Natural infection of parvovirus in wild fishing cats (Prionailurus viverrinus) reveals extant viral localization in kidneys.

Carnivore protoparvovirus-1 (CPPV-1), a viral species containing feline panleukopenia virus (FPV) and canine parvovirus (CPV) variants, are widely spread among domestic and wild carnivores causing systemic fatal diseases. Wild fishing cats (Prionailurus viverrinus), a globally vulnerable species, have been found dead. Postmortem examination of the carcasses revealed lesions in intestine, spleen and kidney. CPPV-1 antigen identification in these tissues, using polymerase chain reaction (PCR) and immunohistochemistry (IHC), supported the infection by the virus. PCR- and IHC-positivity in kidney tissues revealed atypical localization of the virus while in situ hybridization (ISH) and transmission electron microscopy (TEM) with the pop-off technique confirmed the first description of viral localization in kidneys. Complete genome characterization and deduced amino acid analysis of the obtained CPPV-1 from the fishing cats revealed FPV as a causative agent. The detected FPV sequences showed amino acid mutations at I566M and M569R in the capsid protein. Phylogenetic and evolutionary analyses of complete coding genome sequences revealed that the fishing cat CPPV-1 genomes are genetically clustered to the FPV genomes isolated from domestic cats in Thailand. Since the 1970s, these genomes have also been shown to share a genetic evolution with Chinese FPV strains. This study is the first evidence of CPPV-1 infection in fishing cats and it is the first to show its localization in the kidneys. These findings support the multi-host range of this parvovirus and suggest fatal CPPV-1 infections may result in other vulnerable wild carnivores.

Regional adaptations and parallel mutations in Feline panleukopenia virus strains from China revealed by nearly-full length genome analysis.

Protoparvoviruses, widespread among cats and wild animals, are responsible for leukopenia. Feline panleukopenia virus (FPLV) in domestic cats is genetically diverse and some strains may differ from those used for vaccination. The presence of FPLV in two domestic cats from Hebei Province in China was identified by polymerase chain reaction. Samples from these animals were used to isolate FPLV strains in CRFK cells for genome sequencing. Phylogenetic analysis was performed to compare our isolates with available sequences of FPLV, mink parvovirus (MEV) and canine parvovirus (CPV). The isolated strains were closely related to strains of FPLV/MEV isolated in the 1960s. Our analysis also revealed that the evolutionary history of FPLV and MEV is characterized by local adaptations in the Vp2 gene. Thus, it is likely that new FPLV strains are emerging to evade the anti-FPLV immune response.

Analysis of the microRNA expression profiles in feline kidney cell line infected with feline panleukopenia virus.

MicroRNAs (miRNAs) play crucial roles in post-transcriptional regulation of gene expression in many biological processes. Feline panleukopenia virus (FPV) is a highly infectious pathogen that can cause severe disease in pets, economically important animals and wildlife. In this study, miRNAs associated with FPV infection were identified using high-throughput sequencing. Our results showed that 673 known miRNAs and 278 novel miRNAs were identified and 57 significantly differential expression miRNAs were found post-FPV infection in feline kidney cell line. Stem-loop qRT-PCR was applied to validate the expression of the randomly selected miRNAs; the results were consistent with the sequencing data. Furthermore, the target genes of differential expression miRNAs were analyzed and predicated by GO and KEGG pathway. Altogether, our analysis provides a potential link between miRNA expression and the pathogenesis of FPV infection.

Molecular characterization of feline panleukopenia virus isolated from mink and its pathogenesis in mink.

