A Missense Variant Affecting the C-Terminal Tail of UNC93B1 in Dogs with Exfoliative Cutaneous Lupus Erythematosus (ECLE)

Cutaneous lupus erythematosus (CLE) in humans encompasses multiple subtypes that exhibit a wide array of skin lesions and, in some cases, are associated with the development of systemic lupus erythematosus (SLE). We investigated dogs with exfoliative cutaneous lupus erythematosus (ECLE), a dog-specific form of chronic CLE that is inherited as a monogenic autosomal recessive trait. A genome-wide association study (GWAS) with 14 cases and 29 controls confirmed a previously published result that the causative variant maps to chromosome 18. Autozygosity mapping refined the ECLE locus to a 493 kb critical interval. Filtering of whole genome sequence data from two cases against 654 controls revealed a single private protein-changing variant in this critical interval, UNC93B1:c.1438C>A or p.Pro480Thr. The homozygous mutant genotype was exclusively observed in 23 ECLE affected German Shorthaired Pointers and an ECLE affected Vizsla, but absent from 845 controls. UNC93B1 is a transmembrane protein located in the endoplasmic reticulum and endolysosomes, which is required for correct trafficking of several Toll-like receptors (TLRs). The p.Pro480Thr variant is predicted to affect the C-terminal tail of the UNC93B1 that has recently been shown to restrict TLR7 mediated autoimmunity via an interaction with syndecan binding protein (SDCBP). The functional knowledge on UNC93B1 strongly suggests that p.Pro480Thr is causing ECLE in dogs. These dogs therefore represent an interesting spontaneous model for human lupus erythematosus. Our results warrant further investigations of whether genetic variants affecting the C-terminus of UNC93B1 might be involved in specific subsets of CLE or SLE cases in humans and other species.

Septic tularemia in 2 cottontop tamarins(Sanguinus oedipus)

Two captive cottontop tamarins (Sanguinus oedipus) died within 5 d of each other from systemic infection by Francisella tularensis (tularemia). One tamarin experienced mild clinical signs, including malaise, anorexia, and a mucoid nasal discharge for 4 d before death, whereas the other experienced a more rapid progression of disease that lasted less than 24 h. Differential diagnoses included gram-negative septicemia by an organism such as Escherichia coli, Salmonella, or Yersinia; protozoal infection such as Toxoplasma gondii or an acute viral infection such as lymphocytic choriomeningitis. F. tularensis infection was identified by F. tularensis-specific PCR in both primates. Possible sources of infection include aerosol, biting arthropod vectors, and transmission via a rodent reservoir. This case report highlights the importance of tularemia as a differential diagnosis in acute febrile illness in captive nonhuman primates.

Experimental nebulization of American bison (Bison bison) with low doses of ovine herpesvirus 2 from sheep nasal secretions

Malignant catarrhal fever (MCF), caused by ovine herpesvirus 2 (OvHV-2), is an important cause of mortality in ranched American bison and domestic cattle in North America. Previous studies showed that bison can be infected by intranasal nebulization with sheep nasal secretions containing OvHV-2 and provided preliminary information on viral doses required for infection and disease progression. The goals of this study were to establish optimal minimal infectious and minimal lethal doses of OvHV-2 by the intranasal route in bison, evaluate the influence of dose on incubation period and other clinical parameters and determine if bison seropositive for antibody against MCF-group viruses are resistant to developing MCF after intranasal challenge. In this study, the minimal infectious dose and minimal lethal dose overlap, suggesting that experimental production of subclinically infected bison is impractical. Dose is inversely related to both incubation period and the period between nebulization and first detection of >1000 OvHV-2 DNA copies/500 ng total DNA in peripheral blood leukocytes. Interestingly, all of the bison seropositive for anti-MCF-group viral antibody prior to inoculation died of MCF after nebulization. We conclude that previous exposure to an MCF-group virus does not necessarily provide resistance to OvHV-2-induced MCF in bison.

