Vaccination with cancer- and HIV infection-associated endogenous retrotransposable elements is safe and immunogenic.

The expression of endogenous retrotransposable elements, including long interspersed nuclear element 1 (LINE-1 or L1) and human endogenous retrovirus, accompanies neoplastic transformation and infection with viruses such as HIV. The ability to engender immunity safely against such self-antigens would facilitate the development of novel vaccines and immunotherapies. In this article, we address the safety and immunogenicity of vaccination with these elements. We used immunohistochemical analysis and literature precedent to identify potential off-target tissues in humans and establish their translatability in preclinical species to guide safety assessments. Immunization of mice with murine L1 open reading frame 2 induced strong CD8 T cell responses without detectable tissue damage. Similarly, immunization of rhesus macaques with human LINE-1 open reading frame 2 (96% identity with macaque), as well as simian endogenous retrovirus-K Gag and Env, induced polyfunctional T cell responses to all Ags, and Ab responses to simian endogenous retrovirus-K Env. There were no adverse safety or pathological findings related to vaccination. These studies provide the first evidence, to our knowledge, that immune responses can be induced safely against this class of self-antigens and pave the way for investigation of them as HIV- or tumor-associated targets.

Proliferative and non-proliferative lesions of the rat and mouse soft tissue, skeletal muscle and mesothelium.

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in the soft tissues including skeletal muscle as well as the mesothelium of rats and mice. The standardized nomenclature of lesions presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as those induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for lesions in soft tissues, skeletal muscle and mesothelium in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists. (DOI: 10.1293/tox.26.1S; J Toxicol Pathol 2013; 26: 1S-26S).

International consortium for innovation and quality: An industry perspective on the nonclinical and early clinical development of intravitreal drugs.

The eye, which is under constant exposure to environmental pathogens, has evolved various anatomic and immunological barriers critical to the protection of tissues lacking regenerative capacity, and the maintenance of a clear optic pathway essential to vision. By bypassing the ocular barriers, intravitreal (IVT) injection has become the mainstay for the delivery of drugs to treat conditions that affect the back of the eye. Both small molecules and biotherapeutics have been successfully administered intravitreally, and several drugs have been approved for the treatment of (wet) age-related macular degeneration and diabetic macular edema. However, IVT injection is an invasive procedure, which requires sufficient technical expertise from the healthcare professional administering the drug. Potential side effects include bleeding, retinal tear, cataracts, infection, uveitis, loss of vision, and increased ocular pressure. Pharmaceutical companies often differ in their drug development plan, including drug administration techniques, collection of ocular tissues and fluids, ophthalmology monitoring, and overall conduct of nonclinical and clinical studies. The present effort, under the aegis of the Innovation & Quality Ophthalmic Working Group, aims at understanding these differences, identifying pros and cons of the various approaches, determining the gaps in knowledge, and suggesting feasible good practices for nonclinical and early clinical IVT drug development.

The development of subcutaneous sarcomas in rodents exposed to peroxisome proliferators agonists: hypothetical mechanisms of action and de-risking attitude.

Peroxisome proliferator-activated receptors (PPARs) represent therapeutic targets for the management of type 2 diabetes mellitus and dyslipidemia. Rodent carcinogenicity studies have revealed a link between γ and dual γ/α PPAR agonist treatment and the increased incidence of subcutaneous (SC) liposarcomas/fibrosarcomas or hemangiosarcomas, but very little has been reported for potent and selective PPARα agonists. We present a mode of action framework for the development of SC mesenchymal tumors in rodents given PPAR agonists. (1) Tumor promotion results from pharmacologically mediated recruitment (proliferation and differentiation), thermogenesis and adipogenesis of stromovascular cells, and subsequent generation of oxidative free radicals. (2) Tumor initiation consists of chemotype-driven mitochondrial dysfunction causing uncontrolled oxidative stress and permanent DNA damage. Promotion is characterized by enhanced adipogenesis in the SC adipose tissue, where the baseline PPARγ expression and responsiveness to PPARγ ligands is the highest, and by thermogenesis through expression of the uncoupling protein 1 (UCP-1) and the PPARγ co-activator 1 α (PGC-1α), two factors more highly expressed in brown versus white adipose tissue. Initiation is supported by the demonstration of mitochondrial uncoupling and OXPHOS Complexes dysfunction (Complexes III, IV and V) by compounds associated with increased incidences of sarcomas (muraglitazar and troglitazone), but not others lacking malignant tumor effects (pioglitazone, rosiglitazone).

Coordinated expression of multidrug resistance-associated proteins (Mrps) in mouse liver during toxicant-induced injury.

