Cat DiseasesCatsLeukemia Virus, FelineLeukemia, FelineRetroviridae InfectionsSarcoma Viruses, FelineImmunodeficiency Virus, FelineTumor Virus InfectionsFeline Acquired Immunodeficiency SyndromeLynxProvirusesCanarypox virusLeukemia, ExperimentalRetroviridae Proteins, OncogenicViral Envelope ProteinsGenes, envReceptors, VirusTerminal Repeat SequencesAntigens, ViralDNA, ViralThymus NeoplasmsAntibodies, ViralMolecular Sequence DataRetroviridaeViral VaccinesBase SequenceSpecific Pathogen-Free OrganismsHelper Viruses