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Understanding Feline Immunodeficiency Virus Infection

Grant, C. K., E. A. Fink, et al. (2009). “Improved health and survival of FIV-infected cats is associated with the presence of autoantibodies to the primary receptor, CD134.” Proc Natl Acad Sci U S A 106(47): 19980-5.

Feline immunodeficiency virus (FIV) is an important pathogen of cats, causing lifelong infection and ultimately death from immunosuppression. These researchers examined antibody levels to various viral and cellular proteins in stored serum samples collected from FIV-infected cats over 30 years. They found very strong antiviral responses to several virus proteins, including the major surface protein of the virus. Interestingly, they also found evidence of antibodies to the feline cellular protein used by the virus to attach to and infect the cell (CD134). Even more remarkable, they found that this antibody only bound the cellular protein when the viral attachment protein was bound to it. Thus, binding of the virus to this cellular protein reveals a site on the cellular protein that is not normally “visible” to the immune system of the cat, leading to antibody production to this cellular protein. In a laboratory experiment, they found that not only did antibodies to the virus protein inhibited virus infection, but antibodies to the cellular protein targeted by the virus did so as well. When they evaluated antibody levels from cats of known health status, the highest percentage of cats positive for this cell-specific antibody were healthy and asymptomatic. In contrast, samples negative for this antibody were largely acquired from cats that were ill. In assessing viral load in the blood of 20 infected cats and comparing that to antibody levels to the CD134, the researchers found that cats with high viral loads (poorer prognosis) did not have measurable levels of antibody to the CD134. The findings are consistent with a role for anti-cell receptor antibodies in protection from virus spread and disease progression. [MK]
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Related articles:
Hosie, M. J., D. Addie, et al. (2009). “Feline immunodeficiency ABCD guidelines on prevention and management.” J Feline Med Surg 11(7): 575-84.

Levy, J., C. Crawford, et al. (2008). “2008 American Association of Feline Practitioners’ feline retrovirus management guidelines.” Journal of Feline Medicine & Surgery 10(3): 300-316.
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