FeLV-related sequences in DNA from a FeLV-free cat colony

Nash

Menninger

et al. 2005

J Virol

The number, chromosomal distribution, and insertional polymorphisms of endogenous feline leukemia viruses (enFeLVs) were determined in four domestic cats (Burmese, Egyptian Mau, Persian, and nonbreed) using fluorescent in situ hybridization and radiation hybrid mapping. Twenty-nine distinct enFeLV loci were detected across 12 of the 18 autosomes. Each cat carried enFeLV at only 9 to 16 of the loci, and many loci were heterozygous for presence of the provirus. Thus, an average of 19 autosomal copies of enFeLV were present per cat diploid genome. Only five of the autosomal enFeLV sites were present in all four cats, and at only one autosomal locus, B4q15, was enFeLV present in both homologues of all four cats. A single enFeLV occurred in the X chromosome of the Burmese cat, while three to five enFeLV proviruses occurred in each Y chromosome. The X chromosome and nine autosomal enFeLV loci were telomeric, suggesting that ectopic recombination between nonhomologous subtelomeres may contribute to enFeLV distribution. Since endogenous FeLVs may affect the infectiousness or pathogenicity of exogenous FeLVs, genomic variation in enFeLVs represents a candidate for genetic influences on FeLV leukemogenesis in cats.Endogenous feline leukemia virus (enFeLV) sequences are present in the genome of the domestic cat, Felis catus. They are homologous to exogenous feline leukemia viruses, which are oncogenic retroviruses capable of inducing both proliferative and degenerative diseases (15, 34). Whereas exogenous FeLVs are transmitted horizontally, endogenous feline leukemia proviruses are part of the germ line and are transmitted from parent to offspring as integral components of chromosomes (5,20). Endogenous FeLVs are found in wild species of the genus Felis closely related to the domestic cat, although they are not present in species from other lineages within the Felidae (4, 56-58). Thus, enFeLVs are believed to have entered the germ line after the initial radiation of lineages in the cat family but before the radiation of domestic cat lineage species (3,23,25), although subsequent additional integrations into the germ line may also have occurred (50).Endogenous FeLV sequences do not by themselves produce infectious virus but readily recombine with exogenous feline leukemia viruses, notably in the env region that codes for the viral coat, producing recombinant viruses with altered biological activity and pathogenicity (4,17,21,43,44,51,53,54,60). For example, the recombinant subgroup C viruses have been found to induce aplastic anemia (18). Furthermore, portions of the enFeLV env region are transcribed and translated in lymphoma and other cell lines (26), producing a truncated envelope protein that inhibits infection by exogenous subgroup B feline leukemia viruses (26). Transcription and translation of enFeLVs have also been demonstrated in tissues from healthy cats, including lymphoid tissue, suggesting a protective role for enFeLVs in vivo (7, 26). Likewise, inoculation with recombinant subgroup B exogenous FeLV attenuates ...

Section: Discussionsupporting

confidence: 74%

mentioning

confidence: 99%

Insertional Polymorphisms of Endogenous Feline Leukemia Viruses

Nash

Menninger

et al. 2005

J Virol

“…FeLV-B, -C, and -T subgroups arise in vivo through recombination between exogenous FeLV strains and domestic cat endogenous FeLVs (8,15). The endogenous feline leukemia provirus sequences are present in the genome of the domestic cat and are transmitted vertically as integral components of the germline (16). Endogenous feline leukemia virus sequences by themselves do not produce infectious virus.…”

mentioning

confidence: 99%

Genetic Characterization of Feline Leukemia Virus from Florida Panthers

Brown

Cunningham

et al. 2008

Emerg. Infect. Dis.

“…Neither provirus was found in the genomes of related species of the Felis genus, previously shown to harbor enFeLVs. The absence of mutational divergence, polymorphic incidence in cats, and absence in related species suggest that these enFeLVs may have entered the germ line more recently than previously believed, perhaps coincident with domestication, and reopens the question of whether some enFeLVs might be replication competent.Endogenous feline leukemia virus (enFeLV) sequences are present in the genome of the domestic cat, Felis catus, with an estimated 6 to 12 copies per haploid genome (4,17,28,30,31). These sequences are homologous to exogenous FeLVs (exFeLVs), which are horizontally transmitted oncogenic retroviruses capable of inducing both proliferative and degenerative diseases (12,27).…”

mentioning

confidence: 99%

“…Endogenous feline leukemia virus (enFeLV) sequences are present in the genome of the domestic cat, Felis catus, with an estimated 6 to 12 copies per haploid genome (4,17,28,30,31). These sequences are homologous to exogenous FeLVs (exFeLVs), which are horizontally transmitted oncogenic retroviruses capable of inducing both proliferative and degenerative diseases (12,27).…”

mentioning

confidence: 99%

Genomically Intact Endogenous Feline Leukemia Viruses of Recent Origin

Pecon-Slattery

O’Brien

2004

J Virol

We isolated and sequenced two complete endogenous feline leukemia viruses (enFeLVs), designated enFeLV-AGTT and enFeLV-GGAG. In enFeLV-AGTT, the open reading frames are reminiscent of a functioning FeLV genome, and the 5 and 3 long terminal repeat sequences are identical. Neither endogenous provirus is genetically fixed in cats but polymorphic, with 8.9 and 15.2% prevalence for enFeLV-AGTT and enFeLV-GGAG, respectively, among a survey of domestic cats. Neither provirus was found in the genomes of related species of the Felis genus, previously shown to harbor enFeLVs. The absence of mutational divergence, polymorphic incidence in cats, and absence in related species suggest that these enFeLVs may have entered the germ line more recently than previously believed, perhaps coincident with domestication, and reopens the question of whether some enFeLVs might be replication competent.Endogenous feline leukemia virus (enFeLV) sequences are present in the genome of the domestic cat, Felis catus, with an estimated 6 to 12 copies per haploid genome (4,17,28,30,31). These sequences are homologous to exogenous FeLVs (exFeLVs), which are horizontally transmitted oncogenic retroviruses capable of inducing both proliferative and degenerative diseases (12,27). Endogenous feline leukemia proviruses are part of the germ line and are transmitted from parent to offspring as integral components of chromosomes (4, 17). enFeLV sequences do not produce infectious virus, and attempts to rescue or induce endogenous virus by cocultivation in cell lines have failed (3,19). Restriction enzyme mapping has revealed the presence of large deletions in some enFeLVs, which would render them incapable of producing an exogenous virus (41, 42). Molecular copies of enFeLVs without major deletions were found in DNA transfection studies also to be noninfectious, presumably owing either to alterations in sequences regulating gene expression or to coding sequence mutation (42). Both frameshift and nonsense mutations have been identified in the gag and env regions of full-length enFeLVs (5, 27).Although they do not produce infections on their own, enFeLV sequences readily recombine with exFeLVs (32, 37, 43). Transmissible exFeLVs lack recombinant enFeLV segments and are classified as subgroup A (12, 15). The two other exFeLV subgroups, B and C, result from recombination between enFeLV segments and exFeLVs (27,32,35,43). Recombinant viruses may exhibit altered biological activity and pathogenicity (13,33,37,39,47); for example, the recombinant subgroup C viruses have been found to induce aplastic anemia (14). Additionally, segments of enFeLVs are transcribed and translated in lymphoma and other cell lines: a truncated enFeLV envelope protein has been detected that inhibits infection by subgroup B exFeLVs (24). Transcription and translation of enFeLV genes have also been demonstrated in tissues from healthy cats, including lymphoid tissue, raising the prospect of a protective role for enFeLVs in vivo (6,24). In contrast, a protein derived from an enFeLV env...