Page 1335 - Veterinary Immunology, 10th Edition

VetBooks.ir Retrovirus Infections in Cats

Feline leukemia virus (FeLV) and feline immunodeficiency virus
(FIV) are retroviruses. FIV causes an acquired immunodeficiency

syndrome, neurological disease, and some tumors. It is not itself
highly pathogenic, and FIV-infected cats may live for many years.
FeLV is more pathogenic and causes diverse clinical diseases
including lymphomas, leukemia, bone marrow suppression leading
to anemia, and immunosuppression. Effective vaccines against

FeLV have significantly reduced its prevalence.

Feline Leukemia

Feline leukemia virus (FeLV) is an oncogenic retrovirus that causes

both proliferative and degenerative diseases in cats (Fig. 40.2). A
unique surface protein, called feline oncornavirus cell membrane
antigen (FOCMA), is expressed on FeLV-infected cells. It is coded
for by endogenous retroviral genes within the cat genome. It is not

expressed on normal cells but rather on cells infected with FeLV or
feline sarcoma virus (FeSV). It was originally believed that the
presence of FOCMA on a cell membrane identified the cell as a
FeLV-induced tumor cell. Of those cats that fail to make

neutralizing antibodies to FeLV and remain viremic, about 80%
develop antitumor activity by making antibodies against FOCMA.
A cat that makes antibodies to FOCMA can usually destroy virus-
induced tumor cells. Unfortunately, antibodies to FOCMA do not

confer protection against FeLV-induced degenerative diseases, and
viremic cats that fail to produce anti-FOCMA antibodies are fully
susceptible to all FeLV syndromes, including lymphosarcoma.

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