Renal epitheliotropism of feline morbillivirus in two cats

Recombinant expression and characterization of Canine circovirus capsid protein for diagnosis

Canine circovirus (CanineCV) is a contagious virus that causes severe gastroenteritis, diarrhea, respiratory disease, and vasculitis, often resulting in fatality among infected dogs. In this study, a recombinant Capsid protein (rCap) of CanineCV was expressed in the Escherichia coli (E. coli) Rosetta (DE3) pLysS host cell, followed by affinity purification, and then analyzed by SDS-PAGE, revealing a molecular weight of approximately 31 kDa. The antigenicity of the CanineCV rCap protein was confirmed through recognition by a rabbit anti-CanineCV rCap protein polyclonal antibody (PoAb). Additionally, the reactivity and specificity of this PoAb were assessed using indirect enzyme-linked immunosorbent assay (ELISA) and Western blot analysis before applying in an immunohistochemistry (IHC), namely, immunoperoxidase detection. The immunoperoxidase assay using rabbit anti-CanineCV rCap protein PoAb demonstrated that the CanineCV Cap protein was predominantly located in immune cells, especially lymphocytes and macrophages, within the spleen, lung, tracheobronchial lymph nodes, small intestine, and kidney. Similarly, the Cap protein was also found in pneumocytes in the lung and renal tubular epithelial cells in the kidney. These findings reflected the biological activity and cell tropism of the virus. Therefore, the recombinant Cap protein and its PoAb could be used for the development of a valuable diagnostic tool for CanineCV detection.

Detection of feline morbillivirus in cats with symptoms of acute febrile infection

Feline morbillivirus (FeMV) was identified for the first time in cats in 2012 in Hong Kong. Although its association with chronic kidney disease in cats has attracted the attention of researchers, its clinical significance as an acute infection has not been reported. Previously, we reported FeMV detection using next-generation sequence-based comprehensive genomic analysis of plasma samples from cats with suspected acute febrile infections. Here, we conducted an epidemiological survey to detect FeMV by quantitative reverse transcription polymerase chain reaction (qRT-PCR) using blood samples from cats in Japan. FeMV was detected in 32/102 blood samples (31.4%) from cats with suspected acute viral infections. Most of the FeMV-positive cats had clinical findings consistent with acute viral infections, including fever, leukopenia, thrombocytopenia and jaundice. No FeMV was detected in healthy cats or clinically ill cats that visited veterinary hospitals. Phylogenetic analysis classified FeMV L genes into various FeMV subtypes. We also necropsied a FeMV-positive cat that died of a suspected acute infection. On necropsy, FeMV was detected in systemic organs, including the kidneys, lymph nodes and spleen by qRT-PCR and immunohistochemical staining. These results suggest that FeMV infections may cause acute symptomatic febrile infections in cats. A limitation of this study was that the involvement of other pathogens that cause febrile illnesses could not be ruled out and this prevented a definitive conclusion that FeMV causes febrile disease in infected cats. Further studies that include experimental infections are warranted to determine the pathogenicity of FeMV in cats.

Domestic cat hepadnavirus detection in blood and tissue samples of cats with lymphoma

Domestic cat hepadnavirus (DCH), a relative hepatitis B virus (HBV) in human, has been recently identified in cats; however, association of DCH infection with lymphoma in cats is not investigated. To determine the association between DCH infection and feline lymphoma, seven hundred and seventeen cats included 131 cats with lymphoma (68 blood and 63 tumor samples) and 586 (526 blood and 60 lymph node samples) cats without lymphoma. DCH DNA was investigated in blood and formalin-fixed paraffin-embedded (FFPE) tissues by quantitative polymerase chain reaction (qPCR). The FFPE lymphoma tissues were immunohistochemically subtyped, and the localization of DCH in lymphoma sections was investigated using in situ hybridization (ISH). Feline retroviral infection was investigated in the DCH-positive cases. DCH DNA was detected in 16.18% (11/68) (p = 0.002; odds ratio [OR], 5.15; 95% confidence interval [CI], 2.33-11.36) of blood and 9.52% (6/63) (p = 0.028; OR, 13.68; 95% CI, 0.75-248.36) of neoplastic samples obtained from lymphoma cats, whereas only 3.61% (19/526) of blood obtained from non-lymphoma cats was positive for DCH detection. Within the DCH-positive lymphoma, in 3/6 cats, feline leukemia virus was co-detected, and in 6/6 were B-cell lymphoma (p > 0.9; OR, 1.93; 95% CI, 0.09-37.89) and were multicentric form (p = 0.008; OR, 1.327; 95% CI, 0.06-31.18). DCH was found in the CD79-positive pleomorphic cells. Cats with lymphoma were more likely to be positive for DCH than cats without lymphoma, and infection associated with lymphoma development needs further investigations.

