Genomic responses in mouse models greatly mimic human inflammatory diseases

What Is the Predictive Value of Animal Models for Vaccine Efficacy in Humans? Consideration of Strategies to Improve the Value of Animal Models

Animal models are an essential feature of the vaccine design toolkit. Although animal models have been invaluable in delineating the mechanisms of immune function, their precision in predicting how well specific vaccines work in humans is often suboptimal. There are, of course, many obvious species differences that may limit animal models from predicting all details of how a vaccine works in humans. However, careful consideration of which animal models may have limitations should also allow more accurate interpretations of animal model data and more accurate predictions of what is to be expected in clinical trials. In this article, we examine some of the considerations that might be relevant to cross-species extrapolation of vaccine-related immune responses for the prediction of how vaccines will perform in humans.

Whole-organism phenotypic screening for anti-infectives promoting host health

To date, antibiotics have been identified on the basis of their ability to kill bacteria or inhibit their growth rather than directly for their capacity to improve clinical outcomes of infected patients. Although historically successful, this approach has led to the development of an antibiotic armamentarium that suffers from a number of shortcomings, including the inevitable emergence of resistance and, in certain infections, suboptimal efficacy leading to long treatment durations, infection recurrence, or high mortality and morbidity rates despite apparent bacterial sterilization. Conventional antibiotics fail to address the complexities of in vivo bacterial physiology and virulence, as well as the role of the host underlying the complex, dynamic interactions that cause disease. New interventions are needed, aimed at host outcome rather than microbiological cure. Here we review the role of screening models for cellular and whole-organism infection, including worms, flies, zebrafish, and mice, to identify novel therapeutic strategies and discuss their future implications.

Bacterial Dissemination to the Brain in Sepsis

RATIONALE

Sepsis causes brain dysfunction and neuroinflammation. It is unknown whether neuroinflammation in sepsis is initiated by dissemination of bacteria to the brain and sustained by persistent infection, or whether neuroinflammation is a sterile process resulting solely from circulating inflammatory mediators.

OBJECTIVES

To determine if gut bacteria translocate to the brain during sepsis, and are associated with neuroinflammation.

METHODS

Murine sepsis was induced using cecal ligation and puncture, and sepsis survivor mice were compared with sham and unoperated control animals. Brain tissue of patients who died of sepsis was compared with patients who died of noninfectious causes. Bacterial taxa were characterized by 16S ribosomal RNA gene sequencing in both murine and human brain specimens; compared among sepsis and nonsepsis groups; and correlated with levels of S100A8, a marker of neuroinflammation using permutational multivariate ANOVA.

MEASUREMENTS AND MAIN RESULTS

Viable gut-associated bacteria were enriched in the brains of mice 5 days after surviving abdominal sepsis (P < 0.01), and undetectable by 14 days. The community structure of brain-associated bacteria correlated with severity of neuroinflammation (P < 0.001). Furthermore, bacterial taxa detected in brains of humans who die of sepsis were distinct from those who died of noninfectious causes (P < 0.001) and correlated with S100A8/A9 expression (P < 0.05).

CONCLUSIONS

Although bacterial translocation is associated with acute neuroinflammation in murine sepsis, bacterial translocation did not result in chronic cerebral infection. Postmortem analysis of patients who die of sepsis suggests a role for bacteria in acute brain dysfunction in sepsis. Further work is needed to determine if modifying gut-associated bacterial communities modulates brain dysfunction after sepsis.

Comparative Analysis of the Regulatory T Cells Dynamics in Peripheral Blood in Human and Porcine Polytrauma

Background

Severely injured patients experience substantial immunological stress in the aftermath of traumatic insult, which often results in systemic immune dysregulation. Regulatory T cells (Treg) play a key role in the suppression of the immune response and in the maintenance of immunological homeostasis. Little is known about their presence and dynamics in blood after trauma, and nothing is known about Treg in the porcine polytrauma model. Here, we assessed different subsets of Treg in trauma patients (TP) and compared those to either healthy volunteers (HV) or data from porcine polytrauma.

Methods

Peripheral blood was withdrawn from 20 TP with injury severity score (ISS) ≥16 at the admittance to the emergency department (ED), and subsequently on day 1 and at day 3. Ten HV were included as controls (ctrl). The porcine polytrauma model consisted of a femur fracture, liver laceration, lung contusion, and hemorrhagic shock resulting in an ISS of 27. After polytrauma, the animals underwent resuscitation and surgical fracture fixation. Blood samples were withdrawn before and immediately after trauma, 24 and 72 h later. Different subsets of Treg, CD4+CD25+, CD4+CD25+FoxP3+, CD4+CD25+CD127-, and CD4+CD25+CD127-FoxP3+ were characterized by flow cytometry.

Results

Absolute cell counts of leukocytes were significantly increasing after trauma, and again decreasing in the follow-up in human and porcine samples. The proportion of human Treg in the peripheral blood of TP admitted to the ED was lower when compared to HV. Their numbers did not recover until 72 h after trauma. Comparable data were found for all subsets. The situation in the porcine trauma model was comparable with the clinical data. In porcine peripheral blood before trauma, we could identify Treg with the typical immunophenotype (CD4+CD25+CD127-), which were virtually absent immediately after trauma. Similar to the human situation, most of these cells expressed FoxP3, as assessed by intracellular FACS stain.

Conclusion

Despite minor percental differences in the recovery of Treg populations after trauma, our findings show a comparable decrease of Treg early after polytrauma, and strengthen the immunological significance of the porcine polytrauma model. Furthermore, the Treg subpopulation CD4+CD25+CD127- was characterized in porcine samples.

The hepatokines fetuin-A and fetuin-B are upregulated in the state of hepatic steatosis and may differently impact on glucose homeostasis in humans

The liver is a central regulator of whole body glucose, and lipid homeostasis and hepatokines, like fetuin-A, have been identified as markers and mediators of fatty liver-induced cardiometabolic risk. The closely related protein fetuin-B was shown to be upregulated in the fatty liver and to impact on glucose homeostasis in mice. In the present study we aimed to test the relevance of these findings in humans. In 55 subjects, hepatic mRNA expression of both hepatokines, fetuin-A and fetuin-B, associated positively with liver triglyceride content, whereas only fetuin-A expression associated with the homeostatic model assessment of insulin resistance. In 220 subjects who underwent precise metabolic phenotyping, circulating fetuin-A, but not fetuin-B, associated positively with liver fat content, and negatively with insulin sensitivity, measured during the oral glucose tolerance test (OGTT) and during the euglycemic, hyperinsulinemic clamp. Both circulating fetuin-A and fetuin-B correlated positively with the glucose area under the curve during the OGTT, but after additional adjustment for insulin sensitivity this relationship remained significant only for fetuin-B. In conclusion, despite the fact that the two hepatokines, fetuin-A and fetuin-B, are upregulated in the state of hepatic steatosis in humans, it appears that they differently impact on glucose homeostasis. Our data are in agreement with observations that fetuin-A can alter insulin signaling and that fetuin-B may regulate glucose homeostasis via so far unknown effects, possibly on glucose effectiveness.

