Identification of novel subgroup A variants with enhanced receptor binding and replicative capacity in primary isolates of anaemogenic strains of feline leukaemia virus

Feline Leukemia Virus Frequently Spills Over from Domestic Cats to North American Pumas

Feline leukemia virus (FeLV) is a gammaretrovirus with horizontally transmitted and endogenous forms. Domestic cats are the primary reservoir species, but FeLV outbreaks in endangered Florida panthers and Iberian lynxes have resulted in mortalities. To assess prevalence and interspecific/intraspecific transmission, we conducted an extensive survey and phylogenetic analysis of FeLV infection in free-ranging pumas (n = 641) and bobcats (n = 212) and shelter domestic cats (n = 304). Samples were collected from coincident habitats across the United States between 1985 and 2018. FeLV infection was detected in 3.12% of the puma samples, 0.47% of the bobcat samples, and 6.25% of the domestic cat samples analyzed. Puma prevalence varied by location, with Florida having the highest rate of infection. FeLV env sequences revealed variation among isolates, and we identified two distinct clades. Both progressive and regressive infections were identified in cats and pumas. Based on the time and location of sampling and phylogenetic analysis, we inferred 3 spillover events between domestic cats and pumas; 3 puma-to-puma transmissions in Florida were inferred. An additional 14 infections in pumas likely represented spillover events following contact with reservoir host domestic cat populations. Our data provide evidence that FeLV transmission from domestic cats to pumas occurs widely across the United States, and puma-to-puma transmission may occur in genetically and geographically constrained populations. IMPORTANCE Feline leukemia virus (FeLV) is a retrovirus that primarily affects domestic cats. Close interactions with domestic cats, including predation, can lead to the interspecific transmission of the virus to pumas, bobcats, or other feline species. Some infected individuals develop progressive infections, which are associated with clinical signs of disease and can result in mortality. Therefore, outbreaks of FeLV in wildlife, including the North American puma and the endangered Florida panther, are of high conservation concern. This work provides a greater understanding of the dynamics of the transmission of FeLV between domestic cats and wild felids and presents evidence of multiple spillover events and infections in all sampled populations. These findings highlight the concern for pathogen spillover from domestic animals to wildlife but also identify an opportunity to understand viral evolution following cross-species transmissions more broadly.

What role do endogenous retroviruses play in domestic cats infected with feline leukaemia virus?

AbstractFeline leukaemia virus (FeLV) is a retrovirus that infects domestic and wild cats around the world. FeLV infection is associated with the development of neoplasms, bone marrow disorders and immunosuppression. Viral subgroups arise from mutations in the FeLV genome or from recombination of FeLV with ancestral endogenous retroviruses in the cat genome. The retroviral endogenisation process has allowed generation of a diversity of endogenous viruses, both functional and defective. These elements may be part of the normal functioning of the feline genome and may also interact with FeLV to form recombinant FeLV subgroups, enhance pathogenicity of viral subgroups, or inhibit and/or regulate other retroviral infections. Recombination of the env gene occurs most frequently and appears to be the most significant in terms of both the quantity and diversification of pathogenic effects in the viral population, as well as affecting cell tropism and types of disease that occur in infected cats. This review focuses on available information regarding genetic diversity, pathogenesis and diagnosis of FeLV as a result of the interaction between endogenous and exogenous viruses.

Prevalence and Genomic Diversity of Feline Leukemia Virus in Privately Owned and Shelter Cats in Aburrá Valley, Colombia

The feline leukemia virus (FeLV) belongs to the family Retroviridae; it is the first feline retrovirus discovered and one of the agents that has a great impact on cats' health and the ecology of the feline population worldwide. It is associated with the occurrence of several syndromes of fatal diseases, including the development of lymphomas. Studies on FeLV have been reported in Colombia, and most of them have been approached from a clinical point of view. However, only a few studies have focused on the prevalence of the infection, while none have clarified which variant or FeLV viral subgroup is presently circulating in our country. Therefore, the present study investigated the prevalence of the infection associated with the molecular characterization of FeLV present in cats in Aburrá Valley, Colombia. The sampling of privately owned and shelter cats was performed in female (n = 54) and male (n = 46) felines; most of them were seemingly healthy according to the owner's report, with nonspecific clinical history. Immunoassay confirmed that 59.44% (95% confidence interval (CI) = 49.81-69.06%) of felines were FeLV seropositive. The molecular testing of felines using reverse transcription-polymerase chain reaction and sequencing showed that 30% (30/100) of felines were positive, and the most prevalent subgroup in the Aburrá Valley was FeLV-A. In conclusion, the frequency of leukemia virus, as revealed by molecular and serological tests, is one of the highest reported frequencies to date, and a high molecular variation is shown in the Colombian population. More studies on the behaviour of the virus in feline populations in Columbia are warranted to determine its prevalence throughout the country.

Novel Feline Leukemia Virus Interference Group Based on the env Gene

Feline leukemia virus (FeLV) subgroups have emerged in infected cats via the mutation or recombination of the env gene of subgroup A FeLV (FeLV-A), the primary virus. We report the isolation and characterization of a novel env gene, TG35-2, and report that the TG35-2 pseudotype can be categorized as a novel FeLV subgroup. The TG35-2 envelope protein displays strong sequence identity to FeLV-A Env, suggesting that selection pressure in cats causes novel FeLV subgroups to emerge.

On the concept and elucidation of endogenous retroviruses

Endogenous retrovirus (ERV) genomes integrated into the chromosomal DNA of the host were first detected in chickens and mice as Mendelian determinants of Gag and Env proteins and of the release of infectious virus particles. The presence of ERV was confirmed by DNA hybridization. With complete host genomes available for analysis, we can now see the great extent of viral invasion into the genomes of numerous vertebrate species, including humans. ERVs are found at many loci in host DNA and also in the genomes of large DNA viruses, such as herpesviruses and poxviruses. The evolution of xenotropism and cross-species infection is discussed in the light of the dynamic relationship between exogenous and endogenous retroviruses.