Feline leukemia virus: current status of the feline induced immune depression and immunoprevention

Abstract

This is a review of the current knowledge of feline leukemia virus (FeLV) associated with immune depression observed in cats. It will focus on the clinical and experimental observations associated with feline retroviral infection and presence in vivo and in vitro. We will briefly describe retroviral-associated acquired immune deficiency syndrome associated with FeLV infection in the cat and specific cellular pathology associated with FeLV latency. In addition, we will focus on the action of FeLV-p15E in vitro and describe possible mechanisms of the FeLV-associated immunosuppression observed both in vivo and in vitro. Lastly, we will evaluate the current status of immunoprevention of FeLV. We will not attempt an in-depth analysis of the current literature; our focus is to review current findings as they relate to feline AIDS and immunotherapy.

High prevalence of non-productive FeLV infection in necropsied cats and significant association with pathological findings

“…Previous studies have revealed possible pathogenetic mechanisms of latent FeLV infection. Depression of the specific and unspecific cellular immune response has been shown (Lafrado et al, 1989;Olsen et al, 1987). True latent infections are characterized by the possibility to reactivate virus replication.…”

Tumor cells expressing a retroviral envelope escape immune rejectionin vivo

“…In the cat, the feline leukemia virus induces leukemia but also a severe immunosuppression leading to death, without leukemia, in Ͼ30% of the infected animals (reviewed in ref. 31). Immunosuppression of the host could therefore be an important factor not only in the rate of the pathological development of viral infections, but also in the nature of the pathologies themselves.…”

Important mammalian veterinary viral immunodiseases and their control

“…Such affected cats however also produce antibodies to viral antigens (gp70, P15E, P27, P15, and P10) which are continuously produced along with whole virions and feline oncornavirus cell membrane antigen (FOCMA) in tumour bearing cats [98]. The viral antibodies bind respective antigens and form small and mediumsized nephrotoxic circulating immune complexes [102][103][104][105]. This is a continuous process over a long period depleting circulating complement and consequently adversely affecting beneficial antiviral complement requiring functions of immune cytolysis and cytotoxicity.…”