Six feline panleukopenia viruses (FPV) were detected in the intestinal samples from the 176 mink collected in China during 2015 to 2016, named MEV-SD1, MEV-SD2, MEV-SD3, MEV-SD4, MEV-SD5 and MEV-SD6. The VP2 genes of the isolates shared 98.9%-100% identity with the reference sequences. The substitution of residue V300A in VP2 protein differentiates the isolates from the reference MEVs, and A300 is a characteristic of FPV. Furthermore, phylogenetic analysis of VP2 genes indicated that the six isolates were clustered into the same branch of all the reference FPVs. The NS1 genes of the isolates shared 98.2%-100% identity with the reference sequences. The NS1 genes of the six isolates and the three reference FPVs formed one unique evolutionary branch. To clarify the pathogenicity of the isolates, animal experiments were performed on healthy mink, using MEV-SD1. As a result, the morbidity of the inoculated animals was 100% and the mortality was as high as 38.9%. It was implied that the FPV infection caused a high morbidity and mortality in mink and the inoculation dose had an effect on pathogenicity of MEV-SD1 in mink.

Early steps in cell infection by parvoviruses: host-specific differences in cell receptor binding but similar endosomal trafficking.

Canine parvovirus (CPV) and feline panleukopenia virus (FPV) are closely related parvoviruses that differ in their host ranges for cats and dogs. Both viruses bind their host transferrin receptor (TfR), enter cells by clathrin-mediated endocytosis, and traffic with that receptor through endosomal pathways. Infection by these viruses appears to be inefficient and slow, with low numbers of virions infecting the cell after a number of hours. Species-specific binding to TfR controls viral host range, and in this study FPV and strains of CPV differed in the levels of cell attachment, uptake, and infection in canine and feline cells. During infection, CPV particles initially bound and trafficked passively on the filopodia of canine cells while they bound to the cell body of feline cells. That binding was associated with the TfR as it was disrupted by anti-TfR antibodies. Capsids were taken up from the cell surface with different kinetics in canine and feline cells but, unlike transferrin, most did not recycle. Capsids labeled with fluorescent markers were seen in Rab5-, Rab7-, or Rab11-positive endosomal compartments within minutes of uptake, but reached the nucleus. Constitutively active or dominant negative Rab mutants changed the intracellular distribution of capsids and affected the infectivity of virus in cells.

Activation of p38 MAPK by feline infectious peritonitis virus regulates pro-inflammatory cytokine production in primary blood-derived feline mononuclear cells.

Feline infectious peritonitis (FIP) is an invariably fatal disease of cats caused by systemic infection with a feline coronavirus (FCoV) termed feline infectious peritonitis virus (FIPV). The lethal pathology associated with FIP (granulomatous inflammation and T-cell lymphopenia) is thought to be mediated by aberrant modulation of the immune system due to infection of cells such as monocytes and macrophages. Overproduction of pro-inflammatory cytokines occurs in cats with FIP, and has been suggested to play a significant role in the disease process. However, the mechanism underlying this process remains unknown. Here we show that infection of primary blood-derived feline mononuclear cells by FIPV WSU 79-1146 and FIPV-DF2 leads to rapid activation of the p38 MAPK pathway and that this activation regulates production of the pro-inflammatory cytokine tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta). FIPV-induced p38 MAPK activation and pro-inflammatory cytokine production was inhibited by the pyridinyl imidazole inhibitors SB 203580 and SC 409 in a dose-dependent manner. FIPV-induced p38 MAPK activation was observed in primary feline blood-derived mononuclear cells individually purified from multiple SPF cats, as was the inhibition of TNF-alpha production by pyridinyl imidazole inhibitors.

Parvovirus infection in domestic companion animals.

Parvovirus infects a wide variety of species. The rapid evolution, environmental resistance, high dose of viral shedding, and interspecies transmission have made some strains of parvovirus infection difficult to control within domestic animal populations. Some parvoviruses in companion animals, such as canine parvovirus (CPV) 1 and feline parvovirus, have demonstrated minimal evolution over time. In contrast, CPV 2 has shown wide adaptability with rapid evolution and frequent mutations. This article briefly discusses these three diseases, with emphasis on virus evolution and the challenges to protecting susceptible companion animal populations.

Concurrent infection of a cat with cowpox virus and feline parvovirus.

