Resistance of athymic nude mice to experimental cutaneous Bacillus anthracis infection

Reprofiling synthetic glucocorticoid-induced leucine zipper fusion peptide as a novel and effective hair growth promoter

Hair is a biofilament with unique multi-dimensional values. In human, in addition to physiologic impacts, hair loss and hair related disorders can affect characteristic features, emotions, and social behaviors. Despite significant advancement, there is a dire need to explore alternative novel therapies with higher efficacy, less side effects and lower cost to promote hair growth to treat hair deficiency. Glucocorticoid-induced leucine zipper (GILZ) is a protein rapidly induced by glucocorticoids. Studies from our group and many others have suggested that a synthetic form of GILZ, TAT-GILZ, a fusion peptide of trans-activator of transcription and GILZ, can function as a potent regulator of inflammatory responses, re-establishing and maintaining the homeostasis. In this study, we investigate whether TAT-GILZ could promote and contribute to hair growth. For our pre-clinical model, we used 9-12 week-old male BALB/c and nude (athymic, nu/J) mice. We applied TAT-GILZ and/or TAT (vehicle) intradermally to depilated/hairless mice. Direct observation, histological examination, and Immunofluorescence imaging were used to assess the effects and compare different treatments. In addition, we tested two current treatment for hair loss/growth, finasteride and minoxidil, for optimal evaluation of TAT-GILZ in a comparative fashion. Our results showed, for the first time, that synthetic TAT-GILZ peptide accelerated hair growth on depilated dorsal skin of BALB/c and induced hair on the skin of athymic mice where hair growth was not expected. In addition, TAT-GILZ was able to enhance hair follicle stem cells and re-established the homeostasis by increasing counter inflammatory signals including higher regulatory T cells and glucocorticoid receptors. In conclusion, our novel findings suggest that reprofiling synthetic TAT-GILZ peptide could promote hair growth by increasing hair follicle stem cells and re-establishing homeostasis.

Examination of Horizontal Transmission of Nippostrongylus brasiliensis in Mice to Assess Biosecurity Risks

Mice are commonly infected with Nippostrongylus brasiliensis (Nb) to study their immune responses. However, biosecurity measures have not been established for housing Nb-infected mice and rats. Transmission reportedly does not occur when infected mice are cohoused with naive mice. To test this, we inoculated female NOD. Cg-Prkdcscid Il2rgtm1Wjl /Sz(NSG;n = 12) and C57BL/6J (B6;n = 12) mice with 750 Nb L₃ larvae. These mice were then cohoused with naïve NSG ( n = 24) and B6 ( n = 24) mice (1 infected and 2 naïve mice per cage (24 cages) for 28 d in static microisolation cages that were changed every 14 d. We also did several studies to determine the conditions that favor horizontal transmission. First, we assessed in vitro development to the L₃ stage of Nb egg-containing fecal pellets maintained under 4 environmental conditions (dry, moist, soiled bedding, and control). Second, we assessed infection of naïve NSG mice ( n = 9) housed in microisolation cages that contained soiled bedding spiked with infective L₃ larvae (10,000/cage). Third, we gavaged NSG mice ( n = 3) with Nb eggs to model the potential for infection after coprophagy. We found that naïve NSG (9 of 24) and B6 (10 of 24) mice cohoused with an infected cagemate passed Nb eggs in feces as early as 1 d after cohousing and intermittently thereafter for varying periods. This shedding was presumably the result of coprophagy because adult worms were not detected in the shedding mice at euthanasia. Although eggs developed in vitro into L₃ larvae under moist and control environmental conditions, none of the NSG mice housed in cages with L₃ -spiked bedding or gavaged with eggs became infected with Nb. These findings indicate that infectious horizontal transmission does not occur when mice are housed with Nb-shedding cage mates in static microisolation cages with a 14-d cage-changing interval. Results from this study can be used to inform biosecurity practices when working with Nb-infected mice.

