Generation of CD4(+) and CD8(+) T lymphocyte responses by dendritic cells armed with PSA/anti-PSA (antigen/antibody) complexes.

Dendritic cells (DC) acquire antigens through a number of cell surface structures including receptors for the Fc portion of immunoglobulins and mannose. Little is known about the effects of antigen uptake via these receptors on antigen processing and presentation. We compared the capacity of DC to generate CD4(+) and CD8(+) T cell responses after exposure to prostate-specific antigen (PSA) alone, PSA targeted to the mannose receptor (mannosylated PSA (PSA-m)), or PSA targeted to Fc receptors by combining PSA with an anti-PSA antibody (AR47.47). Autologous CD3(+) T cells were added to monocyte-derived immature DC that had been cultured with GM-CSF/IL-4 for 4 days, exposed to antigen, and matured with CD40L or TNFalpha/IFN-alpha. After several rounds of stimulation, T cell responses were assessed by intracellular IFN-gamma production using flow cytometry. Both CD4(+) and CD8(+) T cell responses were observed after stimulation with DC exposed to the PSA/anti-PSA complexes, whereas CD4(+) predominated over CD8(+) T cell responses after stimulation with PSA-armed DC or PSA-m. These CD8(+) T cells responded when rechallenged with DC pulsed with HLA allele-restricted PSA peptides. These results indicate that PSA and PSA-m are processed primarily through pathways that favor HLA Class II presentation, while the PSA/anti-PSA immune complexes are processed through both Class I and Class II pathways in monocyte-derived DC. These findings have potential applications in designing more effective cancer vaccines for prostate cancer.

Developing dendritic cell polynucleotide vaccination for prostate cancer immunotherapy.

Immunotherapy has been successfully used to treat some human malignancies, principally melanoma and renal cell carcinoma. Genetic-based cancer immunotherapies were proposed which prime T lymphocyte recognition of unique neo-antigens arising from specific mutations. Genetic immunization (polynucleotide vaccination, DNA vaccines) is a process whereby gene therapy methods are used to create vaccines and immunotherapies. Recent findings indicate that genetic immunization works indirectly via a bone marrow derived cell, probably a type of dendritic antigen presenting cell (APC). Direct targeting of genetic vaccines to these cells may provide an efficient method for stimulating cellular and humoral immune responses to infectious agents and tumor antigens. Initial studies have provided monocytic-derived dendritic cell (DC) isolation and culture techniques, simple methods for delivering genes into these cells, and have also uncovered potential obstacles to effective cancer immunotherapy which may restrict the utility of this paradigm to a subset of patients.

Escherichia coli isocitrate lyase: properties and comparisons.

The glyoxylate cycle was first discovered during studies on bacteria and fungi with the ability to grow on acetate or ethanol as the sole carbon source. Isocitrate lyase, the first enzyme unique to the glyoxylate cycle, has been studied in numerous prokaryotic and eukaryotic organisms. However, information on this enzyme from Escherichia coli is limited. We have recently reported the purification and in vitro phosphorylation of this enzyme. In the present study we have examined and characterized a variety of inhibitors, the divalent cation requirement and the amino acid composition of E. coli isocitrate lyase and compared these results to those obtained with other organisms.