Idiotypic Vaccine for Treatment of Human B-Cell Lymphoma: Construction of IgG Variable Regions from Single Malignant B Cells

Abstract

ABSTRACT: Immunoglobulin idiotypes (Id) of malignant B cells represent highly specific markers which can be used for vaccination. PCR-amplification of immunoglobulin genes enables the rapid production of large amounts of Id vaccines. However, the separate amplification and subsequent recombination of heavy and light chains can lead to a loss of the relevant Id. To preserve the original chain pairs, we used single malignant B cells derived from an immunocytoma patient. Cytoplasm was extracted and the mRNA transcribed into cDNA. The VH and VL genes were then amplified by PCR and cloned into a vector for expression in E. coli. Id production was checked using an anti-Id mouse monoclonal Ab raised against the patient’s tumor-specific IgG. One out of 3 constructs expressed the relevant Id. Analysis of the first 31 light chain residues revealed an identical sequence for the malignant B cells’ IgG and the recombinant Id construct. Exchange of either the heavy or light chain with an unrelated chain resulted in loss of the Id. An unrelated sequence derived from the c-myc protein is coupled to the Id vaccine. The lymphoma patient was shown to have Abs to the c-myc sequence. This sequence therefore, increases the Id + Ab′s antigenicity. CD spectroscopy showed an α-helical structure for the c-myc epitope. In conclusion, a B-cell lymphoma autovaccine was produced containing immunogenic sequences that do not alter the steric conformation of the tumor-specific Id.