Feline Immunodeficiency Virus (FIV): Evaluation of Viral Load With Quantitative Competitive Polymerase Chain Reaction (QC-PCR) in Cats Treated With AZT
Facultad de Ciencias Veterinarias (UBA), A. Clínica Médica de Pequeños Animales
Buenos Aires, Argentina
Feline Immunodeficiency Virus (FIV) infection in domestic cats results in an acquired immunodeficiency syndrome (AIDS) like to HIV in human.
In Argentina FIV infection is greater than feline leukemia virus what result in an excellent model to study HIV infection as well as to improve pet cats health. The purpose of this study was to evaluate AZT-response in cats with FIV.
Material and Methods
A longitudinal analysis, on 7 cats were performed during 12 months under Zidovudine (AZT) 5mg/kg (bid) every other month as only treatment. CD4/CD8 ratio, AGP, Albumin/Globulin ratio and viral load were studied. These variables were analysed at basal time, 6 and 12 months of treatment.
FIV was confirmed by serology and PCR. In addition to the evaluation of the clinical signs blood chemistry, hematology and other complementary diagnostic methods. CD4/CD8 ratio was performed with: 8100-01 Sowthern Biotechnology, anti CD4 Vpg 34, Willett, Glasgow University, anti CD8, VPG9, Willett, Glasgow University and Fluorescent antimouse IgG Sowthern Biotechnology, Becton and Dickinson Facs Scan Citometer. Feline α-1 glycoprotein (AGP) was performed with radial immunodiffusion test provided by Ecos Institute, Japan. Viral load was measured with Quantitative competitive chain reaction (QC-PCR).
ANOVA-Friedman's test following by Dunn's multiple-comparison test and Spearman's correlation were carried out. Values are expressed as mean ± SEM being significant p<0.05.
CD4/CD8 (Figure 1) showed significant differences among the evaluated times (ANOVA p = 0.016), having a significant increase at 6m vs. basal (p<0.05). Viral load (Figure 2) also showed differences (ANOVA p=0.0003) among the times and there are a significant decrease (p<0.01) between 6m vs. basal. Viral load vs. CD4/CD8 (Figure 3) are negative correlated (r = -0.71; p = 0.0003). The others variables did not show significant differences or correlation among them as long as in the evaluated times. Laboratory results and clinical signs showed a great improve.
After 6 months of treatment a stressed decrease of viral load and increase of CD4/CD8 ratio were observed. These changes were associated with improvement of clinical signs and laboratory finding.
Nevertheless, when the parameters previously mentioned were re-evaluated at 12 months, an escape phenomenon is evidenced. This event could be explained by a resistance developed to AZT when the drug is indicated alone, being necessary to study the effect of therapeutics cocktails.
Click on an image to see a larger view.
Figure 1. Variation of CD4/CD8 ratio
*p<0.05 6m vs. basal.
Figure 2. Variation of viral load
**p<0.01 6m vs. basal.
Figure 3. Correlation between Viral load vs. CD4/CD8