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Lymphocyte population changes in cats naturally infected with feline immunodeficiency virus
C Novotney1, R V English, J Housman
1Department of Companion Animal and Special Species Medicine, College of Veterinary Medicine, North Carolina State University, Raleigh 27606.
Insights
Feline immunodeficiency virus (FIV) infection in cats causes a significant reduction in CD4+ T cells, leading to inverted CD4:CD8 ratios similar to human AIDS. This makes FIV a valuable model for studying acquired immunodeficiency syndrome (AIDS).
Area of Science:
- Veterinary Immunology
- Retroviral Infections
- Comparative Immunology
Background:
- Feline immunodeficiency virus (FIV) is linked to feline acquired immunodeficiency syndrome (FAIDS).
- Human immunodeficiency virus (HIV) infection causes a reduction in CD4+ T cells and an inverted CD4:CD8 ratio, a hallmark of acquired immunodeficiency syndrome (AIDS).
- FIV is considered a potential model for studying HIV-induced AIDS.
Purpose of the Study:
- To investigate CD4:CD8 T cell ratios in cats naturally infected with FIV.
- To determine if FIV infection mirrors the CD4+ T cell reduction observed in HIV infection.
- To establish FIV as a relevant model for acquired immunodeficiency syndrome (AIDS) research.
Main Methods:
- Flow cytometry was used to analyze lymphocyte populations in naturally FIV-infected cats.
- A panel of monoclonal antibodies targeting feline lymphocyte populations was employed.
- CD4:CD8 ratios were compared between FIV-infected cats, normal cats, and cats with other chronic diseases.
Main Results:
- 13 of 19 FIV-infected cats exhibited CD4:CD8 ratios below the normal 5th percentile (0.57).
- 18 of 19 FIV-infected cats had CD4:CD8 ratios below 1, indicating inversion.
- The inverted ratios in FIV-infected cats were consistently due to a decrease in CD4+ T cells, with normal CD8+ T and B cell counts.
- Cats with other chronic diseases, including feline leukemia virus (FeLV) infections, showed near-normal CD4:CD8 ratios.
Conclusions:
- FIV infection selectively reduces CD4+ T cells in cats, mirroring the immunological defect seen in HIV-induced AIDS.
- The consistent inversion of CD4:CD8 ratios in FIV-infected cats supports its utility as a model for studying acquired immunodeficiency syndrome (AIDS).
- FIV provides a valuable animal model for understanding retroviral pathogenesis and developing therapeutic strategies for AIDS.
Abstract:
Feline immunodeficiency virus (FIV) is associated with feline acquired immunodeficiency syndrome (FAIDS) and has been suggested as a model for HIV-induced human AIDS. The most obvious immunological defect in HIV infection is a reduction in CD4+ cell numbers and an inversion of the CD4:CD8 ratio. To determine whether the same is true in FIV infection, we analyzed by flow cytometry using a panel of monoclonal antibodies to feline lymphocyte populations the CD4:CD8 ratios in cats naturally infected with the virus. We report that 13 of 19 FIV-infected cats had ratios below the 5th percentile of normal cats (0.57, established from analysis of 39 normal cats) and 18 of 19 had ratios below 1. Repeated analyses over a period of several months revealed the inverted ratios to be consistent. Analysis of lymphocyte numbers in FIV-infected cats shows that the inverted ratios are due to a decrease in CD4+ T cells, while CD8+ T and B cells remain relatively normal in number. Analysis of a group of cats with a variety of other chronic diseases, including feline leukemia virus (FeLV) infections, revealed a near-normal distribution of CD4:CD8 ratios. These findings are similar to those in HIV infections and indicate that, like HIV, FIV causes a selective reduction in CD4+ cells and should be an excellent model for studying retrovirus-induced AIDS.
