The immune response against foot-and-mouth disease virus: influence of the T lymphocyte growth factors IL-1 and IL-2 on the murine humoral response in vivo.

Recombinant and pure "natural" IL-1 and IL-2 were compared with the muramyl dipeptide (MDP) component of Freund's adjuvant for their capacity to enhance the humoral immune response against foot-and-mouth disease (FMD) virus antigen. Using a dose of this antigen which alone did not give a detectable immune response, anti-FMD virus antibody was measured at 14 and 28 days post-vaccination. Although IL-1 could enhance the response against the virus antigen, in particular when administered 24 h before the vaccine, this was not as strong as that obtained when MDP was adjuvant. In contrast, IL-2 was at least as efficient as MDP when applied concomitantly with the antigen. If the IL-2 treatment preceded the vaccination by 24 h, a diminution in the magnitude of the response was seen; however, this was countered by the fact that 10 times less IL-2 was required, compared with concomitant cytokine/vaccine administration, in order to have the maximum effect. When both IL-1 and IL-2 were used together, an even greater enhancement of the immune response against FMD virus antigen was observed, but only when given concomitantly with the antigen. These results demonstrate the relevance of T lymphocyte growth factors to the immune response against FMD virus, and how current immunological and biotechnological knowledge could be applied to the improvement of adjuvant systems in a chemically and biologically defined manner.