Altered tryptophan metabolism in FIV-positive cats.
BACKGROUND
Feline immunodeficiency virus (FIV) is analogous to human immunodeficiency virus, the causative agent of human acquired immunodeficiency syndrome (AIDS). In AIDS patients, a progressive reduction in serum tryptophan concentration occurs because of activation of an inducible tryptophan degradation pathway mediated by elevated lamda-interferon production.


OBJECTIVE
Cats infected with FIV have increased tryptophan catabolism evidenced by reduced circulating concentrations of tryptophan and increased concentrations of the tryptophan catabolite kynurenine.


METHODS
Convenience sample of 235 cats submitted for diagnostic FIV serology (115 FIV-negative and 120 FIV-positive cats).


METHODS
Retrospective, cross-sectional study. Serum was assayed for tryptophan and kynurenine using a high performance liquid chromatography assay with fluorescence and ultraviolet detection, respectively.


RESULTS
Tryptophan and kynurenine concentrations were log-normally distributed. Geometric mean concentrations were: tryptophan: FIV-positive 30.6 microM (95% CI: 26.8 34.8 microM), FIV-negative 48.9 [microM (95% CI: 43.6-54.9 microM) (P < .001); kynurenine: FIV-positive 22.7 microM (95% CI: 25.5-10.9 microM), FIV-negative 9.9 microM (95% CI: 20.3-9.03 microM) (P < .001). The ratio of kynurenine to tryptophan was: FIV-positive 4.93 (95% CI: 5.62-4.32), FIV-negative 1.34 (95% CI: 1.53 1.17) (P < .0001).


CONCLUSIONS
Serum tryptophan concentration was significantly lower and serum kynurenine concentration was significantly higher in FIV-positive cats. The kynurenine: tryptophan ratio was >3-fold higher in FIV-positive animals, indicating increased tryptophan catabolism in this group. Dietary or pharmacologic intervention to support serum tryptophan concentrations has been shown to be clinically useful in humans with AIDS and might be applicable to cats with FIV infection.
Kenny
Martin J
MJ
School of Clinical Veterinary Sciences, University of Bristol, Langford House, Langford, UK. m.j.kenny@bris.ac.uk
Baxter
Katie J
KJ
Avery
Nicholas C
NC
Addie
Diane
D
Gruffydd-Jones
Tim
T
Tasker
Séverine
S
D000818:Animals; D002371:Cat Diseases / Q000097:blood / Q000378:metabolism*; D002415:Cats / Q000097:blood / Q000378:metabolism*; D003430:Cross-Sectional Studies; D016181:Feline Acquired Immunodeficiency Syndrome / Q000378:metabolism*; D005260:Female; D016089:Immunodeficiency Virus, Feline; D007735:Kynuramine / Q000097:blood; D008297:Male; D012189:Retrospective Studies; D014364:Tryptophan / Q000097:blood / Q000378:metabolism*
D007735:Kynuramine; D014364:Tryptophan