Human Lymphocyte Proliferation Responses following Primary Immunization with Rabies Vaccine as Neoantigen

ABSTRACT Evaluation of the T-cell immune response following primary antigenic challenge with a neoantigen is a critical aspect of assessment of the cellular immune response. While many antigens can be used to accurately assess in vitro T-cell proliferation to a recall antigen, only a few neoantigens have been tested for their capacities to measure T-cell responses in vitro to a primary immunization. Rabies vaccination is an excellent candidate for the testing of T-cell proliferation responses to a primary immunization because few individuals have been exposed to rabies virus antigens. In the present study 14 rabies vaccine-naı̈ve, healthy adult volunteers were immunized against rabies virus, and T-cell proliferation and antibody responses were measured before and after vaccination. Optimal lymphocyte proliferation to soluble rabies virus antigen occurred after 8 days in culture. The average level of uptake of tritiated thymidine postimmunization was 29,620 ± 4,448 cpm, whereas preimmunization levels were 12,660 ± 3,448 cpm (P = 0.002). All individuals showed increases in rabies virus antibody titers from <0.05 to 5.59 ± 1.64 IU/ml. The degree of proliferation to tetanus toxoid as a recall antigen was similar to the response to rabies virus antigen among the cohort. Due to high levels of preimmunization proliferation, four subjects failed to demonstrate a twofold increase in response to rabies virus antigen. The high levels of T-cell responses may be due to a viral superantigen effect in some individuals. Rabies vaccination offers a safe and effective means for measurement of both T- and B-cell immune responses to a neoantigen in healthy and immune suppressed individuals.