Ralf Ross (Gießen / DE), Dr. Seyed Sajjad Hasheminasab (Gießen / DE), Dr. Iván Conejeros (Gießen / DE), PD Dr. Ulrich Gärtner (Gießen / DE), Dr. Faustin Kamena (Buea / CM), Andreas Krueger (Gießen / DE), Prof. Dr. Anja Taubert (Gießen / DE), Prof. Dr. Carlos Hermosilla (Gießen / DE)
Abstract text
ntroduction: Little is known on Cryptosporidium parvum-driven responses of innate immune cells, such as PMN, monocytes, or macrophages, and even less is reported on parasite interactions with dendritic cells (DCs). DCs are sentinel cells residing in nearly all tissues including the small intestine. DCs detect pathogenic microorganisms with a broad range of pattern recognition receptors, take up, process and present antigens and migrate to the lymphoid organs to present them to naïve T cells. They decide, moreover, based on the information obtained, which kind of immune response like Th1-, Th2-, Treg-, or Th17- is elicited.
Objectives: We here intended to analyse early responses of human DCs driven by C. parvum stages.
Materials and methods: Immature human myeloid DCs were generated from monocytic blood precursors derived from buffy coats using GM-CSF and IL-4. Cells were harvested on day 6 of culture and exposed to medium alone (negative control), C. parvum oocysts/sporozoites and/or LPS (positive control) over night. Phagocytosis assays were conducted as well as scanning electron microscopy (SEM) analysis to unveil interactions between DCs and these two C. parvum parasite stages. Flow-cytometry analysis (FACS) demonstrated not only upregulation of classical DC activation markers and costimulatory molecules required for T cell-stimulation after C. parvum exposure but also phagocytosis. Cytokine IL-6 and chemokine IL-8 production in C. parvum-exposed human DCs was analysed by ELISAs. Finally, live cell 3D holotomography microscopy (Nanolive) was performed for visualization of highly motile DCs during first encounters with C. parvum.
Results: SEM shows not only DCs entrapping oocysts/sporozoites with their dendrites but also phagocytizing them. C. parvum induced IL-6- and IL-8- secretion in stimulated human DCs. Human DCs seem capable to phagocyte efficiently both stages of C. parvum (i. e. oocysts and sporozoites). Positive control (LPS stimulation) and C. parvum both upregulated DC maturation markers, i. e. CD83, antigen-presentation molecules (HLA-DR, CD1a), costimulatory molecules (CD40, CD86) and adhesion molecules (CD11b, CD58) as required for eliciting a strong adaptive immune response.
Conclusions: Considering that a strong adaptive immune response is required to protect against C. parvum infection, we investigated how DCs interact with C. parvum to open a new avenue in the search for an effective medication against this zoonotic parasite.