Adenoviral-mediated gene transfer to murine small intestine is more efficient in neonates than adults.

Purpose: The authors sought to assess the feasibility of in vivo gene transfer to the small intestine using recombinant adenovirus in neonatal and adult mice.

Methods: H5.010CMVlacZ is a replication-defective, E1-deleted human type 5 adenovirus, which contains the lacZ gene under the control of a cytomegalovirus promoter and enhancer. The lacZ gene was used as a marker because its gene product, beta-galactosidase, is readily detected by X-gal histochemistry. Sixty neonatal (3 to 5 days old) and 45 adult (6 to 8 weeks old) C57BL/6 mice were investigated. Intestinal gene transfer was attempted with H5.010CMVlacZ by intraperitoneal (i.p.), intraluminal (IL), and intramural (i.m.) injection. Based on prior studies, the optimal dose of H5.010CMVlacZ was 1 x 10(8) plaque forming units (pfu/mL). Control animals received saline injections. Gene transfer on repeat administration of adenovirus has been shown to be prevented by neutralizing antibody. To determine if neonatal inoculation induced a humoral immune response, neonates (n = 5) that received i.p. injections were rechallenged with intravenous H5.010CMV alkphos, a similar adenoviral construct containing the alkaline phosphatase marker gene. Serum samples were analyzed by Western blot to detect the presence of adenoviral-specific antibody.

Results: Gene transfer to neonatal small intestine was successful by IL gastric (n = 8/10), IL jejunal (n = 9/10) and i.p. (n = 10/10) routes 2 days after injection. Macroscopic staining was present in 90% of standardized 2-cm small bowel segments. Transgene expression was identified in intestinal smooth muscle, serosa, and epithelium. Gene transfer to the adult small intestine was successful by IL jejunal (n = 4/5), i.m. (n = 5/5), and i.p. (n = 1/5) injection of adenoviruslacZ with focal staining (< 5% of 2-cm segments) in epithelium including crypts, muscle, and serosa. Three weeks after i.p. H5.010CMVlacZ in neonates, intravenous injection with H5.010CMValkphos resulted in hepatic transgene expression (n = 4/5) that was indistinguishable from a primary intravenous inoculation; persistent, lacZ expression was not detectable in the liver or intestine (n = 0/5). Western blot analysis detected adenoviral-specific antibodies after adult IM but not after neonatal i.p. injection. Furthermore, 3 weeks after neonatal i.p. injection repeat administration by the i.m. route was successful (n = 4/ 4).

Conclusion: Gene transfer to neonatal and adult small intestine is feasible using recombinant adenovirus and is more efficient in neonates as indicated by increased surface area of marker gene expression, effectiveness of intraperitoneal delivery, and the ability to readminister recombinant adenovirus.