Of Mice and Men: Proteasome's Role in LPS-Induced Inflammation and Tolerance

The molecular basis responsible for tolerance following inflammatory response to lipopolysaccharide (LPS) is not well understood. We hypothesized that inflammation/tolerance in monocytes/ macrophages is dependent on the proteases of proteasome. To test our hypothesis, first, we examined the expression of different proteasome subunits in different human and mouse monocytes/macrophages. Secondly, we investigated the effect of proteasome subunits/ proteases on LPS-induced expression of tumor necrosis factor-α (TNF-α) and nitric oxide (NO) during inflammation and tolerance using mouse RAW 264.7 macrophages, THP1 cells, and cluster of differentiation 14 positive (CD14) human monocytes. We found that RAW 264.7 cells (XYZ), mouse peritoneal resident, thioglycollate-elicited macrophages, primed RAW 264.7 (XYZ, LMP), and human monocytes (LMP) expressed different types of proteasome subunits/activities. Cells containing predominantly either LMP subunits (such as THP-1 and human monocytes), or only X, Y, Z subunits (RAW 264.7 cells not primed) could only induce TNF-α, but not NO, while cells containing all five to six subunits (XYZ, LMP) of the proteasome could induce both mediators in response to LPS. Distinct states of inflammation/tolerance in LPS treated cells, strongly correlated with an upregulation or downregulation of proteasome's subunits (proteases), respectively. Moreover, interferon-γ treatment of tolerant cells caused robust induction of proteasome's subunit expression in mouse macrophages and human monocytes, and cells regained their ability to respond to LPS. These studies are vital for understanding function of proteasome's subunits during inflammation/tolerance in mouse and human cells, and for design of therapeutic strategies for all diseases based on inflammation.

Alternatives to animal testing in basic and preclinical research of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease of increasing prevalence, especially in industrialized countries. Roughly 25% of the children and 1%-3% of adults are affected. Although significant progress has been made in the understanding of the pathogenesis of AD, many aspects remain poorly understood. Moreover, there is a pressing need for improved therapeutic options. Studies to elucidate the pathophysiological pathways of AD and to identify novel therapeutic targets over the last few decades have been conducted almost exclusively in animal models. However, in vitro approaches such as 3D skin disease models have recently emerged due to an increasing awareness of distinct interspecies-related differences that hamper the effective translation of results from animal models to humans. In addition, there is growing political and social pressure to develop alternatives to animal models according to the 3Rs principle (reduction, refinement and replacement of animal models).

Bench-to-Bedside: A Translational Perspective on Murine Models of Sepsis

BACKGROUND

Considerable research effort has focused on the development of novel therapies for the treatment of sepsis, yet after decades of clinical trials, few significant advances have been achieved. This limitation persists despite a wealth of data yielded by basic science that has expanded our knowledge of the biology of this disease exponentially.

METHOD

Review of the English-language literature.

RESULTS

Translational researchers may address the resultant gap between the basic science laboratory and clinical research worlds. Herein, we review potential causes for the challenges of translating basic laboratory discovery into clinical benefit.

CONCLUSION

We propose conceptual platforms to further the development of translational sepsis research efforts.

New advances in understanding thyroid-associated ophthalmopathy and the potential role for insulin-like growth factor-I receptor

Thyroid-associated ophthalmopathy (TAO), a localized periocular manifestation of the autoimmune syndrome known as Graves’ disease, remains incompletely understood. Discussions of its pathogenesis are generally focused on the thyrotropin receptor, the proposed role for which is supported by substantial evidence. Considerations of any involvement of the insulin-like growth factor-I receptor (IGF-IR) in the disease are frequently contentious. In this brief, topically focused review, I have attempted to provide a balanced perspective based entirely on experimental results that either favor or refute involvement of IGF-IR in TAO. Discussion in this matter seems particularly timely since the currently available treatments of this disfiguring and potentially sight-threatening disease remain inadequate. Importantly, no medical therapy has thus far received approval from the US Food and Drug Administration. Results from a very recently published clinical trial assessing the safety and efficacy of teprotumumab, an inhibitory human anti–IGF-IR monoclonal antibody, in active, moderate to severe TAO are extremely encouraging. That double-masked, placebo-controlled study involved 88 patients and revealed unprecedented clinical responses in the improvement of proptosis and clinical activity as well as a favorable safety profile. Should those results prove reproducible in an ongoing phase III trial, therapeutic inhibition of IGF-IR could become the basis for paradigm-shifting treatment of this vexing disease.

Effect of hyperbaric oxygen therapy (HBO) on implant-associated osteitis in a femur fracture model in mice

Hyperbaric oxygen therapy (HBO) is applied very successfully in treatment of various diseases such as chronic wounds. It has been already suggested as adjunctive treatment option for osteitis by immune- and fracture modulating effects. This study evaluates the importance of HBO in an early implant-associated localized osteitis caused by Staphylococcus aureus (SA) compared to the standard therapy. In a standardized murine model the left femur of 120 BALB/c mice were osteotomized and fixed by a titanium locking plate. Osteitis has been induced with a defined amount of SA into the fracture gap. Debridément and lavages were progressed on day 7, 14, 28 and 56 to determine the local bacterial growth and the immune reaction. Hyperbaric oxygen (2 ATA, 90%) was applied for 90 minutes on day 7 to 21 for those mice allocated to HBO therapy. To evaluate the effect of HBO therapy the following groups were analyzed: Two sham-groups (12 mice / group) with and without HBO therapy, two osteotomy groups (24 mice / group) with plate osteosynthesis of the femur with and without HBO therapy, and two osteotomy SA infection groups (24 mice / group) with and without HBO therapy. Fracture healing was also quantified on day 7, 14, 28 and 56 by a.p. x-ray and bone healing markers from blood samples. Progression of infection was assessed by estimation of colony-forming units (CFU) and immune response was analyzed by determination of polymorphonuclear neutrophils (PMN), Interleukin (IL) - 6, and the circulating free DNA (cfDNA) in lavage samples. Osteitis induced significantly higher IL-6, cfDNA- and PMN-levels in the lavage samples (on day 7 and 14, each p < 0.05). HBO-therapy did not have a significant influence on the CFU and immune response compared to the standard therapy (each p > 0.05). At the same time HBO-therapy was associated with a delayed bone healing assessed by x-ray radiography and a higher rate of non-union until day 28. In conclusion, osteitis led to significantly higher bacterial count and infection parameters. HBO-therapy neither had a beneficial influence on local infection nor on immune response or fracture healing compared to the standard therapy in an osteitis mouse model.

