Deficiency of the murine fifth complement component (C5). A 2-base pair gene deletion in a 5'-exon

Mouse NOD/Shi and NSY/Hos strains infected with Plasmodium berghei ANKA are models for experimental cerebral malaria

In humans, cerebral malaria is the most common cause of malaria-related mortality. Mouse C57BL/6 (B6) sub-strains are the major model system for experimental cerebral malaria (ECM) as they show similar pathophysiology to human cerebral malaria after infection with the rodent malaria parasite Plasmodium berghei ANKA. This model system has been used to analyze the molecular mechanisms of cerebral malaria. To develop new mouse models, we analyzed the ECM susceptibility of NOD/Shi (NOD) and NSY/Hos (NSY) strains established from the non-inbred ICR strain. Both NOD and NSY strains exhibited clinical symptoms and pathologies similar to ECM in C57BL/6J (B6J) mice and died within 11 days of infection. Thus, the NOD and NSY strains are susceptible to ECM and may be useful as new ECM models. The ECM susceptibility of both strains is suggested to be due to homozygosity for the cerebral malaria susceptibility allele of the ECM susceptible ICR strain. Although analyses using B6 sub-strains have proposed that complement component 5 (C5) plays an important role in ECM pathogenesis, we found that C5 was not essential as the ECM susceptible NOD strain is C5 deficient. Thus, results obtained from B6 sub-strains may not reflect the full picture of ECM in mice. Comparative analyses of multiple ECM models will contribute to a more accurate identification of the factors essential for ECM.

Antibodies and complement are key drivers of thrombosis

Venous thromboembolism (VTE) is a common, deadly disease with an increasing incidence despite preventive efforts. Clinical observations have associated elevated antibody concentrations or antibody-based therapies with thrombotic events. However, how antibodies contribute to thrombosis is unknown. Here, we show that reduced blood flow enabled immunoglobulin M (IgM) to bind to FcμR and the polymeric immunoglobulin receptor (pIgR), initiating endothelial activation and platelet recruitment. Subsequently, the procoagulant surface of activated platelets accommodated antigen- and FcγR-independent IgG deposition. This leads to classical complement activation, setting in motion a prothrombotic vicious circle. Key elements of this mechanism were present in humans in the setting of venous stasis as well as in the dysregulated immunothrombosis of COVID-19. This antibody-driven thrombosis can be prevented by pharmacologically targeting complement. Hence, our results uncover antibodies as previously unrecognized central regulators of thrombosis. These findings carry relevance for therapeutic application of antibodies and open innovative avenues to target thrombosis without compromising hemostasis.

Inbred Mouse Models in Cryptococcus neoformans Research

Animal models are frequently used as surrogates to understand human disease. In the fungal pathogen Cryptococcus species complex, several variations of a mouse model of disease were developed that recapitulate different aspects of human disease. These mouse models have been implemented using various inbred and outbred mouse backgrounds, many of which have genetic differences that can influence host response and disease outcome. In this review, we will discuss the most commonly used inbred mouse backgrounds in C. neoformans infection models.

FVB/NJ strain as a mouse model for cutaneous leishmaniasis by Leishmania (L.) amazonensis

BACKGROUND

Leishmaniases encompass a spectrum of neglected diseases caused by parasites of the genus Leishmania, grouped in two forms: tegumentary and visceral leishmaniasis.

OBJECTIVES

In this study, we propose Friend Virus B NIH Jackson (FVB/NJ) mouse strain as a new experimental model of infection with Leishmania (Leishmania) amazonensis, the second most prevalent agent of tegumentary leishmaniasis in Brazil.

METHODS AND FINDINGS

We performed in vitro infections of FVB/NJ macrophages and compared them with BALB/c macrophages, showing that BALB/c cells have higher infection percentages and a higher number of amastigotes/cell. Phagocytosis assays indicated that BALB/c and FVB/NJ macrophages have similar capacity to uptake parasites after 5 min incubations. We also investigated promastigotes' resistance to sera from FVB/NJ and BALB/c and observed no difference between the two sera, even though FVB/NJ has a deficiency in complement components. Finally, we subcutaneously infected FVB/NJ and BALB/c mice with 2 × 106 parasites expressing luciferase. Analysis of lesion development for 12 weeks showed that FVB/NJ and BALB/c mice have similar lesion profiles and parasite burdens.

MAIN CONCLUSIONS

This work characterises for the first time the FVB/NJ mouse as a new model for tegumentary leishmaniasis caused by Leishmania (L.) amazonensis.

The Role of Complement Dysregulation in Glaucoma

Glaucoma is a progressive neurodegenerative disease characterized by damage to the optic nerve that results in irreversible vision loss. While the exact pathology of glaucoma is not well understood, emerging evidence suggests that dysregulation of the complement system, a key component of innate immunity, plays a crucial role. In glaucoma, dysregulation of the complement cascade and impaired regulation of complement factors contribute to chronic inflammation and neurodegeneration. Complement components such as C1Q, C3, and the membrane attack complex have been implicated in glaucomatous neuroinflammation and retinal ganglion cell death. This review will provide a summary of human and experimental studies that document the dysregulation of the complement system observed in glaucoma patients and animal models of glaucoma driving chronic inflammation and neurodegeneration. Understanding how complement-mediated damage contributes to glaucoma will provide opportunities for new therapies.

Vaccination with a ZNF2oe Strain of Cryptococcus Provides Long-Lasting Protection against Cryptococcosis and Is Effective in Immunocompromised Hosts

Systemic cryptococcosis is fatal without treatment. Even with the current antifungal therapies, this disease kills 180,000 of 225,000 infected people annually. Exposure to the causative environmental fungus Cryptococcus neoformans is universal. Either reactivation of a latent infection or an acute infection after high exposure to cryptococcal cells can result in cryptococcosis. Currently, there is no vaccine to prevent cryptococcosis. Previously, we discovered that Znf2, a transcription factor that directs Cryptococcus yeast-to-hypha transition, profoundly affects cryptococcal interaction with the host. Overexpression of ZNF2 drives filamentous growth, attenuates cryptococcal virulence, and elicits protective host immune responses. Importantly, immunization with cryptococcal cells overexpressing ZNF2, in either live or heat-inactivated form, offers significant protection to the host from a subsequent challenge by the otherwise lethal clinical isolate H99. In this study, we found that the heat-inactivated ZNF2^oe vaccine offered long-lasting protection with no relapse upon challenge with the wild-type H99. Vaccination with heat-inactivated ZNF2^oe cells provides partial protection in hosts with preexisting asymptomatic cryptococcal infection. Importantly, once animals have been vaccinated with heat-inactivated or live short-lived ZNF2^oe cells, they are protected against cryptococcosis even when their CD4⁺ T cells are depleted at the time of fungal challenge. Remarkably, vaccination with live, short-lived ZNF2^oe cells in CD4-depleted hosts still provides strong protection to these hosts with preexisting immunodeficiency at the time of vaccination. This work raises hope for developing effective vaccines with long-lasting protection for individuals who are immunocompromised or could become immunocompromised later in life.