Human Variation in DNA Repair, Immune Function, and Cancer Risk

DNA damage constantly threatens genome integrity, and DNA repair deficiency is associated with increased cancer risk. An intuitive and widely accepted explanation for this relationship is that unrepaired DNA damage leads to carcinogenesis due to the accumulation of mutations in somatic cells. But DNA repair also plays key roles in the function of immune cells, and immunodeficiency is an important risk factor for many cancers. Thus, it is possible that emerging links between inter-individual variation in DNA repair capacity and cancer risk are driven, at least in part, by variation in immune function, but this idea is underexplored. In this review we present an overview of the current understanding of the links between cancer risk and both inter-individual variation in DNA repair capacity and inter-individual variation in immune function. We discuss factors that play a role in both types of variability, including age, lifestyle, and environmental exposures. In conclusion, we propose a research paradigm that incorporates functional studies of both genome integrity and the immune system to predict cancer risk and lay the groundwork for personalized prevention.

Biomarkers and 3D models predicting response to immune checkpoint blockade in head and neck cancer (Review)

Immunotherapy has evolved into a powerful tool in the fight against a number of types of cancer, including head and neck squamous cell carcinomas (HNSCC). Although checkpoint inhibition (CPI) has definitely enriched the treatment options for advanced stage HNSCC during the past decade, the percentage of patients responding to treatment is widely varying between 14-32% in second-line setting in recurrent or metastatic HNSCC with a sporadic durability. Clinical response and, consecutively, treatment success remain unpredictable in most of the cases. One potential factor is the expression of target molecules of the tumor allowing cancer cells to acquire therapy resistance mechanisms. Accordingly, analyzing and modeling the complexity of the tumor microenvironment (TME) is key to i) stratify subgroups of patients most likely to respond to CPI and ii) to define new combinatorial treatment regimens. Particularly in a heterogeneous disease such as HNSCC, thoroughly studying the interactions and crosstalking between tumor and TME cells is one of the biggest challenges. Sophisticated 3D models are therefore urgently needed to be able to validate such basic science hypotheses and to test novel immuno-oncologic treatment regimens in consideration of the individual biology of each tumor. The present review will first summarize recent findings on immunotherapy, predictive biomarkers, the role of the TME and signaling cascades eliciting during CPI. Second, it will highlight the significance of current promising approaches to establish HNSCC 3D models for new immunotherapies. The results are encouraging and indicate that data obtained from patient-specific tumors in a dish might be finally translated into personalized immuno-oncology.

Immune-relevant aspects of murine models of head and neck cancer

Head and neck cancers (HNCs) cause significant mortality and morbidity. There have been few advances in therapeutic management of HNC in the past 4 to 5 decades, which support the need for studies focusing on HNC biology. In recent years, increased recognition of the relevance of the host response in cancer progression has led to novel therapeutic strategies and putative biomarkers of tumor aggressiveness. However, tumor-immune interactions are highly complex and vary with cancer type. Pre-clinical, in vivo models represent an important and necessary step in understanding biological processes involved in development, progression and treatment of HNC. Rodents (mice, rats, hamsters) are the most frequently used animal models in HNC research. The relevance and utility of information generated by studies in murine models is unquestionable, but it is also limited in application to tumor-immune interactions. In this review, we present information regarding the immune-specific characteristics of the murine models most commonly used in HNC research, including immunocompromised and immunocompetent animals. The particular characteristics of xenograft, chemically induced, syngeneic, transgenic, and humanized models are discussed in order to provide context and insight for researchers interested in the in vivo study of tumor-immune interactions in HNC.

