Host Immune Responses after Administration of Inactivated Venezuelan Equine Encephalomyelitis Virus Vaccines. II. Kinetics of Neutralizing Antibody Responses in Donors and Adoptively Immunized Recipients

Abstract

Lymphoid cell responses to immunization with various formalin-inactivated Venezuelan equine encephalomyelitis (VEE) virus vaccines were monitored in mice by assessment of the development of both the neutralizing antibody response in sera of spleen cell donors and the adoptive neutralizing antibody response induced by spleen cell transfer in recipients. Donors immunized intraperitoneally with formalin-inactivated VEE vaccine (a single dose or a dose on three consecutive days) developed early serum neutralizing antibody responses (⩾1:88–1:100) by seven days after immunization. Recipients of spleen cells from such mice were, however, incapable of eliciting a neutralizing antibody response (⩽1:10). Only spleen cells from donors immunized with inactivated VEE vaccine plus adjuvants (particularly complete Freund's adjuvant and Bordetella pertussis) were consistently capable of producing early, high-titer serum neutralizing antibody responses in adoptively immunized recipients (⩾1:50–1:120 on day 4). The magnitude of neutralizing antibody responses of donors to inactivated VEE vaccines did not serve as a useful indicator of whether spleen cells from such mice could adoptively induce antibody responses in recipients. Finally, treatment of immune spleen cells with rabbit antiserum to mouse thymocytes, but not with rabbit antiserum to mouse y-globulin or normal rabbit serum, abolished the capacity of such cells to transfer an antibody response adoptively.