A Naturally Transmitted Epitheliotropic Polyomavirus Pathogenic in Immunodeficient Rats: Characterization, Transmission, and Preliminary Epidemiologic Studies

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

Comparison of Genetically Engineered Immunodeficient Animal Models for Nonclinical Testing of Stem Cell Therapies

For the recovery or replacement of dysfunctional cells and tissue—the goal of stem cell research—successful engraftment of transplanted cells and tissues are essential events. The event is largely dependent on the immune rejection of the recipient; therefore, the immunogenic evaluation of candidate cells or tissues in immunodeficient animals is important. Understanding the immunodeficient system can provide insights into the generation and use of immunodeficient animal models, presenting a unique system to explore the capabilities of the innate immune system. In this review, we summarize various immunodeficient animal model systems with different target genes as valuable tools for biomedical research. There have been numerous immunodeficient models developed by different gene defects, resulting in many different features in phenotype. More important, mice, rats, and other large animals exhibit very different immunological and physiological features in tissue and organs, including genetic background and a representation of human disease conditions. Therefore, the findings from this review may guide researchers to select the most appropriate immunodeficient strain, target gene, and animal species based on the research type, mutant gene effects, and similarity to human immunological features for stem cell research.

Murine and related chapparvoviruses are nephro-tropic and produce novel accessory proteins in infected kidneys

Mouse kidney parvovirus (MKPV) is a member of the provisional genus Chapparvovirus that causes renal disease in immune-compromised mice, with a disease course reminiscent of polyomavirus-associated nephropathy in immune-suppressed kidney transplant patients. Here we map four major MKPV transcripts, created by alternative splicing, to a common initiator region, and use mass spectrometry to identify “p10” and “p15” as novel chapparvovirus accessory proteins produced in MKPV-infected kidneys. p15 and the splicing-dependent putative accessory protein NS2 are conserved in all near-complete amniote chapparvovirus genomes currently available (from mammals, birds and a reptile). In contrast, p10 may be encoded only by viruses with >60% amino acid identity to MKPV. We show that MKPV is kidney-tropic and that the bat chapparvovirus DrPV-1 and a non-human primate chapparvovirus, CKPV, are also found in the kidneys of their hosts. We propose, therefore, that many mammal chapparvoviruses are likely to be nephrotropic.

Parvoviruses are small, genetically simple single-strand DNA viruses that remain viable outside their hosts for very long periods of time. They cause disease in several domesticated species and in humans. Mouse kidney parvovirus (MKPV) is a causative agent of kidney failure in immune-compromised mice and is the only member of the provisional Chapparvovirus genus for which the complete genome including telomeres is known. Here, we show that MKPV propagates almost exclusively in the kidneys of mice infected naturally, wherein it produces novel accessory proteins whose coding regions are conserved in amniote-associated chapparvovirus sequences. We assemble a closely related complete viral genome present in DNA extracted from the kidney of a wild Cebus imitator monkey, and show that another related chapparvovirus is preferentially found in kidneys of the vampire bat Desmodus rotundus. We conclude that many mammal-hosted chapparvovirus are adapted to the kidney niche and may therefore cause disease following kidney stress in multiple species.

Viral Disease

This chapter discusses infections of rats with viruses in the following 14 virus families: Adenoviridae, Arenaviridae, Coronaviridae, Flaviviridae, Hantaviridae, Hepeviridae, Herpesviridae, Paramyxoviridae, Parvoviridae, Picornaviridae, Pneumoviridae, Polyomaviridae, Poxviridae, and Reoviridae . Serological surveys indicate that parvoviruses, coronaviruses, cardioviruses, and pneumoviruses are the most prevalent in laboratory rats. A new polyomavirus and a new cardiovirus that cause disease in laboratory rats are described. Metagenomic analyses of feces or intestinal contents from wild rats have detected viruses from an additional nine virus families that could potentially cause infections in laboratory rats.

Medical Management and Diagnostic Approaches

This chapter reviews the basic principles of medical management of rat colonies and diagnostic approaches to detect infectious diseases of rats. As is the case with all other species, rats are susceptible to a variety of injuries and diseases that can cause distress, morbidity, or mortality. Any facility that houses rats must develop monitoring programs designed to rapidly identify health-related problems so they can be communicated to appropriate veterinary or animal care personnel to be resolved. These programs generally consist of multiple components, some of which are directed toward individual animals and others that assess the health status of rat populations as a whole. Topics include individual animal monitoring and care, signs of illness and distress, colony health management, components of microbiological monitoring programs, including agents commonly targeted and sentinel programs, quarantine, biological material screening, diagnostic testing methodologies, including culture, serology, molecular diagnostic and histopathology, test profiles and interpretation, management of disease outbreaks, and treatment and prevention strategies for infectious agents.

