Animal Models to Understand Immunity

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1 Animal Models to Understand Immunity Hussein El Saghire

2 Innate Adaptive immunity Immunity MAPK and NF-kB TLR pathways receptors Fast Slow Non-specific Specific NOD-like receptors T-cell Receptor RIG-I-like receptors MAPK and NF-κB pathways MAPK and NF-kB pathways B-cell Receptor

3 Non-human Primates for Immunity Studies: Advantages High level of homology Frequent blood and bone marrow sampling Similar to human antibodies Vaccine research (mainly HIV)

4 Non-human Primates for Immunity Studies: Disadvantages Low breeding efficiency High cost of purchase Need general anaesthesia Ethical ban (Europe) Viral infections

5 Large Animals for Immunity Studies: Applications (1) Developmental immunity: fetuses with populated blood circulation (not in rodents) Regional immunity: ease of lymph and blood collection for disease and vaccination studies Surgical intervention: organ transplantation, stem cell transplantation and gene therapy

6 Large Animals for Immunity Studies: Applications (2) Disease pathogenesis and infectious immunity: similarity to human infections Innate immunity: activation of TLRs, IL-8 and PRR (not in rodents) Mucosal immunity: tissue specific vaccine delivery (lungs, GI tract ; not in rodents) Skin immunity: tissue composition recapitulate human more than that of rodents

7 Large Animals for Immunity Studies: Disadvantages Cost is high Experienced personnel: surgeries Differences with human immune-cell composition

8 Mice for Immunity Studies: Differences with Humans Mouse Human Neutrophils 10-25% 50-70% Lymphocytes 75-90% 30-50% TLR2 Low expression Constitutive expression TLR3 LPS stimulated No LPS stimulation TLR9 Expressed on all myeloid cells, DC and B cells Leukocyte defensins Absent Present Expressed only on B cells

9 Mice for Immunity Studies: Differences with Humans MHC II expression on T cells Mouse Absent Human Present CXCR1 Absent Present IL-8 (among other chemokines) Lungkine (among other chemokines) Absent Present Present Absent

10 Humanized Mice (Hu-mice) immunodeficient mice that have been engrafted with human hematopoietic cells and tissues to generate functional human immune system Shultz et al. 2012

11 Advances in Humanized Mice Started with SCID mice (severe combined immune-deficiency mice) IL-2 receptor gamma chain mutations

12 Three Main Types of Humanized Mice Hu-PBL-SCID: engraftment with PBMCs Hu-SRC-SCID: engraftment with hematopoietic stem cells BLT: engraftment with human liver and thymus tissues

13 Main Limitations in Mice Experiments Hematopoietic and immune system development: Necessary cytokines and growth factors are not expressed Lymph nodes: deficiencies in development

14 Overcoming Limitations cdna constructs nonphysiological expression of proteins Bacterial Artificial Chromosomes physiological expression of proteins Knock-in mice mouse gene replaced by human one

15 Hu-SRC-SCID Hu-PBL-SCID BLT Allograft rejection Generation of B cells and macrophages Graft versus host disease HIV therapeutic modalities Innate immunity Systemic Lupus Erythematosus Salmonella pathogensis Osteoarthritis Type I diabetes Tumor immunology Immune Studies on Hu-Mice HIV therapeutic modalities HIV therapeutic modalities Tumor immunology

16 Zebrafish Innate Immune System Cytokines and interferon production Complement activation Cells with cytotoxic and macrophage-like activity Expression of toll-like receptors with downstream activation of NF-κB and MAPK pathways

17 Immune Responses in Zebrafish Recognition of tissue damage and infection: neutrophils are the most abundant, similar to humans Inflammation resolution and immune cell removal: in humans neutrophils die; in zebrafish neutrophils migrate away Eosinophils and other immune cell types: eosinophils were characterized; cells sharing histochemical and biochemical with mast cells

18 Studies Improved Immunity Understanding Phagocytosis in neutrophils Visualization of inflammatory process Macrophages clearance after inflammation Immunity to infections Leukemia models

19 C. elegans as a Model for Infections Investigation Immune system: secretion of antimicrobial molecules like lysozymes, antibacterial factors Activation of inflammatory pathways: ERK, p38, and TGF-β

20 C. elegans as a Model for Infections Investigation Naturally C. elegans can be infected by bacteria, parasites and viruses. This facilitate the understanding the pathogenesis C. elegans can act as a model host, examples: Pseudomonas aeruginosa, Salmonella enterica, Escherichia coli.

21 Open Discussion Immunity research: what is a perfect model? Depending on the questions: Vaccines, pathogenesis mechanisms, inflammation, tumor immunobiology Applications of animal models on radiation immune studies: tumor immunobiology / radiotherapy