Following acute chemical injury, hepatocytes are generally more resistant to toxicant re-exposure. Alterations in expression of hepatobiliary transport systems may contribute to this resistance by preventing accumulation of potentially toxic chemicals. Previous data demonstrate the concomitant reduction of uptake transporter and induction of efflux transporter mRNA during chemical liver injury. The present study further characterizes the expression of multidrug resistance-associated proteins 1-4 (Mrp1-4), breast cancer resistance protein (Bcrp) and sodium-taurocholate co-transporting polypeptide (Ntcp) in mouse liver following administration of the hepatotoxicants acetaminophen (APAP) and carbon tetrachloride (CCl4). Mice received hepatotoxic doses of APAP (400 mg/kg), CCl4 (10 or 25 microl/kg), or vehicle, ip. Livers were collected at 6, 24, and 48 h for Western blot quantification and immunofluorescence analysis. Protein expression of Bcrp was unchanged with treatment. Ntcp levels were preserved in APAP-exposed livers and reduced to 30-50% of control after CCl4. Conversely, Mrp1-4 expression was differentially up-regulated. CCl4 increased Mrp1 (3.5-fold), Mrp2 (1.4-fold), and Mrp4 (26-fold) while reducing Mrp3 levels to 20% of control. Administration of APAP enhanced expression of Mrp2 (1.6-fold), Mrp3 (3.5-fold), and Mrp4 (16-fold). Immunostaining of liver sections obtained 48 h after hepatotoxicant treatment confirmed expression patterns of a subset of transporters (Bcrp, Ntcp, Mrp3, and Mrp4). Double immunofluorescence imaging demonstrated the simultaneous down-regulation of Ntcp and up-regulation of Mrp4 in hepatocytes adjacent to the central vein after CCl4. Altered expression of transporters may reduce the overall chemical burden of an injured liver during recovery and contribute to the resistance of hepatocytes to subsequent toxicant exposure.

Induction of hepatobiliary efflux transporters in acetaminophen-induced acute liver failure cases.

Alterations in transporter expression may represent a compensatory mechanism of damaged hepatocytes to reduce accumulation of potentially toxic compounds. The present study was conducted to investigate the expression of hepatobiliary efflux transporters in livers from patients after toxic acetaminophen (APAP) ingestion, with livers from patients with primary biliary cirrhosis (PBC) serving as positive controls. mRNA and protein expression of multidrug resistance-associated protein (MRP) 1-6, multidrug resistance protein (MDR) 1-3/P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP) in normal (n = 6), APAP overdose (n = 5), and PBC (n = 6) human liver samples were determined by branched DNA and Western blot analysis, respectively. Double immunohistochemical staining of P-gp and proliferating cell nuclear antigen (PCNA), a marker of proliferation, was performed on paraffin-embedded tissue sections. Compared with normal liver specimens, MRP1 and MRP4 mRNA levels were elevated after APAP overdose and in PBC. Up-regulation of MRP5, MDR1, and BCRP mRNA occurred in PBC livers. Protein levels of MRP4, MRP5, BCRP, and P-gp were increased in both disease states, with MRP1 and MRP3 protein also being induced in PBC. Increased P-gp protein was confirmed immunohistochemically and was found to localize to areas of PCNA-positive hepatocytes, which were detected in APAP overdose and PBC livers. The findings from this study demonstrate that hepatic efflux transporter expression is up-regulated in cases of APAP-induced liver failure and PBC. This adaptation may aid in reducing retention of byproducts of cellular injury and bile constituents within hepatocytes. The close proximity of P-gp and PCNA-positive hepatocytes during liver injury suggests that along with cell regeneration, increased efflux transporter expression is a critical response to hepatic damage to protect the liver from additional insult.

Using laser scanning cytometry to measure PPAR-mediated peroxisome proliferation and beta oxidation.

Laser scanning cytometry (LSC) is a new technology that combines the properties and advantages of flow cytometry (FC) and immunohistochemistry (IHC), thus providing qualitative and quantitative information on protein expression with the additional perspective provided by cell and tissue localization. Formalin-fixed, paraffin embedded liver sections from rats exposed to a Peroxisome Proliferator Activated Receptor (PPAR) agonist were stained with antibodies against peroxisomal targeting signal-1 (PTS-1) (a highly conserved tripeptide contained within all peroxisomal enzymes), Acyl CoA oxidase (AOX) (the rate limiting enzyme of peroxisomal beta oxidation), and catalase (an inducible peroxisomal antioxidant enzyme) to evaluate peroxisomal beta oxidation, oxidative stress, and peroxisome proliferation. The LSC showed increased AOX, catalase, and PTS-1 expression in centrilobular hepatocytes that correlated favorably with the microscopic observation of centrilobular hepatocellular hypertrophy and with the palmitoyl CoA biochemical assay for peroxisomal beta oxidation, and provided additional morphologic information about peroxisome proliferation and tissue patterns of activation. Therefore, the LSC provides qualitative and quantitative evaluation of peroxisome activity with similar sensitivity but higher throughput than the traditional biochemical methods. The additional benefits of the LSC include the direct correlation between histopathologic observations and peroxisomal alterations and the potential utilization of archived formalin-fixed tissues from a variety of organs and species.