Efficient generation of CD34+ progenitor-derived dendritic cells from G-CSF-mobilized peripheral mononuclear cells does not require hematopoietic stem cell enrichment

Harnessing the Complete Repertoire of Conventional Dendritic Cell Functions for Cancer Immunotherapy

The onset of checkpoint inhibition revolutionized the treatment of cancer. However, studies from the last decade suggested that the sole enhancement of T cell functionality might not suffice to fight malignancies in all individuals. Dendritic cells (DCs) are not only part of the innate immune system, but also generals of adaptive immunity and they orchestrate the de novo induction of tolerogenic and immunogenic T cell responses. Thus, combinatorial approaches addressing DCs and T cells in parallel represent an attractive strategy to achieve higher response rates across patients. However, this requires profound knowledge about the dynamic interplay of DCs, T cells, other immune and tumor cells. Here, we summarize the DC subsets present in mice and men and highlight conserved and divergent characteristics between different subsets and species. Thereby, we supply a resource of the molecular players involved in key functional features of DCs ranging from their sentinel function, the translation of the sensed environment at the DC:T cell interface to the resulting specialized T cell effector modules, as well as the influence of the tumor microenvironment on the DC function. As of today, mostly monocyte derived dendritic cells (moDCs) are used in autologous cell therapies after tumor antigen loading. While showing encouraging results in a fraction of patients, the overall clinical response rate is still not optimal. By disentangling the general aspects of DC biology, we provide rationales for the design of next generation DC vaccines enabling to exploit and manipulate the described pathways for the purpose of cancer immunotherapy in vivo. Finally, we discuss how DC-based vaccines might synergize with checkpoint inhibition in the treatment of malignant diseases.

[Dendritic cell vaccines in neurological oncology]

Dendritic cell-based vaccines are an intensively studied active immunotherapy technology. Aim of this article is to review the results of the key clinical studies of such vaccines in the treatment of neuro-oncological diseases. Their effectiveness was studied most widely in the treatment of malignant glial tumors, the study went from experimental work to phase III clinical studies, preliminary results of which indicate some positive results of this immunotherapy method in adults. Currently, emphasis is also being placed on the identification of clinical and immunological correlates of the patient's response to therapy and on the search for new antigens for sensitization of dendritic cells Studies of dendritic cell vaccines also include a number of other neuro-oncological diseases. A separate part of this article is devoted to the treatment of intracerebral tumors in children, for example, medulloblastomas and gliomas of the pons. In addition, the potential use of dendritic cell vaccines for intracerebral metastases is considered.

Human dendritic cell culture and bacterial infection

Dendritic cells (DC) play a key role in the development of natural immunity to microbes. The DC form a bridge between the innate and adaptive immune system by providing key instructions particularly to antigen naïve T-cells. The interaction of DC with T lymphocytes involves three signals: (1) antigen processing and presentation in context of MHC Class I and/or II, (2) expression of T cell co-stimulatory molecules, and (3) cytokine production. Studying the interactions of DCs with specific pathogens allows for better understanding of how protective immunity is generated, and may be particularly useful for assessing vaccine components. In this chapter, we describe methods to generate human monocyte-derived DCs and assess their maturation, activation, and function, using interaction with the gram-negative bacterial pathogen Neisseria meningitidis as a model.

Non-human primate dendritic cells

Non-human primates (NHP) are essential translational models for biomedical research. Dendritic cells (DC) are a group of antigen presenting cells (APC) that play pivotal roles in the immunobiology of health and disease and are attractive cells for adoptive immunotherapy to stimulate and suppress immunity. DC have been studied extensively in humans and mice but until recently, have not been well characterized in NHP. This review considers the available data about DC across a range of NHP species and summarizes the understanding of in vitro-propagated DC and in vivo-isolated DC, which is now established. It is clear that although NHP DC exist within the paradigm of human DC, there are important functional and phenotypic differences when compared with human DC subsets. These differences need to be taken into account when designing preclinical, translational studies of DC therapy using NHP models.