A comprehensive approach to modeling maternal immune activation in rodents

Prenatal brain development is a highly orchestrated process, making it a very vulnerable window to perturbations. Maternal stress and subsequent inflammation during pregnancy leads to a state referred to as, maternal immune activation (MIA). If persistent, MIA can pose as a significant risk factor for the manifestation of neurodevelopmental disorders (NDDs) such as autism spectrum disorder and schizophrenia. To further elucidate this association between MIA and NDD risk, rodent models have been used extensively across laboratories for many years. However, there are few uniform approaches for rodent MIA models which make not only comparisons between studies difficult, but some established approaches come with limitations that can affect experimental outcomes. Here, we provide researchers with a comprehensive review of common experimental variables and potential limitations that should be considered when designing an MIA study based in a rodent model. Experimental variables discussed include: innate immune stimulation using poly I:C and LPS, environmental gestational stress paradigms, rodent diet composition and sterilization, rodent strain, neonatal handling, and the inclusion of sex-specific MIA offspring analyses. We discuss how some aspects of these variables have potential to make a profound impact on MIA data interpretation and reproducibility.

Cardiac myosin-specific autoimmune T cells contribute to immune-checkpoint-inhibitor-associated myocarditis

Immune checkpoint inhibitors (ICIs) are an effective therapy for various cancers; however, they can induce immune-related adverse events (irAEs) as a side effect. Myocarditis is an uncommon, but fatal, irAE caused after ICI treatments. Currently, the mechanism of ICI-associated myocarditis is unclear. Here, we show the development of myocarditis in A/J mice induced by anti-PD-1 monoclonal antibody (mAb) administration alone without tumor cell inoculation, immunization, or viral infection. Mice with myocarditis have increased cardiac infiltration, elevated cardiac troponin levels, and arrhythmia. Anti-PD-1 mAb treatment also causes irAEs in other organs. Autoimmune T cells recognizing cardiac myosin are activated and increased in mice with myocarditis. Notably, cardiac myosin-specific T cells are present in naive mice, showing a phenotype of antigen-experienced T cells. Collectively, we establish a clinically relevant mouse model for ICI-associated myocarditis and find a contribution of cardiac myosin-specific T cells to ICI-associated myocarditis development and pathogenesis.

Generation of Novel Human Red Blood Cell-Bearing Humanized Mouse Models Based on C3-Deficient NOG Mice

Despite recent advances in immunodeficient mouse models bearing human red blood cells (hRBCs), the elimination of circulating hRBCs by residual innate immune systems remains a significant challenge. In this study, we evaluated the role of mouse complement C3 in the elimination of circulating hRBCs by developing a novel NOG substrain harboring a truncated version of the murine C3 gene (NOG-C3^ΔMG2-3). Genetic C3 deletion prolonged the survival of transfused hRBCs in the circulation. Chemical depletion and functional impairment of mouse macrophages, using clodronate liposomes (Clo-lip) or gadolinium chloride (GdCl₃), respectively, further extended the survival of hRBCs in NOG-C3^ΔMG2-3 mice. Low GdCl₃ toxicity allowed the establishment of hRBC-bearing mice, in which hRBCs survived for more than 4 weeks with transfusion once a week. In addition, erythropoiesis of human hematopoietic stem cells (hHSCs) was possible in NOG-C3^ΔMG2-3/human GM-CSF-IL-3 transgenic mice with Clo-lip treatment. These findings indicate that mouse models harboring hRBCs can be achieved using NOG-C3^ΔMG2-3 mice, which could facilitate studies of human diseases associated with RBCs.

C(3)1-TAg in C57BL/6 J background as a model to study mammary tumor development

Diagnosis and prognosis of breast cancer is based on disease staging identified through histopathological and molecular biology techniques. Animal models are used to gain mechanistic insights into the development of breast cancer. C(3)1-TAg is a genetically engineered mouse model that develops mammary cancer. However, carcinogenesis caused by this transgene was characterized in the Friend Virus B (FVB) background. As most genetic studies are done in mice with C57BL/6 J background, we aimed to define the histological alterations in C3(1)-TAg C57BL/6 J animals. Our results showed that C3(1)-TAg animals with C57BL/6 J background develop solid-basaloid adenoid cystic carcinomas with increased fibrosis, decreased area of adipocytes, and a high proliferative index, which are triple-negative for progesterone, estrogen, and human epidermal growth factor receptor 2 (HER2) receptors. Our results also revealed that tumor development is slower in the C57BL/6 J background when compared with the FVB strain, providing a better model to study the different stages in breast cancer progression.

Complement C5 is not critical for the formation of sub-RPE deposits in Efemp1 mutant mice

The complement system plays a role in the formation of sub-retinal pigment epithelial (RPE) deposits in early stages of age-related macular degeneration (AMD). But the specific mechanisms that connect complement activation and deposit formation in AMD patients are unknown, which limits the development of efficient therapies to reduce or stop disease progression. We have previously demonstrated that C3 blockage prevents the formation of sub-RPE deposits in a mouse model of EFEMP1-associated macular degeneration. In this study, we have used double mutant Efemp1R345W/R345W:C5-/- mice to investigate the role of C5 in the formation of sub-RPE deposits in vivo and in vitro. The data revealed that the genetic ablation of C5 does not eliminate the formation of sub-RPE deposits. Contrarily, the absence of C5 in RPE cultures promotes complement dysregulation that results in increased activation of C3, which likely contributes to deposit formation even in the absence of EFEMP1-R345W mutant protein. The results also suggest that genetic ablation of C5 alters the extracellular matrix turnover through an effect on matrix metalloproteinases in RPE cell cultures. These results confirm that C3 rather than C5 could be an effective therapeutic target to treat early AMD.

Advances in Genome Editing and Application to the Generation of Genetically Modified Rat Models

The rat has been extensively used as a small animal model. Many genetically engineered rat models have emerged in the last two decades, and the advent of gene-specific nucleases has accelerated their generation in recent years. This review covers the techniques and advances used to generate genetically engineered rat lines and their application to the development of rat models more broadly, such as conditional knockouts and reporter gene strains. In addition, genome-editing techniques that remain to be explored in the rat are discussed. The review also focuses more particularly on two areas in which extensive work has been done: human genetic diseases and immune system analysis. Models are thoroughly described in these two areas and highlight the competitive advantages of rat models over available corresponding mouse versions. The objective of this review is to provide a comprehensive description of the advantages and potential of rat models for addressing specific scientific questions and to characterize the best genome-engineering tools for developing new projects.

