Allen, Kathleen

Abstract One limitation to the development of targeted tumor immunity is the availability of safe vectors that can drive strong T-cell responses capable of eradicating tumors. We have designed viral vectors using Theiler’s murine encephalomyelitis virus (TMEV) that effectively inhibit melanoma outgrowth. By cloning the TMEV genome into a eukaryotic expression vector that can easily be manipulated we were able to generate several novel tumor specific virus vaccines. We find that incorporation of defined MHC class I epitopes into sites within the leader protein of the virus can drive strong CD8+ T-cell responses against these target peptides. Further, we find that the site of incorporation can change the elicited cytokine profile and the virulence of the virus. Incorporation of the ovalbumen peptide after the third amino acid of the L protein (p3) generates a strong IFNβ response, whereas insertion within the downstream XhoI restriction site elicits a strong IL6 response similar to wild-type TMEV. Further, the p3 virus is not lethal to RAG-deficient mice, where the XhoI and wild-type TMEV virus are. However, p3 virus persists and kills IFNα/β receptor-deficient mice, suggesting that innate immune responses are responsible for viral clearance. In spite of these differences the p3 and XhoI viruses can stimulate antigen specific T-cell responses and inhibit tumor outgrowth equivalently, demonstrating the efficacy of TMEV and its potential as a therapeutic intervention.

18037 Background: Platinum compounds are major chemotherapeutic agents in lung cancer and are metabolized by the glutathione pathway enzymes. We reported that genotypes of glutathione-related enzymes, especially GCLC, may be host factors in predicting survival of patients with stage IIIB/IV non-small cell lung cancer who were stable or responding from prior platinum-based chemotherapy (Yang et al., ASCO 2006). NCCTG investigators previously correlated allelic variants in 5-FU metabolizing genes with QOL in colorectal cancer patients (Sloan et al., ASCO 2004). We sought to evaluate the role of glutathione pathway genotypes on QOL. Methods: DNA samples were analyzed using 6 polymorphic DNA markers in the glutathione metabolic pathway. The contrasting genotypes in the analysis were GSTM1 and GSTT1 (null vs. present), GSTP1-I105V (AA vs. GA/GG), GSTP1-A114V (CC vs. CT/TT), GPX1 (CC vs. TT/TC), and GCLC (homozygous repeat 77 vs. heterozygous 7*). Forty-six patients completed the FACT-L and the UNISCALE QOL questionnaires at baseline and week-8, and we have results for all 6 genotypes. A clinically significant decline (CSD) in QOL was defined as a 10% decrease from baseline to week-8. A multivariate logistic regression model was used to evaluate the association of all 6 genotypes with a CSD in QOL. Results: Patients carrying the GPX1-CC genotype had a CSD in the UNISCALE (Odds Ratio (OR): 10.0; p=0.02), total FACT-L score (OR: 7.9; p=0.03), the FACT-L physical well being construct (OR: 13.7; p=0.02), and the FACT-L functional well being construct (OR: 5.3; p=0.05). Other constructs, i.e., emotional, social and family, and additional concerns were not significantly associated with the genotypes. Conclusions: Genotypes of glutathione-related enzymes, especially GPX1 may be inherited factors in predicting patients’ QOL after platinum-based chemotherapy. Further investigation to define and measure the direct or indirect effects of these genes on QOL is critical, particularly, via drug responses, toxicities, and disease recurrence. (This work was partly supported by NIH grants CA77118, CA80127, and CA84354.) No significant financial relationships to disclose.

Abstract Natural selection drives diversification of MHC class I proteins, but the mechanism by which selection for polymorphism occurs is not known. New variant class I alleles differ from parental alleles both in the nature of the CD8 T cell repertoire formed and the ability to present pathogen-derived peptides. In the current study, we examined whether T cell repertoire differences, Ag presentation differences, or both account for differential viral resistance between mice bearing variant and parental alleles. We demonstrate that nonresponsive mice have inadequate presentation of viral Ag, but have T cell repertoires capable of mounting Ag-specific responses. Although previous work suggests a correlation between the ability to present an Ag and the ability to generate a repertoire responsive to that Ag, we show that the two functions of MHC class I are independent.