Feline morbillivirus infection associated with fatal encephalitis in a Bengal cat

Feline morbillivirus (FeMV) is a recently discovered morbillivirus of the family Paramyxoviridae, which include several highly contagious viruses with zoonotic potential. In this case report we describe the detection of FeMV in archived brain tissue of a 2-month-old Bengal cat with nonsuppurative encephalitis from the year 2011 in Switzerland by high-throughput sequencing (HTS). Our metagenomics approach was able to obtain a full-length sequence covering the entire FeMV genome. Phylogenetic analysis showed that our FeMV strain clustered within FeMV genotype 1. We were able to detect FeMV RNA by in situ hybridization (ISH) in brain sections with inflammatory lesions and demonstrated its potential neurotropism and association with encephalitis. Our results provide further insight into this recently discovered morbillivirus and encourage further investigations into the pathogenesis and epidemiology of associated diseases in cats and potentially other species.

Feline Morbillivirus: Clinical Relevance of a Widespread Endemic Viral Infection of Cats

Feline morbillivirus (FeMV) was first isolated in 2012 from stray cats in Hong Kong. It has been found in association with tubulointerstitial nephritis (TIN), the most common cause of feline chronic kidney disease (CKD). However, viral host spectrum and virus tropism go beyond the domestic cat and kidney tissues. The viral genetic diversity of FeMV is extensive, but it is not known if this is clinically relevant. Urine and kidney tissues have been widely tested in attempts to confirm associations between FeMV infection and renal disease, but samples from both healthy and sick cats can test positive and some cross-sectional studies have not found associations between FeMV infection and CKD. There is also evidence for acute kidney injury following infection with FeMV. The results of prevalence studies differ greatly depending on the population tested and methodologies used for detection, but worldwide distribution of FeMV has been shown. Experimental studies have confirmed previous field observations that higher viral loads are present in the urine compared to other tissues, and renal TIN lesions associated with FeMV antigen have been demonstrated, alongside virus lymphotropism and viraemia-associated lymphopenia. Longitudinal field studies have revealed persistent viral shedding in urine, although infection can be cleared spontaneously.

FeMV is a cathepsin-dependent unique morbillivirus infecting the kidneys of domestic cats

Feline morbillivirus (FeMV) is a recently discovered pathogen of domestic cats and has been classified as a morbillivirus in the Paramyxovirus family. We determined the complete sequence of FeMV^US5 directly from an FeMV-positive urine sample without virus isolation or cell passage. Sequence analysis of the viral genome revealed potential divergence from characteristics of archetypal morbilliviruses. First, the virus lacks the canonical polybasic furin cleavage signal in the fusion (F) glycoprotein. Second, conserved amino acids in the hemagglutinin (H) glycoprotein used by all other morbilliviruses for binding and/or fusion activation with the cellular receptor CD150 (signaling lymphocyte activation molecule [SLAM]/F1) are absent. We show that, despite this sequence divergence, FeMV H glycoprotein uses feline CD150 as a receptor and cannot use human CD150. We demonstrate that the protease responsible for cleaving the FeMV F glycoprotein is a cathepsin, making FeMV a unique morbillivirus and more similar to the closely related zoonotic Nipah and Hendra viruses. We developed a reverse genetics system for FeMV^US5 and generated recombinant viruses expressing Venus fluorescent protein from an additional transcription unit located either between the phospho-protein (P) and matrix (M) genes or the H and large (L) genes of the genome. We used these recombinant FeMVs to establish a natural infection and demonstrate that FeMV causes an acute morbillivirus-like disease in the cat. Virus was shed in the urine and detectable in the kidneys at later time points. This opens the door for long-term studies to address the postulated role of this morbillivirus in the development of chronic kidney disease.

In Vitro Growth, Receptor Usage and Pathogenesis of Feline Morbillivirus in the Natural Host

Feline morbillivirus (FeMV) is a recently discovered virus belonging to the genus Morbillivirus of the virus family Paramyxoviridae. Often, the virus has been detected in urine of cats with a history of urinary disease and has a worldwide distribution. Currently, it is unclear which receptor the virus uses to enter the target cells. Furthermore, many aspects of FeMV biology in vivo, including tissue tropism, pathogenesis, and virus excretion in the natural host remain unclear. In this study we analyzed the replication of FeMV in various cell lines. Secondly, we tested if the presence of feline SLAMF1 (Signaling Lymphocytic Activation Molecule family 1/CD150, principal entry receptor for other members of the Morbillivirus genus) improved FeMV replication efficiency in vitro. Finally, to elucidate in vivo biology in cats, as a natural host for FeMV, we experimentally infected a group of cats and monitored clinical symptoms, viremia, and excretion of the virus during the course of 56 days. Our study showed that FeMV shares some features with other morbilliviruses like the use of the SLAMF1 receptor. For the first time, experimental infection of SPF cats showed that FeMV does not induce an acute clinical disease like other morbilliviruses but can induce lesions in the kidneys, including tubulointerstitial nephritis. Further investigations are needed to confirm the site and dynamics of replication of FeMV in the urinary tract and the longer-term impact of FeMV-induced lesions on the renal function. Whether FeMV infection can result in chronic kidney disease will require the monitoring of cats over a longer period.