Acute cardiovascular syndromes, including myocardial infarction or stroke, are the principal cause of death in the Western society. The main underlying pathology of cardiovascular diseases is... Show moreAcute cardiovascular syndromes, including myocardial infarction or stroke, are the principal cause of death in the Western society. The main underlying pathology of cardiovascular diseases is atherosclerosis, which is caused by the accumulation of lipids and inflammatory cells in the vessel wall, in so-called atherosclerotic plaques. Current therapies mainly target the disturbed lipid homeostasis, but recent clinical trials have shown a clear benefit in treating patients with anti-inflammatory drugs. However, more specific targeting is required to avoid unwanted side effects. In this thesis, we have generated a detailed atlas of all the cells present in human atherosclerotic plaques using a novel state-of-the-art technique called single-cell RNA sequencing. This data set can be applied as a powerful tool to select potential drug targets with a functional relevance for atherosclerosis. We showed that the majority of the immune cells in the human atherosclerotic plaque consisted of T cells. Subsequently, we identified a pro-inflammatory population of T cells that likely responds to a plaque-derived antigen, suggesting that atherosclerosis has an autoimmune-like component. Finally, we have applied our single-cell atlas to define and validate targets to intervene with the recruitment and activation of mast cells and other immune cells in atherosclerosis. Show less
A deeper understanding of the parameters driving response and resistance to immunotherapy is needed to improve the low response rates observed in breast cancer patients. Research into immunotherapy... Show moreA deeper understanding of the parameters driving response and resistance to immunotherapy is needed to improve the low response rates observed in breast cancer patients. Research into immunotherapy response has predominantly focused on T cells, however effective immune responses require tightly regulated crosstalk between innate and adaptive immune cells. By combining profiling of blood and tumors from metastatic breast cancer patients with mechanistic studies in mouse models, we uncovered the critical role of eosinophils in immunotherapy response, and we provide proof-of-principle for eosinophil engagement to enhance immunotherapy efficacy. Focusing on resistance mechanisms to immunotherapy, we demonstrate that neoadjuvant immunotherapy triggers persistent and systemic regulatory T cell activation which blunts therapeutic efficacy against metastatic spread of breast tumors. In addition, we demonstrate that neutrophils in the tumor microenvironment pose a barrier to immunotherapy response through T cell suppression. Lastly, we demonstrate that combining the immunomodulatory agent PD1-IL2v with cisplatin is a powerful approach to induce a broad activation of systemic and intratumoral adaptive and innate immunity, resulting in effective immunotherapy responses. Overall, this work identifies several key players and their interconnectivities in anti-tumor immunity and tumor-induced immunosuppression that may be therapeutically exploited to improve immunotherapy responses for breast cancer patients. Show less
Historically platelets are mostly known for their crucial contribution to hemostasis, but there is growing understanding of their role in inflammation and immunity. The immunomodulatory role of... Show moreHistorically platelets are mostly known for their crucial contribution to hemostasis, but there is growing understanding of their role in inflammation and immunity. The immunomodulatory role of platelets entails interaction with pathogens, but also with immune cells including macrophages and dendritic cells (DCs), to activate adaptive immune responses. In our previous work, we have demonstrated that splenic CD169(+) macrophages scavenge liposomes and collaborate with conventional type 1 DCs (cDC1) to induce expansion of CD8(+) T cells. Here, we show that platelets associate with liposomes and bind to DNGR-1/Clec9a and CD169/Siglec-1 receptors in vitro. In addition, platelets interacted with splenic CD169(+) macrophages and cDC1 and further increased liposome internalization by cDC1. Most importantly, platelet depletion prior to liposomal immunization resulted in significantly diminished antigen-specific CD8(+) T cell responses, but not germinal center B cell responses. Previously, complement C3 was shown to be essential for platelet-mediated CD8(+) T cell activation during bacterial infection. However, after liposomal vaccination CD8(+) T cell priming was not dependent on complement C3. While DCs from platelet-deficient mice exhibited unaltered maturation status, they did express lower levels of CCR7. In addition, in the absence of platelets, CCL5 plasma levels were significantly reduced. Overall, our findings demonstrate that platelets engage in a cross-talk with CD169(+) macrophages and cDC1 and emphasize the importance of platelets in induction of CD8(+) T cell responses in the context of liposomal vaccination. Show less