A/J mice are more susceptible than C57BL/6 to acetaminophen-induced hepatotoxicity

Acetaminophen (APAP) is commonly used to treat fever and pain. However, when in overdose is the predominant cause of hepatotoxicity. Despite advances in understanding the mechanisms of APAP-induced hepatotoxicity, the management of acute liver failure remains a challenge. Thus, more relevant experimental models are crucial to provide a better understanding of this condition. The aim of this study is to evaluate the effect of APAP-induced hepatotoxicity on A/J mice using C57BL/6 as reference experimental model. Eight- to ten-week-old male A/J and C57BL/6 mice were treated with APAP (300 or 500 mg/kg) by intraperitoneal injection. After 24 h total blood leukocyte counting, plasma levels of alanine amino transferase (ALT) and aspartate amino transferase (AST), histopathological analysis of liver, lung and kidney were evaluated. A/J mice presented reduction in circulating leukocytes concomitant with the increase in plasma levels of ALT and AST, and liver necrosis when treated with 300 and 500 mg/kg of APAP. C57BL/6 mice presented similar results only with 500 mg/kg of APAP. Our results show that A/J mice have a marked susceptibility to the effects of APAP and could be considered as an experimental model to study APAP-induced toxicity.

Humanization of Immunodeficient Animals for the Modeling of Transplantation, Graft Versus Host Disease, and Regenerative Medicine

The humanization of animals is a powerful tool for the exploration of human disease pathogenesis in biomedical research, as well as for the development of therapeutic interventions with enhanced translational potential. Humanized models enable us to overcome biologic differences that exist between humans and other species, while giving us a platform to study human processes in vivo. To become humanized, an immune-deficient recipient is engrafted with cells, tissues, or organoids. The mouse is the most well studied of these hosts, with a variety of immunodeficient strains available for various specific uses. More recently, efforts have turned to the humanization of other animal species such as the rat, which offers some technical and immunologic advantages over mice. These advances, together with ongoing developments in the incorporation of human transgenes and additional mutations in humanized mouse models, have expanded our opportunities to replicate aspects of human allotransplantation and to assist in the development of immunotherapies. In this review, the immune and tissue humanization of various species is presented with an emphasis on their potential for use as models for allotransplantation, graft versus host disease, and regenerative medicine.

Susceptibility Analysis in Several Mouse Strains Reveals Robust T-Cell Responses After Mycoplasma pneumoniae Infection in DBA/2 Mice

Mycoplasma pneumoniae (Mp) is a highly contagious respiratory pathogen responsible for human community-acquired pneumonia. The number of antibiotic-resistant Mp strains is increasing; therefore, to develop novel therapeutics, it is crucial to precisely understand the pathogenesis of mycoplasma pneumonia. Herein, we examined the susceptibility and response to Mp among eight inbred mouse strains. Following infection, the bacterial load in the bronchoalveolar lavage fluid (BALF) from DBA/2 mice was higher than that in the other tested strains such as BALB/c mice, which are frequently used in Mp research. In contrast, the numbers of CD45⁺ immune cells and neutrophils in BALF were comparable between BALB/c and DBA/2 mice, with lower numbers observed in C57BL/6J and CBA/N mice than in BALB/c mice. Among the tested strains, the BALF level of interleukin 12 subunit p40 was highest in DBA/2 mice; however, significant differences in other cytokines levels were not observed between BALB/c and DBA/2 mice. After Mp infection, Mp-specific Th1 and Th17 responses were significantly enhanced in DBA/2 mice when compared with BALB/c mice. Furthermore, prior infection with Mp increased the number of neutrophils in BALF after the reinfection of DBA/2 mice through an Mp-specific CD4⁺ T cell-dependent mechanism. Thus, DBA/2 may be an appropriate strain for evaluating Mp infection. Moreover, a comparison of responses revealed by various inbred mouse strains could be useful for elucidating the pathogenesis of Mycoplasma pneumonia.

Improved Detection of in vivo Human NK Cell-Mediated Antibody-Dependent Cellular Cytotoxicity Using a Novel NOG-FcγR-Deficient Human IL-15 Transgenic Mouse

We generated an NOD/Shi-scid-IL2Rγ^null (NOG) mouse deficient for the Fcer1g and Fcgr2b genes (NOG-FcγR^−/− mice), in which monocytes/macrophages do not express activating (FcγRI, III, and IV) or inhibitory (FcγRIIB) Fcγ receptors. Antibody-dependent cellular cytotoxicity (ADCC) by innate immune cells was strongly reduced in this strain. Thus, while the growth of xenogeneic human tumors engrafted in conventional NOG mice was suppressed by innate cells upon specific antibody treatment, such growth inhibition was abrogated in NOG-FcγR^−/− mice. Using this novel strain, we further produced NOG-FcγR^−/−-mice expressing human IL-15 (NOG-FcγR^−/−-hIL-15 Tg). The mice inherited unique features from each strain, i.e., the long-term sustenance of human natural killer (NK) cells, and the elimination of mouse innate cell-mediated ADCC. As a result, segregation of human NK cell-mediated ADCC from mouse cell-mediated ADCC was possible in the NOG-FcγR^−/−-hIL-15 Tg mice. Our results suggest that NOG-FcγR^−/−-hIL-15 Tg mice are useful for validating the in vivo function of antibody drug candidates.

Liver-Specific siRNA-Mediated Stat3 or C3 Knockdown Improves the Outcome of Experimental Autoimmune Myocarditis

Myocarditis can lead to autoimmune disease, dilated cardiomyopathy, and heart failure, which is modeled in the mouse by cardiac myosin immunization (experimental autoimmune myocarditis [EAM]). Signal transducer and activator of transcription 3 (STAT3) systemic inhibition exerts both preventive and therapeutic effects in EAM, and STAT3 constitutive activation elicits immune-mediated myocarditis dependent on complement C3 and correlating with activation of the STAT3-interleukin 6 (IL-6) axis in the liver. Thus, liver-specific STAT3 inhibition may represent a therapeutic option, allowing to bypass the heart toxicity, predicted by systemic STAT3 inhibition. We therefore decided to explore the effectiveness of silencing liver Stat3 and C3 in preventing EAM onset and/or the recovery of cardiac functions. We first show that complement C3 and C5 genetic depletion significantly prevents the onset of spontaneous myocarditis, supporting the complement cascade as a viable target. In order to interfere with complement production and STAT3 activity specifically in the liver, we took advantage of liver-specific Stat3 or C3 small interfering (si)RNA nanoparticles, demonstrating that both siRNAs can significantly prevent myocarditis onset and improve the recovery of heart functions in EAM. Our data demonstrate that liver-specific Stat3/C3 siRNAs may represent a therapeutic option for autoimmune myocarditis and suggest that complement levels and activation might be predictive of progression to dilated cardiomyopathy.

