ISPO

Anti-idiotypic antibodies induced by genetic immunization are directed exclusively against combined VL/VH determinants: implications on the mechanism of protection

F. Benevenuti a, M. Cesco-Gaspere b, O.R. Burrone b

a Institute Curie, INSERM U520, 12 Rue Lhomond, 75005 Paris, France b International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy

Anti-idiotypic antibodies induced by genetic immunization are directed exclusively against combined VL/VH determinants: implications on the mechanism of protection F. Benvenuti Ph.D. (a), M. Cesco-Gaspere Ph.D. student* (b), O.R. Burrone Ph.D. (b) (a) Institute Curie, INSERM U520, 12 Rue Lhomond, 75005 Paris, France (b) International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012-Trieste, Italy DNA vaccination with the idiotype (Id) of tumour B-cells immunoglobulins is a validated strategy to induce anti-Id antibodies and tumour protection in several mice lymphoma models. Aim We have investigated the structural basis of the idiotypic/anti-idiotypic interaction following Id-DNA vaccination and the role of anti-Id antibodies in tumour protection. Methods ScFvs encoding either a complete tumour idiotype or only one of the two tumour-derived V regions paired to an irrelevant V region partner (chimeric scFv) were used as immunogens to induce anti-Id antibodies. Cells transfected with a membrane version of the same scFvs were used to analyze immunized mice sera. Vaccinated mice were also monitored for survival after tumour challenge. Results We found that only mice immunized with scFv encoding both tumour derived V regions elicited an anti-tumour Id response. Consistently, analysis of the specificity of the polyclonal antibody response showed that it is restricted to conformational epitopes formed by the immunizing VL/VH pair. Moreover, only animals vaccinated with the complete tumour idiotype (and not those immunized with either of the two chimeric construct or a mixture of the two) survived or presented tumour progression delay. Conclusions Our findings indicate that the presentation of properly folded Ids through DNA vaccination results in a highly specific antibody response, directed exclusively to idiotypic determinants of the immunizing VL/VH combination. In addition we conclude that the mechanism of tumour protection is entirely dependent on the presence of antibodies, since mice vaccinated with both chimeric constructs died despite the exposure to all tumour Id CD8+ T cell epitopes.

KEY WORDS: Idiotype, scFv, DNA vaccination, lymphoma.

For more information, contact cesco@icgeb.trieste.it

Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Immunotherapy.

This presentation received an honorable mention in our poster contest and was recognized with the Symposium Presidents' Award for Scientific Excellence.

http://www.cancerprev.org/Journal/Issues/26/101/1295/4703