2.5 Serology
Serum samples were being collected at specific time-points from all cats for detection of SARS-CoV-2-specific antibodies (Figure 1). For this reason, the cats were mildly sedated with the alpha-2 adrenoceptor agonist dexmedetomidine (10 μg/kg, im). Approximately 40 minutes after administration and once the procedures were completed, sedation was rapidly reversed by the administration of the specific alpha-2 adrenoceptor antagonist, atipamezol (100 μg/kg, im).
The commercially available ID Screen® SARS-CoV-2 Double Antigen Multi-species ELISA (ID.vet, Montpellier, France) kit was used. The antigen in this immunological assay is the N protein of SARS-CoV-2, and its format enables the detection of SARS-CoV-2-specific antibodies in the tested sera, irrespective of their isotype. Testing was performed following the manufacturer’s instructions. Optical density (OD) values were recorded using a Stat Fax 3200 microplate photometer (Awareness Technology Inc., Palm City, FL, USA). For each sample, S/P% percentages were calculated as follows: (ODSample-ODNegative Control)/(ODPositive Control-ODNegative Control) × 100, with serum samples presenting S/P% ≥ 60% being considered as positive.
Additionally, anticoagulated blood samples from all cats obtained on D16 were tested for Feline immunodeficiency virus (FIV)-specific antibodies and Feline leukemia virus (FeLV) antigens, using a rapid enzyme immunoassay test (SNAP® FIV/FeLV Combo Test; IDEXX Laboratories Inc., Westbrook, ME, USA).