title: Diagnostic utility of CD4%:CD8 low% T-lymphocyte ratio to differentiate feline immunodeficiency virus (FIV)-infected from FIV-vaccinated cats.
abstract: Antibody testing based on individual risk assessments is recommended to determine feline immunodeficiency virus (FIV) status, but ELISA and Western blot tests cannot distinguish between anti-FIV antibodies produced in response to natural infection and those produced in response to FIV vaccination. The aim of this cross-sectional study was to test the hypothesis that FIV-infected cats could be differentiated from FIV-vaccinated uninfected cats using lymphocyte subset results, specifically the CD4%:CD8(low)% T-lymphocyte ratio. Comparisons of the CD4%:CD8(low)% T-lymphocyte ratio were made among the following four groups: Group 1 - FIV-infected cats (n=61; FIV-antibody positive by ELISA and FIV PCR positive); Group 2 - FIV-uninfected cats (n=96; FIV-antibody negative by ELISA); Group 3 - FIV-vaccinated uninfected cats (n=31; FIV-antibody negative by ELISA before being vaccinated against FIV, after which they tested FIV ELISA positive); and Group 4 - FIV-uninfected but under chronic/active antigenic stimulation (n=16; FIV-antibody negative by ELISA; all had active clinical signs of either upper respiratory tract disease or gingival disease for ≥ 21 days). The median CD4%:CD8(low)% T-lymphocyte ratio was lower in Group 1 (1.39) than in each of the other three groups (Group 2 - 9.77, Group 3 - 9.72, Group 4 - 5.64; P<0.05). The CD4%:CD8(low)% T-lymphocyte ratio was also the most effective discriminator between FIV-infected cats and the other three groups, and areas under ROC curves ranged from 0.91 (compared with Group 4) to 0.96 (compared with Group 3). CD4%:CD8(low)% shows promise as an effective test to differentiate between FIV-infected cats and FIV-vaccinated uninfected cats.
authors.affiliation: Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, 625 Harrison St., West Lafayette, IN 47907, USA. Electronic address: catvet@purdue.edu.
authors.forename: Annette
authors.initials: A
authors.lastname: Litster
authors.affiliation: Research and Development Department, IDEXX Laboratories, Westbrook, ME, USA.
authors.forename: Jui-Ming
authors.initials: JM
authors.lastname: Lin
authors.affiliation: Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, 625 Harrison St., West Lafayette, IN 47907, USA.
authors.forename: Jamieson
authors.initials: J
authors.lastname: Nichols
authors.affiliation: Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, 785 Harrison Street, West Lafayette, IN 47907, USA.
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Weng
mesh_terms: D000818:Animals; D016516:CD4-CD8 Ratio / Q000662:veterinary*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002415:Cats; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D016181:Feline Acquired Immunodeficiency Syndrome / Q000175:diagnosis* / Q000276:immunology / Q000517:prevention & control; D005260:Female; D016089:Immunodeficiency Virus, Feline / Q000276:immunology*; D008297:Male; D014611:Vaccination / Q000662:veterinary*
keywords: CD4; CD8(low); Cat; Diagnosis; FIV Vaccine; Retrovirus