Vaccination with protein-transduced dendritic cells elicits a sustained response to hepatitis C viral antigens

BACKGROUND & AIMS: Professional antigen-presenting dendritic cells are capable of eliciting a vigorous antiviral response in naive T cells. The administration of antigen-loaded dendritic cells offers a potential approach to induce high-level immunity against hepatitis C virus. METHODS: The dendritic cell population in mice was expanded in vivo by hydrodynamic delivery of naked DNA that encoded the secreted form of human fms-like tyrosine kinase 3 ligand. The CD11c-enriched dendritic cell population obtained from the spleen was transduced in vitro with recombinant hepatitis C virus core and nonstructural 5 proteins by using macromolecular-based protein delivery. Vaccine efficacy was assessed with a cytotoxic T-lymphocyte assay, cytokine enzyme-linked immunosorbent assays, and intracellular cytokine staining in vitro and by a tumor challenge model in vivo. RESULTS: Relative to mice inoculated with nontransduced dendritic cells, splenocytes derived from mice immunized with either hepatitis C virus core-transduced or nonstructural 5-transduced dendritic cells showed 3- to 5-fold greater antigen-specific cytotoxic T lymphocyte activity. The CD4(+) T cells obtained from mice immunized with nonstructural 5-transduced dendritic cells produced interferon gamma, but not interleukin 4, when stimulated with nonstructural 5. In contrast, T cells derived from mice immunized with hepatitis C virus core-transduced dendritic cells produced neither interferon gamma nor interleukin 4 when stimulated with core protein. Mice vaccinated with nonstructural 5-transduced dendritic cells, but not a nonstructural 5-expressing plasmid, showed a sustained antiviral response to nonstructural 5 as evidenced by reduced growth of nonstructural 5-expressing tumor cells inoculated 10 weeks after vaccination. CONCLUSIONS: These findings suggest that vaccination with protein-transduced dendritic cells may constitute an important antiviral strategy for hepatitis C virus.     

Activated virus-specific T cells are early indicators of anti-CMV immune reactions in liver transplant patients

BACKGROUND & AIMS: Cytomegalovirus (CMV) infection represents the most common infectious complication after liver transplantation. Because CMV-associated complications in liver transplantation patients are often liver-restricted and clinically unrecognized, diagnosis of early infection or reactivation is still very difficult. Because cytotoxic T cells (CTLs) are crucial for the immune control of CMV, analysis of virus-specific CTLs could contribute to diagnosis and management of CMV infection. METHODS: Major histocompatibility complex class I tetramers and intracellular cytokine staining were used to determine frequencies and phenotypes of peripheral blood CMV/pp65-specific CD8(+) T cells in HLA-A2, -B7, and -B35 positive liver transplantation patients and in healthy individuals. RESULTS: After liver transplantation (6-33 months after liver transplantation), frequencies of CMV-specific T cells were significantly elevated compared with healthy individuals. In contrast to immunoglobulin (Ig) M-negative patients and healthy blood donors, patients with increasing CMV IgM titers or IgG seroconversion had high percentages of activated (CD38(high)) CMV-specific T cells. In recently transplanted patients, activation of CMV-specific T cells was associated with increased transaminases and histopathological abnormalities in the absence of positive CMV-polymerase chain reaction results from peripheral blood. CONCLUSIONS: These data indicate that T-cell analysis based on MHC tetramer staining may be a valuable parameter in the early diagnosis of CMV-induced, liver-restricted complications after liver transplantation.     

The translation of Helicobacter pylori basic research to patient care

In 1984, Barry Marshall and Robin Warren proposed a role for bacterial infections in the pathogenesis of gastroduodenal disease, which triggered an avalanche of research intended to prove or disprove their theory. The result has been a series of advances that have enhanced our understanding of these diseases and completely modernized the clinical approach to their management. In just over 20 years, many aspects of the immunopathogenesis of these diseases have been dissected at the molecular level, with key pathogenic mechanisms being validated by the identification of genes that are associated with the development of gastric cancer. There has been particular emphasis on understanding the molecular structures associated with Helicobacter pylori and their role in modifying the host responses. Gastric immune and inflammatory responses have emerged as key elements in the pathogenesis of gastritis and epithelial cell damage. This review summarizes important findings emanating from basic research primarily related to the immunopathogenesis of H pylori that have advanced the practice of medicine or our understanding of gastroduodenal disease.     

CD4+NKG2D+ T cells in Crohn's disease mediate inflammatory and cytotoxic responses through MICA interactions

BACKGROUND & AIMS: Crohn's disease (CD) is an inflammatory bowel disease characterized by uncontrolled immune responses to bacterial flora, with excessive activation of T lymphocytes. MICA is a stress-induced major histocompatibility complex-related molecule expressed on normal intestinal epithelial cells (IECs) and recognized by the NKG2D-activating receptor on CD8(+) T cells, gammadelta T cells, and natural killer cells. We examined the role of MICA-NKG2D interactions in the activation of T lymphocytes in CD. METHODS: MICA expression was analyzed by flow cytometry on IECs isolated from patients with active inflammatory bowel disease and controls. NKG2D expression and function were analyzed on lamina propria and peripheral blood lymphocytes. RESULTS: MICA expression was significantly increased on IECs in CD, with higher expression in macroscopically involved areas. A subset of CD4(+) T cells expressing NKG2D was increased in the lamina propria from patients with CD compared with controls and patients with ulcerative colitis. CD4(+)NKG2D(+) T cells with a Th1 cytokine profile and expressing perforin were increased in the periphery and in the mucosa in CD. CD4(+)NKG2D(+) T-cell clones were functionally active through MICA-NKG2D interactions, producing interferon-gamma and killing targets expressing MICA. IECs from patients with CD had the ability to expand this subset in vitro. CD4(+)NKG2D(+) lamina propria lymphocytes from patients with CD highly expressed interleukin-15R alpha, and interleukin-15 increased NKG2D and DAP10 expression in CD4(+)NKG2D(+) T-cell clones. CONCLUSIONS: These findings highlight the role of MICA-NKG2D in the activation of a unique subset of CD4(+) T cells with inflammatory and cytotoxic properties in CD.