0 EID50/animal (1 ml per nostril) was performed using a system designed for administration of the Flu Avert™ IN vaccine (Heska Corporation, Loveland, CO, USA). Booster vaccination was performed using the same dose and method. The control groups were administered Selleckchem CP673451 phosphate buffered saline (PBS) in the same manner. Monitoring of the general condition of the yearlings was carried out for 21 days post-vaccination (PV)

using the point system [11], in which the following parameters are scored: general health: normal general state (score = 0), illness/depression/normal appetite (1), illness/depression/loss of appetite (2), dehydration (2), exhaustion (4), inability to stand (30), on the edge of death (50), and death (100); respiratory observations: shortness of breath (2), dyspnea (4), cough 2–5 times in 10 min (1), cough 6–20 times in 10 min (2), cough more than 20 times in 10 min (3); ocular observations: lacrimation (1), moderate mucopurulent secretion (2), severe mucopurulent secretion (4), mild conjunctivitis (2), strong conjunctivitis (4); nasal observations: MK0683 molecular weight serous secretion of mucus nasal discharge (1), moderate mucopurulent nasal discharge

(2), severe mucopurulent nasal discharge (4), sneezing 2–5 times in 10 min (1), sneezing 6–20 times in 10 min (2), sneezing more than 20 times in 10 min (3); rectal temperature: 38.5–39.0 °C (1), 39.1–39.5 °C (2), and above 39.6 °C (3). Nasopharyngeal swabs were collected from all groups on days 1, 3, 5 and 7 PV, placed into tubes containing 1 ml of viral transport medium (phosphate-buffered

saline containing 40% glycerol and 2% antibiotic solution [1000 U/ml benzylpenicillin, 1000 U/ml streptomycin, 250 mg/ml fungizone]) and stored at −70 °C until analysis. The viral titers were determined using 10-day-old CE, calculated using the method of Reed and Muench [26] and expressed as log10 EID50/0.2 ml. The specificity of the virus was determined using the commercial Directigen Flu Casein kinase 1 A rapid assay (Becton Dickinson, Franklin Lakes, NJ, USA). Blood samples were collected from the animals in each group 1, 2, 3, 4, 5, 6, 9 and 12 months PV for the detection of antibodies against EIV using the hemagglutination inhibition (HAI) assay. Before sampling, the animals were sedated with 20–40 μg/kg detomidine (Pfizer Animal Health, New York, NY, USA). Blood samples were collected via jugular venipuncture into serum separator tubes (Vacutainer; Becton Dickinson, USA) for isolation of serum. The HAI assay was performed according to Ref. [18] using chicken red blood cell suspensions (1%). The native virus A/HK/Otar/6:2/2010 (working dose of 4 hemagglutinating units) was used as the antigen. Ten yearlings from single vaccinated group or double vaccinated group or control group were challenged with the homologous wild-type virus A/equine/Otar/764/07 (Н3N8) at 1, 2, 3, 4, 5, 6, 9 and 12 months PV.