Concurrent infection with cowpox and feline parvovirus was diagnosed in a 5-month-old male European Short Hair cat. Microscopical examination of the facial skin, ears and foot pads revealed multifocal to coalescing, ulcerative to necrotizing dermatitis and panniculitis with ballooning epidermal degeneration and eosinophilic cytoplasmic inclusion bodies. Immunohistochemistry, polymerase chain reaction testing and virus isolation confirmed infection with a strain of cowpox virus similar to that isolated from a cat in Germany 5 years previously. Lymphoid tissues were depleted and there was catarrhal enteritis caused by feline parvovirus as confirmed by immunohistochemistry and in-situ hybridization. This co-infection did not result in a more severe and rapid course of the poxvirus-associated disease.

Purified feline and canine transferrin receptors reveal complex interactions with the capsids of canine and feline parvoviruses that correspond to their host ranges.

The cell infection processes and host ranges of canine parvovirus (CPV) and feline panleukopenia virus (FPV) are controlled by their capsid interactions with the transferrin receptors (TfR) on their host cells. Here, we expressed the ectodomains of wild-type and mutant TfR and tested those for binding to purified viral capsids and showed that different naturally variant strains of the viruses were associated with variant interactions with the receptors which likely reflect the optimization of the viral infection processes in the different hosts. While all viruses bound the feline TfR, reflecting their tissue culture host ranges, a naturally variant mutant of CPV (represented by the CPV type-2b strain) that became the dominant virus worldwide in 1979 showed significantly lower levels of binding to the feline TfR. The canine TfR ectodomain did not bind to a detectable level in the in vitro assays, but this appears to reflect the naturally low affinity of that interaction, as only low levels of binding were seen when the receptor was expressed on mammalian cells; however, that was sufficient to allow endocytosis and infection. The apical domain of the canine TfR controls the specific interaction with CPV capsids, as a canine TfR mutant altering a glycosylation site in that domain bound FPV, CPV-2, and CPV-2b capsids efficiently. Enzymatic removal of the N-linked glycans did not allow FPV binding to the canine TfR, suggesting that the protein sequence difference is itself important. The purified feline TfR inhibited FPV and CPV-2 binding and infection of feline cells but not CPV-2b, indicating that the receptor binding may be able to prevent the attachment to the same receptor on cells.

[Evolution and host variation of the canine parvovirus: molecular basis for the development of a new virus]. / Evolution und Wirtswechsel des Caninen Parvovirus: Molekulare Grundlagen der Entstehung eines neuen Virus.

Canine parvovirus (CPV) evolved as a new pathogen in dogs between 1976 and 1978 from feline panleukopenia virus (FPV). The new virus hit an unprotected population, caused a dramatic pandemic and infected virtually all populations of domestic and wild carnivores worldwide. The great similarity between the two viruses and their differences in host range, both in vivo as well as in vitro, make it a good model system for emerging diseases and host range shifts of viruses. Recent results showed that CPV expanded its host range by binding to the canine transferrin receptor (Tfr). Residues in the capsid protein that had been defined as host range controlling regions also control the binding to the canine transferrin receptor. These residues are located on a raised region of the capsid at the three-fold axis of symmetry. Interestingly, adaption of the new virus to the new host appears to correlate with an improved binding to the Tfr receptor.

Characterisation of cross-reactivity of virus neutralising antibodies induced by feline panleukopenia virus and canine parvoviruses.

It was recently reported that canine parvoviruses (CPV) had entered cat populations and induced disease in infected cats, while they had affected only dogs in the past. It is important to determine whether conventional feline panleukopenia virus (FPLV) vaccines protect against recent CPV infections. In this study, the cross-reactivity of virus-neutralising (VN) and haemagglutinin-inhibition (HI) antibodies in cats induced by FPLV and CPV s were examined. Lower cross-reactivities of VN and HI antibodies against each CPV strain were observed in cats experimentally inoculated with FPLV or vaccinated with an inactivated FPLV vaccine. In addition, we revealed the existence of a novel type of FPLV, which reacted weakly with antibodies induced by the conventional FPLV vaccine.

