Staggered starts in the race to T cell activation

Integrative single-cell multi-omics of CD19-CARpos and CARneg T cells suggest drivers of immunotherapy response in B cell neoplasias

The impact of phenotypic, clonal, and functional heterogeneity of chimeric antigen receptor (CAR)-T cells on clinical outcome remains understudied. Here, we integrate clonal kinetics with transcriptomic heterogeneity resolved by single-cell omics to interrogate cellular dynamics of non-transduced (CARneg) and transduced (CARpos) T cells, in the infusion product (IP) and at the CAR-T cell expansion peak in five B cell acute lymphoblastic leukemia (B-ALL) patients treated with CD19CAR-T cells (varni-cel). We identify significant differences in cellular dynamics in response to therapy. CARpos T cells at IP of complete response patients exhibit a significantly higher CD4:CD8 ratio, validated in a larger cohort B-ALL patients (n = 47). Conversely, at the expansion peak, there is a clonal expansion of CD8+ effector memory and cytotoxic T cells. Cytotoxic CARpos γδ-T cells expansion correlates with treatment efficacy validated in a cohort of B-ALL (n = 18) and diffuse large B cell lymphoma (DLBCL) patients (n = 58). Our data provide insights into the complexity of T cell responses following CAR-T cell therapy and suggest drivers of immunotherapy response.

Tuning the potency and selectivity of ImmTAC molecules by affinity modulation

T-cell-engaging bispecifics have great clinical potential for the treatment of cancer and infectious diseases. The binding affinity and kinetics of a bispecific molecule for both target and T-cell CD3 have substantial effects on potency and specificity, but the rules governing these relationships are not fully understood. Using immune mobilizing monoclonal TCRs against cancer (ImmTAC) molecules as a model, we explored the impact of altering affinity for target and CD3 on the potency and specificity of the redirected T-cell response. This class of bispecifics binds specific target peptides presented by human leukocyte antigen on the cell surface via an affinity-enhanced T-cell receptor and can redirect T-cell activation with an anti-CD3 effector moiety. The data reveal that combining a strong affinity TCR with an intermediate affinity anti-CD3 results in optimal T-cell activation, while strong affinity of both targeting and effector domains significantly reduces maximum cytokine release. Moreover, by optimizing the affinity of both parts of the molecule, it is possible to improve the selectivity. These results could be effectively modelled based on kinetic proofreading with limited signalling. This model explained the experimental observation that strong binding at both ends of the molecules leads to reduced activity, through very stable target-bispecific-effector complexes leading to CD3 entering a non-signalling dark state. These findings have important implications for the design of anti-CD3-based bispecifics with optimal biophysical parameters for both activity and specificity.

Larval T Cells Are Functionally Distinct from Adult T Cells in Xenopus laevis

The amphibian Xenopus laevis tadpole provides a unique comparative experimental organism for investigating the roles of innate-like T (iT) cells in tolerogenic immunity during early development. Unlike mammals and adult frogs, where conventional T cells are dominant, tadpoles rely mostly on several prominent distinct subsets of iT cells interacting with cognate nonpolymorphic MHC class I-like molecules. In the present study, to investigate whole T cell responsiveness ontogenesis in X. laevis, we determined in tadpoles and adult frogs the capacity of splenic T cells to proliferate in vivo upon infection with two different pathogens, ranavirus FV3 and Mycobacterium marinum, as well as in vitro upon PHA stimulation using the thymidine analogous 5-ethynyl-2'-deoxyuridine and flow cytometry. We also analyzed by RT-quantitative PCR T cell responsiveness upon PHA stimulation. In vivo tadpole splenic T cells showed limited capacity to proliferate, whereas the in vitro proliferation rate was higher than adult T cells. Gene markers for T cell activation and immediate-early genes induced upon TCR activation were upregulated with similar kinetics in tadpole and adult splenocytes. However, the tadpole T cell signature included a lower amplitude in the TCR signaling, which is a hallmark of mammalian memory-like T cells and iT or "preset" T cells. This study suggests that reminiscent of mammalian neonatal T cells, tadpole T cells are functionally different from their adult counterpart.

