Uptake of amplifiable fragments of retrotransposon DNA from the human alimentary tract.

Abstract

Few attempts have been made to study the transfer of DNA from ingested food across the intestinal barrier. A low uptake of ingested DNA has been observed in mice, cattle and poultry. There have been no reports on humans so far. Maintenance of species barriers, protection against retrotransposons, optimisation of oral DNA vaccines and the fate of genetically modified foodstuffs are issues where this topic is of importance. We therefore used the high-copy-number rabbit retrotransposon RERV-H, and rabbit mitochondrial DNA, to study the transfer of DNA from ingested rabbit meat into the bloodstream of two human volunteers. A quantitative PCR was used to measure RERV-H levels in food and in the blood. Amplification with the primers selected results in the generation of a 250-bp fragment of RERV-H. Transfer across the intestinal epithelium could be demonstrated in both subjects. Levels of the fragment in the bloodstream peaked at 1-3 h after ingestion of the experimental meal. One hour after a meal of rabbit meat containing 10(14) copies of RERV-H DNA, a maximum concentration of 200 copies of RERV-H DNA per ml of peripheral blood was observed, which corresponds to the uptake of approximately 10(6) RERV-H DNA copies in 1 h. RERV-H DNA was detected in both cellular and plasma compartments. Both rabbit retrotransposon and mitochondrial DNA was taken up from the human alimentary tract. The size of the fragments detected is similar to that of SINE retrotransposons (approximately 300 bp). The fate and functionality of alimentary DNA in humans will require further study.