Reduced memory responses to vaccination in cows naturally infected with bovine leukemia virus.

Abstract

Abstract Bovine leukemia virus (BLV) is an extremely prevalent retrovirus infecting US dairy herds. Approximately 83% of US dairy herds are BLV-positive, and the within-herd infection rate is typically between 25–50%, with the prevalence increasing as the herd size increases. Historically, BLV infection has been considered benign, leading to a lack of control for its spread. However, recent research suggests that BLV infection negatively impacts the health of the host immune system. If BLV impairs host immunity, it would have a large economic impact on the dairy industry. To assess the immune competence of dairy cattle naturally infected with BLV, both BLV- and BLV+ cows were boosted on their regular schedule with BoviShield Gold FP5 L5 HB. Samples were collected over 28 days to characterize the strength of the immune response to the vaccine stimulus. BLV+ cows produced significantly lower titers of antigen-specific antibodies in comparison to healthy, BLV- cows. In vitro assays suggest that the difference in antibody titers is related to lower interferon-γ production from T cells in response to antigenic stimulation. Our results support the hypothesis that BLV+ cows have a reduced immune response to a commonly used commercial vaccine, which suggests that BLV+ cows may be less protected by vaccines and, thus, at an increased risk of developing secondary infections.