Time required for commitment to T cell proliferation depends on TCR affinity and cytokine response

T cell activation and effector functions are determined by the affinity of the interaction between T cell receptor (TCR) and its antigenic peptide MHC (pMHC) ligand. A better understanding of the quantitative aspects of TCR-pMHC affinity-dependent T cell activation is critical for the development of new immunotherapeutic strategies. However, the role of TCR-pMHC affinity in regulating the kinetics of CD8+ T cell commitment to proliferation and differentiation is unknown. Here, we show that the stronger the TCR-pMHC affinity, the shorter the time of T cell-APC co-culture required to commit CD8+ T cells to proliferation. The time threshold for T cell cytokine production is much lower than that for cell proliferation. There is a strong correlation between affinity-dependent differences in AKT phosphorylation and T cell proliferation. The cytokine IL-15 increases the poor proliferation of T cells stimulated with low affinity pMHC, suggesting that pro-inflammatory cytokines can override the affinity-dependent features of T cell proliferation.

Immunological function and prognostic value of lymphoid-specific helicase in liver hepatocellular carcinoma

BACKGROUND

Lymphoid-specific helicase (HELLS), a SNF2-like chromatin-remodeling enzyme, plays a key role in tumor progression via its DNA methylation function. However, the effects of HELLS on immune infiltration and prognosis in liver hepatocellular carcinoma (LIHC) remain uncertain.

METHODS

The Tumor Immune Estimation Resource (TIMER) database was employed to explore the pan-cancer mRNA expression of HELLS and its correlation with immunity. GEPIA2 was used to verify the correlation between HELLS expression and survival. The role of HELLS in cancer was explored via gene set enrichment analysis (Gene Ontology and Kyoto Encyclopedia of Genes and Genomes) and the construction of gene-gene and protein-protein interaction networks (PPI). Additionally, correlations between DNA methylation, HELLS expression, and immune-related genes were explored in LIHC. HELLS expression in LIHC clinical samples was determined using qRT-PCR and western blotting. The effects of downregulated HELLS expression in hepatocellular carcinoma cells was explored via transfection experiments in vitro.

RESULTS

High HELLS mRNA expression was identified in several cancers and was significantly associated with poorer prognosis in LIHC. Furthermore, HELLS expression was positively correlated with tumor-infiltrating lymphocytes and immune checkpoint genes in LIHC. Bioinformatics analysis suggested that DNA methylation of HELLS may be associated with the immune response. Results from the TCGA-LIHC dataset, clinical samples, and functional analysis indicated that HELLS contributed to tumor progression in LIHC.

CONCLUSION

The study findings demonstrate that HELLS is an important factor in promoting LIHC malignancy and might serve as a potential biomarker for LIHC.

Divide and Conquer: Phenotypic and Temporal Heterogeneity Within CD8+ T Cell Responses

The advent of technologies that can characterize the phenotypes, functions and fates of individual cells has revealed extensive and often unexpected levels of diversity between cells that are nominally of the same subset. CD8+ T cells, also known as cytotoxic T lymphocytes (CTLs), are no exception. Investigations of individual CD8+ T cells both in vitro and in vivo have highlighted the heterogeneity of cellular responses at the levels of activation, differentiation and function. This review takes a broad perspective on the topic of heterogeneity, outlining different forms of variation that arise during a CD8+ T cell response. Specific attention is paid to the impact of T cell receptor (TCR) stimulation strength on heterogeneity. In particular, this review endeavors to highlight connections between variation at different cellular stages, presenting known mechanisms and key open questions about how variation between cells can arise and propagate.

Locked and loaded: strong TCR signaling primes anti-PD-1 therapy

With continuous T cell receptor (TCR) signaling, T cells can attenuate subsequent antigen responses through adaptive tolerance, thus averting autoimmunity, but potentially also providing refuge to developing cancers. Elliot and coworkers add to our understanding of adaptation via immune checkpoints by exploiting accelerated in vivo adaptive tolerance in the face of strong TCR signaling.