Dr. Philip J. Griebel and colleagues, from the University of Saskatchewan in Canada, had previously shown that oral DNA vaccination in utero could induce high serum antibody titers and cell-mediated immunity in fetal lambs.

In the current study, Dr. Griebel's team shows that this vaccination strategy can induce mucosal immunity and immune memory in newborn lambs.

At 121 to 124 days gestation, an incision was made in the abdomen of the pregnant sheep. The uterus was then exposed and vaccine delivered through small needle passed through the uterine wall into the fetal oral cavity. After the needle was withdrawn the abdomen was closed in standard fashion.

The immune effects of bovine herpesvirus-1 (BHV-1) and hepatitis B surface antigen DNA vaccines were assessed, the authors note in the February 15th issue of The Journal of Immunology.

Twelve of 15 newborn lambs that received the BHV-1 vaccine in utero had a detectable immune response, the authors report. Both mucosal and systemic immune responses were noted and a strong anamnestic response remained for at least 3 months after birth. In addition, responding animals demonstrated less viral shedding than control animals after intranasal challenge with BHV-1.

Three of the four lambs that received hepatitis B vaccine in utero demonstrated protective antibody levels, the investigators state.

"The present investigation supports the conclusion that a competent immune system is present before birth and adaptive immune responses induced in utero are functional in the neonate," the researchers write. "If efficient and consistent oral DNA delivery can be achieved in utero, then this route of delivery might provide new strategies for both vaccination and gene therapy."

J Immunol 2002;168:1877-1885.