Sluijs, J.V. van der; Ens, D. van; Brummelman, J.; Heister, D.; Sareen, A.; Truijen, L.; ... ; Hobo, W. 2023
Allogeneic stem cell transplantation (alloSCT) can be curative for hemato-oncology patients due to effective graft-versus-tumor immunity. However, relapse remains the major cause of treatment... Show moreAllogeneic stem cell transplantation (alloSCT) can be curative for hemato-oncology patients due to effective graft-versus-tumor immunity. However, relapse remains the major cause of treatment failure, emphasizing the need for adjuvant immunotherapies. In this regard, post-transplantation dendritic cell (DC) vaccination is a highly interesting strategy to boost graft-versus-tumor responses. Previously, we developed a clinically applicable protocol for simultaneous large-scale generation of end-stage blood DC subsets from donor-derived CD34(+) stem cells, including conventional type 1 and 2 DCs (cDC1s and cDC2s), and plasmacytoid DCs (pDCs). In addition, the total cultured end-product (DC-complete vaccine), also contains non-end-stage-DCs (i.e. non-DCs). In this study, we aimed to dissect the phenotypic identity of these non-DCs and their potential immune modulatory functions on the potency of cDCs and pDCs in stimulating tumor-reactive CD8(+ )T and NK cell responses, in order to obtain rationale for clinical translation of our DC-complete vaccine. The non-DC compartment was heterogeneous and comprised of myeloid progenitors and (immature) granulocyte- and monocyte-like cells. Importantly, non-DCs potentiated toll-like receptor-induced DC maturation, as reflected by increased expression of co-stimulatory molecules and enhanced cDC-derived IL-12 and pDC-derived IFN-alpha production. Additionally, antigen-specific CD8(+) T cells effectively expanded upon DC-complete vaccination in vitro and in vivo. This effect was strongly augmented by non-DCs in an antigen-independent manner. Moreover, non-DCs did not impair in vitro DC-mediated NK cell activation, degranulation nor cytotoxicity. Notably, in vivo i.p. DC-complete vaccination activated i.v. injected NK cells. Together, these data demonstrate that the non-DC compartment potentiates DC-mediated activation and expansion of antigen-specific CD8+ T cells and do not impair NK cell responses in vitro and in vivo. This underscores the rationale for further clinical translation of our CD34+-derived DC-complete vaccine in hemato-oncology patients post alloSCT. Show less
A proper immune system is essential to fight off pathogens such as viruses, bacteria, and fungi. The immune system also plays a huge role in the protection against cancer, as it can eradicate tumor... Show moreA proper immune system is essential to fight off pathogens such as viruses, bacteria, and fungi. The immune system also plays a huge role in the protection against cancer, as it can eradicate tumor cells. All immune cells are derived from hematopoietic stem cells (HSC) that undergo differentiation in a highly regulated succession of developmental steps. Each of the cell types from the immune system perform a unique specialized role, and where most of these lineages develop in the bone marrow, the T cells that make part of our adaptive immunity, develop in the thymus within a specialized environment. To achieve this, the development of each of these cell types is regulated by a variety of transcription factors.In Chapter 2 of this thesis, we reviewed the complexity of one of the important signaling pathways of hematopoietic development, the Wnt pathway. While this serves as an introduction to the fundamental research we performed, it also shines light onto potential therapeutic targets within the Wnt pathway. For further study of the Wnt pathway, we generated a novel reporter mouse, which is described in Chapter 3 of this thesis. Here we developed a reporter mouse for the Axin2 gene with the fluorescent tag mTurquoise2 with CRISPR/Cas9 genome editing tools. Based on how the genetic engineering was done to create this reporter