Feline Immunodeficiency Virus (FIV) is a Lentivirus that infects cats and is closely related to Human Immunodeficiency Virus (HIV). A vaccine for FIV is available but its efficiency is uncertain. Vaccinated cats become sero-positive which may make it difficult to maintain an accurate surveillance program that uses antibody presence to determine infection rates. Unvaccinated cats with antibody titers to FIV always have active virus that can be isolated from their lymphoid tissues, often at very low levels (less than 10 virions per 1,000 cells). FIV can cause Acquired Immune Deficiency, but with supportive therapy most FIV infected cats can live for many years with the virus.
The virus is spread primarily through saliva (via bites), and through blood to blood contact. Male cats are most often infected because of territorial fights with other cats. FIV targets CD4 and CD8 lymphocytes and macrophages. The virus often causes these cells to go through a programmed suicide called Apoptosis, over time causing a depletion of these cells and immunosuppression, which can lead to secondary bacterial, viral, and fungal infections.
Our test for FIV antibodies is an Indirect Fluorescent Antibody (IFA) procedure that is carried out on Teflon matted slides that contain fixed virus infected cells (UCD Petaluma Strain/CRFK cells). This method requires the use of diluted patient serum being placed on the slides and incubated for 60-minutes. The slide is then washed and a fluorescein conjugated anti-cat globulin is placed on the slide. If any antibodies to FIV are present in the patient serum they will combine with the FIV antigen fixed to the slide surface. The IFA conjugate will then be bound to the FIV antibodies and the resulting antibody-conjugate complex viewed with an ultraviolet microscope are seen as bright areas of fluorescence in the cytoplasm of infected cells. The total number of infected cells on our slides does not exceed 40% which leaves the negative cells to enhance contrast with the infected ones.
