Purification of transiently transfected cells by magnetic-affinity cell sorting

A recombinant immunotoxin that is active on prostate cancer cells and that is composed of the Fv region of monoclonal antibody PR1 and a truncated form of Pseudomonas exotoxin

Monoclonal antibody PR1 binds to the surface of normal prostate cells and to adenocarcinomas of the prostate. The cDNAs coding for the heavy and light chain variable regions of monoclonal antibody PR1 were cloned by PCR techniques. A recombinant toxin was then constructed that has the heavy chain variable region of monoclonal antibody PR1 connected to the light chain variable region by a flexible peptide linker to create a single-chain Fv; the Fv in turn is fused to a truncated form of Pseudomonas exotoxin. The resulting recombinant immunotoxin PR1(Fv)-PE38KDEL was produced in Escherichia coli and accumulated in inclusion bodies. After denaturation and renaturation, active monomeric molecules with a molecular mass of approximately 65 kDa were purified to homogeneity. PR1(Fv)-PE38KDEL binds specifically to cells containing the PR1 antigen and is very cytotoxic toward a subset of LNCaP cells that express the PR1 antigen on their surface.

Immunomagnetic separation and analysis of non-malignant variants and parental malignant mouse lymphoma cells

We have devised conditions whereby non-tumorigenic, immunogenic cell variants of S49 mouse lymphoma were analyzed and separated from parental tumorigenic lymphoma cells. This was carried out using polyclonal antibodies (raised against the immunogenic variants) and immunomagnetic beads. The efficacy of the procedure depended on the amount of polyclonal antiserum, the immunobead to cell ratio, incubation time and the number of repetitions of the procedure. Experiments with mixed tumorigenic and non-tumorigenic cells have resulted in an enrichment of up to 200-fold of the non-tumorigenic, immunogenic cells in the population. These findings indicate the potential use of this procedure (in conjunction with other approaches) to isolate from a population of tumorigenic cells those variant cells that might be used to immunize against the parental tumor.