Immunological Studies with Group B Arthropod-Borne Viruses
V. Evaluation of Cross-Immunity against Type 1 Dengue Fever in Human Subjects Convalescent from Subclinical Natural Japanese Encephalitis Virus Infection and Vaccinated with 17D Strain Yellow Fever Vaccine
The capacity of cross-reacting antibodies to type 1 dengue virus, induced by the administration of 17D yellow fever vaccine to human subjects who possessed naturally occurring Japanese encephalitis virus neutralizing antibodies, to protect volunteers against dengue fever upon challenge with unmodified type 1 dengue virus was investigated. These studies, along with the necessary controls, provided the following information:
1.Man appears to be somewhat more susceptible to infection with unmodified type 1 dengue virus than suckling white swiss mice.
2.Subjects, whose only prior Group B arbovirus experience had been the 17D yellow fever vaccination, did not develop detectable type 1 dengue neutralizing antibodies in response to the YF vaccine and did not display any immunity against type 1 dengue fever.
3.Subjects, whose only previous Group B arbovirus experience had been a subclinical natural infection with Japanese encephalitis virus, did not possess detectable type 1 dengue neutralizing antibodies and did not exhibit immunity against type 1 dengue fever.
4.Subjects with pre-existing Japanese encephalitis virus antibodies developed low levels of type 1 dengue neutralizing antibodies following vaccination with the 17D yellow fever vaccine. Despite this, these subjects developed classical dengue fever when exposed to unmodified type 1 dengue virus. At the onset of symptoms, which was uniformly accompanied by viremia, moderately high levels of neutralizing antibodies had already appeared in the serum.