Influenza Ha Dna Induces Th1 Cells And Protection Despite Limited Antibody Responses

The relative ability of influenza HA DNA vaccines to induce cellular and humoral immunity after one or more doses and the persistence of this response have not been fully elucidated. HA DNA induces a potent Th1 response. Although this response wanes 12 weeks after a single immunisation, Th1 cells persist in the spleen for at least 6 months after two booster immunisations. In contrast, influenza specific ELISA IgG titres reached significant levels only after booster immunisations and 141 antibodies were generally weak or undetectable. Nevertheless, two doses of HA DNA confer almost complete protection against respiratory challenge with live virus. (C) 2001 Elsevier Science B.V. All rights reserved.