An update on the microbiology, immunology and genetics of seborrheic dermatitis

The underlying mechanism of seborrheic dermatitis (SD) is poorly understood but major scientific progress has been made in recent years related to microbiology, immunology and genetics. In light of this, the major goal of this article was to summarize the most recent articles on SD, specifically related to underlying pathophysiology. SD results from Malassezia hydrolysation of free fatty acids with activation of the immune system by the way of pattern recognition receptors, inflammasome, IL-1β and NF-kB. M. restricta and M. globosa are likely the most virulent subspecies, producing large quantities of irritating oleic acids, leading to IL-8 and IL-17 activation. IL-17 and IL-4 might play a big role in pathogenesis, but this needs to be further studied using novel biologics. No clear genetic predisposition has been established; however, recent studies implicated certain increased-risk human leucocyte antigen (HLA) alleles, such as A*32, DQB1*05 and DRB1*01 as well as possible associations with psoriasis and atopic dermatitis (AD) through the LCE3 gene cluster while SD, and SD-like syndromes, shares genetic mutations that appear to impair the ability of the immune system to restrict Malassezia growth, partially due to complement system dysfunction. A paucity of studies exists looking at the relationship between SD and systemic disease. In HIV, SD is thought to be secondary to a combination of immune dysregulation and disruption in skin microbiota with unhindered Malassezia proliferation. In Parkinson's disease, SD is most likely secondary to parasympathetic hyperactivity with increased sebum production as well as facial immobility which leads to sebum accumulation.

Compensatory role of C3 convertase on the strain difference for C3 protein expression in FVB/N, C3H/HeN and C57BL/6N mice

To investigate the role of complement C3 (C3) convertase on the strain difference for C3 protein expression in three inbred mice strains, we compared the levels of C2, C3 and C4 mRNA, as well as C3 protein and C3 convertase activity in the serum and liver tissue of FVB/N, C3H/HeN and C57BL/6N mice. The level of mRNA, inactive form (InACF) and active form (ACF) for C3 showed a regular pattern, which they were higher in the FVB/N and C57BL/6N mice than C3H/HeN mice. However, the level of C3b fragments (C3bα and β) derived from C3 protein were constantly maintained in the liver of FVB/N, C3H/HeN and C57BL/6N mice in spite of the strain difference on the transcriptional and translation level of C3. Especially, a reverse pattern of the level of mRNA, InACF and ACF for C3 was observed on the activity level of C3 convertase activity. The highest level of C3 convertase activity was measured in C3H/HeN mice, followed by C57BL/6N and FVB/N mice. In case of C3 convertase components, the level of C2 mRNA was higher in C3H/HeN mice than FVB/N and C57BL/6 N mice, while levels of C4 mRNA were higher in FVB/N and C57BL/6N mice than C3H/HeN mice. The current study results provide the first scientific evidence that C3 convertase may play complementary role to overcome the strain difference on the C3 protein expression in FVB/N, C3H/HeN and C57BL/6N mice.

Immune Relevant and Immune Deficient Mice: Options and Opportunities in Translational Research

In 1989 ILAR published a list and description of immunodeficient rodents used in research. Since then, advances in understanding of molecular mechanisms; recognition of genetic, epigenetic microbial, and other influences on immunity; and capabilities in manipulating genomes and microbiomes have increased options and opportunities for selecting mice and designing studies to answer important mechanistic and therapeutic questions. Despite numerous scientific breakthroughs that have benefitted from research in mice, there is debate about the relevance and predictive or translational value of research in mice. Reproducibility of results obtained from mice and other research models also is a well-publicized concern. This review summarizes resources to inform the selection and use of immune relevant mouse strains and stocks, aiming to improve the utility, validity, and reproducibility of research in mice. Immune sufficient genetic variations, immune relevant spontaneous mutations, immunodeficient and autoimmune phenotypes, and selected induced conditions are emphasized.

Heart disease in a mutant mouse model of spontaneous eosinophilic myocarditis maps to three loci

Background

Heart disease (HD) is the major cause of morbidity and mortality in patients with hypereosinophilic diseases. Due to a lack of adequate animal models, our understanding of the pathophysiology of eosinophil-mediated diseases with heart complications is limited. We have discovered a mouse mutant, now maintained on an A/J inbred background, that spontaneously develops hypereosinophilia in multiple organs. Cellular infiltration into the heart causes an eosinophilic myocarditis, with affected mice of the mutant line (i.e., A/J^HD) demonstrating extensive myocardial damage and remodeling that leads to HD and premature death, usually by 15-weeks old.

Results

Maintaining the A/J^HD line for many generations established that the HD trait was heritable and implied the mode of inheritance was not too complex. Backcross and intercross populations generated from mating A/J^HD males with females from four different inbred strains produced recombinant populations with highly variable rates of affected offspring, ranging from none in C57BL/6 J intercrosses, to a few mice with HD using 129S1/SvImJ intercrosses and C57BL/6 J backcrosses, but nearly 8% of intercrosses and > 17% of backcrosses from SJL/J related populations developed HD. Linkage analyses of these SJL/J derived recombinants identified three highly significant loci: a recessive locus mapping to distal chromosome 5 (LOD = 4.88; named Emhd1 for eosinophilic myocarditis to heart disease-1); and two dominant variants mapping to chromosome 17, one (Emhd2; LOD = 7.51) proximal to the major histocompatibility complex, and a second (Emhd3; LOD = 6.89) that includes the major histocompatibility region. Haplotype analysis identified the specific crossovers that defined the Emhd1 (2.65 Mb), Emhd2 (8.46 Mb) and Emhd3 (14.59 Mb) intervals.

Conclusions

These results indicate the HD trait in this mutant mouse model of eosinophilic myocarditis is oligogenic with variable penetrance, due to multiple segregating variants and possibly additional genetic or nongenetic factors. The A/J^HD mouse model represents a unique and valuable resource to understand the interplay of causal factors that underlie the pathology of this newly discovered eosinophil-associated disease with cardiac complications.

Cytokine Profile in Early Infection by Leptospira interrogans in A/J Mice

Leptospirosis is considered a neglected disease with an estimated more than one million cases every year. Since rodents are at the same time the main reservoir and generally asymptomatic to Leptospira infection, understanding why some animal species are resistant and others are susceptible to this infection would shed some light in how to control this important zoonosis. The innate immune response against Leptospira is mainly dependent on phagocytosis and activation of the Complement System. In this context, cytokines may drive the early control of infection and the adaptive response. Since the Complement System is important to eliminate leptospires in vivo, we investigated if Complement C5 in A/J mice would modulate the cytokine production during infection by Leptospira interrogans serovar Kennewicki type Pomona Fromm (LPF). Thus, our aim was to investigate the systemic levels of pro- and anti-inflammatory cytokines during Leptospira infection in the blood, liver, lung, and kidney on the third and sixth days of infection in A/J C5^+/+ and A/J C5^-/- mice. Blood levels of TNF-α, IL-6, IFN-γ, and MCP-1 reached a peak on the third day. Although both mouse strains developed splenomegaly, similar histopathological alterations in the liver and the lung, levels of pro- and anti-inflammatory cytokines were different. A/J C5^+/+ mice had higher levels of liver IL-10, IL-1β, IL-12p40, and IL-12p70 and kidney IL-1β, IL-12p40, and IL-12p70 on the sixth day of infection when compared to A/J C5^-/- mice. Our results showed that in A/J genetic background, the Complement component C5 modulates a cytokine profile in the liver and kidney of infected mice, which may play a role in the control of disease progression.

