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Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are globally distributed retroviruses that infect domestic cats and cause various syndromes that can lead to death. The aim of this study was to detect and genotype feline retroviruses in Mexican domestic cats. We used PCR assays to identify proviral DNA and viral RNA in 50 domestic cats with different clinical signs and hematological alterations. Endogenous FeLV (enFeLV) was identified in the genomic DNA of all cats in the study, and we detected transcripts of the LTR region of enFeLV in 48 individuals. Exogenous FeLV (exFeLV) was found in 13 cats. Furthermore, we detected FIV proviral DNA in 10 cats. The enFeLV sequences were shown to be the most variable, while the exFeLV sequences were highly conserved and related to previously reported subgroup A sequences. Sequencing of the FIV gag gene revealed the presence of subtype B in the infected cats., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The leopard cat (Prionailurus bengalensis) was listed as an endangered species under the Wildlife Conservation Act in Taiwan in 2009. However, no study has evaluated the possible direct or indirect effects of pathogens on the Taiwanese leopard cat population. Here, we targeted viral pathogens, including carnivore protoparvovirus 1 (genus Protoparvovirus), feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), coronaviruses (CoVs), and canine distemper virus (CDV), through molecular screening. The spatial and temporal dynamics of the target pathogens were evaluated. Through sequencing and phylogenetic analysis, we clarified the phylogenetic relationship of viral pathogens isolated from leopard cats and domestic carnivores. Samples from 23 live-trapped leopard cats and 29 that were found dead were collected from 2015 to 2019 in Miaoli County in northwestern Taiwan. Protoparvoviruses and CoVs were detected in leopard cats, and their prevalence (95% confidence interval) was 63.5% (50.4%-76.6%) and 8.8% (0%-18.4%), respectively. Most of the protoparvovirus sequences amplified from Taiwanese leopard cats and domestic carnivores were identical. All of the CoV sequences amplified from leopard cats were identified as feline CoV. No spatial or temporal aggregation of protoparvovirus infection in leopard cats was found in the sampling area, indicating a wide distribution of protoparvoviruses in the leopard cat habitat. We consider sympatric domestic carnivores to be the probable primary reservoir for the identified pathogens. We strongly recommend management of protoparvoviruses and feline CoV in the leopard cat habitat, particularly vaccination programs and population control measures for free-roaming dogs and cats.

Feline lymphomas are associated with the transduction and activation of cellular proto-oncogenes, such as c-myc, by feline leukemia virus (FeLV). We describe a polymerase chain reaction assay for detection of myc transduction usable in clinical diagnosis. The assay targets c-myc exons 2 and 3, which together result in a FeLV-specific fusion gene following c-myc transduction. When this assay was conducted on FeLV-infected feline tissues submitted for clinical diagnosis of tumors, myc transduction was detected in 14% of T-cell lymphoma/leukemias. This newly established system could become a useful diagnostic tool in veterinary medicine.

Oncogene-containing retroviruses are generated by recombination events between viral and cellular sequences, a phenomenon called "oncogene capture". The captured cellular genes, referred to as "v-onc" genes, then acquire new oncogenic properties. We report a novel feline leukemia virus (FeLV), designated "FeLV-AKT", that has captured feline c-AKT1 in feline lymphoma. FeLV-AKT contains a gag-AKT fusion gene that encodes the myristoylated Gag matrix protein and the kinase domain of feline c-AKT1, but not its pleckstrin homology domain. Therefore, it differs structurally from the v-Akt gene of murine retrovirus AKT8. AKT may be involved in the mechanisms underlying malignant diseases in cats.

Feline leukemia virus (FeLV) is a retrovirus with variable rates of infection globally. DNA was obtained from cats' peripheral blood mononuclear cells, and proviral DNA of pol and env genes was detected using PCR. Seventy-six percent of cats scored positive for FeLV using env-PCR; and 54 %, by pol-PCR. Phylogenetic analysis of both regions identified sequences that correspond to a group that includes endogenous retroviruses. They form an independent branch and, therefore, a new group of endogenous viruses. Cat gender, age, outdoor access, and cohabitation with other cats were found to be significant risk factors associated with the disease. This strongly suggests that these FeLV genotypes are widely distributed in the studied feline population in Mexico.