Human Pulmonary 3D Models For Translational Research

Lung diseases belong to the major causes of death worldwide. Recent innovative methodological developments now allow more and more for the use of primary human tissue and cells to model such diseases. In this regard, the review covers bronchial air-liquid interface cultures, precision cut lung slices as well as ex vivo cultures of explanted peripheral lung tissue and de-/re-cellularization models. Diseases such as asthma or infections are discussed and an outlook on further areas for development is given. Overall, the progress in ex vivo modeling by using primary human material could make translational research activities more efficient by simultaneously fostering the mechanistic understanding of human lung diseases while reducing animal usage in biomedical research.

Mouse Injury Model of Polytrauma and Shock

Severe injury and shock remain major sources of morbidity and mortality worldwide. Immunologic dysregulation following trauma contributes to these poor outcomes. Few, if any, therapeutic interventions have benefited these patients, and this is due to our limited understanding of the host response to injury and shock. The Food and Drug Administration requires preclinical animal studies prior to any interventional trials in humans; thus, animal models of injury and shock will remain the mainstay for trauma research. However, adequate animal models that reflect the severe response to trauma in both the acute and subacute phases have been limited. Here we describe a novel murine model of polytrauma and shock that combines hemorrhagic shock, cecectomy, long bone fracture, and soft-tissue damage. This model produces an equivalent Injury Severity Score associated with adverse outcomes in humans, and may better recapitulate the human leukocyte, cytokine, transcriptomic, and overall inflammatory response following injury and hemorrhagic shock.

Protection of macrophages from intracellular pathogens by miR-182-5p mimic-a gene expression meta-analysis approach

The goals of this study were to (a) define which host genes are of particular importance during the interactions between macrophages and intracellular pathogens, and (b) use this knowledge to gain fresh, experimental understanding of how macrophage activities may be manipulated during host defense. We designed an in silico method for meta-analysis of microarray gene expression data, and used this to combine data from 16 different studies of cells in the monocyte-macrophage lineage infected with seven different pathogens. Three thousand four hundred ninety-eight genes were identified, which we call the macrophage intracellular pathogen response (macIPR) gene set. As expected, the macIPR gene set showed a strong bias toward genes previously associated with the immune response. Predicted target sites for miR-182-5p (miR-182) were strongly over-represented among macIPR genes, indicating an unexpected role for miR-182-regulatable genes during intracellular pathogenesis. We therefore transfected primary human alveolar macrophage-like monocyte-derived macrophages from multiple different donors with synthetic miR-182, and found that miR-182 overexpression (a) increases proinflammatory gene induction during infection with Francisella tularensis live vaccine strain (LVS), (b) primes macrophages for increased autophagy, and (c) enhances macrophage control of both gram negative F. tularensisLVS and gram positive Bacillus anthracisANR-1 spores. These data therefore suggest a new application for miR-182 in promoting resistance to intracellular pathogens.

Model answers: Rational application of murine models in arthritis research

Advances in targeted immune therapeutics have profoundly improved clinical outcomes for patients with inflammatory arthropathies particularly rheumatoid arthritis. The landscape of disease that is observed and the treatment outcomes desired for the future have also progressed. As such there is an increasing move away from traditional models of end‐stage, chronic disease with recognition of the need to consider the earliest phases of pathogenesis as a target for treatment leading to resolution and/or cure. In order to continue the discovery process and enhance our understanding of disease and treatment, we therefore need to continuously revisit the animal models we employ and assess their relevance and utility in the light of contemporary therapeutic goals. In this review, we highlight the areas where we consider new developments in animal models and their application are most required. Thus, we have contextualised the relevant mouse models and their use within the current concepts of human inflammatory arthritis pathogenesis and highlight areas of need.

Clinical and Experimental Sepsis Impairs CD8 T-Cell-Mediated Immunity

Septic patients experience chronic immunosuppression resulting in enhanced susceptibility to infections normally controlled by T cells. Clinical research on septic patients has shown increased apoptosis and reduced total numbers of CD4 and CD8 T cells, suggesting contributing mechanism driving immunosuppression. Experimental models of sepsis, including cecal ligation and puncture, reverse translated this clinical observation to facilitate hypothesis-driven research and allow the use of an array of experimental tools to probe the impact of sepsis on T-cell immunity. In addition to numerical loss, sepsis functionally impairs the antigen-driven proliferative capacity and effector functions of CD4 and CD8 T cells. Sepsis-induced impairments in both the quantity and quality of T cells results in reduced protective capacity and increased susceptibility of mice to new or previously encountered infections. Therefore, the combined efforts of clinical and experimental sepsis research have begun to elucidate the impact of sepsis on T-cell-mediated immunity and potential T-cell-intrinsic and -extrinsic mechanisms driving chronic immunosuppression. Future work will explore the impact of sepsis on the recently appreciated tissue-resident memory (TRM) T cells, which provide robust protection against localized infections, and dendritic cells, which are needed to activate T cells and promote effective T-cell responses.

Characterising Pre-pubertal Resistance to Death from Endotoxemia

Sepsis is a common and deadly syndrome in which a dysregulated host response to infection causes organ failure and death. The current lack of treatment options suggests that a new approach to studying sepsis is needed. Pre-pubertal children show a relative resistance to death from severe infections and sepsis. To explore this phenomenon experimentally, we used an endotoxemia model of sepsis in mice. Following intra-peritoneal injection of endotoxin, pre-pubertal mice showed greater survival than post-pubertal mice (76.3% vs. 28.6%), despite exhibiting a similar degree of inflammation after two hours. Age-associated differences in the inflammatory response only became evident at twenty hours, when post-pubertal mice showed prolonged elevation of serum cytokines and differential recruitment of peritoneal immune cells. Mechanistically, prevention of puberty by hormonal blockade or acceleration of puberty by oestrogen treatment led to increased or decreased survival from endotoxemia, respectively. Additionally, the adoptive transfer of pre-pubertal peritoneal cells improved the survival of post-pubertal recipient mice, while post-pubertal peritoneal cells or vehicle did not. These data establish a model for studying childhood resistance to mortality from endotoxemia, demonstrate that oestrogen is responsible for an increased susceptibility to mortality after puberty, and identify peritoneal cells as mediators of pre-pubertal resistance.

Innovative Approaches to Improve Anti-Infective Vaccine Efficacy

Safe and efficacious vaccines are arguably the most successful medical interventions of all time. Yet the ongoing discovery of new pathogens, along with emergence of antibiotic-resistant pathogens and a burgeoning population at risk of such infections, imposes unprecedented public health challenges. To meet these challenges, innovative strategies to discover and develop new or improved anti-infective vaccines are necessary. These approaches must intersect the most meaningful insights into protective immunity and advanced technologies with capabilities to deliver immunogens for optimal immune protection. This goal is considered through several recent advances in host-pathogen relationships, conceptual strides in vaccinology, and emerging technologies. Given a clear and growing risk of pandemic disease should the threat of infection go unmet, developing vaccines that optimize protective immunity against high-priority and antibiotic-resistant pathogens represents an urgent and unifying imperative.

