Protection against challenge with measles virus (MV) in infant macaques by an MV DNA vaccine administered in the presence of neutralizing antibody.

Measles virus (MV) infection is the major cause of vaccine-preventable death in infants and children worldwide. It is difficult to achieve immunity to MV infection by use of vaccines in infants during the first 6-9 months of life because of the presence of maternal antibody. Morbidity and mortality due to MV infection would decrease substantially if a vaccine administered at birth could prime immunity in the presence of maternal antibody. We demonstrate here that an MV DNA vaccine administered to infant macaques in the presence of maternal antibody primes MV-specific T cell responses but not de novo neutralizing antibody. This vaccine protected 80% of the infant macaques from skin rash and MV-induced immunosuppression. A molecular interleukin-2 adjuvant was required for protection with this vaccine. This macaque model shows that infants can be vaccinated against MV in the presence of maternal antibody. These results suggest that it is possible to develop an MV DNA vaccine that could protect infants in developing countries during the first months of life.