mouse, mice that are homozygous for this reporter knock-in are also a functional knockout for Axin2. For proper functional studies, the heterozygous mice should be used.The Axin2-mTurquoise2 mouse was used in Chapter 4 of this thesis to study Wnt involvement in hematopoiesis and T cell development. We observed an increase of canonical Wnt-signaling in thymocytes from mice that have a loss of Axin2 (Axin2-TQtg/tg mice). This confirms the Wnt dosage effect that was reported previously in literature. Conclusively, these results indicate that Axin2 is required to fine-tune Wnt activity to the levels that are “just right” and cannot be maintained by Wnt activator Axin1 alone.Chapters 2, 3 and 4 focused on fundamental research on hematopoiesis and T cell development. Chapter 5 is more translational oriented and is an introductory review to thymic regenerative therapies. In Chapter 6 of this thesis, we describe the development of a combined cell and gene therapy effort to regenerate a functional thymus transplant from human Induced Pluripotent Stem Cells (iPSCs). We generated an iPSC-derived thymus by directed differentiation of human iPSCs towards thymic epithelial progenitor cells (TEPCs) using FOXN1, formation of 3-D structures from these cells which we named iPSC-derived TEPCs, or iTEPCs, and transplantation of these organoids into mice that lack a functional thymus. Functionality was demonstrated by reconstitution of functional T cells from iPSC-derived grafts, which was introduced by FOXN1 gene therapy (FOXN1 iTEPCs).Chapter 7 is the final translational research chapter of this thesis and investigated the use of iPSCs for the modeling of PIDs and the initial steps towards T cell regeneration in SCID patients. This chapter describes the iPSC generation, and its repair to use gene-corrected iPSCs from a RAG2 SCID patient to repair their disrupted immune system. The resulting iPSC model was used for disease modelling and provided novel insights into the T cell development in these RAG2-SCID patients, as we observed developmental blocks at every investigated stage of T cell development. The findings in this chapter also provide a proof-of-principle to treat a variety of SCID patients by utilizing ex vivo cell and gene therapy.Altogether, this thesis tackles two sides of the same coin: fundamentals of hematopoiesis and T cell development, and regenerative therapies for the immune system. The fundamental tools and findings in this thesis can lead to important insights to find new treatment options or improve existing therapies. Furthermore, we provide the basis for two potential therapies to treat patients with a variety of immune disorders, including DiGeorge Syndrome, SCID, age-related immune deficiencies and (post-transplant) leukemia patients that received ablative therapies. Show less
Stouten, I.; Montfoort, N. van; Hawinkels, L.J.A.C. 2023
The lack of response to therapy in pancreatic ductal adenocarcinoma (PDAC) patients has contributed to PDAC having one of the lowest survival rates of all cancer types. The poor survival of PDAC... Show moreThe lack of response to therapy in pancreatic ductal adenocarcinoma (PDAC) patients has contributed to PDAC having one of the lowest survival rates of all cancer types. The poor survival of PDAC patients urges the exploration of novel treatment strategies. Immunotherapy has shown promising results in several other cancer types, but it is still ineffective in PDAC. What sets PDAC apart from other cancer types is its tumour microenvironment (TME) with desmoplasia and low immune infiltration and activity. The most abundant cell type in the TME, cancer-associated fibroblasts (CAFs), could be instrumental in why low immunotherapy responses are observed. CAF heterogeneity and interactions with components of the TME is an emerging field of research, where many paths are to be explored. Understanding CAF-immune cell interactions in the TME might pave the way to optimize immunotherapy efficacy for PDAC and related cancers with stromal abundance. In this review, we discuss recent discoveries on the functions and interactions of CAFs and how targeting CAFs might improve immunotherapy. Show less