Animal Models in Translational Research: Rosetta Stone or Stumbling Block?

Leading animal models are powerful tools for translational research, but they also present obstacles. Poorly conducted preclinical research in animals is a common cause of translational failure, but even when such research is well-designed and carefully executed, challenges remain. In particular, dominant models may bias research directions, elide essential aspects of human disease, omit important context, or subtly shift research targets. Recognizing these stumbling blocks can help us find ways to avoid them: employing a wider range of models, incorporating more realistic environmental conditions, better aligning studies between animals and patients, and focusing on human biology and therapeutic goals. Such changes are costly; but insisting it would be impractical or unrealistic to change strategies offers no way out of the current impasse. Rather, we must acknowledge the obstacles as well as the advantages presented by core models, and direct some of our investments in translational research toward getting around them.

Time Response of Oxidative/Nitrosative Stress and Inflammation in LPS-Induced Endotoxaemia-A Comparative Study of Mice and Rats

Sepsis is a severe and multifactorial disease with a high mortality rate. It represents a strong inflammatory response to an infection and is associated with vascular inflammation and oxidative/nitrosative stress. Here, we studied the underlying time responses in the widely used lipopolysaccharide (LPS)-induced endotoxaemia model in mice and rats. LPS (10 mg/kg; from Salmonella Typhosa) was intraperitoneally injected into mice and rats. Animals of every species were divided into five groups and sacrificed at specific points in time (0, 3, 6, 9, 12 h). White blood cells (WBC) decreased significantly in both species after 3 h and partially recovered with time, whereas platelet decrease did not recover. Oxidative burst and iNOS-derived nitrosyl-iron hemoglobin (HbNO) increased with time (maxima at 9 or 12 h). Immune cell infiltration (CD68 and F4/80 content) showed an increase with time, which was supported by increased vascular mRNA expression of VCAM-1, P-selectin, IL-6 and TNF-α. We characterized the time responses of vascular inflammation and oxidative/nitrosative stress in LPS-induced endotoxaemic mice and rats. The results of this study will help to interpret and compare data from different animal species in LPS-induced endotoxaemia models for the identification of new drug targets.

Perinatal western-type diet and associated gestational weight gain alter postpartum maternal mood

INTRODUCTION

The role of perinatal diet in postpartum maternal mood disorders, including depression and anxiety, remains unclear. We investigated whether perinatal consumption of a Western-type diet (high in fat and branched-chain amino acids [BCAA]) and associated gestational weight gain (GWG) cause serotonin dysregulation in the central nervous system (CNS), resulting in postpartum depression and anxiety (PPD/A).

METHODS

Mouse dams were fed one of four diets (high-fat/high BCAA, low-fat/high BCAA, high-fat, and low-fat) prior to mating and throughout gestation and lactation. Postpartum behavioral assessments were conducted, and plasma and brain tissues assayed. To evaluate potential clinical utility, we conducted preliminary human studies using data from an extant sample of 17 primiparous women with high GWG, comparing across self-reported postpartum mood symptoms using the Edinburgh Postnatal Depression Scale (EPDS) for percent GWG and plasma amino acid levels.

RESULTS

Mouse dams fed the high-fat/high BCAA diet gained more weight per kcal consumed, and BCAA-supplemented dams lost weight more slowly postpartum. Dams on BCAA-supplemented diets exhibited increased PPD/A-like behavior, decreased dopaminergic function, and decreased plasma tyrosine and histidine levels when assessed on postnatal day (P)8. Preliminary human data showed that GWG accounted for 29% of the variance in EPDS scores. Histidine was also lower in women with higher EPDS scores.

CONCLUSIONS

These findings highlight the role of perinatal diet and excess GWG in the development of postpartum mood disorders.

Translational Aspects of Diet and Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of diseases ranging from simple steatosis without inflammation or fibrosis to nonalcoholic steatohepatitis (NASH). Despite the strong association between dietary factors and NAFLD, no dietary animal model of NAFLD fully recapitulates the complex metabolic and histological phenotype of the disease, although recent models show promise. Although animal models have significantly contributed to our understanding of human diseases, they have been less successful in accurate translation to predict effective treatment strategies. We discuss strategies to overcome this challenge, in particular the adoption of big data approaches combining clinical phenotype, genomic heterogeneity, transcriptomics, and metabolomics changes to identify the ideal NAFLD animal model for a given scientific question or to test a given drug. We conclude by noting that novel big data approaches may help to bridge the translational gap for selecting dietary models of NAFLD.

Highly Variable Genomic Landscape of Endogenous Retroviruses in the C57BL/6J Inbred Strain, Depending on Individual Mouse, Gender, Organ Type, and Organ Location

Transposable repetitive elements, named the "TREome," represent ~40% of the mouse genome. We postulate that the germ line genome undergoes temporal and spatial diversification into somatic genomes in conjunction with the TREome activity. C57BL/6J inbred mice were subjected to genomic landscape analyses using a TREome probe from murine leukemia virus-type endogenous retroviruses (MLV-ERVs). None shared the same MLV-ERV landscape within each comparison group: (1) sperm and 18 tissues from one mouse, (2) six brain compartments from two females, (3) spleen and thymus samples from four age groups, (4) three spatial tissue sets from two females, and (5) kidney and liver samples from three females and three males. Interestingly, males had more genomic MLV-ERV copies than females; moreover, only in the males, the kidneys had higher MLV-ERV copies than the livers. Perhaps, the mouse-, gender-, and tissue/cell-dependent MLV-ERV landscapes are linked to the individual-specific and dynamic phenotypes of the C57BL/6J inbred population.

Influenza Pathogenesis in Genetically Defined Resistant and Susceptible Murine Strains

The murine infection model is a cornerstone for influenza virus research and includes aspects such as disease pathogenesis, immunobiology, and vaccine and antiviral drug development. One compelling feature of the murine model is the availability of inbred mouse strains, each with a unique genetic makeup and potential for variable responses to influenza infection. Using highly controlled infection studies, the response to influenza virus infection is classified on a spectrum from susceptible to resistant, reflecting severe morbidity and high mortality, to limited or no morbidity and no mortality. Although there have been a variety of studies establishing disparate pathogenesis amongst various murine strains, thus far, there is no consensus regarding the determinants of the outcome of infection. The goal of this review is to explore and discuss the differences in pathogenesis, as well as the innate and adaptive immune responses to influenza infection that have been described in susceptible and resistant mouse strains. Understanding how host genetics influences the response to influenza infection provides valuable insight into the variable responses seen in vaccine or drug efficacy studies, as well as indicates possible mechanisms contributing to increased disease severity in humans infected with influenza virus with no known risk factors.