Impaired insulin signaling in the B10.D2-Hc0 H2d H2-T18c/oSnJ mouse model of complement factor 5 deficiency

Given the chemoattractant potential of complement factor 5 (C5) and its increased expression in adipose tissue (AT) of obese mice, we determined whether this protein of the innate immune system impacts insulin action. C5 control (C5cont) and spontaneously C5-deficient (C5def, B10.D2-Hc0 H2d H2-T18c/oSnJ) mice were placed on low- and high-fat diets to investigate their inflammatory and metabolic phenotypes. Adenoviral delivery was used to evaluate the effects of exogenous C5 on systemic metabolism. C5def mice gained less weight than controls while fed a high-fat diet, accompanied by reduced AT inflammation, liver mass, and liver triglyceride content. Despite these beneficial metabolic effects, C5def mice demonstrated severe glucose intolerance and systemic insulin resistance, as well as impaired insulin signaling in liver and AT. C5def mice also exhibited decreased expression of insulin receptor (INSR) gene and protein, as well as improper processing of pro-INSR. These changes were not due to the C5 deficiency alone as other C5-deficient models did not recapitulate the INSR processing defect; rather, in addition to the mutation in the C5 gene, whole genome sequencing revealed an intronic 31-bp deletion in the Insr gene in the B10.D2-Hc0 H2d H2-T18c/oSnJ model. Irrespective of the genetic defect, adenoviral delivery of C5 improved insulin sensitivity in both C5cont and C5def mice, indicating an insulin-sensitizing function of C5.

Recent Advances in Allergy Research Using Humanized Mice

The prevalence rates of allergic diseases are increasing worldwide, particularly in industrial countries. To date, many mouse models have been generated for allergy research; studies conducted using these models have suggested the importance of cross-talk between immune cells and tissue-resident non-immune cells in the onset of allergic diseases. However, there are several differences between the immune systems of rodents and humans, and human studies are limited. Thus, mice reconstituted with human immune cells are a novel tool for the preclinical evaluation of the efficacy and safety of developing drugs. Genetic technologies for generating humanized mice have improved markedly in recent years. In this review, we will discuss recent progress in allergy research using humanized mice and introduce our recent humanized mouse model of airway inflammation in human immune cells.

Mouse NC/Jic strain provides novel insights into host genetic factors for malaria research

Malaria is caused by Plasmodium parasites and is one of the most life-threatening infectious diseases in humans. Infection can result in severe complications such as cerebral malaria, acute lung injury/acute respiratory distress syndrome, and acute renal injury. These complications are mainly caused by P. falciparum infection and are major causes of death associated with malaria. There are a few species of rodent-infective malaria parasites, and mice infected with such parasites are now widely used for screening candidate drugs and vaccines and for studying host immune responses and pathogenesis associated with disease-related complications. We found that mice of the NC/Jic strain infected with rodent malarial parasites exhibit distinctive disease-related complications such as cerebral malaria and nephrotic syndrome, in addition to a rapid increase in parasitemia. Here, we focus on the analysis of host genetic factors that affect malarial pathogenesis and describe the characteristic features, utility, and future prospects for exploitation of the NC/Jic strain as a novel mouse model for malaria research.

Expression and contribution to virulence of each polysaccharide capsule of Bacillus cereus strain G9241

Bacillus cereus strain G9241 was isolated from a patient with pneumonia who had an anthrax-like illness. Like Bacillus anthracis, the virulence of G9241 is dependent on two large plasmids. In G9241 those plasmids are pBCXO1 and pBC210. There is a multi-gene capsule locus on each of these virulence plasmids, and both capsules are produced by G9241 in vitro and in mice. The hasACB operon on pBCXO1 is responsible for production of a hyaluronic acid (HA) capsule. The locus on pBC210 encodes a putative tetrasaccharide (TS) capsule that assembles in a Wzy-dependent manner. We found that the pBC210 capsule locus is transcribed as two operons and identified the promoter regions responsible for transcription. We constructed isogenic mutants to assess the role of genes in the two TS capsule operons in production of the capsule. Spores of strains deficient in production of either the HA or TS capsule were inoculated subcutaneously or intranasally into A/J and C57BL/6 mice to determine the lethal dose 50% of each bacterial mutant by each route of infection. The loss of the HA capsule attenuated G9241 more than the loss of the TS capsule for both infection routes in both mouse strains. Overall, our data further characterize the unique TS capsule on pBC210 and demonstrate that the two capsules do not have the same impact on virulence of G9241.

Alternative Pathway Is Essential for Glomerular Complement Activation and Proteinuria in a Mouse Model of Membranous Nephropathy

Membranous nephropathy is an immune kidney disease caused by IgG antibodies that form glomerular subepithelial immune complexes. Proteinuria is mediated by complement activation, as a result of podocyte injury by C5b-9, but the role of specific complement pathways is not known. Autoantibodies-mediating primary membranous nephropathy are predominantly of IgG4 subclass, which cannot activate the classical pathway. Histologic evidence from kidney biopsies suggests that the lectin and the alternative pathways may be activated in membranous nephropathy, but the pathogenic relevance of these pathways remains unclear. In this study, we evaluated the role of the alternative pathway in a mouse model of membranous nephropathy. After inducing the formation of subepithelial immune complexes, we found similar glomerular IgG deposition in wild-type mice and in factor B-null mice, which lack a functional alternative pathway. Unlike wild-type mice, mice lacking factor B did not develop albuminuria nor exhibit glomerular deposition of C3c and C5b-9. Albuminuria was also reduced but not completely abolished in C5-deficient mice. Our results provide the first direct evidence that the alternative pathway is necessary for pathogenic complement activation by glomerular subepithelial immune complexes and is, therefore, a key mediator of proteinuria in experimental membranous nephropathy. This knowledge is important for the rational design of new therapies for membranous nephropathy.

