Exploring NK cell receptor dynamics in paediatric leukaemias: implications for immunotherapy and prognosis

Objectives

Immunotherapies targeting natural killer (NK) cell receptors have shown promise against leukaemia. Unfortunately, cancer immunosuppressive mechanisms that alter NK cell phenotype prevent such approaches from being successful. The study utilises advanced cytometry to examine how cancer immunosuppressive pathways affect NK cell phenotypic changes in clinical samples.

Methods

In this study, we conducted a high-dimensional examination of the cell surface expression of 16 NK cell receptors in paediatric patients with acute myeloid leukaemia and acute lymphoblastic leukaemia, as well as in samples of non-age matched adult peripheral blood (APB) and umbilical cord blood (UCB). An unsupervised analysis was carried out in order to identify NK cell populations present in paediatric leukaemias.

Results

We observed that leukaemia NK cells clustered together with UCB NK cells and expressed relatively higher levels of the NKG2A receptor compared to APB NK cells. In addition, CD56dimCD16+CD57- NK cells lacking NKG2A expression were mainly absent in paediatric leukaemia patients. However, CD56br NK cell populations expressing high levels of NKG2A were highly represented in paediatric leukaemia patients. NKG2A expression on leukaemia NK cells was found to be positively correlated with the expression of its ligand, suggesting that the NKG2A-HLA-E interaction may play a role in modifying NK cell responses to leukaemia cells.

Conclusion

We provide an in-depth analysis of NK cell populations in paediatric leukaemia patients. These results support the development of immunotherapies targeting immunosuppressive receptors, such as NKG2A, to enhance innate immunity against paediatric leukaemia.

High dimensional analysis reveals distinct NK cell subsets but conserved response to stimulation in umbilical cord blood and adult peripheral blood

Growing interest surrounds adoptive cellular therapies utilising Natural Killer (NK) cells, which can be obtained from various sources, including umbilical cord blood (UCB) and adult peripheral blood (APB). Understanding NK cell receptor expression and diversity in such cellular sources will guide future therapeutic designs. We used a 20-colour flow cytometry panel to compare unstimulated and cytokine-activated UCB and APB NK cells. Our analysis showed that UCB NK cells express slightly higher levels of the immune checkpoints PD-1, TIGIT and CD96 compared to their APB counterparts. Unsupervised hierarchical clustering and dimensionality reduction analyses revealed an enrichment in CD56^neg as well as mature NKp46^neg and CD56⁺ CD16⁺ NK cell populations in UCB whereas CD57⁺ terminally differentiated NK cells with variable expression of KIRs and CD16 were found in APB. These populations were conserved following stimulation with IL-12, IL-15, and IL-18. Cytokine stimulation was associated with the downregulation of TIGIT and CD16 on multiple NK cell subsets in UCB and APB. Among UCB CD16^- NK cell populations, TIGIT⁺ NK cells produced more IFN-γ than their TIGIT^- counterparts. Our data demonstrate higher immune checkpoint expression on UCB NK cells compared to APB. However, expression of TIGIT immune checkpoint is not indicative of NK cell exhaustion. This article is protected by copyright. All rights reserved.

Cytokines as a marker of central nervous system autoantibody associated epilepsy

OBJECTIVE

Autoantibodies to central nervous system (CNS) antigens are increasingly identified in patients with epilepsy. Alterations in cytokines and chemokines have also been demonstrated in epilepsy, but this has not been explored in subjects with autoantibodies. If antibody positive and antibody negative subjects show a difference in immune activation, as measured by cytokine levels, this could improve diagnostic and therapeutic approaches, and provide insights into the underlying pathophysiology. We aimed to evaluate serum and CSF cytokines and chemokines in patients with and without autoantibody positivity to identify any differences between the two groups.

METHODS

We studied participants who had undergone serum and CSF testing for CNS autoantibodies, as part of their clinical evaluation. Cases were classified as antibody positive or antibody negative for comparison. Stored CSF and sera were analysed for cytokine and chemokine concentrations.

RESULTS

25 participants underwent testing. 8 were antibody positive, 17 were antibody negative. Significant elevations in the mean concentration of IL-13 and RANTES in CSF were found in the antibody positive cases and significant elevation of CSF VEGF was found in the antibody negative cases. Significant elevations in the mean concentrations of serum TNFβ, INFγ, bNGF, IL-8, and IL-12 were seen in the antibody negative group, and there was poor correlation between the majority of serum and CSF concentrations.

SIGNIFICANCE

Measurement of cytokines and chemokines such as IL-13 and RANTES could be useful in diagnosis of autoimmune associated epilepsy. Such markers might also guide targeted immunotherapy to improve seizure control and provide insights into the underlying pathophysiology of epilepsy associated with CNS autoantibodies.