Local inflammation exacerbates the severity of Staphylococcus aureus skin infection

Staphylococcus aureus is the leading cause of skin infections. In a mouse model of S. aureus skin infection, we found that lesion size did not correlate with bacterial burden. Athymic nude mice had smaller skin lesions that contained lower levels of myeloperoxidase, IL-17A, and CXCL1, compared with wild type mice, although there was no difference in bacterial burden. T cell deficiency did not explain the difference in lesion size, because TCR βδ (-/-) mice did not have smaller lesions, and adoptive transfer of congenic T cells into athymic nude mice prior to infection did not alter lesion size. The differences observed were specific to the skin, because mortality in a pneumonia model was not different between wild type and athymic nude mice. Thus, the clinical severity of S. aureus skin infection is driven by the inflammatory response to the bacteria, rather than bacterial burden, in a T cell independent manner.

Characterization of locomotor activity circadian rhythms in athymic nude mice

Background

The relation between circadian dysregulation and cancer incidence and progression has become a topic of major interest over the last decade. Also, circadian timing has gained attention regarding the use of chronopharmacology-based therapeutics. Given its lack of functional T lymphocytes, due to a failure in thymus development, mice carrying the Foxn1^(Δ/Δ) mutation (nude mice) have been traditionally used in studies including implantation of xenogeneic tumors. Since the immune system is able to modulate the circadian clock, we investigated if there were alterations in the circadian system of the athymic mutant mice.

Methods

General activity circadian rhythms in 2–4 month-old Foxn1^(Δ/Δ) mice (from Swiss Webster background) and their corresponding wild type (WT) controls was recorded. The response of the circadian system to different manipulations (constant darkness, light pulses and shifts in the light–dark schedule) was analyzed.

Results

Free-running periods of athymic mice and their wild type counterpart were 23.86 ± 0.03 and 23.88 ± 0.05 hours, respectively. Both strains showed similar phase delays in response to 10 or 120 minutes light pulses applied in the early subjective night and did not differ in the number of c-Fos-expressing cells in the suprachiasmatic nuclei, after a light pulse at circadian time (CT) 15. Similarly, the two groups showed no significant difference in the time needed for resynchronization after 6-hour delays or advances in the light–dark schedule. The proportion of diurnal activity, phase-angle with the zeitgeber, subjective night duration and other activity patterns were similar between the groups.

Conclusions

Since athymic Foxn1^(Δ/Δ) mice presented no differences with the WT controls in the response of the circadian system to the experimental manipulations performed in this work, we conclude that they represent a good model in studies that combine xenograft implants with either alteration of the circadian schedules or chronopharmacological approaches to therapeutics.

Updating perspectives on the initiation of Bacillus anthracis growth and dissemination through its host

Since 1957, it has been proposed that the dissemination of inhalational anthrax required spores to be transported from the lumena of the lungs into the lymphatic system. In 2002, this idea was expanded to state that alveolar macrophages act as a "Trojan horse" capable of transporting spores across the lung epithelium into draining mediastinal lymph nodes. Since then, the Trojan horse model of dissemination has become the most widely cited model of inhalational infection as well as the focus of the majority of studies aiming to understand events initiating inhalational anthrax infections. However, recent observations derived from animal models of Bacillus anthracis infection are inconsistent with aspects of the Trojan horse model and imply that bacterial dissemination patterns during inhalational infection may be more similar to the cutaneous and gastrointestinal forms than previously thought. In light of these studies, it is of significant importance to reassess the mechanisms of inhalational anthrax dissemination, since it is this form of anthrax that is most lethal and of greatest concern when B. anthracis is weaponized. Here we propose a new "jailbreak" model of B. anthracis dissemination which applies to the dissemination of all common manifestations of the disease anthrax. The proposed model impacts the field by deemphasizing the role of host cells as conduits for dissemination and increasing the role of phagocytes as central players in innate defenses, while moving the focus toward interactions between B. anthracis and lymphoid and epithelial tissues.

