Transduction of murine and human tumors using recombinant adenovirus vectors

AFP-specific CD4+ helper T-cell responses in healthy donors and HCC patients

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and is often diagnosed at an advanced stage. We have investigated alpha-fetoprotein (AFP) as a tumor-associated antigen for HCC. We identified major histocompatibility complex class I-restricted peptide epitopes derived from AFP and studied CD8 T-cell responses in vivo and in vitro in ongoing immunotherapy studies. Helper T cells are of critical importance in shaping the immune response; therefore, we investigated the frequency and function of AFP-specific CD4 T cells in the general population and among HCC patients. CD4 T-cell responses were assessed by direct ex vivo multicytokine enzyme-linked immunospot assay and by measurement of cytokine levels using a multicytokine assay. Our analysis indicates that healthy donors have very low frequencies of AFP-specific CD4 T-cell responses, which are of TH1 type, detectable ex vivo. In contrast, these T cells were either reduced or eliminated in HCC patients at advanced stages of disease. To better activate these cells, we compared the stimulatory capacity of both AFP protein-fed and AdVhAFP-engineered dendritic cells (DC). Healthy donors have CD4 T-cell responses, which were activated in response to AFP protein-fed DC whereas HCC patients do not demonstrate significant responses to AFP protein. AdVhAFP-transduced DC were capable of activating higher frequency TH1 CD4 responses to AFP in both healthy donors and AFP-positive HCC patients. Importantly, CD4 T-cell cytokine expression profiles were skewed towards interleukin-2 and interferon-gamma production when activated by adenovirally engineered DC, which has therapeutic implications for vaccination efforts.

A microsphere-liposome (microplex) vector for targeted gene therapy of cancer. II. In vivo biodistribution study in a solid tumor model

Cationic liposomes are commonly used for transfection of plasmids into mammalian cells, while microspheres have been traditionally used for selective delivery of anticancer agents into tumor vasculature. We have developed a novel vector, comprised of cationic liposomes electrostatically bound to ion-exchange microspheres (termed 'microplex') for targeted gene therapy of solid tumors. The delivery modes tested in a rat solid tumor model were free plasmids, plasmids bound to microspheres, to liposomes, or to the combination vector. The greatest amount of chloramphenicol acetyltransferase (CAT) reporter gene expression in tumors was achieved using the microplex vector; 3.4-fold compared with free, and 1.8-fold compared with both microspherical and liposomal deliveries (p < 0.01). Tumor-to-normal kidney tissue CAT expression ratios were as follows: free 1.9:1; microspherical 3.7:1; liposomal 1.4:1 and microplexical 2.7:1. Expression between the two types of tissues was significantly different (p < 0.01) for all delivery modes. Microspheres targeted the plasmids to the tumors, while the action of cationic liposomes on cellular membranes allowed more plasmids to breach the cell membrane. This study has proven that the novel microplex vector is capable of selective delivery of genes to tumors and has the potential to target genes in clinical trials.

Gene therapy in lung cancer

The poor overall survival rates associated with non- small-cell lung cancer despite advances in chemotherapy, radiotherapy, and surgery mandate the search for novel approaches. Advances in gene transfer technology have allowed gene therapy strategies to develop that act in such a way as to stimulate the immune system, transfer "suicide" genes, inactivate oncogenes, replace tumor suppressor genes, and transfer pro-apoptotic genes. Clinical trials evaluating these possibilities have begun, and findings indicate that the transfer of tumor sup- pressor genes (wild-type p53) is feasible and has low overall toxicity. Subsequent clinical trials have begun to evaluate the clinical potential of these approaches in non-small-cell lung cancer.

Construction and characterization of encapsidated poliovirus replicons that express biologically active murine interleukin-2

Poliovirus genomes have been constructed in which the capsid genes have been substituted with the murine gene encoding interleukin-2 (IL-2) (referred to as replicons). One replicon contained the gene for IL-2 in place of the poliovirus capsid VP2 and VP3 genes, and a second replicon was constructed that contained the murine IL-2 substituted for the poliovirus VP3 and VP1 genes. The IL-2 genes were cloned into the replicon so as to maintain the translational reading frame with the remaining poliovirus proteins. Transfection of either replicon into cells resulted in the expression of replicon-encoded proteins and replication of replicon RNA. Using a procedure developed in this laboratory, we have encapsidated these replicons into authentic polio virions by passaging the replicons in the presence of a recombinant vaccinia virus, VVP1, which expresses the capsid precursor, P1, protein. Using a quantitative immunoassay, we determined that the majority of the IL-2 produced remained intracellular, with approximately 1%-2% released from the infected cells, and that the IL-2 was biologically active. The results of these studies demonstrate the utility of poliovirus replicons for expression of small bioactive molecules and are discussed with respect to future applications as immune adjuvants as well as potential new tumor therapies.