Quantification of viral ribonucleic acid in plasma of cats naturally infected with feline immunodeficiency virus.

Objective-To assess plasma viral RNA concentration in cats naturally infected with feline immunodeficiency virus (FIV). Animals-28 FIV-infected cats. Procedure-Cats were categorized into 1 of the 3 following stages on the basis of clinical signs: asymptomatic (nonclinical) carrier (AC; n = 11), acquired immunodeficiency syndrome-related complex (ARC; 9), or acquired immunodeficiency syndrome (AIDS; 8). Concentration of viral RNA in plasma (copies per mi) was determined by use of a quantitative competitive polymerase chain reaction (QC-PCR) assay. Total lymphocyte count, CD4(+) cell and CD8(+) cell counts, and the CD4(+) cell count-to-CD8(+) cell count ratio were determined by use of flow cytometry. Results-Plasma viral RNA concentration was significantly higher in cats in the AIDS stage, compared with cats in AC and ARC stages, Most (5/7) cats in the AIDS stage had low total lymphocyte, CD4(+) cell, and CD8(+) cell counts. Conclusions and Clinical Relevance-Concentration of plasma viral RNA is a good indicator of disease progression in FIV-infected cats, particularly as cats progress from the ARC to the AIDS stage. Determination of CD4(+) and CD8' cell counts can be used as supportive indicators of disease progression. (Am J Vet Res 2000;61:1609-1613).