Genetic characterization of feline parvovirus sequences from various carnivores.

Infections with viruses of the feline parvovirus subgroup such as feline panleukopenia virus (FPV), mink enteritis virus (MEV) and canine parvovirus (CPV-2) [together with its new antigenic types (CPV-2a, CPV-2b)] have been reported from several wild carnivore species. To examine the susceptibility of different species to the various parvoviruses and their antigenic types, samples from wild carnivores with acute parvovirus infections were collected. Viral DNA was amplified, and subsequently analysed, from faeces or formalin-fixed small intestines from an orphaned bat-eared fox (Otocyon megalotis), a free-ranging honey badger (Mellivora capensis), six captive cheetahs (Acinonyx jubatus), a captive Siberian tiger (Panthera tigris altaica) and a free-ranging African wild cat (Felis lybica). Parvovirus infection in bat-eared fox and honey badger was demonstrated for the first time. FPV-sequences were detected in tissues of the African wild cat and in faeces of one cheetah and the honey badger, whereas CPV-2b sequences were found in five cheetahs and the bat-eared fox. The Siberian tiger (from a German zoo) was infected with a CPV-type 2a virus. This distribution of feline parvovirus antigenic types in captive large cats suggests an interspecies transmission from domestic dogs. CPV-2 sequences were not detected in any of the specimens and no sequences with features intermediate between FPV and CPV were found in any of the animals examined.

Dynamics of a feline virus with two transmission modes within exponentially growing host populations.

Feline panleucopenia virus (FPLV) was introduced in 1977 on Marion Island (in the southern Indian Ocean) with the aim of eradicating the cat population and provoked a huge decrease in the host population within six years. The virus can be transmitted either directly through contacts between infected and healthy cats or indirectly between a healthy cat and the contaminated environment: a specific feature of the virus is its high rate of survival outside the host. In this paper, a model was designed in order to take these two modes of transmission into account. The results showed that a mass-action incidence assumption was more appropriate than a proportionate mixing one in describing the dynamics of direct transmission. Under certain conditions the virus was able to control the host population at a low density. The indirect transmission acted as a reservoir supplying the host population with a low but sufficient density of infected individuals which allowed the virus to persist. The dynamics of the infection were more affected by the demographic parameters of the healthy hosts than by the epidemiological ones. Thus, demographic parameters should be precisely measured in field studies in order to obtain accurate predictions. The predicted results of our model were in good agreement with observations.

Enterocolitis associated with dual infection by Clostridium piliforme and feline panleukopenia virus in three kittens.

Dual infection by Clostridium piliforme and feline panleukopenia virus (FPLV) was found in three kittens. In all cases, we found focal necrosis and desquamation of epithelial cells with occasional neutrophil infiltration in the large intestine. Large filamentous bacilli and spores were observed in the epithelium by using the Warthin-Starry method. Electron microscopy revealed the vegetative forms with characteristic peritrichous flagella and spore forms. Immunohistochemically, these bacilli showed a positive reaction with mouse antisera against the RT and MSK C. piliforme strains. Polymerase chain reaction (PCR) using cecum specimens demonstrated the 196-bp band specific to C. piliforme 16S rRNA. All three kittens were also diagnosed as FPLV-infected on the basis of the characteristic mucosal lesions, including intranuclear inclusions and PCR study for the FPLV genomic DNA. The PCR techniques are useful for confirming the C. piliforme and FPLV infection in spontaneous cases.

Feline coronavirus participation in diarrhea of cats.

Fecal samples were examined for viruses participated in gastrointestinal disorders of cats, especially focusing on feline coronavirus (FCoV) by a reverse transcriptase-polymerase chain reaction assay. It was found that a primary viral pathogen was feline panleukopenia parvovirus (FPLV; 28.5% of the positive rate) and the secondary was FCoV (10.7%). Commonly reported clinical signs of cats of which feces were FCoV-positive were vomiting, diarrhea and dehydration with an exception of one serious case with concurrent FPLV infection.