Immune checkpoint therapies that aim to (re)activate the immune response against cancer cells have shown promising results in a variety of tumor types. Yet, a large fraction of cancer patients does... Show moreImmune checkpoint therapies that aim to (re)activate the immune response against cancer cells have shown promising results in a variety of tumor types. Yet, a large fraction of cancer patients does not benefit from these therapies. While the presence of a substantial number of immune cells, and in particular T cells, in the tumor is generally related with a better clinical response to checkpoint therapies, the T cells in the tumor are diverse in their capacity to eliminate the tumor. In order to improve treatment outcome of cancer patients, we require a better understanding of the roles of different T cells in the response (and resistance) to immune checkpoint therapy. The development of single cell profiling technologies has provided us with a powerful tool to analyze the state and functionality of individual cells. In this thesis, I have used single cell profiling methods in combination with innovative experimental technologies to unravel the diversity of T cells in human tumors and define the changes in the profiles of T cells that occur in response to treatment with immune checkpoint therapy to dissect which T cells are important for therapy response. Show less
Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV- 2) specific CD4(+ )and CD8(+) T cells in SARS- CoV- 2-unexposed donors has been explained by the presence of T cells primed... Show moreDetection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV- 2) specific CD4(+ )and CD8(+) T cells in SARS- CoV- 2-unexposed donors has been explained by the presence of T cells primed by other coronaviruses. However, based on the relatively high frequency and prevalence of cross-reactive T cells, we hypothesized cytomegalovirus (CMV) may induce these cross-reactive T cells. Stimulation of pre-pandemic cryo-preserved peripheral blood mononuclear cells (PBMCs) with SARS- CoV- 2 peptides revealed that frequencies of SARS- CoV- 2-specific T cells were higher in CMVseropositive donors. Characterization of these T cells demonstrated that membrane-specific CD4(+ )and spike-specific CD8(+) T cells originate from cross-reactive CMVspecific T cells. Spike-specific CD8(+ )T cells recognize SARS- CoV- 2 spike peptide FVSNGTHWF (FVS) and dissimilar CMV pp65 peptide IPSINVHHY (IPS) presented by HLA- B*35:01. These dual IPS/FVS-reactive CD8(+) T cells were found in multiple donors as well as severe COVID- 19 patients and shared a common T cell receptor (TCR), illustrating that IPS/FVS- cross-reactivity is caused by a public TCR. In conclusion, CMVspecific T cells cross react with SARS-CoV- 2, despite low sequence homology between the two viruses, and may contribute to the pre-existing immunity against SARS-CoV- 2. Show less
This thesis describes the research that was performed to unravel the function and development of human lymphoid tissue-resident (lt)NK cells in relation to the circulating CD56bright and CD56dim NK... Show moreThis thesis describes the research that was performed to unravel the function and development of human lymphoid tissue-resident (lt)NK cells in relation to the circulating CD56bright and CD56dim NK cells. Two methods, RNA sequencing and flow cytometry, both commonly used in the field of immunology, were employed at the bulk and single-cell level. We highlighted the complexity of single-cell analysis that could potentially lead to misinterpretation, but also the additional value over bulk approaches by uncovering the cellular heterogeneity and developmental trajectories. Finally, our workflow for single-cell analysis was applied on a patient more than 50 years after hematopoietic stem cell transplantation to perform combined analysis of the T cell phenotype and T cell receptor repertoire. Show less
Transplantation is the golden standard for the treatment of end-stage renal disease. During this process, the transplanted organ is often damaged. In this thesis, we investigated whether activation... Show moreTransplantation is the golden standard for the treatment of end-stage renal disease. During this process, the transplanted organ is often damaged. In this thesis, we investigated whether activation of the complement system, part of our innate immune system, plays a local role. We reviewed that properdin, the only known positive regulator of the complement system, was detected in serum, plasma and urine from patients with various complement-mediated renal diseases. In protocol biopsies obtained 10 days after transplantation, properdin was found deposited in addition to complement activation markers. Next, we showed that dendritic cells secrete properdin and a decrease in properdin levels during dendritic cell- T-cell interaction resulted in reduced T-cell proliferation and activation. We also showed that properdin is able to bind to surfaces of both viable and dead cells, contributing to complement activation. Macrophages can also produce properdin and negative regulators factor H and its splice variant FHL-1. Increasing knowledge on complement factor production by other cells than hepatocytes, including immune cells, hints towards a local role of the complement system in various processes. These findings contribute to a better understanding of the local role of the complement system and are important for the applications of (new) complement-inhibiting drugs. Show less