Molecular characterization of the transition from acute to chronic kidney injury following ischemia/reperfusion

Though an acute kidney injury (AKI) episode is associated with an increased risk of chronic kidney disease (CKD), the mechanisms determining the transition from acute to irreversible chronic injury are not well understood. To extend our understanding of renal repair, and its limits, we performed a detailed molecular characterization of a murine ischemia/reperfusion injury (IRI) model for 12 months after injury. Together, the data comprising RNA-sequencing (RNA-seq) analysis at multiple time points, histological studies, and molecular and cellular characterization of targeted gene activity provide a comprehensive profile of injury, repair, and long-term maladaptive responses following IRI. Tubular atrophy, interstitial fibrosis, inflammation, and development of multiple renal cysts were major long-term outcomes of IRI. Progressive proximal tubular injury tracks with de novo activation of multiple Krt genes, including Krt20, a biomarker of renal tubule injury. RNA-seq analysis highlights a cascade of temporal-specific gene expression patterns related to tubular injury/repair, fibrosis, and innate and adaptive immunity. Intersection of these data with human kidney transplant expression profiles identified overlapping gene expression signatures correlating with different stages of the murine IRI response. The comprehensive characterization of incomplete recovery after ischemic AKI provides a valuable resource for determining the underlying pathophysiology of human CKD.

Concordant and discordant gene expression patterns in mouse strains identify best-fit animal model for human tuberculosis

Immunity in infection, inflammation and malignancy differs markedly in man and mouse. Still, we learn about human immunity in large extent from experimental mouse models. We propose a novel data integration approach which identifies concordant and discordant gene expression patterns of the immune responses in heterologous data sets. We have conducted experiments to compare human and murine transcriptional responses to Mycobacterium tuberculosis (Mtb) infection in whole blood (WB) as well as macrophages and compared them with simulated as well as publicly available data. Our results indicate profound differences between patterns of gene expression in innate and adaptive immunity in man and mouse upon Mtb infection. We characterized differential expression of T-cell related genes corresponding to the differences in phenotype between tuberculosis (TB) highly and low susceptible mouse strains. Our approach is general and facilitates the choice of optimal animal model for studies of the human immune response to a particular disease.

Tumor necrosis factor superfamily ligand mRNA expression profiles differ between humans and mice during homeostasis and between various murine kidney injuries

BACKGROUND

Several tumour necrosis factor (TNF) based therapeutics have already been approved for human use and several others are emerging. Therefore, we determined the mRNA expression levels of the TNF superfamily ligands (TNFSF) - e.g. TNF-α, lymphotoxin (LT)-α, LT-β, Fas-L (CD95-L), TNF-related apoptosis-inducing ligand (TRAIL), TNF-related weak inducer of apoptosis (TWEAK), 4-1BBL, OX40-L (CD252) and amyloid precursor protein (APP) in healthy human and mouse solid organs.

METHODS

We used quantitative real time-PCR to analyse mRNA expression levels of TNFSF ligands. Murine models of acute ischemic renal injury, chronic oxalate nephropathy, and immune complex glomerulonephritis were used. Renal injury was assessed by PAS staining, and infiltrating immune cells were analysed by immunohistochemistry. Data was analysed using non-parametric ANOVA (non-parametric; Kruskal-Wallis test).

RESULTS

We observed significant differences in the mRNA expression levels of TNFSF ligands in human and mouse solid organs. Furthermore, we determined their mRNA expressions during acute and chronic kidney injuries in mice. Our data demonstrate that the mRNA expression levels of TNFSF vary depending on the type of tissue injury - for example, acute ischemic renal injury, chronic crystalline nephropathy, and immune complex glomerulonephritis. In addition, we observed that mRNA expressions of TNFSF ligands are differentially regulated during the course of a transient ischemic renal injury (IRI) and chronic kidney modelling. We observed that TNF-α, LT-β, and 4-1BBL were significantly upregulated during the progression of IRI and crystal-induced chronic kidney disease (CKD), whereas only 4-1BBL and TNF-α were significantly upregulated and LT-β was significantly downregulated during the progression of immune complex glomerulonephritis. The mRNA expression of Fas-L was higher during IRI whereas it decreased in a time dependent manner during the progression of crystal-induced CKD.

CONCLUSION

We conclude that the injury- and species-specific differences of TNFSF ligands must be considered in order to avoid the misinterpretation and wrong conclusions during data extrapolation between species.

Responses of rat and mouse primary microglia to pro- and anti-inflammatory stimuli: molecular profiles, K+ channels and migration

BACKGROUND

Acute CNS damage is commonly studied using rat and mouse models, but increasingly, molecular analysis is finding species differences that might affect the ability to translate findings to humans. Microglia can undergo complex molecular and functional changes, often studied by in vitro responses to discrete activating stimuli. There is considerable evidence that pro-inflammatory (M1) activation can exacerbate tissue damage, while anti-inflammatory (M2) states help resolve inflammation and promote tissue repair. However, in assessing potential therapeutic targets for controlling inflammation, it is crucial to determine whether rat and mouse microglia respond the same.

METHODS

Primary microglia from Sprague-Dawley rats and C57BL/6 mice were cultured, then stimulated with interferon-γ + tumor necrosis factor-α (I + T; M1 activation), interleukin (IL)-4 (M2a, alternative activation), or IL-10 (M2c, acquired deactivation). To profile their activation responses, NanoString was used to monitor messenger RNA (mRNA) expression of numerous pro- and anti-inflammatory mediators, microglial markers, immunomodulators, and other molecules. Western analysis was used to measure selected proteins. Two potential targets for controlling inflammation-inward- and outward-rectifier K⁺ channels (Kir2.1, Kv1.3)-were examined (mRNA, currents) and specific channel blockers were applied to determine their contributions to microglial migration in the different activation states.

RESULTS

Pro-inflammatory molecules increased after I + T treatment but there were several qualitative and quantitative differences between the species (e.g., iNOS and nitric oxide, COX-2). Several molecules commonly associated with an M2a state differed between species or they were induced in additional activation states (e.g., CD206, ARG1). Resting levels and/or responses of several microglial markers (Iba1, CD11b, CD68) differed with the activation state, species, or both. Transcripts for several Kir2 and Kv1 family members were detected in both species. However, the current amplitudes (mainly Kir2.1 and Kv1.3) depended on activation state and species. Treatment-induced changes in morphology and migratory capacity were similar between the species (migration reduced by I + T, increased by IL-4 or IL-10). In both species, Kir2.1 block reduced migration and Kv1.3 block increased it, regardless of activation state; thus, these channels might affect microglial migration to damage sites.

CONCLUSIONS

Caution is recommended in generalizing molecular and functional responses of microglia to activating stimuli between species.