Mink enteritis parvovirus. Stability of virus kept under outdoor conditions.

Feces from mink with acute mink enteritis were pooled and then allowed to dry out in open tubes kept under a roof in an open shed for one year starting in January. Samples of feces were harvested approximately once a month. These were reconstituted to their original volume and tested for antigen content and infectivity both in in vitro cell cultures and - on selected samples - in vivo. During the first 8 months, the antigen level in the feces samples decreased slowly. At this time point, a plateau was reached at 30-40% of the original viral antigen contents. The infectivity in vitro was unchanged for the first 5 months, but after mid-summer it decreased abruptly to below the detection level. Based on the in vitro infectivity, 10 samples were selected for inoculation into mink to measure the in vivo infectivity. The transmission of the infection to the experimental animals was successful for all samples showing infective virus by cultivation. In addition, it was possible to infect mink using material harvested one month after the cell culture test had turned negative. One mink inoculated with material collected in October excreted virus. We conclude that parvovirus can survive for at least 5-10 months (or during the winter period) under natural conditions, but complete drying out seems to lead to its inactivation. Mechanical cleaning of the premises is thus as critical as disinfection since virus can only survive the dry summer period if protected by protein or buried in moist soil on the premises.

The polymerase chain reaction for the detection of defective interfering canine parvovirus particles.

The PCR assay was used to amplify a portion of the genome of virulent and vaccinal canine parvovirus strains and of a vaccinal feline panleukopenia virus strain. A DNA fragment corresponding to the gene that encodes the VP1/VP2 proteins was amplified. The size of the PCR products was 2.2 Kbp except for CPV vaccinal 17-80 strain. The PCR product of 17-80 was 1.1 Kbp leading to the hypothesis of the presence of defective particles. All the restriction enzymes digested the 2.2 Kbp amplified products giving restriction fragments of the expected size whereas Hind III, Hpa II and Pvu II did not digest the PCR fragment of 1.1 Kbp.

Differences in virus receptor for type I and type II feline infectious peritonitis virus.

Feline infectious peritonitis viruses (FIPVs) are classified into type I and type II serogroups. Here, we report that feline aminopeptidase N (APN), a cell-surface metalloprotease on the intestinal, lung and kidney epithelial cells, is a receptor for type II FIPV but not for type I FIPV. A monoclonal antibody (MAb) R-G-4, which blocks infection of Felis catus whole fetus (fcwf-4) cells by type II FIPV, was obtained by immunizing mice with fcwf-4 cells which are highly susceptible to FIPV. This MAb also blocked infection of fcwf-4 cells by type II feline enteric coronavirus (FECV), canine coronavirus (CCV), and transmissible gastroenteritis virus (TGEV). On the other hand, it did not block infection by type I FIPVs. MAb R-G-4 recognized a polypeptide of relative molecular mass 120-130 kDa in feline intestinal brush-border membrane (BBM) proteins. The polypeptide possessed aminopeptidase activity, and the first 15 N-terminal amino acid sequence was identical to that of the feline APN. Feline intestinal BBM proteins and the polypeptide reacted with MAb R-G-4 (feline APN) inhibited the infectivity of type II FIPV, type II FECV, CCV and TGEV to fcwf-4 cells, but did not inhibit the infectivity of type I FIPVs.

Detection of feline parvovirus in dying pedigree kittens.

Feline parvovirus (FPV) was detected in the intestinal tract contents of 13 pedigree kittens which were fading or died suddenly by the use of a new chromatographic test strip for canine parvovirus (CPV) and FPV. The test appeared to be sensitive and specific for the detection of FPV and was a useful diagnostic aid. In three cases in which virus was grown in cell culture, the isolates were characteristic of FPV and not CPV. Cats in the households in which the kittens were reared were regularly immunised with FPV vaccines. The most likely explanation for the occurrence of FPV-associated disease was exposure of the young kittens to large doses of virus contaminating the environment.