Effect of complement component 5 polymorphisms on mastitis resistance in Egyptian buffalo and cattle

Mastitis is one of the costliest diseases affecting the world's dairy industry. The important contribution of complement Component 5 (C5) to phagocytosis, which plays a major role in the defence of the bovine mammary gland against infection, makes this component of innate immunity a potential contributor in defending udder against mastitis. The objectives of this study were to sequence and analyse the whole coding region of the C5 gene in Egyptian buffalo and cattle, to detect any nucleotide variations (polymorphisms) and to investigate their associations with milk somatic cell score (SCS) as an indicator of mastitis in dairy animals. We sequenced a buffalo C5 cDNA fragment of 5336 bp (KP221293) and a cattle C5 cDNA fragment of 5303 bp (KP221294), which included the whole coding region and 3-UTR. Buffalo and cattle C5 cDNA shared sequence identity of 99%. The predicted complement C5 proteins consist of 1677 amino acid residues in both animals, one amino acid less than in humans and three amino acids more than in mouse C5 protein. Comparing cDNA sequences of different animals revealed nine novel SNPs in buffalo and seven SNPs in cattle, with two of them being novel. The association analysis revealed that five SNPs in buffalo are highly associated with SCS; indicating the contribution of complement C5 variants in buffalo mastitis resistance. No significant associations were detected between C5 variants and SCS in cattle. This is the first report about C5 variants in buffalo and its association with SCS.

Individual variation is the key to the development of a vaccine against Staphylococcus aureus: a comparative study between mice lineages

Bacterial infections occur worldwide and are a major public health problem. Among pathogens, Staphylococcus aureus is the main causative agent of bacterial diseases in the world. This study aimed to evaluate which components of the immune system could act protectively against a S. aureus infection in intradermally immunized mice. C57BL/6 and A/j mice were immunized intradermally with S. aureus inactivated by heat and then challenged with viable strains in an air pouch model. At 6, 12, and 24 h after the challenge, euthanasia was performed, and the cellular profile of the inflammatory infiltrate, cytokines, and the bacterial load were evaluated in the air pouch lavages. Immunized mice demonstrated that the intradermal immunization with S. aureus promoted protection in C57BL/6 mice by reducing the bacterial, which was correlated with increased serum concentration of IgG antibodies (IgG1 and IgG2a) against S. aureus. The increase in IgG2a antibody levels was correlated with a decrease of bacterial load in intradermally immunized C57BL/6 mice, along with production of IL-17A at the inflammation site, as well as IgG1consumption. Similar results were not found in the A/j lineage. In conclusion, a vaccine against S. aureus should focus more on the individual characteristics of the host because it is a determinant factor for the success of the immunization.

A methodological review of induced animal models of autoimmune diseases

Autoimmune disorders are characterized by a loss of immune tolerance and consequent autoimmunity-mediated disease manifestation. Experimental models are invaluable research tools helping us to understand disease pathogenesis and to search for novel therapeutics. Animal models of autoimmune diseases consist of two groups, spontaneous and induced models. In this review article, we focus on the induced models of autoimmune diseases. Due to the complex nature of autoimmune disorders, many strategies have been applied for the induction of corresponding experimental models in animals like monkeys, rabbits, rats, and mice. Methodologically, these strategies can be categorized into three categories, namely immunization with autoantigen, transfer of autoimmunity, and induction by environmental factors. In this review article, we aim to provide a comprehensive overview of the field of induced experimental autoimmune diseases. On the one hand, we describe and summarize the different strategies used for induction of experimental autoimmune disease. On the other hand, we discuss how to select a strategy for modeling human disease, including the choice of an appropriate species and method for such an approach.

C5aR activation in the absence of C5a: A new disease mechanism of autoimmune hemolytic anemia in mice

IgG Fc receptors (FcγRs) and the C5a anaphylatoxin receptor (C5aR) were identified as key regulators of type II autoimmune injury in mice. However, and with respect to C5aR, the relative importance of C5a for IgG autoantibody-induced cellular destruction remained unclear. Using an experimental model of autoimmune hemolytic anemia (AIHA), we here report marked differences in the development of AIHA between mice lacking C5aR and C5-deficient (Hc⁰ ) strain, indicating a limited role of C5 in this type of C5aR-regulated disease. Ex-vivo-analyses of liver homogenates from anemic Hc⁰ mice demonstrate C5a-independent C5aR activation, upregulation of FcγR expression and amplification of erythrophagocytosis by macrophages. As assessed by pharmacological inhibition studies, targeting of C5aR, but not of C5, is effective in treating experimental AIHA. Collectively, these results define a previously unrecognized disease mechanism of C5aR activation in AIHA that does not necessarily involve C5 and C5a.

Sexual dimorphism of liver metastasis by murine pancreatic neuroendocrine tumors is affected by expression of complement C5

In a mouse model for neuroendocrine tumors of the pancreas (PanNETs), liver metastasis occurred at a higher frequency in males. Male mice also had higher serum and intratumoral levels of the innate immunity protein complement C5. In mice that lost the ability to express complement C5, there was a lower frequency of metastasis, and males no longer had a higher frequency of metastasis than females. Treatment with PMX53, a small molecule antagonist of C5aR1/CD88, the receptor for complement C5a, also reduced metastasis. Mice lacking a functional gene for complement C5 had smaller primary tumors, which were less invasive and lacked the CD68+ macrophages that have previously been associated with metastasis in this type of tumor. This is the first report of a gene that causes sexual dimorphism of metastasis in a mouse model. In the human disease, which also shows sexual dimorphism for metastasis, clinically advanced tumors expressed more complement C5 than less advanced tumors.

Immunization of mice with LRP4 induces myasthenia similar to MuSK-associated myasthenia gravis

Since the first report of experimental animal models of myasthenia gravis (MG) with autoantibodies against low-density lipoprotein receptor-related protein 4 (LRP4), there have not been any major reports replicating the pathogenicity of anti-LRP4 antibodies (Abs). Recent clinical studies have cast doubt on the specificity and pathogenicity of anti-LRP4 antibodies for MG, highlighting the need for further research. In this study, we purified antigens corresponding to the extracellular region of human LRP4 stably expressed with chaperones in 293 cells and used these antigens to immunize female A/J mice. Immunization with LRP4 protein caused mice to develop myasthenia having similar electrophysiological and histological features as are observed in MG patients with circulating Abs against muscle-specific kinase (MuSK). Our results clearly demonstrate that active immunization of mice with LRP4 proteins causes myasthenia similar to the MG induced by anti-MuSK Abs. Further experimental and clinical studies are required to prove the pathogenicity of anti-LRP4 Abs in MG patients.

Translating Mouse Models

Mice and humans branched from a common ancestor approximately 80 million years ago. Despite this, mice are routinely utilized as animal models of human disease and in drug development because they are inexpensive, easy to handle, and relatively straightforward to genetically manipulate. While this has led to breakthroughs in the understanding of genotype-phenotype relationships and in the identification of therapeutic targets, translation of beneficial responses to therapeutics from mice to humans has not always been successful. In a large part, these differences may be attributed to variations in the alignment of protein expression and signaling in the immune systems between mice and humans. Well-established inbred strains of "The Laboratory Mouse" vary in their immune response patterns as a result of genetic mutations and polymorphisms arising from intentional selection for research relevant traits, and even closely related substrains vary in their immune response patterns as a result of genetic mutations and polymorphisms arising from genetic drift. This article reviews some of the differences between the mouse and human immune system and between inbred mouse strains and shares examples of how these differences can impact the usefulness of mouse models of disease.

