Cross-presentation of HLA class I epitopes from influenza matrix protein produced in Saccharomyces cerevisiae.

Here we report that genetically engineered yeast of the strain Saccharomyces cerevisiae expressing full-length influenza matrix protein (IMP) attached to the yeast cell wall are a very versatile host for antigen delivery. Feeding of dendritic cells with either intact yeast expressing IMP protein or soluble IMP protein cleaved off the cell wall resulted in protein uptake, processing and cross-presentation of IMP-derived peptides. This process was analysed using previously established T-cell lines recognizing the immuno-dominant 58-66 peptide when presented by HLA-A2*0201 complexes. In addition, IMP(58-66)/HLA-A2*0201-specific antibodies were selected from a naive phage library which confirmed that peptide presentation was an active process of endocellular uptake and not just a result of external peptide loading. Moreover, MHC peptide antibodies could block the recognition of peptide-presenting dendritic cells by IMP(58-66)-specific T-cells in a dose dependent manner. There was no difference in T-cell recognition when either intact yeast or yeast cell extracts were used for DC feeding. Together, these data demonstrate that yeast derived proteins either in their soluble form or as part of a whole yeast vaccine are taken up, processed and presented by dendritic cells in HLA class I context.

Serological immune response to cancer testis antigens in patients with pancreatic cancer.

Serological screening approaches have allowed for the identification of a large number of potentially relevant tumor antigens in cancer patients. Within this group, cancer testis antigens represent promising targets for cancer immunotherapy, since they are widely expressed in a variety of human cancer entities. In pancreatic cancer, however, there are only few data available about the expression pattern and serological response to cancer testis antigens and other serological-defined tumor antigens. Therefore, we investigated the IgG antibody response against 11 cancer testis antigens (SCP-1, GAGE, LAGE-1a,-1b, CT-7, NY-ESO-1, SSX-1-5) recombinantly expressed on yeast surface (RAYS) in patients with pancreatic cancer (n = 96), chronic pancreatitis (n = 18) and healthy donors (n = 48). We found in 14% of all patients antibody responses to SCP-1, but not to other cancer testis antigens (GAGE, LAGE-1a,-1b, CT-7, NY-ESO-1, SSX-1-5). Antibody response correlated with the expression of SCP-1 in the primary tumor of the respective patient as shown by RT-PCR, immunohistochemistry and Western blot. In contrast, no serological response to cancer testis antigens was observed in healthy donors. The humoral immune response against SCP-1 was associated with the size of tumor, but not with other clinico-pathological parameters such as histology, stage, presence of lymph node metastases, grading, age, gender or gemcitabine treatment. In conclusion, antibody response to cancer testis antigen SCP-1 is found in a proportion of pancreatic carcinoma patients. These results indicate that identification of additional tumor antigens by serological screening of tumor cDNA expression libraries by RAYS is a promising goal in pancreatic cancer.