Chapter 127 - Animal Models for Lentivirus Infections — Feline Immunodeficiency Virus

Abstract

Feline immunodeficiency virus (FIV) is a naturally occurring feline lentivirus analog of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). FIV causes immunodeficiency disease in its natural host and represents a non-primate model, which is useful to study certain aspects of HIV infection not addressable in humans. Domestic cats are the natural host for FIV, for which no specialized treatment is required. As with HIV, SIV, and all known retroviruses, susceptibility to FIV is inversely related to age as younger animals, especially neonates, have more rapid disease progression than adults. Inoculation dose varies immensely in experimental transmission studies due to the influence of route, inoculum source, and study design. The inocula used in this method include whole blood, plasma, infected cells, and tissue culture supernatant. FIV is infectious via intravenous, intraperitoneal, intradermal, or subcutaneous injection as well as by atraumatic instillation on to the oral, vaginal, or rectal mucosa. Detection methods for FIV parallel those for HIV. Plasma viral RNA, as measured by quantitative competitive reverse transcriptase-polymerase chain reaction (QCPCR), is the most relevant means to monitor active virus burden. One of the hallmarks of FIV infection, as with HIV infection, is the loss of CD4+ T lymphocytes (CD4 cells). CD4 cytopenia typically occurs late in the course of disease, but can occur within weeks of infection in accelerated disease models and in neonates. Antibodies directed against FIV can be detected in serum or plasma by ELISA or western blot as early as two weeks post-infection, and typically persist throughout the disease. Neutropenia, lymphopenia, and anemia are typical of FIV infection in cats. Because of the similarities between FIV and HIV infections, FIV can be useful in testing of antiviral drugs directed toward targets shared by the two viruses.