Pasmans, H.; Berkowska, M.A.; Diks, A.M.; Mooij, B. de; Groenland, R.J.; Rond, L. de; ... ; Buisman, A.M. 2022
Introduction: Current human papillomavirus (HPV) vaccines consist of virus-like particles (VLPs) which are based on the L1 protein, but they are produced by different expression systems and use... Show moreIntroduction: Current human papillomavirus (HPV) vaccines consist of virus-like particles (VLPs) which are based on the L1 protein, but they are produced by different expression systems and use different adjuvants. We performed in-depth immunophenotyping of multiple innate and adaptive immune cells after vaccination with bivalent versus nonavalent HPV vaccines. Method: Twenty pre-menopausal HPV-seronegative women were enrolled and randomized to receive three-doses of either the bivalent or the nonavalent HPV vaccine. Blood samples were collected at multiple time points from baseline up to 7 months after first vaccination. Four extensive EuroFlow flow cytometry antibody panels were used to monitor various immune cell subsets. Additionally, HPV-specific memory B- and T cells were determined by ELISPOT and HPV-specific antibody levels were measured by a VLP-based multiplex immunoassay. Results: In both cohorts, the numbers of plasma cells expanded in the first week after both primary and tertiary vaccination. HPV16 and HPV18-specific antibody levels and memory B and T-cell responses were higher in the bivalent than in the nonavalent vaccinees one month post third vaccination. For HPV31 and HPV45-specific antibody levels this pattern was reversed. Monocytes showed an expansion one day after vaccination in both cohorts but were significantly higher in the bivalent vaccine cohort. Large heterogeneity in responses of the other cell subsets was observed between donors. Conclusion: This pilot study showed a consistent response of monocytes and plasma cells after vaccination and a considerable variation in other circulating immune cells in both types of HPV vaccines between donors. Show less
Essen, M.F. van; Schlagwein, N.; Gijlswijk-Janssen, D.J. van; Ruben, J.M.; Kooten, C. van; COMBAT Consortium 2022
The complement system does not only play an important role in the defence against microorganism and pathogens, but also contributes to the regulation of innate and adaptive immunity. Especially... Show moreThe complement system does not only play an important role in the defence against microorganism and pathogens, but also contributes to the regulation of innate and adaptive immunity. Especially activation fragments C3a and C5a and complement activation at the interface of antigen presenting cell (APC) and T cell, were shown to have a role in T cell activation and proliferation. Whereas most complement factors are produced by the liver, properdin, a positive regulator of the C3 convertase, is mainly produced by myeloid cells. Here we show that properdin can be detected in myeloid cell infiltrate during human renal allograft rejection. In vitro, properdin is produced and secreted by human immature dendritic cells (iDCs), which is further increased by CD40-L-matured DCs (mDCs). Transfection with a specific properdin siRNA reduced properdin secretion by iDCs and mDCs, without affecting the expression of co-stimulatory markers CD80 and CD86. Co-culture of properdin siRNA-transfected iDCs and mDCs with human allogeneic T cells resulted in reduced T cell proliferation, especially under lower DC-T cell ratio's (1:30 and 1:90 ratio). In addition, T cell cytokines were altered, including a reduced TNF-alpha and IL-17 secretion by T cells co-cultured with properdin siRNA-transfected iDCs. Taken together, these results indicate a local role for properdin during the interaction of DCs and allogeneic T cells, contributing to the shaping of T cell proliferation and activation. Show less