Gene Expression Analysis to Assess the Relevance of Rodent Models to Human Lung Injury

The relevance of animal models to human diseases is an area of intense scientific debate. The degree to which mouse models of lung injury recapitulate human lung injury has never been assessed. Integrating data from both human and animal expression studies allows for increased statistical power and identification of conserved differential gene expression across organisms and conditions. We sought comprehensive integration of gene expression data in experimental acute lung injury (ALI) in rodents compared with humans. We performed two separate gene expression multicohort analyses to determine differential gene expression in experimental animal and human lung injury. We used correlational and pathway analyses combined with external in vitro gene expression data to identify both potential drivers of underlying inflammation and therapeutic drug candidates. We identified 21 animal lung tissue datasets and three human lung injury bronchoalveolar lavage datasets. We show that the metasignatures of animal and human experimental ALI are significantly correlated despite these widely varying experimental conditions. The gene expression changes among mice and rats across diverse injury models (ozone, ventilator-induced lung injury, LPS) are significantly correlated with human models of lung injury (Pearson r = 0.33-0.45, P < 1E^-16). Neutrophil signatures are enriched in both animal and human lung injury. Predicted therapeutic targets, peptide ligand signatures, and pathway analyses are also all highly overlapping. Gene expression changes are similar in animal and human experimental ALI, and provide several physiologic and therapeutic insights to the disease.

A Protocol for Using Gene Set Enrichment Analysis to Identify the Appropriate Animal Model for Translational Research

Recent studies that compared transcriptomic datasets of human diseases with datasets from mouse models using traditional gene-to-gene comparison techniques resulted in contradictory conclusions regarding the relevance of animal models for translational research. A major reason for the discrepancies between different gene expression analyses is the arbitrary filtering of differentially expressed genes. Furthermore, the comparison of single genes between different species and platforms often is limited by technical variance, leading to misinterpretation of the con/discordance between data from human and animal models. Thus, standardized approaches for systematic data analysis are needed. To overcome subjective gene filtering and ineffective gene-to-gene comparisons, we recently demonstrated that gene set enrichment analysis (GSEA) has the potential to avoid these problems. Therefore, we developed a standardized protocol for the use of GSEA to distinguish between appropriate and inappropriate animal models for translational research. This protocol is not suitable to predict how to design new model systems a-priori, as it requires existing experimental omics data. However, the protocol describes how to interpret existing data in a standardized manner in order to select the most suitable animal model, thus avoiding unnecessary animal experiments and misleading translational studies.

Warming the mouse to model human diseases

Humans prefer to live within their thermal comfort or neutral zone, which they create by making shelters, wearing clothing and, more recently, by regulating their ambient temperature. These strategies enable humans to maintain a constant core temperature (a trait that is conserved across all endotherms, including mammals and birds) with minimal energy expenditure. Although this primordial drive leads us to seek thermal comfort, we house our experimental animals, laboratory mice (Mus musculus), under conditions of thermal stress. In this Review, we discuss how housing mice below their thermoneutral zone limits our ability to model and study human diseases. Using examples from cardiovascular physiology, metabolic disorders, infections and tumour immunology, we show that certain phenotypes observed under conditions of thermal stress disappear when mice are housed at thermoneutrality, whereas others emerge that are more consistent with human biology. Thus, we propose that warming the mouse might enable more predictive modelling of human diseases and therapies.

TFOS DEWS II pathophysiology report

The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjögren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.

Hurdles in Basic Science Translation

In the past century there have been incredible advances in the field of medical research, but what hinders translation of this knowledge into effective treatment for human disease? There is an increasing focus on the failure of many research breakthroughs to be translated through the clinical trial process and into medical practice. In this mini review, we will consider some of the reasons that findings in basic medical research fail to become translated through clinical trials and into basic medical practices. We focus in particular on the way that human disease is modeled, the understanding we have of how our targets behave in vivo, and also some of the issues surrounding reproducibility of basic research findings. We will also look at some of the ways that have been proposed for overcoming these issues. It appears that there needs to be a cultural shift in the way we fund, publish and recognize quality control in scientific research. Although this is a daunting proposition, we hope that with increasing awareness and focus on research translation and the hurdles that impede it, the field of medical research will continue to inform and improve medical practice across the world.

Of Mice, Dirty Mice, and Men: Using Mice To Understand Human Immunology

Mouse models have enabled breakthroughs in our understanding of the immune system, but it has become increasingly popular to emphasize their shortcomings when translating observations to humans. This review provides a brief summary of mouse natural history, husbandry, and the pros and cons of pursuing basic research in mice versus humans. Opportunities are discussed for extending the predictive translational value of mouse research, with an emphasis on exploitation of a "dirty" mouse model that better mimics the diverse infectious history that is typical of most humans.

Genomic Responses of Mouse Synovial Fibroblasts During Tumor Necrosis Factor-Driven Arthritogenesis Greatly Mimic Those in Human Rheumatoid Arthritis

OBJECTIVE

Aberrant activation of synovial fibroblasts is a key determinant in the pathogenesis of rheumatoid arthritis (RA). The aims of this study were to produce a map of gene expression and epigenetic changes occurring in this cell type during disease progression in the human tumor necrosis factor (TNF)-transgenic model of arthritis and to identify commonalities with human synovial fibroblasts.

METHODS

We used deep sequencing to probe the transcriptome, the methylome, and the chromatin landscape of cultured mouse arthritogenic synovial fibroblasts at 3 stages of disease, as well as synovial fibroblasts stimulated with human TNF. We performed bioinformatics analyses at the gene, pathway, and network levels, compared mouse and human data, and validated selected genes in both species.

RESULTS

We found that synovial fibroblast arthritogenicity was reflected in distinct dynamic patterns of transcriptional dysregulation, which was especially enriched in pathways of the innate immune response and mesenchymal differentiation. A functionally representative subset of these changes was associated with methylation, mostly in gene bodies. The arthritogenic state involved highly active promoters, which were marked by histone H3K4 trimethylation. There was significant overlap between the mouse and human data at the level of dysregulated genes and to an even greater extent at the level of pathways.

CONCLUSION

This study is the first systematic examination of the pathogenic changes that occur in mouse synovial fibroblasts during progressive TNF-driven arthritogenesis. Significant correlations with the respective human RA synovial fibroblast data further validate the human TNF-transgenic mouse as a reliable model of the human disease. The resource of data generated in this work may serve as a framework for the discovery of novel pathogenic mechanisms and disease biomarkers.

Comparative transcriptomics in human and mouse

Cross-species comparisons of genomes, transcriptomes and gene regulation are now feasible at unprecedented resolution and throughput, enabling the comparison of human and mouse biology at the molecular level. Insights have been gained into the degree of conservation between human and mouse at the level of not only gene expression but also epigenetics and inter-individual variation. However, a number of limitations exist, including incomplete transcriptome characterization and difficulties in identifying orthologous phenotypes and cell types, which are beginning to be addressed by emerging technologies. Ultimately, these comparisons will help to identify the conditions under which the mouse is a suitable model of human physiology and disease, and optimize the use of animal models.

