IL-2 as adjuvant for vaccination with cells malignantly converted by HPV 16 or 3-MC

Experiments were designed to investigate the effects of murine recombinant IL-2 used as adjuvant for tumour vaccines in two model systems. The first system employed the Syrian hamster K3/II cell line transformed malignantly in vitro with DNA from E6-E7 oncogenes from HPV 16 and transplanted in Syrian hamsters. The second system made use of murine sarcoma Mc 12 induced with MC and transplanted in histocompatible mice. Both tumours were previously shown to express TRA capable of inducing transplantation resistance. It has been demonstrated here that the effect of the immunization in both tumour model systems could be substantially increased by IL-2 injected repeatedly at the site of vaccination. Some of the experimental mice were sacrificed after immunization and their spleen as well as regional lymph node cells were used for phenotypic analysis. IL-2 administration was found to be accompanied with an increase of TCR alpha beta(+), CD4(+) T cells in the spleen. Also in regional lymph nodes the T cell subsets showed a characteristic kinetics due to IL-2 administration. Following the IL-2 treatment, the percentage of lymph node TCR alpha beta(+), CD4(+) and CD8(+) cells dropped to less than half of the pretreatment values and then again gradually increased. No such kinetics was observed in vaccinated mice that did not receive IL-2. These results suggest that local administration of IL-2 at the site of vaccination elicits, in addition to the reaction in regional lymph nodes, a systemic reaction detectable in the spleen; they also suggest that the increase of CD4(+), TCR alpha beta(+) T splenocytes may play an important role in the mechanism of the observed adjuvant effect of IL-2. The adjuvant IL-2 effect augmenting the function of cell vaccines expressing HPV 16 E6-E7 oncoproteins deserves further studies, particularly with regard to its prospective utilization for treatment of human cervical carcinoma.