The first successful European hematopoietic stem cell transplantation (HSCT) was performed in 1968 as treatment in a newborn with IL2RG deficiency using an HLA-identical sibling donor. Because of... Show moreThe first successful European hematopoietic stem cell transplantation (HSCT) was performed in 1968 as treatment in a newborn with IL2RG deficiency using an HLA-identical sibling donor. Because of declining naive T and natural killer (NK) cells, and persistent human papilloma virus (HPV)-induced warts, the patient received a peripheral stem cell boost at the age of 37 years. NK and T cells were assessed before and up to 14 years after the boost by flow cytometry. The boost induced renewed reconstitution of functional NK cells that were 14 years later enriched for CD56(dim)CD27(+) NK cells. T-cell phenotype and T-cell receptor (TCR) repertoire were simultaneously analyzed by including TCR V beta antibodies in the cytometry panel. Naive T-cell numbers with a diverse TCR V beta repertoire were increased by the boost. Before and after the boost, clonal expansions with a homogeneous TIGIT and PD-1 phenotype were identified in the CD27(-) and/or CD28(-) memory population in the patient, but not in the donor. TRB sequencing was applied on sorted T-cell subsets from blood and on T cells from skin biopsies. Abundant circulating CD8 memory clonotypes with a chronic virus-associated CD57(+)KLRG1(+)CX3CR1(+) phenotype were also present in warts, but not in healthy skin of the patient, suggesting a link with HPV. In conclusion, we demonstrate in this IL2RG-deficient patient functional NK cells, a diverse and lasting naive T-cell compartment, supported by a stem cell boost, and an oligoclonal memory compartment half a century after HSCT. Show less
For many years, hematopoietic stem cell kinetics and/or cell signaling pathway activity has been studied through fluorescent in vitro or in vivo models. However, inaccurate measurement of the... Show moreFor many years, hematopoietic stem cell kinetics and/or cell signaling pathway activity has been studied through fluorescent in vitro or in vivo models. However, inaccurate measurement of the fluorescent proteins or lack of knowlegde about the genetic design of these models lead to incomplete conclusions. In the present thesis, in vivo fluorescent models are improved and new models are proposed together with analysis protocols to ensure precise measurement of fluorescent protein dynamics. Show less
Human cytomegalovirus (HCMV) is an ubiquitous herpesvirus that can cause serious morbidity and mortality in immunocompromised or immune-immature individuals. A vaccine that induces immunity to CMV... Show moreHuman cytomegalovirus (HCMV) is an ubiquitous herpesvirus that can cause serious morbidity and mortality in immunocompromised or immune-immature individuals. A vaccine that induces immunity to CMV in these target populations is therefore highly needed. Previous attempts to generate efficacious CMV vaccines primarily focused on the induction of humoral immunity by eliciting neutralizing antibodies. Current insights encourage that a protective immune response to HCMV might benefit from the induction of virus-specific T cells. Whether addition of antiviral T cell responses enhances the protection by antibody-eliciting vaccines is however unclear. Here, we assessed this query in mouse CMV (MCMV) infection models by developing synthetic vaccines with humoral immunity potential, and deliberately adding antiviral CD8(+) T cells. To induce antibodies against MCMV, we developed a DNA vaccine encoding either full-length, membrane bound glycoprotein B (gB) or a secreted variant lacking the transmembrane and intracellular domain (secreted (s)gB). Intradermal immunization with an increasing dose schedule of sgB and booster immunization provided robust viral-specific IgG responses and viral control. Combined vaccination of the sgB DNA vaccine with synthetic long peptides (SLP)-vaccines encoding MHC class I-restricted CMV epitopes, which elicit exclusively CD8(+) T cell responses, significantly enhanced antiviral immunity. Thus, the combination of antibody and CD8(+) T cell-eliciting vaccines provides a collaborative improvement of humoral and cellular immunity enabling enhanced protection against CMV. Show less
The mechanisms involved in the autoimmune hypothesis of narcolepsy are investigated in this thesis. The role of HLA, auto- and cross-reactive T cells is explored and immune cell populations of... Show moreThe mechanisms involved in the autoimmune hypothesis of narcolepsy are investigated in this thesis. The role of HLA, auto- and cross-reactive T cells is explored and immune cell populations of interest are identified by a new technique, called mass cytometry. The second part of the thesis assesses unexplored clinical features of narcolepsy, such as weight gain and sleep state misperception. Show less
