An immunisation technique for vaccinating foetuses has been developed by researchers from the University of Saskatchewan, Canada. They believe the technique could be useful for protecting against neonatal infections that are contracted at, or shortly after, birth.
Dr Philip Griebel and colleagues delivered a DNA vaccine for bovine herpes virus-1 into the amniotic fluid in the oral cavity of lambs in utero. They found that a single immunisation effectively induced systemic immune responses combined with induction of local immunity in the oral cavity. High serum antibody titres were seen, as well as a cell-mediated immune response. The researchers comment that the foetal lambs were of normal size and showed normal organ development.
The researchers say that most infectious agents enter the newborn through mucosal surfaces and that induction of effective mucosal immunity is a "chief factor for preventing an initial infection of the infant." High levels of mucosal antibody production to the bovine virus were seen.
The researchers add that DNA vaccines have a level of biological safety similar to that of inactivated vaccines. They also comment that DNA vaccines can be injected repeatedly to boost the level of immune response and that a second vaccination at birth could enhance the level of disease protection. A primary foetal immunisation combined with secondary immunisation at birth may confer protective immunity against typical "first-week infections", they say (Nature Medicine 2000;6:929).