Enteric administration of a live attenuated measles vaccine does not induce protective immunity in a macaque model

To test the option of oral vaccination with a live attenuated measles vaccine (LAV), we have evaluated the potential of an orally administered enteric-coated tablet containing a candidate LAV (strain Leningrad-16, MV-L16). To this end three groups of two cynomolgus macaques each were vaccinated via different routes with 10(3.8) TCID(50) MV-L16 vaccine: intramuscularly (i.m.), intraintestinally (i.i.) upon laparotomy and via enteric-coated tablets. Upon vaccination, MV-L16 could only be isolated from one of the i.m.-vaccinated monkeys and not from any of the other five. Both the i.m.-infected monkeys and one of the i.i.-infected monkeys developed a MV-specific serum antibody response. Also, MV-specific CD8(+) IFN gamma-producing T cells could be demonstrated in all three monkeys that had seroconverted. Upon challenge with wild-type MV 1 year after vaccination, only these three monkeys proved to be protected. These data do not support the viability of the concept of oral vaccination with LAVs.