Abstract B42: Human CD141+ dendritic cells (cDC1) are impaired in advanced melanoma patients but can be targeted to increase efficacy of anti-PD-1 checkpoint inhibitor therapy

Dendritic cells (DCs) as professional antigen-presenting cells with unique T-cell stimulatory capacity represent a potential means by which to improve response rates towards immune checkpoint inhibitor antibodies (ICIs) such as anti-PD-1 (pembrolizumab) in melanoma. The conventional type 1 DC subset (cDC1) is indispensable for the efficacy of ICIs in animal models; however, very little is known about the role of cDC1 in human cancer patients. To address this, we developed a whole-blood assay for quantifying and characterizing human DC subsets (cDC1, cDC2 and plasmacytoid DCs [pDCs]) by flow cytometry and compared these in healthy donors and stage III and IV metastatic melanoma patients. cDC1 and pDC numbers were significantly reduced in stage IV melanoma patients compared to healthy controls. Moreover, cDC1s in melanoma patients were selectively impaired in their ability to upregulate CD83 expression after stimulation with TLR3 and TLR7/8 agonists ex vivo. Although DC numbers did not correlate with responses to anti-PD-1 and/or anti-CTLA-4 ICIs, their numbers and capacity to upregulate CD83 declined further during treatment in nonresponding patients. To examine whether harnessing cDC1 could improve responses to ICIs in human melanoma, we developed a humanized mouse model by engrafting immunodeficient NSG-SGM3 mice with CD34+ hematopoietic stem cells from umbilical cord blood followed by transplantation of a human melanoma cell line. Treatment with anti-PD-1 in this model was ineffective at controlling tumor growth, but efficacy was enhanced by indirectly expanding and activating DCs in vivo with Flt-3 ligand (Flt3L) and TLR3 agonist polyI:C. Moreover, intratumoral injection of cDC1s, but not cDC2s, resulted in reduced tumor growth when combined with anti-PD-1 treatment. Together, these data illustrate impairments in cDC1 in advanced melanoma patients and provide rationale for harnessing them to increase immunogenicity and response rates to ICIs.

Citation Format: Liam O’Brien, Yoke Seng Lee, Carina Walpole, Ingrid Leal Rojas, Kelly-Anne Masterman, Victoria Atkinson, Andrew Barbour, Kristen Radford. Human CD141+ dendritic cells (cDC1) are impaired in advanced melanoma patients but can be targeted to increase efficacy of anti-PD-1 checkpoint inhibitor therapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B42.

Human CD141+ Dendritic Cell and CD1c+ Dendritic Cell Undergo Concordant Early Genetic Programming after Activation in Humanized Mice In Vivo

Human immune cell subsets develop in immunodeficient mice following reconstitution with human CD34⁺ hematopoietic stem cells. These "humanized" mice are useful models to study human immunology and human-tropic infections, autoimmunity, and cancer. However, some human immune cell subsets are unable to fully develop or acquire full functional capacity due to a lack of cross-reactivity of many growth factors and cytokines between species. Conventional dendritic cells (cDCs) in mice are categorized into cDC1, which mediate T helper (Th)1 and CD8⁺ T cell responses, and cDC2, which mediate Th2 and Th17 responses. The likely human equivalents are CD141⁺ DC and CD1c⁺ DC subsets for mouse cDC1 and cDC2, respectively, but the extent of any interspecies differences is poorly characterized. Here, we exploit the fact that human CD141⁺ DC and CD1c⁺ DC develop in humanized mice, to further explore their equivalency in vivo. Global transcriptome analysis of CD141⁺ DC and CD1c⁺ DC isolated from humanized mice demonstrated that they closely resemble those in human blood. Activation of DC subsets in vivo, with the TLR3 ligand poly I:C, and the TLR7/8 ligand R848 revealed that a core panel of genes consistent with DC maturation status were upregulated by both subsets. R848 specifically upregulated genes associated with Th17 responses by CD1c⁺ DC, while poly I:C upregulated IFN-λ genes specifically by CD141⁺ DC. MYCL expression, known to be essential for CD8⁺ T cell priming by mouse DC, was specifically induced in CD141⁺ DC after activation. Concomitantly, CD141⁺ DC were superior to CD1c⁺ DC in their ability to prime naïve antigen-specific CD8⁺ T cells. Thus, CD141⁺ DC and CD1c⁺ DC share a similar activation profiles in vivo but also have induce unique signatures that support specialized roles in CD8⁺ T cell priming and Th17 responses, respectively. In combination, these data demonstrate that humanized mice provide an attractive and tractable model to study human DC in vitro and in vivo.