G. Pluhar - Academia.edu (original) (raw)

Papers by G. Pluhar

Journal of the American Veterinary Medical Association, Jan 15, 1994

Communications biology, 2018

Neurofibromatosis Type 1 (NF1) is a genetic disease caused by mutations in (). NF1 patients prese... more Neurofibromatosis Type 1 (NF1) is a genetic disease caused by mutations in (). NF1 patients present with a variety of clinical manifestations and are predisposed to cancer development. Many NF1 animal models have been developed, yet none display the spectrum of disease seen in patients and the translational impact of these models has been limited. We describe a minipig model that exhibits clinical hallmarks of NF1, including café au lait macules, neurofibromas, and optic pathway glioma. Spontaneous loss of heterozygosity is observed in this model, a phenomenon also described in NF1 patients. Oral administration of a mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor suppresses Ras signaling. To our knowledge, this model provides an unprecedented opportunity to study the complex biology and natural history of NF1 and could prove indispensable for development of imaging methods, biomarkers, and evaluation of safety and efficacy of NF1-targeted therapies.

Veterinary Pathology, 2021

Gliomas are relatively common tumors in aged dogs (especially brachycephalic breeds), and the dog... more Gliomas are relatively common tumors in aged dogs (especially brachycephalic breeds), and the dog is proving to be useful as a translational model for humans with brain tumors. Hitherto, there is relatively little prognostic data for canine gliomas and none on outcome related to specific histological features. Histologic sections of tumor biopsies from 33 dogs with glioma treated with surgical resection and immunotherapy and 21 whole brains obtained postmortem were reviewed. Tumors were diagnosed as astrocytic, oligodendroglial, or undefined glioma using Comparative Brain Tumor Consortium criteria. Putative features of malignancy were evaluated, namely, mitotic counts, glomeruloid vascularization, and necrosis. For biopsies, dogs with astrocytic tumors lived longer than those with oligodendroglial or undefined tumor types (median survival 743, 205, and 144 days, respectively). Dogs with low-grade gliomas lived longer than those with high-grade gliomas (median survival 734 and 194 da...

Neuro-Oncology, 2021

Cancer immunotherapy has revolutionized clinical management of malignancies by generating long-te... more Cancer immunotherapy has revolutionized clinical management of malignancies by generating long-term, durable control of tumors. Unfortunately, these therapies often cause serious immune-related adverse events. In addition, only a small percentage of solid tumors respond to these therapies and there is little efficacy in CNS tumors. Our research is focused on the CD200 immune checkpoint, which modulates the immune system through the inhibitory receptor (CD200R1) and activation receptors (CD200AR). We demonstrated that targeting the CD200AR with a checkpoint peptide ligand (CD200AR-L) activates the immune system and renders it impervious to the inhibitory effects of CD200. In a pre-clinical canine spontaneous high-grade glioma trial, CD200AR-L, with autologous tumor lysate vaccination, resulted in a 20% two-year progression-free survival; no toxicities or adverse effects were observed. We suggest this result was due to the ability of the CD200AR-L to modulate multiple immune checkpoin...

Canadian journal of veterinary research = Revue canadienne de recherche vétérinaire, 1991

Several monoclonal antibodies (McAbs) against pili of Bacteroides nodosus were examined to determ... more Several monoclonal antibodies (McAbs) against pili of Bacteroides nodosus were examined to determine their reactivity with 11 different serotypes. One McAb was identified by enzyme-linked immunosorbent assay (ELISA) analysis that bound to nine of the 11 serotypes and another that bound to the remaining two serotypes tested. In addition, some McAbs demonstrated specificity for a single serotype, while others displayed specificities for up to five other serotypes. Comparison of immunoblot analysis with the ELISA revealed that the former method was not as sensitive in that all McAbs positive by the ELISA, were not positive by immunoblot. Possible explanations of these findings are discussed. There appear to be several antigenic determinants on B. nodosus pili and considerable sharing of these determinants between pili types. The 11 serotypes analyzed by the McAbs in this report are representative of all 20 US serotypes as well as the A-set and D-set categories of Australia. Therefore, ...

Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2005

Neuro-Oncology, 2019

Given the modest effects current immune checkpoint-inhibitors have on patients with CNS tumors, w... more Given the modest effects current immune checkpoint-inhibitors have on patients with CNS tumors, we focused our studies on the novel CD200 immune checkpoint. The CD200 checkpoint suppresses the immune system through binding of the inhibitory CD200 protein to the inhibitory receptor (CD200R1) expressed on immune cells. In addition to CD200R1, the CD200 checkpoint includes activation receptors (CD200AR), which we are targeting with a peptide ligand (CD200AR-L) to reverse the inhibitory effects of the CD200 protein. We showed that spontaneous high-grade glioma dogs receiving a canine specific CD200AR-L in combination with autologous tumor lysate vaccine had an increased median overall survival of 9 months, compared to 6.3 months with lysate alone, resulting in an overall 36-month survival of 21%. However, we have a 45% event-free (progression-free) group of dogs that died of non-tumor related deaths with an extended median survival of 18 months. Six dogs remain on trial, 87% of the dogs...

Critical Reviews in Immunology, 2014

American Journal of Veterinary Research, 1996

To determine the effect of craniectomy and durotomy on intracranial pressure (ICP) in clinically ... more To determine the effect of craniectomy and durotomy on intracranial pressure (ICP) in clinically normal dogs. Two-part study (experiments A and B) involving craniectomy and durotomy, with and without treatments to lower ICP. Six (experiment A) and 7 (experiment B) healthy dogs. In experiment A, craniectomy was performed in combination with durotomy, diuretic administration, methylprednisolone sodium succinate administration, and hyperventilation, and effect of these manipulations on ICP was determined. In experiment B, dogs had only craniectomy and durotomy without associated ICP-lowering treatments. During both experiments, ICP was monitored throughout the surgical procedure with a fiber optic ICP monitoring device. Intracranial pressure decreased after the combination of craniectomy, durotomy, and other ICP-lowering treatments in dogs of experiment A. Similar magnitude of decrease in ICP was observed in dogs of experiment B after craniectomy and durotomy. Comparison of these exper...

Journal of the American Veterinary Medical Association, 1994

Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics, 2021

Synthetic grafting materials, such as calcium phosphates (hydroxyapatite, HA; tricalcium phosphat... more Synthetic grafting materials, such as calcium phosphates (hydroxyapatite, HA; tricalcium phosphate, TCP), polymers, or composites thereof, can be used as osteoconductive scaffolds and delivery vehicles for osteoinductive growth factors. Carrier materials must be engineered to deliver these factors in a controlled fashion at a rate and dose consistent with the biological need and responsiveness of the system to optimize bone formation and ingrowth. They should also simultaneously provide mechanical support and slowly resorb as new bone is formed. This investigation assessed the elution characteristics of BMP-7 (OP-1) from hollow calcium phosphate spheres of varying chemical composition (HA/beta-TCP) and porosity (dense/porous). The pharmacokinetics indicated a bimodal trend of protein release with protein elution peaking between fifteen and thirty minutes in solution (bolus release) and continuing through the eight-week time point (sustained release). Eluted OP-1 bioactivity was char...

This study compared the effect of augmentation of allograft–host bone junctions with recombinant ... more This study compared the effect of augmentation of allograft–host bone junctions with recombinant human bone morphogenetic protein‐2 (rhBMP‐2) on an absorbable collagen sponge (ACS), autogenous cancellous bone graft (CBG), and a collagen sponge alone in a canine intercalary femoral defect model repaired with a frozen allograft. Outcome assessment included serial radiographs, dual energy X‐ray absorptiometry scans, and gait analyses, and mechanical testing and histology of post‐mortem specimens. The distal junction healed more quickly and completely with rhBMP‐2 than ACS alone based on qualitative radiography and histologic evaluations. The primary tissue in the unhealed gaps in the ACS group was fibrous connective tissue. The proximal allograft–host bone junction had complete bone union in the three treatment groups. There was significantly greater new bone callus formation at both junctions with rhBMP‐2 than with CBG or ACS alone that resulted in increased bone density around the al...

