Humoral immune response of asymptomatic cats naturally infected with feline leukemia virus.

The humoral immune response of cats that were naturally infected with the feline leukemia virus (FeLV) was examined after antigenic stimulation with the synthetic antigen poly(L-Tyr, L-Glu)-poly(DL-Ala)-poly(L-Lys). The primary humoral antibody response in FeLV-infected cats was both delayed and greatly reduced, compared with that seen in uninfected control cats. A similar discordance was observed after secondary stimulation with the antigen, in the FeLV-infected cats had both a delayed response and a reduced response, compared with uninfected cats. The levels of total immunoglobulins of the immunoglobulin G and immunoglobulin M classes in the sera of FeLV-infected cats were significantly higher (two- and threefold, respectively) than were those of the uninfected control animals. The presence of an impaired humoral immune response to newly presented antigens in the presence of elevated immunoglobulin levels has been thoroughly documented in the case of people with the acquired immunodeficiency syndrome. This further emphasizes the potential value of FeLV-infected cats as a model for human acquired immunodeficiency syndrome.