immunogenicity of the cell lines. It is interesting to note that vaccine 
studies have been conducted for years, using either autologous tumor or 
allogeneic tumor cell lines admixed with BCG, or lysates of allogeneic 
melanoma cell lines combined with strong immunologic adjuvants. Regression of 
advanced disease has been observed in a small number of patients, and at 
least one group is claiming an improvement in survival of advanced stage 
patients who were immunized with a panel of allogeneic melanoma cell lines and 
BCG (12). Unfortunately, these claims are made on the basis of comparisons to 
matched historical control groups; to be certain of efficacy, the results 
must be confirmed in randomized controlled trials. Nevertheless, the previous 
efforts to administer 'therapeutic' vaccines provide evidence that active 
immunization alone may have some antitumor activity in metastatic melanoma. 
The melanoma tumor vaccine study we plan to conduct is based on the following 
principles and recent developments, which are explained in greater detail 
below: 
1. Melanomas from a subset of patients express the same tumor-related 
antigen(s). Distinct antigens are presented by HLA-A2 . 1 (subsequently 
referred to as HLA-A2) and HLA-A1 and are recognized by the host T cell 
response. Therefore, immunizations can be attempted with allogeneic melanoma 
cell lines that express the melanoma antigen (s) and HLA-class I phenotype of 
the patient's tumor, and in vivo T cell responses to immunization can be 
measured against melanoma cell lines that also express the common antigen (s) 
and HLA class I type. 
2. Effective antigen presentation to T cells in vivo requires both the 
crosslinking of the T cell receptor by the peptide/MHC complex and a second 
costimulatory signal. The costimulatory signal can be generated by an 
interaction between the molecule B7 on the antigen-presenting cell (APC) and 
its ligand CD28 on the surface of the T cell. The presence of B7 on the APC 
induces T cell activation and proliferation, while its absence during antigen 
presentation can induce T cell tolerance under certain circumstances. The 
melanoma cell lines used for immunization in this study will be transfected 
with the human B7 gene to enable them to directly stimulate melanoma antigen- 
specific T cell responses. 
Evidence for a shared melanoma antigens presented by HLA-A2 and HLA-A1 
CD8+ cytotoxic T cells derived from TIL or mixed lymphocyte-tumor cultures 
(MLTC) from HLA-A2 melanoma patients have been shown to kill a majority of 
HLA-A2 allogeneic melanoma cell lines (13, 14). For example, Crowley et al 
Recombinant DNA Research, Volume 18 
[723] 
