Evaluating the Safety and Efficacy of Capromorelin in Rhesus Macaques (Macaca mulatta).

Nonhuman primates used in biomedical research may experience clinically significant weight loss for a variety of reasons. Episodes of anorexia (complete loss of appetite) or hyporexia (decreased appetite) can result in significant weight loss, potentially altering animal welfare and scientific studies. The FDA has approved several appetite stimulants for use in domestic species, but currently none are approved for use in NHP. Treatment of inappetence and weight loss in NHP often relies on the extralabel use of these compounds. Capromorelin is a ghrelin receptor agonist. As a growth hormone secretagogue, capromorelin increases appetite, leading to weight gain. Studies in several species have shown a positive correlation between capromorelin administration and weight gain; in 2017, an oral solution of capromorelin received FDA approval for use in dogs. We tested this solution in healthy adult rhesus macaques (n = 3 males and 3 females) for its effects on body weight and insulin like growth factor-1 (IGF-1). A control group (n = 2 males and 2 females) was used for comparison. Treated macaques received a 3mg/kg oral dose daily for 7 d. Clinical signs were observed daily. Weights were collected before, during and at the end of treatment. Blood was drawn before, during and after treatment for measurement of IGF-1 levels and standard hematology and biochemistry parameters. Baseline-adjusted mean body weights and IGF-1 levels were significantly higher in treated as compared with control monkeys after 7 d of beginning treatment (body weight of 10.5±0.1kg (mean ± SEM) and 10.1±0.1kg, respectively; IGF-1 of 758±43ng/mL and 639±22ng/mL, respectively). Capromorelin administration was not associated with appreciable changes in hematologic and biochemical values in treated macaques. These findings suggest that capromorelin may be useful for treating inappetence and weight loss in NHP, and based on blood analysis, a 7-d course of treatment does not appear to cause acute toxicity.

Corticosteroids and methotrexate as adjuvants to costimulation blockade in non-human primate renal transplantation.

Belatacept, the CD28-B7 costimulation pathway inhibitor, has been approved as a calcineurin inhibitor (CNI) alternative in kidney transplantation. Although costimulation blockade (CoB) allows for CNI avoidance, it is associated with increased rates of early rejection, prompting a search for agents to pair with belatacept. Methotrexate (MTX) is an antimetabolite that has been found to be complimentary with abatacept, a lower affinity CD28-B7-specific analogue of belatacept, in the treatment of rheumatoid arthritis (RA). We examined whether this synergy would extend to prevention of kidney allograft rejection. Rhesus macaques underwent kidney transplantation treated with abatacept maintenance therapy with either a steroid taper, MTX, or both. The combination of abatacept maintenance with steroids prolonged graft survival compared to untreated historical controls and previous reports of abatacept monotherapy. The addition of MTX did not provide additional benefit. These data demonstrate that abatacept with adjuvant therapy may delay the onset of acute rejection, but fail to show synergy between abatacept and MTX beyond that of steroids. These findings indicate that MTX is unlikely to be a suitable adjuvant to CoB in kidney transplantation, but also suggest that with further modification, a CoB regimen used for advanced RA may suffice for RA patients requiring kidney transplantation.

Long-term survival of pig-to-rhesus macaque renal xenografts is dependent on CD4 T cell depletion.

The shortage of available organs remains the greatest barrier to expanding access to transplant. Despite advances in genetic editing and immunosuppression, survival in experimental models of kidney xenotransplant has generally been limited to <100 days. We found that pretransplant selection of recipients with low titers of anti-pig antibodies significantly improved survival in a pig-to-rhesus macaque kidney transplant model (6 days vs median survival time 235 days). Immunosuppression included transient pan-T cell depletion and an anti-CD154-based maintenance regimen. Selective depletion of CD4+ T cells but not CD8+ T cells resulted in long-term survival (median survival time >400 days vs 6 days). These studies suggested that CD4+ T cells may have a more prominent role in xenograft rejection compared with CD8+ T cells. Although animals that received selective depletion of CD8+ T cells showed signs of early cellular rejection (marked CD4+ infiltrates), animals receiving selective CD4+ depletion exhibited normal biopsy results until late, when signs of chronic antibody rejection were present. In vitro study results suggested that rhesus CD4+ T cells required the presence of SLA class II to mount an effective proliferative response. The combination of low pretransplant anti-pig antibody and CD4 depletion resulted in consistent, long-term xenograft survival.

A polyvalent inactivated rhinovirus vaccine is broadly immunogenic in rhesus macaques.

As the predominant aetiological agent of the common cold, human rhinovirus (HRV) is the leading cause of human infectious disease. Early studies showed that a monovalent formalin-inactivated HRV vaccine can be protective, and virus-neutralizing antibodies (nAb) correlated with protection. However, co-circulation of many HRV types discouraged further vaccine efforts. Here, we test the hypothesis that increasing virus input titres in polyvalent inactivated HRV vaccine may result in broad nAb responses. We show that serum nAb against many rhinovirus types can be induced by polyvalent, inactivated HRVs plus alhydrogel (alum) adjuvant. Using formulations up to 25-valent in mice and 50-valent in rhesus macaques, HRV vaccine immunogenicity was related to sufficient quantity of input antigens, and valency was not a major factor for potency or breadth of the response. Thus, we have generated a vaccine capable of inducing nAb responses to numerous and diverse HRV types.

Post-transplant lymphoproliferative disorder associated with immunosuppressive therapy for renal transplantation in rhesus macaques (Macaca mulatta).