The PF4/PPBP/CXCL5 Gene Cluster Is Associated with Periodontitis

Periodontitis is a common dysbiotic inflammatory disease with an estimated heritability of 50%. Due to the limited sample size of available periodontitis cohorts and the underlying trait heterogeneity, genome-wide association studies (GWAS) of chronic periodontitis (CP) have been unsuccessful in discovering susceptibility factors. A strategy that combines agnostic GWAS with a well-powered candidate-gene approach has the potential to discover novel loci. We combined RNA-seq data from gingival tissues with quantitative trait loci (QTLs) that were identified in a F2-cross of mice resistant and susceptible to infection with oral bacterial pathogens. Four genes, which were located within the mapped QTLs, showed differential expression. The chromosomal regions across the human orthologous were interrogated for putative periodontitis-associated variants using existing GWAS data from a German case-control sample of aggressive periodontitis (AgP; 651 cases, 4,001 controls), the most severe and early onset form of periodontitis. Two haplotype blocks, one upstream to the coding region of UGT2A1 (rs146712414, P = 9.1 × 10-5; odds ratio [OR], 1.34; 95% confidence interval [CI], 1.16-1.56) and one downstream of the genes PF4/PPBP/CXCL5 (rs1595009, P = 1.3 × 10-4; OR, 1.32; 95% CI, 1.15-1.52), were associated with AgP. The association of rs1595009 was validated in an independent cohort of CP of European Americans (1,961 cases and 1,864 controls; P = 0.03; OR, 1.45; 95% CI, 1.01-1.29). This association was further replicated in another sample of 399 German CP cases (disease onset <60 y of age) and 1,633 controls ( P = 0.03; OR, 1.75; 95% CI, 1.06-2.90). The combined estimates of association from all samples were P = 2.9 × 10-5 (OR, 1.2; 95% CI, 1.1-1.3). This study shows the strength of combining QTL mapping and RNA-Seq data from a mouse model with association studies in human case-control samples to identify genetic risk variants of periodontitis.

Murine Models of Sepsis and Trauma: Can We Bridge the Gap?

Sepsis and trauma are both leading causes of death in the United States and represent major public health challenges. Murine models have largely been used in sepsis and trauma research to better understand the pathophysiological changes that occur after an insult and to develop potential life-saving therapeutic agents. Mice are favorable subjects for this type of research given the variety of readily available strains including inbred, outbred, and transgenic strains. In addition, they are relatively easy to maintain and have a high fecundity. However, pharmacological therapies demonstrating promise in preclinical mouse models of sepsis and trauma often fail to demonstrate similar efficacy in human clinical trials, prompting considerable criticism surrounding the capacity of murine models to recapitulate complex human diseases like sepsis and traumatic injury. Fundamental differences between the two species include, but are not limited to, the divergence of the transcriptomic response, the mismatch of temporal response patterns, differences in both innate and adaptive immunity, and heterogeneity within the human population in comparison to the homogeneity of highly inbred mouse strains. Given the ongoing controversy, this narrative review aims to not only highlight the historical importance of the mouse as an animal research model but also highlight the current benefits and limitations of the model as it pertains to sepsis and trauma. Lastly, this review will propose future directions that may promote further use of the model.

A Comprehensive Mouse Transcriptomic BodyMap across 17 Tissues by RNA-seq

The mouse has been widely used as a model organism for studying human diseases and for evaluating drug safety and efficacy. Many diseases and drug effects exhibit tissue specificity that may be reflected by tissue-specific gene-expression profiles. Here we construct a comprehensive mouse transcriptomic BodyMap across 17 tissues of six-weeks old C57BL/6JJcl mice using RNA-seq. We find different expression patterns between protein-coding and non-coding genes. Liver expressed the least complex transcriptomes, that is, the smallest number of genes detected in liver across all 17 tissues, whereas testis and ovary harbor more complex transcriptomes than other tissues. We report a comprehensive list of tissue-specific genes across 17 tissues, along with a list of 4,781 housekeeping genes in mouse. In addition, we propose a list of 27 consistently and highly expressed genes that can be used as reference controls in expression-profiling analysis. Our study provides a unique resource of mouse gene-expression profiles, which is helpful for further biomedical research.

An oligodeoxynucleotide with AAAG repeats significantly attenuates burn-induced systemic inflammatory responses via inhibiting interferon regulatory factor 5 pathway

Previously, we showed that an oligodeoxynucleotide with AAAG repeats (AAAG ODN) rescued mice from fatal acute lung injury (ALI) induced by influenza virus and inhibited production of tumor necrosis factor-α (TNF-α) in the injured lungs. However, the underlying mechanisms remain to be elucidated. Upon the bioinformatic analysis revealing that the AAAG ODN is consensus to interferon regulatory factor 5 (IRF5) binding site in the cis-regulatory elements of proinflammatory cytokines, we tried to explore whether the AAAG ODN could attenuate burn injury induced systemic inflammatory responses via inhibiting IRF5 pathway. Using the mouse model with sterile systemic inflammation induced by burn injury, we found that AAAG ODN prolonged the life span of the mice, decreased the expression of IRF5 at injured skin, reduced the production of TNF-α and IL-6 in blood and injured skin, and attenuated the ALI. Furthermore, AAAG ODN could bind IRF5 and inhibit the nuclear translocation of IRF5 in THP-1 cells. The data suggested that the AAAG ODN could act as a cytoplasmic decoy capable of interfering the function of IRF5, and be developed as a drug candidate for the treatment of inflammatory diseases.

Resveratrol distinctively modulates the inflammatory profiles of immune and endothelial cells

Background

The phenolic substance resveratrol (RES) is a plant metabolite known to modulate numerous physiological functions and to exert beneficial effects as a cancer-chemopreventing agent and on neurological, hepatic, and cardiovascular systems. Since the compound affects the lifespan of yeast and flies it might be an anti-aging substance. Mechanistically, RES is involved in down regulating the inflammatory response. The pleiotropic effects of RES in cells of the immune and endothelial system were examined in this study.

Results

Murine macrophages (RAW264.7 cells), human monocytic/leukemia cells (THP-1), PBLs and HUVECs were incubated with RES and activated with inflammatory stimuli such as LPS or TNF-α. Inflammatory mediators and adhesion molecules were measured by multiplex analysis and gene expression was quantified by RT-PCR. In PBLs, which were activated with LPS, RES blunted the production of TNF-α, CCL2/MCP-1, CCL5/RANTES, CXCL8/IL-8, whereas it increased the production of IL-1β, IL-6, CCL4/MIP-1β and CXCL10/IP-10. Thus, in the blood compartment chemokines attracting mainly monocytes were up-regulated by RES, while those attracting T lymphocytes or neutrophils were diminished. At conditions of endothelial dysfunction (ED), RES reduced the expression of cytokines, chemokines, ICAM and GM-CSF in TNF-α activated HUVECs, whereas eNOS expression was corrected to pre-ED homeostasis. In macrophages nitric oxide, PGE₂, cytokines (TNF-α, IL-1β, IL-6) and chemokines (CCL2/MCP-1, CCL4/MIP-1β, CCL5/RANTES, CXCL10/IP-10) were reduced by the phenolic substance.