The roles of AtxA orthologs in virulence of anthrax-like Bacillus cereus G9241

AtxA is a critical transcriptional regulator of plasmid-encoded virulence genes in Bacillus anthracis. Bacillus cereus G9241, which caused an anthrax-like infection, has two virulence plasmids, pBCXO1 and pBC210, that each harbor toxin genes and a capsule locus. G9241 also produces two orthologs of AtxA: AtxA1, encoded on pBCXO1, and AtxA2, encoded on pBC210. The amino acid sequence of AtxA1 is identical to that of AtxA from B. anthracis, while the sequences of AtxA1 and AtxA2 are 79% identical and 91% similar to one another. We found by qRT-PCR that AtxA1 and AtxA2 function as positive regulators of toxin (AtxA1) and capsule operon (both) transcription in G9241 and that a ΔatxA1 mutant produced lower levels of the anthrax toxins and no hyaluronic acid capsule. Deletion of atxA1 or atxA2 decreased the virulence of spores administered intranasally or subcutaneously to C57BL/6 mice but not to A/J mice, and deletion of both genes rendered spores avirulent in A/J mice. In addition, unlike AtxA1, AtxA2 did not form stable homomultimers in vitro, although AtxA1 and AtxA2 formed heterodimers. Our data show that AtxA1 is the primary regulator of G9241 virulence factor expression and that AtxA1 and AtxA2 are both required for full virulence.

Experimentally-induced anti-myeloperoxidase vasculitis does not require properdin, MASP-2 or bone marrow-derived C5

Anti-neutrophil cytoplasmic antibody vasculitis is a systemic autoimmune disease with glomerulonephritis and pulmonary haemorrhage as major clinical manifestations. The name reflects the presence of autoantibodies to myeloperoxidase and proteinase-3, which bind to both neutrophils and monocytes. Evidence of the pathogenicity of these autoantibodies is provided by the observation that injection of anti-myeloperoxidase antibodies into mice causes a pauci-immune focal segmental necrotizing glomerulonephritis which is histologically similar to the changes seen on renal biopsy in patients. Previous studies in this model have implicated the alternative pathway of complement activation and the anaphylatoxin C5a. Despite this progress, the factors that initiate complement activation have not been defined. In addition, the relative importance of bone marrow-derived and circulating C5 is not known. This is of interest given the recently identified roles for complement within leukocytes. We induced anti-myeloperoxidase vasculitis in mice and confirmed a role for complement activation by demonstrating protection in C3-deficient mice. We showed that neither MASP-2- nor properdin-deficient mice were protected, suggesting that alternative pathway activation does not require properdin or the lectin pathway. We induced disease in bone marrow chimaeric mice and found that circulating and not bone marrow-derived C5 was required for disease. We have therefore excluded properdin and the lectin pathway as initiators of complement activation and this means that future work should be directed at other potential factors within diseased tissue. In addition, in view of our finding that circulating and not bone marrow-derived C5 mediates disease, therapies that decrease hepatic C5 secretion may be considered as an alternative to those that target C5 and C5a. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Deep genome sequencing and variation analysis of 13 inbred mouse strains defines candidate phenotypic alleles, private variation and homozygous truncating mutations

BACKGROUND

The Mouse Genomes Project is an ongoing collaborative effort to sequence the genomes of the common laboratory mouse strains. In 2011, the initial analysis of sequence variation across 17 strains found 56.7 M unique single nucleotide polymorphisms (SNPs) and 8.8 M indels. We carry out deep sequencing of 13 additional inbred strains (BUB/BnJ, C57BL/10J, C57BR/cdJ, C58/J, DBA/1J, I/LnJ, KK/HiJ, MOLF/EiJ, NZB/B1NJ, NZW/LacJ, RF/J, SEA/GnJ and ST/bJ), cataloguing molecular variation within and across the strains. These strains include important models for immune response, leukaemia, age-related hearing loss and rheumatoid arthritis. We now have several examples of fully sequenced closely related strains that are divergent for several disease phenotypes.

RESULTS

Approximately 27.4 M unique SNPs and 5 M indels are identified across these strains compared to the C57BL/6 J reference genome (GRCm38). The amount of variation found in the inbred laboratory mouse genome has increased to 71 M SNPs and 12 M indels. We investigate the genetic basis of highly penetrant cancer susceptibility in RF/J finding private novel missense mutations in DNA damage repair and highly cancer associated genes. We use two highly related strains (DBA/1J and DBA/2J) to investigate the genetic basis of collagen-induced arthritis susceptibility.

CONCLUSIONS

This paper significantly expands the catalogue of fully sequenced laboratory mouse strains and now contains several examples of highly genetically similar strains with divergent phenotypes. We show how studying private missense mutations can lead to insights into the genetic mechanism for a highly penetrant phenotype.

The complement component C5 promotes liver steatosis and inflammation in murine non-alcoholic liver disease model

Non-Alcoholic Fatty Liver Disease (NALD) is considering a hepatic manifestation of metabolic syndrome. Although the pathogenesis of NALD is not completely understood, insulin resistance and inflammatory cytokines are implicated. Considering that component C5 is a central mediator of inflammation, we investigated the role of C5 in the establishment of NALD. Eight to ten-week old B6 C5(+) and A/J C5(-) male mice were fed a high fat diet containing glucose (HFDG) for 6 and 10 weeks. We observed that B6 C5(+) mice HFDG-fed for 10 weeks developed hepatomegaly, triglycerides (TG) accumulation, steatosis and enhanced liver TNF-α, IL-6, IL-12p70 and IL-17 levels when compared to A/J C5(-) mice. Next, B6 C5(+) mice were compared with congenic B6 C5(-) mice. Again, B6 C5(+) HFDG-fed mice developed more steatosis, liver centro-lobular inflammation and presented higher levels of liver IL-1β, IL-12p70, IL-17 and TFG-β than B6 C5(-) mice under the same conditions. B6 C5(+) mice HFDG-fed also presented lower concentrations of serum albumin, serum cholesterol, blood leukocytes and liver NO production when compared with B6 C5(-) mice. We concluded that murine C5 contributes effectively to liver steatosis and inflammation in NALD pathogenesis. In addition, C5 is also important to control serum cholesterol and albumin levels in the C57BL/6 genetic background.

