows that the use of RMC-4550 restores T-cell function in XLP patient cells and a SAP^y/- model, demonstrating restoration of T_FH cell function through immunoglobulin and cytokine secretion analysis alongside rescue of cytotoxicity and restimulation-induced cell death.

CONCLUSIONS

These data suggest that SHP2 inhibitors could offer a novel and effective targeted treatment approach for patients with XLP.

An Oil-in-Water adjuvant significantly increased influenza A/H7N9 split virus Vaccine-Induced circulating follicular helper T (cTFH) cells and antibody responses

BACKGROUND

Unadjuvanted A/H7N9 vaccines are poorly immunogenic. The immune response is improved with the addition of MF59, an oil-in-water adjuvant. However, the cellular immunologic responses of MF59-adjuvanted A/H7N9 vaccine are not fully understood.

METHODS

37 participants were vaccinated with 2 doses of 2013 influenza A/H7N9 vaccine (at Days 1 and 21) with or without MF59 and enrolled in an immunology substudy. Responses were assessed at multiple timepoints (Days 0, 8, 21, 29, and 42) for hemagglutination inhibition (HAI) and neutralizing antibody (Neut) assays, memory B cell responses by enzyme-linked ImmunoSpot; circulating follicular helper T cells (cT_FH) and CD4 + T cells by intracellular cytokine staining.

RESULTS

MF59-adjuvanted influenza A/H7N9 vaccine induced significantly higher hemagglutination inhibition (HAI) and neutralizing antibody (Neut) responses when compared to unadjuvanted vaccine. The adjuvanted vaccine elicited significantly higher levels of Inducible T-cell Co-Stimulator (ICOS) expression by CXCR3⁺CXCR5⁺CD4⁺ cT_FH cells, compared to unadjuvanted vaccine. The magnitude of increase in cT_FH cells (from baseline to Day 8) and in IL-21 expressing CD154⁺CD4⁺ T cells (from baseline to Days 8 and 21) correlated with HAI (at Day 29) and Neut antibody (at Days 8 and 29) titers. The increase in frequency of IL-21 expressing CD154⁺CD4⁺T cells (from baseline to Day 21) correlated with memory B cell frequency (at Day 42).

CONCLUSION

cT_FH activation is associated with HAI and Neut responses in recipients of MF59-adjuvanted influenza A/H7N9 vaccine relative to unadjuvanted vaccine. Future studies should focus on optimizing the cT_FH response and use cT_FH as an early biomarker of serological response to vaccination. This trial was registered at clinicaltrials.gov, trial number NCT01938742.

Impaired NFAT and NFκB activation are involved in suppression of CD40 ligand expression by Δ(9)-tetrahydrocannabinol in human CD4(+) T cells

We have previously reported that Δ(9)-tetrahydrocannabinol (Δ(9)-THC), the main psychoactive cannabinoid in marijuana, suppresses CD40 ligand (CD40L) expression by activated mouse CD4(+) T cells. CD40L is involved in pathogenesis of many autoimmune and inflammatory diseases. In the present study, we investigated the molecular mechanism of Δ(9)-THC-mediated suppression of CD40L expression using peripheral blood human T cells. Pretreatment with Δ(9)-THC attenuated CD40L expression in human CD4(+) T cells activated by anti-CD3/CD28 at both the protein and mRNA level, as determined by flow cytometry and quantitative real-time PCR, respectively. Electrophoretic mobility shift assays revealed that Δ(9)-THC suppressed the DNA-binding activity of both NFAT and NFκB to their respective response elements within the CD40L promoter. An assessment of the effect of Δ(9)-THC on proximal T cell-receptor (TCR) signaling induced by anti-CD3/CD28 showed significant impairment in the rise of intracellular calcium, but no significant effect on the phosphorylation of ZAP70, PLCγ1/2, Akt, and GSK3β. Collectively, these findings identify perturbation of the calcium-NFAT and NFκB signaling cascade as a key mechanistic event by which Δ(9)-THC suppresses human T cell function.

Co-culture of the 55-6 B cell hybridoma with the EL-4 thymoma cell. Effect on cell growth and monoclonal antibody production

The cell growth and monoclonal antibody production of the 55-6 hybridoma cell co-cultured with the murine thymoma cell line EL-4 at different initial 55-6:EL-4 ratios were investigated. Both populations were seeded in co-culture without previous stimulation and therefore with low constitutive CD40 and CD40 ligand (CD154) expression levels, and in the absence of exogenous co-stimuli. Viable cell density and growth rate data seem to suggest a competition for nutrients, which is detrimental for both cells in terms of biomass production and also of growth rate for 55-6. Final concentrations of antibody and specific antibody production rates were affected by the initial 55-6:EL-4 ratio. The 4:1 ratio yielded the highest IgG2a concentration, whereas the highest specific antibody production rate was obtained at the 2:1 ratio. Changes mainly in CD154 and also in CD40 expression in co-cultures could suggest cross-talk between both populations. In conclusion, different types of interactions are probably present in this co-culture system: competition for nutrients, cognate interaction and/or autocrine or paracrine interactions that influence the proliferation of both cells and the hybridoma antibody secretion. We are hereby presenting a pre-scale-up process that could speed up the optimization of large-scale monoclonal antibodies production in bioreactors by emulating the in vivo cell-cell interaction between B and T cells without previous stimulation or the addition of co-stimulatory molecules.