Hemagglutination-inhibiting antibody responses with selected Group B arthropod-borne virus antigens were studied following administration of living attenuated 17D strain yellow fever vaccine to human subjects who had (a) no previous Group B arbovirus experience, (b) only 17D strain vaccine previously, (c) previous inapparent natural Japanese encephalitis virus infection and (d) complex Group B arbovirus experience previously. The results indicate the following:
1.Previous homologous or heterologous immunological experience did not suppress the yellow fever HI response to the living vaccine. On the contrary, the response was sometimes enhanced.
2.Heterologous HI responses depended upon the nature of the previous Group B arbovirus experience. (a) Subjects with no prevaccination Group B arbovirus experience developed a limited array of low-titered heterologous antibodies. (b) Subjects previously vaccinated with the 17D strain but with no other Group B arbovirus experience exhibited limited intensification and broadening of heterologous HI antibodies. (c) Subjects who had experienced some other Group B virus infection prior to yellow fever vaccination displayed a broad heterologous antibody response producing at times significantly higher HI antibody titers to other viruses.
3.Subjects with relatively low, but not with high, yellow fever neutralization indices prior to revaccination tended to show a significant increase in neutralizing antibody level in response to the vaccines.
Trainee in Virology, Training Grant No. 2E-16, N.I.H. (U.S.P.H.S.). Currently, Chief of the Serology Section, Department of Microbiology.