Metastatic malignant melanoma in an alpaca (Vicugna pacos)

A case of malignant melanoma in a 7-year-old, intact, black, male Huacaya alpaca with a history of a chronic, nonhealing wound involving the left external nostril, weight loss, and inappetence is described. Malignant melanoma was diagnosed by histology of punch biopsy specimens from a mass on the maxilla associated with the nonhealing wound and from a mass in the submandibular region. The alpaca was humanely euthanized 10 days after the diagnosis on the basis of the poor prognosis and rapid clinical deterioration. At postmortem examination, the alpaca had an ulcerated, multilobulated, black pigmented mass (8.0 cm x 6.0 cm x 4.0 cm) that infiltrated the left rostral maxilla extending into the marrow space and into the left nasal cavity. Numerous, discrete, coalescing masses were present in the subcutaneous tissue of the submandibular area, peritracheal connective tissue, pericardium, and diaphragmatic parietal pleura and were disseminated throughout the pulmonary parenchyma. The masses were diffusely black on cut surface and exuded black pigment. Histologically, all masses were composed of spindloid to polygonal cells with indistinct cell borders and moderate amounts of cytoplasm that contained abundant fine, black granules (melanin), confirming metastasis of a primary mucocutaneous melanoma. To the authors' knowledge, this is the first report of a malignant melanoma involving bone in a New World camelid.

Ovine herpesvirus 2 replicates initially in the lung of experimentally infected sheep

Ovine herpesvirus 2 (OvHV-2), a rhadinovirus in the subfamily Gammaherpesvirinae, is the causative agent of sheep-associated malignant catarrhal fever (SA-MCF), a frequently fatal lymphoproliferative disease primarily of ruminants worldwide. Inability to propagate the virus in vitro has made it difficult to study OvHV-2 replication. Aerosol inoculation of sheep with OvHV-2 from nasal secretions collected from naturally infected sheep during shedding episodes results in infection of naive sheep, providing an excellent system to study OvHV-2 initial replication in the natural host. In this study, we showed that OvHV-2 delivered through the nasal route by nebulization resulted in infection in all lambs, but no infection was established in any lambs after intravenous or intraperitoneal injection. In nebulized lambs, while it was not detected initially in any other tissues, OvHV-2 DNA became detectable in the lung at 3 days post-infection (p.i.), increased to about 900 copies per 50 ng DNA at 5 days p.i., reached peak levels (∼7500 copies) at 7 days p.i., and then declined to an average of 800 copies at 9 days p.i. Transcripts of OvHV-2 open reading frame 25 (coding for the capsid protein), an indicator of virus replication, were only detected in lung tissues, and were positively correlated with OvHV-2 DNA levels in the lungs. In addition, selected immune response genes were also highly expressed in the lung at 5 and 7 days p.i. The data indicate that lung is the primary replication site for OvHV-2 during initial infection in sheep and suggest that viral replication is promptly controlled by a host defence mechanism.

Experimental infection of rabbits with ovine herpesvirus 2 from sheep nasal secretions

Malignant catarrhal fever (MCF) is a generally fatal disease that primarily occurs in ruminants and is caused by a group of gammaherpesviruses. Outside of Africa MCF is mainly caused by ovine herpesvirus 2 (OvHV-2) which is carried subclinically by sheep. Cell-free virus is present in nasal secretions of shedding sheep and aerosol is the primary mode of transmission. Although OvHV-2 has never been propagated in vitro, experimental infection involving intranasal nebulization with nasal secretions from shedding sheep has been used to induce MCF in cattle and bison. This method of inoculation has never been tested in rabbits, which are the primary small animal model. The objectives of this study were to determine whether rabbits become infected with OvHV-2 after intranasal nebulization with cell-free virus from sheep nasal secretions and whether they develop MCF with consistent gross and histologic lesions. Five of eight rabbits became infected, showed clinical signs and developed histologic lesions typical of MCF including multisystemic vasculitis and perivascular lymphoid accumulation. These lesions are similar to those reported in rabbits infected by intravenous injection with tissues from clinically affected animals containing cell-associated virus. Viral DNA and mRNA transcripts of a structural viral protein were present in tissues from affected rabbits suggesting that viral replication occurred, although the significance in terms of pathogenesis is unknown. This work demonstrates that OvHV-2 infection of rabbits by intranasal nebulization is a potentially useful model that mimics the natural route of infection and may be used to study viral replication and pathogenesis.