Target deletion of complement component 9 attenuates antibody-mediated hemolysis and lipopolysaccharide (LPS)-induced acute shock in mice

Terminal complement membrane attack complex (MAC) formation is induced initially by C5b, followed by the sequential condensation of the C6, C7, C8. Polymerization of C9 to the C5b-8 complex forms the C5b-9 (or MAC). The C5b-9 forms lytic or non lytic pores in the cell membrane destroys membrane integrity. The biological functionalities of MAC has been previously investigated by using either the mice deficient in C5 and C6, or MAC’s regulator CD59. However, there is no available C9 deficient mice (mC9^−/−) for directly dissecting the role of C5b-9 in the pathogenesis of human diseases. Further, since C5b-7 and C5b-8 complexes form non lytic pore, it may also plays biological functionality. To better understand the role of terminal complement cascades, here we report a successful generation of mC9^−/−. We demonstrated that lack of C9 attenuates anti-erythrocyte antibody-mediated hemolysis or LPS-induced acute shock. Further, the rescuing effect on the acute shock correlates with the less release of IL-1β in mC9^−/−, which is associated with suppression of MAC-mediated inflammasome activation in mC9^−/−. Taken together, these results not only confirm the critical role of C5b-9 in complement-mediated hemolysis and but also highlight the critical role of C5b-9 in inflammasome activation.

C1q acts in the tumour microenvironment as a cancer-promoting factor independently of complement activation

Complement C1q is the activator of the classical pathway. However, it is now recognized that C1q can exert functions unrelated to complement activation. Here we show that C1q, but not C4, is expressed in the stroma and vascular endothelium of several human malignant tumours. Compared with wild-type (WT) or C3- or C5-deficient mice, C1q-deficient (C1qa^−/−) mice bearing a syngeneic B16 melanoma exhibit a slower tumour growth and prolonged survival. This effect is not attributable to differences in the tumour-infiltrating immune cells. Tumours developing in WT mice display early deposition of C1q, higher vascular density and an increase in the number of lung metastases compared with C1qa^−/− mice. Bone marrow (BM) chimeras between C1qa^−/− and WT mice identify non-BM-derived cells as the main local source of C1q that can promote cancer cell adhesion, migration and proliferation. Together these findings support a role for locally synthesized C1q in promoting tumour growth.

C1q is known to initiate the activation of the complement classical pathway. Here, the authors show the C1q is expressed in the tumour microenvironment and can promote cancer cell migration and adhesion in a complement activation-independent manner.

Exploring multiple quantitative trait loci models of hepatic fibrosis in a mouse intercross

Most common diseases are attributed to multiple genetic variants, and the feasibility of identifying inherited risk factors is often restricted to the identification of alleles with high or intermediate effect sizes. In our previous studies, we identified single loci associated with hepatic fibrosis (Hfib1-Hfib4). Recent advances in analysis tools allowed us to model loci interactions for liver fibrosis. We analysed 322 F2 progeny from an intercross of the fibrosis-susceptible strain BALB/cJ and the resistant strain FVB/NJ. The mice were challenged with carbon tetrachloride (CCl4) for 6 weeks to induce chronic hepatic injury and fibrosis. Fibrosis progression was quantified by determining histological fibrosis stages and hepatic collagen contents. Phenotypic data were correlated to genome-wide markers to identify quantitative trait loci (QTL). Thirteen susceptibility loci were identified by single and composite interval mapping, and were included in the subsequent multiple QTL model (MQM) testing. Models provided evidence for susceptibility loci with strongest association to collagen contents (chromosomes 1, 2, 8 and 13) or fibrosis stages (chromosomes 1, 2, 12 and 14). These loci contained the known fibrosis risk genes Hc, Fasl and Foxa2 and were incorporated in a fibrosis network. Interestingly the hepatic fibrosis locus on chromosome 1 (Hfib5) connects both phenotype networks, strengthening its role as a potential modifier locus. Including multiple QTL mapping to association studies adds valuable information on gene-gene interactions in experimental crosses and human cohorts. This study presents an initial step towards a refined understanding of profibrogenic gene networks.

C57BL/6 and A/J Mice Have Different Inflammatory Response and Liver Lipid Profile in Experimental Alcoholic Liver Disease

Alcoholic liver disease (ALD) is an important worldwide public health issue characterized by liver steatosis, inflammation, necrosis, and apoptosis of hepatocytes with eventual development of fibrosis and cirrhosis. Comparison of murine models with different inflammatory responses for ALD is important for an evaluation of the importance of genetic background in the interpretation of ethanol-induced phenotypes. Here, we investigated the role of inflammation and genetic background for the establishment of ALD using two different mouse strains: C57BL/6 (B6) and A/J. B6 and A/J mice were treated with a high fat diet containing ethanol (HFDE) and compared to the controls for 10 weeks. Hepatomegaly and steatohepatitis were similar in B6 and A/J mice, but only A/J mice were resistant to weight gain. On the other hand, HFDE-fed B6 accumulated more triglycerides (TG) and cholesterol and presented more intense cellular infiltrate in the liver when compared to HFDM-fed mice. Liver inflammatory environment was distinct in these two mouse strains. While HFDE-fed B6 produced more liver IL-12, A/J mice increased the TNF-α production. We concluded that mouse genetic background could dictate the intensity of the HFDE-induced liver injury.

Hyporeactivity of Alveolar Macrophages and Higher Respiratory Cell Permissivity Characterize DBA/2J Mice Infected by Influenza A Virus

Influenza A virus remains a major public health problem. Mouse models have been widely used to study influenza infection in mammals. DBA/2J and C57BL/6J represent extremes in terms of susceptibility to influenza A infection among inbred laboratory mouse strains. Several studies focused specifically on the factors responsible for the susceptibility of DBA/2J or the resistance of C57BL/6J and resulted in impressive lists of candidate genes or factors over- or underexpressed in one of the strains. We adopted a different phenotypical approach to identify the critical steps of the infection process accounting for the differences between DBA/2J and C57BL/6J strains. We concluded that both a dysfunction of alveolar macrophages and an increased permissivity of respiratory cells rendered DBA/2J more susceptible to influenza infection.

Complement activation and expression during chronic relapsing experimental autoimmune encephalomyelitis in the Biozzi ABH mouse

Chronic relapsing experimental autoimmune encephalomyelitis (crEAE) in mice recapitulates many of the clinical and histopathological features of human multiple sclerosis (MS), making it a preferred model for the disease. In both, adaptive immunity and anti-myelin T cells responses are thought to be important, while in MS a role for innate immunity and complement has emerged. Here we sought to test whether complement is activated in crEAE and important for disease. Disease was induced in Biozzi ABH mice that were terminated at different stages of the disease to assess complement activation and local complement expression in the central nervous system. Complement activation products were abundant in all spinal cord areas examined in acute disease during relapse and in the progressive phase, but were absent in early disease remission, despite significant residual clinical disease. Local expression of C1q and C3 was increased at all stages of disease, while C9 expression was increased only in acute disease; expression of the complement regulators CD55, complement receptor 1-related gene/protein y (Crry) and CD59a was reduced at all stages of the disease compared to naive controls. These data show that complement is activated in the central nervous system in the model and suggest that it is a suitable candidate for exploring whether anti-complement agents might be of benefit in MS.