311 RISK ANALYSIS OF α-LACTALBUMIN TRANSGENE TRANSFER TO NON-TRANSGENIC CONTROL ANIMALS DURING REARING AND BREEDING

Abstract

Assessment of general risk posed from transgenic (T) animals is important to their future contributions to society. Identification of potentially harmful properties of transgenic livestock is the initial step in a risk assessment. Direct and indirect impacts of potential harmful properties of T livestock need to be evaluated at 3 levels, namely (1) characterization of how the transgene, its product, and the T livestock behave in their immediate environment, that is, in their barn or pen; (2) determination of possible impacts of large-scale release of T livestock, that is, if they were to be integrated into the larger population of food animal livestock; and (3) determination of the more complex environmental and safety consequences of their release into livestock populations. We previously developed and characterized transgenic swine containing a mammary-specific transgene (bovine α-lactalbumin, bALAC) that results in increased milk production in sows. We currently are determining whether bALAC is expressed in tissues of T swine other than the lactating mammary gland and whether the transgene DNA (Tg) crosses into non-transgenic control (C) swine under various physiological and physical conditions. The specific aims addressed in the present study were to determine: (1) whether the Tg can be transferred directly from T animals to C animals by physical association or contact and (2) whether the Tg can be transferred directly from an adult T animal to an adult C animal via mating. The T animals utilized in these studies are in at least generation 10 and have stable incorporation of the Tg. Comparable age- and weight-matched animals, T and C, were housed together allowing for general contact that is normal within swine production, for either 180, 220, or 250 d of age after weaning. Swine due to their behavior ingest saliva, regurgitated food, and stool or urinary products, as well as other bodily fluids and cells during normal housing. In a second study, vaginal, cervical, uterine, oviductal, and ovarian tissues from C females on 2, 7, or 90 d after mating to T males and penis, bulbourethral gland, urethra, testis, and epididymis tissues from C males on 2 or 7 days after mating to Tg females were collected. The presence of Tg in tissues from all C animals was tested via PCR. We have analyzed for the presence of the Tg in various tissues [including mammary gland, salivary gland, skin (sebaceous gland), muscle, lung, liver, kidney, brain, ovary, oviduct, uterus, cervix, vagina, penis, bulbourethral gland, urethra, testis, epididymis, and intestine]. Results indicate no presence of the Tg in tissues of C animals (n = 28) after co-habitation for 180, 220, or 250 d (n = 305 samples analyzed) or at 2 (n = 5), 7(n = 14), or 90 (n = 2) d post-mating (n = 60, 174, or 24 samples analyzed, respectively). The present results suggest that there is no horizontal Tg transmission between T and C pigs due to rearing or mating. This work provides a critical step toward providing rigorous scientific data for risk assessment of transgenic livestock.

This project supported by the USDA BRAG Project #2005-03799.