311 RISK ASSESSMENT OF α-LACTALBUMIN TRANSGENIC PIGS

Abstract

Assessment of the general risk posed by transgenic 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 transgenic livestock need to be evaluated at 3 levels: (1) characterization of how the transgene, the transgene product, and the transgenic livestock behave in their immediate environment; that is, in their barn or pen; (2) determination of possible impacts of large-scale release of transgenic 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 the livestock population. We previously developed and characterized transgenic swine containing a mammary-specific transgene (bovine α-lactalbumin, bALAC) that results in increased milk production in sows (Bleck et al. 1998). We are currently determining whether bALAC is expressed in tissues of transgenic (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 were in generation 10 at least 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 180, 220, or 250 days after weaning. Due to the nature of swine behavior, these animals may ingest saliva, regurgitated food, and stool and urinary products as well as other bodily fluids and cells during normal housing and establishment of dominance hierarchy. In a second study, vaginal, cervical, uterine, oviductal, and ovarian tissues were collected from C females on 2 or 7 days after mating to T males. 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, and intestine. Preliminary results indicate no presence of the Tg in tissues of C animals (n = 20) after cohabitation for 180, 220, or 250 days (n = 201 samples analyzed) or at 2 (n = 3) or 7 (n = 5) days post-mating (n = 38 and 59 samples analyzed, respectively). This work provides a critical first step toward providing rigorous scientific data for risk assessment of transgenic livestock.

The USDA BRAG Program, Project No. 2005–03799, supported this work.