Immucothel(Biosyn Corp.)

The multimeric/higher oligomeric states of the two isoforms of Haliotis tuberculata hemocyanin (HtH1 and HtH2) have been assessed by transmission electron microscopy (TEM) of negatively stained specimens, for comparison with previously published structural data from keyhole limpet hemocyanin (KLH1 and KLH2) [see Harris, J.R., Gebauer, W., Guderian, F.U., Markl, J., 1997a. Keyhole limpet hemocyanin (KLH), I: Reassociation from Immucothel followed by separation of KLH1 and KLH2. Micron, 28, 31-41; Harris, J.R., Gebauer, W., Söhngen, S.M., Nermut, M.V., Markl, J., 1997b. Keyhole limpet hemocyanin (KLH). II: Characteristic reassociation properties of purified KLH1 and KLH2. Micron, 28, 43-56; Harris, J.R., Gebauer, W., Adrian, M., Markl, J., 1998. Keyhole limpet hemocyanin (KLH): Slow in vitro reassociation of KLH1 and KLH2 from Immucothel. Micron, 29, 329-339]. In purified samples of both HtH isoforms, the hollow cylindrical ca 8MDa didecamer predominates together with a small number of decamers, but tri- and longer multidecamers are detectable only in the HtH2. The stability of the two HtH isoforms under varying ionic conditions have been monitored, thereby enabling conditions for the production of stable decamers to be established. The ability of these decamers to reform multimers in the presence of 10 and 100mM concentrations of calcium and magnesium ions in Tris-HCl buffer (pH 7.4), and also of individual HtH1 and HtH2 subunits (produced by pH 9.6 dissociation in glycine-NaOH buffer), to reassociate in the presence of calcium and magnesium ions, has been assessed. For the HtH1 decamers, the predominant multimeric product is the didecamer at 10 and 100mM calcium and magnesium concentrations, whereas for the HtH2 decamers, large numbers of multidecamers are produced, with the reaction proceeding more completely at the higher calcium and magnesium concentration. With the HtH1 subunit, reassociation in the presence of 10 and 100mM calcium and magnesium ions yielded an almost 100% conversion into didecamers, whereas the HtH2 subunit produced a mixture containing large numbers of short multidecamers and relatively few didecamers, together with a considerable number of smaller diameter helical/tubular polymers. The association properties of the HtH1 and HtH2 decamers, and the subunit reassociation, firmly indicate the integrity and structural competency of the protein under the experimental conditions used. Data on the association of KLH2 decamers is also presented, which together with previously published data on the association KLH1 decamers and the reassociation of KLH1 and KLH2 subunits, enables a detailed comparison of the two hemocyanin isoforms from both molluscan species to be made. Biochemical manipulation of the oligomer states and the subunit reassociation of molluscan hemocyanins can usefully be assessed by the study of negatively stained TEM specimens.

Since the serendipitous observation by Olsson in 1974 that patients immunized with 5 mg of keyhole limpet hemocyanin (KLH) had a marked reduction in recurrence of superficial bladder cancer, multiple laboratory and clinical studies have confirmed the efficacy of KLH immunotherapy.

In 1981, we reported that KLH immunotherapy reduced tumor growth and prolonged survival in the MBT-2 murine model of transitional cell carcinoma (TCC), and in 1988, Jurincic and co-workers demonstrated that KLH was superior to mitomycin C chemotherapy in preventing bladder tumor recurrence. Subsequent studies using Immucothel (Biosyn), crude KLH, and endotoxin-free KLH confirmed the efficacy of KLH immunotherapy in the MBT-2 murine bladder cancer model (p < 0.05), and resulted in up to 100% survival.

To evaluate the efficacy of KLH immunotherapy in patients, a multicenter clinical trial was performed. Sixty-four patients with CIS or residual stage T(a), T(1) TCC, or both were enrolled in a phase I-II trial of escalating doses of weekly KLH given intravesically for 6 weeks. Patients were followed with cystoscopic examination, urine cytology, and bladder biopsy. Complete response was seen in 50% of patients with CIS, 20% of patients with residual T(a), T(1) TCC, and 33% of patients with both CIS and residual T(a), T(1) TCC. Responses occurred at all doses tested: 0.4, 2, 10 and 50 mg. No significant difference in response according to dose was noted, but optimal overall complete response was seen with a dose of only 2 mg. The toxicity of KLH is minimal. KLH appears to be a safe and highly effective immunotherapy for superficial bladder cancer.