The Iberian lynx is the most endangered felid species. During winter/spring 2006/7, a feline leukemia virus (FeLV) outbreak of unexpected virulence killed about 2/3 of the infected Iberian lynxes. All FeLV-positive animals were co-infected with feline hemoplasmas. To further characterize the Iberian lynx FeLV strain and evaluate its potential virulence, the FeLV envelope gene variable region A (VRA) mutant spectrum was analyzed using the Roche 454 sequencing technology, and an in vivo transmission study of lynx blood to specified-pathogen-free cats was performed. VRA mutations indicated weak apolipoprotein B mRNA editing enzyme and catalytic polypeptide-like cytidine deaminase (APOBEC) restriction of FeLV replication, and variants characteristic of aggressive FeLV strains, such as FeLV-C or FeLV-A/61C, were not detected. Cats exposed to FeLV/Candidatus Mycoplasma haemominutum-positive lynx blood did not show a particularly severe outcome of infection. The results underscore the special susceptibility of Iberian lynxes to infectious diseases.

A nested polymerase chain reaction (PCR) was established to detect exogenous feline leukaemia virus (FeLV) proviral DNA in feline peripheral blood leukocytes (PBL). The assay detected a single copy of plasmid DNA of an infectious molecular clone of FeLV subgroup A in the sample by ethidium bromide staining in agarose gels. The utility of the nested PCR in the diagnosis of FeLV infections was compared with the detection of FeLV p27 antigen by enzyme-linked immunosorbent assay (ELISA) and virus isolation (VI). FeLV genomes were detected by PCR in all 4 samples that were positive by ELISA and VI but in none of 7 samples that were negative by the two methods. FeLV genomes were found by PCR in 13 of 39 samples from cats that were antigenaemic but from which no virus was isolated ('discordant' cats). These results demonstrated that a proportion of discordant cats harboured FeLV genome in their PBL.

Feline leukemia virus (FeLV) is a horizontally transmitted agent of the domestic cat which is known to be associated with wide spectrum of diseases of the hematopoietic system. In the present study, proviral DNAs of FeLV proviruses were examined in the tumor cells of natural killer cell lineage which is very rare in cats. In the chromosomal DNA of the tumor cells, 5 distinct bands corresponding to exogenous FeLV provirus genomes were detected by digestion with EcoRI which does not cut most FeLV isolates. Five clones of pLC1, pLC2, pLC3, pLC4, and pLC5 obtained from the 5 respective bands were analysed by restriction endonuclease mapping and Southern blot hybridization using gene-specific probes of FeLV. The results have clearly demonstrated that pLC4 and pLC5 contained large deletions in the pol and part of gag regions, while the full-length proviruses could be observed in pLC1 and pLC2. Furthermore, pLC3 contained part of a variant FeLV genome having an EcoRI site in its gag region. The molecular clones of defective and variant FeLV in this study may be useful for the further examination of tumorigenesis of large granular lymphoma in the cat.

A lambda L 47.1 clone library was constructed from BamHI digests of cellular cat DNA and was screened with cDNA probes specific for the 3'-terminus of the replication competent RD-114 virus. The first analysis of one clone (lambda-ECE 1) shows that it consists at least of a 3'-LTR and a 5' adjacent env gene. The LTR nucleotide sequences of the RD-114 cDNA clones and ECE 1 are identical within the R region and unrelated to FeLV. Otherwise, the region upstream from the 3'-LTR of ECE 1 shows homology to the transmembrane protein encoding gene of FeLV, but not to RD-114. These results imply that ECE 1 is a recombinant between an RD-114-like 3'-LTR and a FeLV-related env portion.