A large number of mature and functional dendritic cells can be efficiently generated from umbilical cord blood-derived mononuclear cells by a simple two-step culture method

BACKGROUND

Advances in the past two decades in dendritic cell (DC) biology paved the way to exploit them as a promising tool in cancer immunotherapy. The prerequisite for DC vaccine preparations is large-scale in vitro generations of homogeneous, mature, and functional DCs. Frequent improvements are being made in the existing in vitro DC production protocols to achieve this goal. In our previous study we reported a large-scale generation of mature, functional DCs from umbilical cord blood (UCB) CD34+ cells. Here we report that this method can be used for the efficient generation of DCs from UCB mononuclear cells (MNCs) and thus the hematopoietic stem cell isolation step is not essential.

STUDY DESIGN AND METHODS

MNCs or CD34+ cells isolated from the same cord blood (CB) samples were used for the generation of DCs. DCs were characterized for morphology, phenotype, and functional assays including antigen uptake, chemotaxis, and mixed leukocyte reaction. Similarly DCs generated from the MNCs of same fresh and frozen CB units were compared.

RESULTS

The morphologic, phenotypic, and functional characterization of the DCs generated from various sets show that they were comparable in nature irrespective of the starting population used.

CONCLUSION

We conclude that the CD34+ isolation step is not essential for the generation of mature, functional DCs and thus can be eliminated. More importantly, we show that DCs can be generated with equal efficiency from the MNCs of frozen CB units. Our culture method will be useful for exploiting the potential of UCB as an additional source for allogeneic DCs in the clinical settings.

Propagation and characterisation of dendritic cells from G-CSF mobilised peripheral blood monocytes and stem cells in common marmoset monkeys

The common marmoset is a small New World Primate that has been used as an immunological model for a number of human diseases. Dendritic cells (DC) have not been extensively characterised in this species and in particular protocols to derive DC from living donors without the need for animal sacrifice are presently lacking. This study establishes new protocols to generate substantial numbers of marmoset DC for use in cell therapy studies. Recombinant human G-CSF was used to mobilise peripheral blood monocytes and CD34(+) stem cells in sufficient numbers for large scale in-vitro DC propagation using cytokine conditioning including IL-4, GM-CSF, FLT3-L, stem cell factor and thrombopoietin. Marmoset DC exhibited morphology similar to human DC, were capable of antigen uptake and presentation and had moderate allo-stimulatory ability. Monocyte-derived DC had a maturation-resistant immature phenotype, whereas haematopoietic precursor-derived DC were semi-mature in phenotype and function. This study confirms the feasibility of the marmoset as a unique small primate model in which to pursue DC-based immunotherapy strategies.

Human cytomegalovirus and human immunodeficiency virus type-1 co-infection in human cervical tissue

Human cytomegalovirus (HCMV) and human immunodeficiency virus type-1 (HIV-1) infect the female genital tract. A human cervical explant model was developed to study single and dual infection by these viruses in the genital compartment. An HCMV strain expressing green fluorescent protein, and two clinical HCMV strains produced peak viral DNA copies at 14 to 21 days post-infection. Peak levels of HIV-1(Ba-L) p24 antigen occurred at 7 days post-infection. HIV-1(Ba-L) appeared to enhance HCMV in co-infected tissues. Singly and dually infected explants produced increased levels of cytokines IL-6, IL-8, and GRO-alpha in culture supernatants. Immunohistochemical and flow cytometric analysis showed HCMV infection of leukocytes with the phenotype CD45+/CD1a+/CD14+/HLA-DR+ but not stromal or endothelial cells. Cells expressing both GFP and HIV-1 p24 antigen were detected in co-infected tissues. The cervical explants provide an ex vivo human model for examining mechanisms of virus-virus interaction and pathogenesis in clinically relevant tissue.