Research overview: FeLV subgroups A, B, C and T

Feline leukemia virus exists as distinct subgroups defined by receptor usage and biological behavior. Subgroup A is the transmissible form present in all infections; subgroups B, C, and T arise within an infected cat through recombination or mutation and are associated with specific disease outcomes. Subgroup B links to neoplasia, C to severe nonregenerative anemia, and T to immunodeficiency through cytopathic effects on T-cells. This overview compiles the subgroup literature rather than a single source, describing how viral evolution within a host shapes which disease develops, why understanding receptor biology clarified these patterns, and why subgroup identity helps explain the diverse clinical syndromes a single initiating virus can produce in different infected cats.