Lactoferrin is an iron-binding glycoprotein found in milk, saliva, tears, and other exocrine secretions. It is known to have in vitro antiviral effects against human, feline, and canine herpesviruses. In addition, lactoferrin is known to be safe in cell culture. Bovine herpesvirus-1 (BHV-1) is a likely contaminant of in vitro embryo production. Further, trypsin treatment is not completely effective in removing the virus from these embryos. We hypothesized that a nontoxic concentration of lactoferrin might prevent replication of BHV-1 within in vitro embryo production systems. Thus, the specific objectives of this research were to determine if lactoferrin from bovine milk would inhibit BHV-1 in cell culture and to determine if in vitro-produced embryos could develop normally when cultured in lactoferrin. Two-fold dilutions of lactoferrin (from 10 to 0.625 mg/mL) were added to Madin Darby bovine kidney cells, followed in 15 min by the addition 104 PFU/mL of BHV-1 (Colorado strain). Samples of cell lysate were taken at Day 2 and virus was quantified by plaque assay. The percent of virus inhibited by the antiviral agent at each concentration was determined by comparison to equivalent samples from temporal control cultures in which no compound was added before or after inoculation (Percentage of virus inhibited = [Quantity of virus in the control sample - Quantity of virus in the compound sample]/Quantity of virus in the control sample � 100). Next, the effect of lactoferrin was determined on in vitro-produced embryos. Cumulus oocyte complexes were received from an abattoir, matured in transit, placed in fertilization drops for 6 h, and then placed in culture drops containing lactoferrin (10, 5, and 2.5 mg/mL). At Day 3.5, embryos > 4 cell stage were placed into fresh culture drops containing lactoferrin. On Day 7.5, blastocyst development was noted and the developed embryos were stained to count viable cells. Blastocyst development rate and nucleated cell count of the treated embryos were compared to those of the controls using Chi square test, and ANOVA and Tukey-Kramer HSD, respectively. Lactoferrin (10 mg/mL) inhibited 2 to 5 logs of virus. At concentrations of 5 and 2.5 mg/mL, 1 to 3 logs of virus were inhibited, and concentrations of 1.25 and 0.625 mg/mL inhibited 0 to 2 logs of virus. Lactoferrin did not affect the nucleated cell count of the treated embryos. In addition, unlike 10 and 5 mg/mL, 2.5 mg/mL of lactoferrin did not affect blastocyst development. These preliminary results indicate that lactoferrin from bovine milk can significantly inhibit BHV-1 in cell culture. Furthermore, supplementation of in vitro culture with 2.5 mg/mL of lactoferrin does not affect blastocyst development or cell count of in vitro-produced embryos.
Intraspecific bovine herpesvirus 1 recombinants carrying glycoprotein E deletion as a vaccine marker are virulent in cattle