Bacillus anthracis HssRS signalling to HrtAB regulates haem resistance during infection

Bacillus anthracis proliferates to high levels within vertebrate tissues during the pathogenesis of anthrax. This growth is facilitated by the acquisition of nutrient iron from host haem. However, haem acquisition can lead to the accumulation of toxic amounts of haem within B. anthracis. Here, we show that B. anthracis resists haem toxicity by sensing haem through the HssRS two-component system, which regulates expression of the haem-detoxifying transporter HrtAB. In addition, we demonstrate that B. anthracis exhibits elevated HssRS function compared with its evolutionary relative Staphylococcus aureus. Elevated haem sensing is likely required by B. anthracis due to the significant haem sensitivity exhibited by members of the genus Bacilli. We also demonstrate that B. anthracis depends on conserved residues within the previously uncharacterized sensing domain of the histidine kinase HssS for HssS function. Finally, we show that the haem- and HssRS-regulated hrtAB promoter is activated in a murine model of anthrax. These results demonstrate the evolutionary conservation of haem sensing among multiple Gram-positive bacteria and begin to provide a mechanistic explanation for the haem resistance of B. anthracis. Further, these data suggest that haem stress is experienced by bacterial pathogens during infection.

Diabetic rats and mice are resistant to porcine and human insulin: flawed experimental models for testing islet xenografts

BACKGROUND

Islet transplantation is potentially a promising therapy for the restoration of carbohydrate control to diabetic patients. However, the global application of islet transplantation requires a ubiquitous source of beta cells. The xenotransplantation of porcine islets would provide such a source. Success in porcine islet xenografting has been achieved in diabetic primates. However, there are few reports of reversal of diabetes with porcine islet xenografts in rodent models of diabetes, relative to the number of successful rodent experiments performed as allografts. Here we report for the first time the inability of porcine (and human) insulin to control blood glucose levels in diabetic rodents determined by a series of dose escalating studies.

METHODS

Insulin was administered intravenously to streptozotocin induced diabetic Lewis rats, Balb/c and athymic Balb/c mice (n = 5 per group) at the following doses: Group I "physiological dose" (pd) of 0.16 U/kg for a total dose of 40 mU to a 250 g rat. Group II received 0.64 U/kg (4xpd), group III 1.6 U/kg (10xpd) and group IV 6.4 U/kg (40xpd). Blood glucose levels were monitored in each animal at seven time points: 0 (pre-injection), 10 min, 20 min, 30 min, 45 min, 1 h, 1.5 h, 2 h and 3 h post-injection. Serum insulin levels were also determined.

RESULTS

Diabetic Lewis rats achieved a maximum reduction in blood glucose from 22.1 +/- 1.8mmol/l to 8.0 +/- 3.1 mmol/l (a 63.7% reduction), 90 minutes post-injection of 6.4 U/kg dose of porcine insulin (40xpd). Human insulin was less effective at reducing blood glucose levels in rats than porcine insulin (P < 0.001). Porcine insulin reduced blood glucose levels in Balb/c mice from a mean of 18.2 +/- 2.1 mmol/l to a hypoglycemic minimum of 1.26 +/- 0.18 mmol/l a reduction of 93.0%, 60 min post-injection of the maximum dose of 6.4 U/kg. Balb/c mice were significantly more responsive to porcine insulin than Lewis rats at doses of 0.64 U/kg (P < 0.001), 1.6 U/kg (P < 0.05) and 6.4 U/kg (P < 0.001). Athymic Balb/c nude mice reached a maximum reduction in blood glucose from 21.6 +/- 1.8 mmol/l to 3.6 +/- 0.9 mmol/l (a 83.4% reduction) 120 min post-injection at a dose of 6.4 U/kg. Overall, athymic Balb/c nude mice were more resistant to porcine insulin than immunocompetent Balb/c mice at doses of 0.64 U/kg (P < 0.001), 1.6 U/kg (P < 0.001) and 6.4 U/kg (P < 0.05). Insulin diluent alone marginally increased blood glucose levels in all animals tested.

CONCLUSIONS

Our results suggest that restoration of normoglycemia in diabetic rodents is not ideal for testing porcine islets xenografts since the reversals of diabetes in these species requires 20 to 40 times the dose of porcine insulin used in humans.