Conclusions

RES had cell-specific and context-dependent effects, in particular on the expression of IL-1β, IL-6, CCL4/MIP-1β and CXCL10/IP-10. It enhanced cellular features that mirror increased alertness to disturbed immune homeostasis in the vascular-endothelial compartment (e.g. increased production of IL-1β or IL-6), whereas it blunted inflammatory mediators in macrophages and consequently chronic inflammation. We infer from the present in vitro study, that RES has unique properties in the regulation of inflammatory and immune responses, which are controlled in a complex hierarchical and temporal order.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1823-z) contains supplementary material, which is available to authorized users.

Translational Rodent Models for Research on Parasitic Protozoa-A Review of Confounders and Possibilities

Rodents, in particular Mus musculus, have a long and invaluable history as models for human diseases in biomedical research, although their translational value has been challenged in a number of cases. We provide some examples in which rodents have been suboptimal as models for human biology and discuss confounders which influence experiments and may explain some of the misleading results. Infections of rodents with protozoan parasites are no exception in requiring close consideration upon model choice. We focus on the significant differences between inbred, outbred and wild animals, and the importance of factors such as microbiota, which are gaining attention as crucial variables in infection experiments. Frequently, mouse or rat models are chosen for convenience, e.g., availability in the institution rather than on an unbiased evaluation of whether they provide the answer to a given question. Apart from a general discussion on translational success or failure, we provide examples where infections with single-celled parasites in a chosen lab rodent gave contradictory or misleading results, and when possible discuss the reason for this. We present emerging alternatives to traditional rodent models, such as humanized mice and organoid primary cell cultures. So-called recombinant inbred strains such as the Collaborative Cross collection are also a potential solution for certain challenges. In addition, we emphasize the advantages of using wild rodents for certain immunological, ecological, and/or behavioral questions. The experimental challenges (e.g., availability of species-specific reagents) that come with the use of such non-model systems are also discussed. Our intention is to foster critical judgment of both traditional and newly available translational rodent models for research on parasitic protozoa that can complement the existing mouse and rat models.

Late Therapeutic Intervention with Antibiotics and Fluid Resuscitation Allows for a Prolonged Disease Course with High Survival in a Severe Murine Model of Sepsis

Current animal models of sepsis often incorporate antibiotics to be consistent with clinical standards for treatment of patients in the intensive care unit. However, such experimental intervention is commonly initiated very early after infectious insult, which likely blunts the progression of systemic inflammation and downstream pathology. The objective of this study was to establish an animal model of sepsis with delayed therapeutic intervention, allowing a longer disease course and downstream pathology, but still resulting in a high survival rate. Severe lethal abdominal infection was initiated in young adult (17-18-week-old) C57BL/6 mice by cecal slurry (CS) injection. When initiated early (1- or 6-h post-CS injection), antibiotic treatment (imipenem, 1.5 mg/mouse i.p., twice/day for 5 days) rescued the majority of mice; however, few of these mice showed evidence of bacteremia, cytokinemia, or organ injury. When antibiotic treatment was delayed until late time-points (12- or 24-h post-CS injection) the majority of animals did not survive beyond 48 h. When fluid resuscitation (physiological saline, s.c.) was performed in combination with antibiotic treatment (twice daily) beginning at these late time-points, the majority of mice survived (75%) and showed bacteremia, cytokinemia, organ dysfunction, and prolonged body weight loss (<90% for 4 weeks). We recommend that this new repeated combination treatment with antibiotics and fluids resuscitation be initiated at a late time point after bacteremia becomes evident because this model more closely mimics the downstream pathological characteristics of severe clinical sepsis yet maintains a high survival rate. This model would be advantageous for studies on severe sepsis and postintensive care illness.

In Vivo Murine-Matured Human CD3+ Cells as a Preclinical Model for T Cell-Based Immunotherapies

Adoptive cellular immunotherapy is a promising and powerful method for the treatment of a broad range of malignant and infectious diseases. Although the concept of cellular immunotherapy was originally proposed in the 1990s, it has not seen successful clinical application until recent years. Despite significant progress in creating engineered receptors against both malignant and viral epitopes, no efficient preclinical animal models exist for rapidly testing and directly comparing these engineered receptors. The use of matured human T cells in mice usually leads to graft-versus-host disease (GvHD), which severely limits the effectiveness of such studies. Alternatively, adult apheresis CD34⁺ cells engraft in neonatal non-obese diabetic (NOD)-severe combined immunodeficiency (SCID)-common γ chain^–/– (NSG) mice and lead to the development of CD3⁺ T cells in peripheral circulation. We demonstrate that these in vivo murine-matured autologous CD3⁺ T cells from humans (MATCH) can be collected from the mice, engineered with lentiviral vectors, reinfused into the mice, and detected in multiple lymphoid compartments at stable levels over 50 days after injection. Unlike autologous CD3⁺ cells collected from human donors, these MATCH mice did not exhibit GvHD after T cell administration. This novel mouse model offers the opportunity to screen different immunotherapy-based treatments in a preclinical setting.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.

Humanized Mouse Models of Staphylococcus aureus Infection

Staphylococcus aureus is a successful human pathogen that has adapted itself in response to selection pressure by the human immune system. A commensal of the human skin and nose, it is a leading cause of several conditions: skin and soft tissue infection, pneumonia, septicemia, peritonitis, bacteremia, and endocarditis. Mice have been used extensively in all these conditions to identify virulence factors and host components important for pathogenesis. Although significant effort has gone toward development of an anti-staphylococcal vaccine, antibodies have proven ineffective in preventing infection in humans after successful studies in mice. These results have raised questions as to the utility of mice to predict patient outcome and suggest that humanized mice might prove useful in modeling infection. The development of humanized mouse models of S. aureus infection will allow us to assess the contribution of several human-specific virulence factors, in addition to exploring components of the human immune system in protection against S. aureus infection. Their use is discussed in light of several recently reported studies.

p38γ and p38δ: From Spectators to Key Physiological Players

Although the physiological roles of p38γ and p38δ signalling pathways are largely unknown, new genetic and pharmacological tools are providing groundbreaking information on the function of these two stress-activated protein kinases. Recent studies show the importance of p38γ and p38δ in the regulation of processes as diverse as cytokine production, protein synthesis, exocytosis, cell migration, gene expression, and neuron activity, which have an acute impact on the development of pathologies related to inflammation, diabetes, neurodegeneration, and cancer. These recent breakthroughs are resolving some of the questions that have long been asked regarding the function of p38γ and p38δ in biology and pathology.