Human post-transplant lymphoproliferative disorder (PTLD) is an abnormal lymphoid proliferation that arises in 1-12% of transplant recipients as a consequence of prolonged immunosuppression and Epstein-Barr viral infection (EBV). Nonhuman primates, primarily rhesus macaques (Macaca mulatta), have been used extensively in research models of solid organ transplantation, as the nonhuman primate immune system closely resembles that of the human. Lymphocryptovirus of rhesus monkeys has been characterized and shown to be very similar to EBV in humans in regards to its cellular tropism, host immune response, and ability to stimulate B lymphocyte proliferation and lymphomagenesis. Thus, it appears that the NHP may be an appropriate animal model for EBV-associated lymphoma development in humans. The clinical management of post-transplant nonhuman primates that are receiving multiple immunosuppressive agents can be complicated by the risk of PTLD and other opportunistic infections. We report 3 cases of PTLD in rhesus macaques that illustrate this risk potential in the setting of potent immunosuppressive therapies for solid organ transplantation.

Sleep is increased in mice with obesity induced by high-fat food.

Excessive daytime sleepiness has been associated with obesity in humans. However, experimental studies on sleep in obese animals are scarce and the results are not consistent. To test the hypothesis that obesity is associated with increased sleep, we examined the effects of obesity, induced by high-fat food, on sleep in mice. We first determined baseline sleep in adult C57BL/6 mice (6 months of age). In the following 6 weeks, the experimental mice (n = 12) were switched to high-fat food, in which fat provided 59% of calories, and the control mice (n = 11) were continuously fed with regular lab chows, in which fat provided 16% of calories. The body weights increased steadily in the high-fat group, but maintained constant in the controls. Wakefulness was reduced when assessed after 2, 4, and 6 weeks of high-fat feeding. Concurrently, there were large increases (about 80-100 min/day) in non-rapid eye movement sleep (NREMS). Rapid eye movement sleep (REMS) was not altered. The numbers of NREMS and REMS episodes were increased, whereas the duration of waking episodes was reduced, mainly during the dark period. These alterations in sleep were not observed in the controls. In the high-fat group, the increases of body weight, but not the amounts of energy intake, were negatively correlated with the change in the amounts of wakefulness and positively correlated with the change in the amounts of NREMS. These results indicate that the obese animals have increased sleep pressure and difficulties in maintaining wakefulness during the active phase.

Ibandronate for prevention of femoral head deformity after ischemic necrosis of the capital femoral epiphysis in immature pigs.

BACKGROUND: Femoral head deformity is the most serious sequela of ischemic necrosis of the immature femoral head. The purpose of this study was to determine if a highly potent antiresorptive agent, ibandronate, can inhibit bone resorption during the repair of the infarcted femoral head and thus alter the repair process. We hypothesized that preservation of the trabecular framework by inhibiting osteoclastic bone resorption would minimize the development of deformity in a piglet model of ischemic necrosis. The effect of ibandronate on long-bone growth was also assessed. METHODS: Ischemic necrosis of the right femoral head was produced in twenty-four piglets by placing a ligature tightly around the femoral neck. The animals were divided into three groups according to whether they received saline solution, prophylactic treatment, or post-ischemia treatment. The contralateral, untreated femoral heads from the animals that had received saline solution served as the normal control group. At eight weeks, the femoral heads were assessed for deformity with radiography and for trabecular bone indices with histomorphometry. Also, the length of femur from the untreated side was measured on the radiographs and compared among the groups. RESULTS: Radiographic assessment showed that the epiphyseal quotient, determined by dividing the maximum height of the osseous epiphysis by the maximum diameter, was better preserved in the prophylactic (p < 0.001) and post-ischemia (p = 0.02) treatment groups than in the group treated with saline solution. Histomorphometric assessment also showed that the trabecular bone indices were better preserved in the prophylactic and the post-ischemia treatment groups than in the group treated with saline solution (p < 0.01). The mean femoral length on the untreated side of the animals treated with ibandronate was reduced compared with the length on the untreated side of the animals that had received saline solution (p

Naltrexone, an opioid antagonist, facilitates reepithelialization of the cornea in diabetic rat.

Ulcers and erosions of the corneal epithelium, as well as delays in resurfacing of the cornea after wounding, are major causes of ocular morbidity and visual loss in diabetes. To study whether intervention by the opioid antagonist naltrexone (NTX; 30 mg/kg, twice daily) can restore reepithelialization in diabetic cornea, we induced diabetes in rats by intravenous injection of 65 mg/kg streptozotocin. After confirmation of diabetes, 5-mm-diameter epithelial defects that did not include the limbus were created by mechanical scraping of the cornea. At 4 and 8 weeks, corneal reepithelialization was markedly subnormal, with delays ranging from 11% to 17-fold in the diabetic animals compared with control counterparts. Rats that were diabetic for 8 weeks also had a significant decrease in the incidence of complete wound closure. At 4 and 8 weeks, diabetic animals that were receiving NTX had an acceleration in reepithelialization compared with diabetic animals that were receiving vehicle and even surpassed controls. DNA synthesis in the corneal epithelium of diabetic rats was decreased up to 90% of control levels, and NTX exposure of diabetic subjects elevated the labeling index by up to eightfold from diabetic animals that were receiving vehicle. Opioid growth factor and opioid growth factor receptor distribution were comparable in diabetic and control animals. These results indicate a delay in reepithelialization that is dependent on the duration of diabetes and that intervention of endogenous opioid-receptor interfacing with an opioid antagonist can facilitate the process of wound healing.