The
gangliosides GD3, GD2 and GM2 are expressed on the cell surface of
malignant melanomas, GD3 being the most abundant. We have shown that immunization of
melanoma patients with GM2 adherent to Bacillus Calmette-Guerin (GM2/BCG) induced an
IgM antibody response.
Vaccines containing GM2-keyhole limpet
hemocyanin (KLH) conjugate and the
immunological adjuvant QS-21 induced a higher titer
IgM response and consistent
IgG antibodies. Patients with
antibodies against GM2 survived longer than patients without antibody. On the other hand, our previous trials with GD3/BCG, GD3 derivatives including GD3-lactone (GD3-L)/BCG failed to induce
antibodies against GD3. In our continuing efforts to induce antibody against GD3, we have immunized groups of 6
melanoma patients with GD3-KLH or
GD3-L-KLH conjugates containing 30 microg of
ganglioside plus 100 microg of
QS-21 at 0, 1, 2, 3, 7 and 19 weeks. Prior to vaccination, no serological reactivity against GD3 or GD3-L was detected. After immunization,
IgM and
IgG antibodies were detected against both GD3 and GD3-L in the GD3-L group exclusively. The
GD3-L-KLH vaccine induced
IgM titers against GD3-L of 1:40-1/1,280 in all patients and
IgG titers of 1/160-1/1,280 in 4 patients. These
antibodies also strongly cross-reacted with GD3. ELISA reactivity was confirmed by immune thin-layer chromatography on GD3 and
melanoma extracts. Sera obtained from 4 of these 6 patients showed cell surface reactivity by FACS and from 2 showed strong cell surface reactivity by immune adherence (IA) assay and
complement lysis against the GD3 positive cell line SK-Mel-28.