Bovine respiratory syncytial virus-specific IgG-1 in nasal secretions of colostrum-fed neonatal calves.

In order to determine whether nasal secretions of young calves contain passively derived antibodies to bovine respiratory syncytial virus (BRSV) and if there are differences in presence and/or subclass of these antibodies between calves fed different colostrum replacement products, 17 Holstein calves were fed 150 g of IgG in either a sprayed-dried colostrum-based (CR; n = 8) or a plasma-based colostrum replacement product (PR; n = 9) within 6 h of birth. Venous blood and nasal secretions obtained before feeding and at 24 h of age were assayed for total IgG (serum) by radial immunodiffusion and for BRSV-specific total IgG, IgG-1, and IgG-2 by indirect enzyme-linked immunosorbent assay (ELISA). Calves that were fed a CR had higher concentrations of BRSV-specific IgG and IgG-1 in their serum and nasal secretions compared to calves fed product PR; calves fed the PR had higher levels of serum BRSV-specific IgG-2. The only subclass of antibodies detected in nasal secretions was IgG-1. Re-secretion of passive IgG with neutralizing activity, onto the nasal mucosa could contribute to BRSV-associated disease-sparing observed in the laboratory and in the field. Use of PR will result in lower nasal antibodies since IgG-2 is not re-secreted.