Simple SummaryCytotoxic T lymphocytes (CTLs) play an important role in controlling tumours, and an improved understanding of how they accomplish this will benefit immunotherapeutic cancer treatment... Show moreSimple SummaryCytotoxic T lymphocytes (CTLs) play an important role in controlling tumours, and an improved understanding of how they accomplish this will benefit immunotherapeutic cancer treatment strategies. Stimulation of CTLs by targeting their CD137 receptor is a strategy currently under investigation for enhancing responses against tumours, yet so far only limited quantitative knowledge regarding the effects of such stimulation upon CTLs has been obtained. Here, we develop mathematical models to describe dynamic in vivo two-photon imaging of tumour infiltrating CTLs, to characterise differences in their function either in the presence or absence of a CD137 agonist antibody. We showed that an increased antiproliferative effect and a more sustained presence of CTLs within the tumour were the most important effects associated with anti-CD137 treatment.Several immunotherapeutic strategies for the treatment of cancer are under development. Two prominent strategies are adoptive cell transfer (ACT) of CTLs and modulation of CTL function with immune checkpoint inhibitors or with costimulatory antibodies. Despite some success with these approaches, there remains a lack of detailed and quantitative descriptions of the events following CTL transfer and the impact of immunomodulation. Here, we have applied ordinary differential equation models to two photon imaging data derived from a B16F10 murine melanoma. Models were parameterised with data from two different treatment conditions: either ACT-only, or ACT with intratumoural costimulation using a CD137 targeted antibody. Model dynamics and best fitting parameters were compared, in order to assess the mode of action of the CTLs and examine how the CD137 antibody influenced their activities. We found that the cytolytic activity of the transferred CTLs was minimal without CD137 costimulation, and that the CD137 targeted antibody did not enhance the per-capita killing ability of the transferred CTLs. Instead, the results of our modelling study suggest that an antiproliferative effect of CTLs exerted upon the tumour likely accounted for the majority of the reduction in tumour growth after CTL transfer. Moreover, we found that CD137 most likely improved tumour control via enhancement of this antiproliferative effect, as well as prolonging the period in which CTLs were inside the tumour, leading to a sustained duration of their antitumour effects following CD137 stimulation. Show less
Several immunotherapeutic strategies for the treatment of cancer are under development. Two prominent strategies are adoptive cell transfer (ACT) of CTLs and modulation of CTL function with immune... Show moreSeveral immunotherapeutic strategies for the treatment of cancer are under development. Two prominent strategies are adoptive cell transfer (ACT) of CTLs and modulation of CTL function with immune checkpoint inhibitors or with costimulatory antibodies. Despite some success with these approaches, there remains a lack of detailed and quantitative descriptions of the events following CTL transfer and the impact of immunomodulation. Here, we have applied ordinary differential equation models to two photon imaging data derived from a B16F10 murine melanoma. Models were parameterised with data from two different treatment conditions: either ACT-only, or ACT with intratumoural costimulation using a CD137 targeted antibody. Model dynamics and best fitting parameters were compared, in order to assess the mode of action of the CTLs and examine how the CD137 antibody influenced their activities. We found that the cytolytic activity of the transferred CTLs was minimal without CD137 costimulation, and that the CD137 targeted antibody did not enhance the per-capita killing ability of the transferred CTLs. Instead, the results of our modelling study suggest that an antiproliferative effect of CTLs exerted upon the tumour likely accounted for the majority of the reduction in tumour growth after CTL transfer. Moreover, we found that CD137 most likely improved tumour control via enhancement of this antiproliferative effect, as well as prolonging the period in which CTLs were inside the tumour, leading to a sustained duration of their antitumour effects following CD137 stimulation. Show less