Diverse picornaviruses are prevalent among free-living and laboratory rats (Rattus norvegicus) in Hungary and can cause disseminated infections

In this study, the full length genomes of three phylogenetically distant picornaviruses (family Picornaviridae) belonging to the genus Rosavirus (rat08/rRoB/HUN, MN116648), Kobuvirus (rat08/rAiA/HUN, MN116647), and Cardiovirus (rat08/rCaB/HUN, MN116646) were obtained from a single faecal sample of a free-living Norway rat (Rattus norvegicus) in Hungary using viral metagenomics and RT-PCR/Sanger sequencing. The acquired complete genomes were in silico analyzed in detail revealing the presence of a second minor open reading frame encoding an alternative Leader peptide (L*) in rat08/rCaB/HUN and a ca. 222 nt-long sequence repeat with compact secondary RNA structure in the 3' UTR of rat08/rRoB/HUN. The studied rat picornaviruses were frequently detectable by RT-PCR with relatively high viral loads ranged between 8.99E+02 and 1.29E+06 copies/ml in rat faecal samples collected from five geographically distant locations throughout Hungary. The VP1 sequence-based phylogenetic analyses show the presence of multiple, mostly location-specific lineages for all three picornaviruses. Rat rosavirus and rat cardiovirus were identified in spleen while rat cardiovirus was also detected in liver, muscle and kidney samples with variable copy numbers (6.42E+01-1.90E+05 copies/μg total RNA) suggesting extra-intestinal dissemination. Both viruses were also prevalent (70.0% and 18.2%) among two populations of laboratory rats ("Wistar-type" and "hooded-type") held in different, isolated laboratory animal units.

Rat polyomavirus 2 infection in a colony of X-linked severe combined immunodeficiency rats in Japan

Polyomaviruses (PyVs) infect a wide range of animals and provoke wasting diseases, particularly in immunosuppressed hosts. Recently, a novel Rattus norvegicus polyomavirus 2 (RatPyV2) has been identified in a colony of X-linked severe combined immunodeficiency (X-SCID) rats in the United States. Here, we describe the first report of the RatPyV2 infection in an X-SCID rat colony in Japan. The affected rats exhibited adult-onset wasting. Histologically, we observed large basophilic intranuclear inclusion bodies within the hyperplastic or dysplastic epithelial cells in the salivary glands, Harderian glands, extraorbital lacrimal glands, and in respiratory and reproductive tissues. Among these organs, the parotid salivary, Harderian, and extraorbital lacrimal glands were most obviously affected. In particular, the parotid salivary glands were the most severely and diffusely affected and atrophic lesions were prominent even at 1 month of age, which suggested that the parotid salivary glands would be highly susceptible to RatPyV2 in X-SCID rats. RatPyV2 inclusion bodies were also detected in the tail of the epididymis and deferent duct. Such reproductive lesions developed significantly in the later stage of breeding age, and therefore may be associated with the reduced fecundity observed in the infected X-SCID rats. We also established a simple, rapid, and non-invasive diagnostic method based on the Amp-FTA method, using buccal swabs for the detection of RatPyV2 in immunodeficient rats. Our findings contribute to the early detection and diagnosis of RatPyV2 infections.

Histology, immunohistochemistry, and in situ hybridization reveal overlooked Ebola virus target tissues in the Ebola virus disease guinea pig model

Survivors of Ebola virus infection may become subclinically infected, but whether animal models recapitulate this complication is unclear. Using histology in combination with immunohistochemistry and in situ hybridization in a retrospective review of a guinea pig confirmation-of-virulence study, we demonstrate for the first time Ebola virus infection in hepatic oval cells, the endocardium and stroma of the atrioventricular valves and chordae tendinae, satellite cells of peripheral ganglia, neurofibroblasts and Schwann cells of peripheral nerves and ganglia, smooth muscle cells of the uterine myometrium and vaginal wall, acini of the parotid salivary glands, thyroid follicular cells, adrenal medullary cells, pancreatic islet cells, endometrial glandular and surface epithelium, and the epithelium of the vagina, penis and, prepuce. These findings indicate that standard animal models for Ebola virus disease are not as well-described as previously thought and may serve as a stepping stone for future identification of potential sites of virus persistence.

Lung, Pleura, and Mediastinum

The lung is constantly exposed to a large volume of inhaled air that may contain toxicant xenobiotics. With the possibility of exposure to a variety of respiratory toxicants from airborne pollutants in our environment during the course of daily activities, in occupational settings, the use of aerosol sprays for household products, and the development of inhalant bronchial therapies, pulmonary toxicology has become an important subspecialty of toxicology. The lung is susceptible to injury following hematogenous exposure to toxicants. Susceptibility to injury and the type of response following exposure to air- or blood-borne toxicants is largely dependent on the physiochemical characteristics and concentration of the toxicant, duration of exposure, site/tissue specific sensitivity, and the integrity of the defense mechanisms of the lung. In this chapter, nonneoplastic and neoplastic spontaneous lesions and those that develop in the lungs of rats following exposure to toxicants by various routes, but primarily by inhalation, are discussed in detail which provides insight into our understanding of how human lungs respond to toxic chemicals. In addition, the gross and microscopic anatomy of the rat lung is also discussed some detail. Although inhalation is the primary route of exposure in experimental studies, in the past, many studies used intratracheal instillation or direct injection of known carcinogens into the lung. These experiments often resulted in the development of squamous cell carcinomas even though they are very rare as a naturally occurring neoplasm. Instillation of chemicals or particles into the trachea or pleura or direct injection into the lung results in lesions or responses that may not be as relevant to understanding the mechanism of pulmonary carcinogenesis as inhalation of materials under more normal conditions. There remain, however, many areas where our understanding of the response of the lung to toxic chemicals is incomplete.