Scientists Explore ways to Vaccinate in the Face of Maternal Antibodies

November 8, 2006 — 

Veterinarians and producers attempting to vaccinate young livestock have always had to battle the very same immune system that they were trying to stimulate. USDA scientists are exploring new technologies to find ways around this problem.

Maternal antibodies pose a challenge when attempting to promote active immunity in very young animals. USDA scientists with the Agricultural Research Service (ARS) in Ames, IA are experimenting with using cold viruses or T-cells as mechanisms to avoid the pitfalls of passive immunity. The theory is that the vaccine antigens could be presented to the immune system by way of either a virus vector or through stimulation of the cell mediated immune system.

One experiment uses attenuated human adenoviruses, to which animals have no maternal antibody resistance, as vectors for the delivery of swine influenza genes. Researchers were able to stimulate active immunity even in pigs having suckled maternal influenza-fighting antibodies. The recombinant adenoviruses are self-limiting and thus will not spread to other cells or littermates of vaccinated pigs.

Another experimental study examined exposing young calves to Bovine Viral Diarrhea Virus (BVDV) in the presence of maternal antibodies. It was observed that this resulted in a T-cell response to fight off the infection. This process gets around circulating maternal antibodies by stimulating T-cell-mediated immunity to BVDV. According to Cyril Gay, national program leader for ARS's Animal Health research programs, the results "indicate that the cellular branch of the immune system is responsible for the protective immunity seen after a challenge with a fully virulent virus."

Source:
Agricultural Research magazine, November/December, 2006