Mesenteric portography, using a C-arm fluoroscope equipped with digital subtraction capability, w... more Mesenteric portography, using a C-arm fluoroscope equipped with digital subtraction capability, was performed intraoperatively to locate a single, intrahepatic portocaval shunt. An ultrasonic aspirator was used to isolate the shunt, which was ligated completely. Typical portal venous arborization was seen on postligation intraoperative mesenteric portography. Subtraction angiography used intraoperatively and dissection with the ultrasonic aspirator improve the surgeon's ability to localize and isolate intrahepatic portocaval shunts and can reduce surgical time. Film development and patient repositioning and transport, before and after shunt ligation, are not necessary when mesenteric portography is performed intraoperatively, using a C-arm fluoroscope and digital subtraction. Dissection around intrahepatic portocaval shunts is facilitated by the ultrasonic aspirator, which selectively fractures and suctions tissue from around the shunt. Hemorrhage is decreased, because hepatic d...

Clinical Cancer Research

Purpose: Advances in immunotherapy have revolutionized care for some patients with cancer. Howeve... more Purpose: Advances in immunotherapy have revolutionized care for some patients with cancer. However, current checkpoint inhibitors are associated with significant toxicity and yield poor responses for patients with central nervous system tumors, calling into question whether cancer immunotherapy can be applied to glioblastoma multiforme. We determined that targeting the CD200 activation receptors (CD200AR) of the CD200 checkpoint with a peptide inhibitor (CD200AR-L) overcomes tumor-induced immunosuppression. We have shown the clinical efficacy of the CD200AR-L in a trial in companion dogs with spontaneous high-grade glioma. Addition of the peptide to autologous tumor lysate vaccines significantly increased the median overall survival to 12.7 months relative to tumor lysate vaccines alone, 6.36 months. Experimental Design: This study was developed to elucidate the mechanism of the CD200ARs and develop a humanized peptide inhibitor. We developed macrophage cell lines with each of four CD200ARs knocked out to determine their binding specificity and functional response. Using proteomics, we developed humanized CD200AR-L to explore their effects on cytokine/chemokine response, dendritic cell maturation and CMV pp65 antigen response in human CD14+ cells. GMP-grade peptide was further validated for activity. Results: We demonstrated that the CD200AR-L specifically targets a CD200AR complex. Moreover, we developed and validated a humanized CD200AR-L for inducing chemokine response, stimulating immature dendritic cell differentiation and significantly enhanced an antigen-specific response, and determined that the use of the CD200AR-L downregulated the expression of CD200 inhibitory and PD-1 receptors. Conclusions: These results support consideration of a CD200AR-L as a novel platform for immunotherapy against multiple cancers including glioblastoma multiforme.

Purpose: Advances in immunotherapy have revolutionized care for some cancer patients. However, cu... more Purpose: Advances in immunotherapy have revolutionized care for some cancer patients. However, current checkpoint inhibitors are associated with significant toxicity and yield poor responses for patients with central nervous system tumors, calling into question whether cancer immunotherapy can be applied to glioblastoma multiforme. We determined that targeting the CD200 activation receptors (CD200AR) of the CD200 checkpoint with a peptide inhibitor overcomes tumor-induced immunosuppression. We have shown the clinical efficacy of the peptide inhibitor in a trial in companion dogs with spontaneous high-grade glioma; adding the peptide to autologous tumor lysate vaccines significantly increased overall survival relative to tumor lysate alone (median survival of 12.7 and 6.36 months, respectively). Experimental design: This study was developed to elucidate the mechanism of the CD200ARs and develop a humanized peptide inhibitor. We developed macrophage cell lines with each of four CD200A...