Human cytomegalovirus vaccine based on the envelope gH/gL pentamer complex.

Human Cytomegalovirus (HCMV) utilizes two different pathways for host cell entry. HCMV entry into fibroblasts requires glycoproteins gB and gH/gL, whereas HCMV entry into epithelial and endothelial cells (EC) requires an additional complex composed of gH, gL, UL128, UL130, and UL131A, referred to as the gH/gL-pentamer complex (gH/gL-PC). While there are no established correlates of protection against HCMV, antibodies are thought to be important in controlling infection. Neutralizing antibodies (NAb) that prevent gH/gL-PC mediated entry into EC are candidates to be assessed for in vivo protective function. However, these potent NAb are predominantly directed against conformational epitopes derived from the assembled gH/gL-PC. To address these concerns, we constructed Modified Vaccinia Ankara (MVA) viruses co-expressing all five gH/gL-PC subunits (MVA-gH/gL-PC), subsets of gH/gL-PC subunits (gH/gL or UL128/UL130/UL131A), or the gB subunit from HCMV strain TB40/E. We provide evidence for cell surface expression and assembly of complexes expressing full-length gH or gB, or their secretion when the corresponding transmembrane domains are deleted. Mice or rhesus macaques (RM) were vaccinated three times with MVA recombinants and serum NAb titers that prevented 50% infection of human EC or fibroblasts by HCMV TB40/E were determined. NAb responses induced by MVA-gH/gL-PC blocked HCMV infection of EC with potencies that were two orders of magnitude greater than those induced by MVA expressing gH/gL, UL128-UL131A, or gB. In addition, MVA-gH/gL-PC induced NAb responses that were durable and efficacious to prevent HCMV infection of Hofbauer macrophages, a fetal-derived cell localized within the placenta. NAb were also detectable in saliva of vaccinated RM and reached serum peak levels comparable to NAb titers found in HCMV hyperimmune globulins. This vaccine based on a translational poxvirus platform co-delivers all five HCMV gH/gL-PC subunits to achieve robust humoral responses that neutralize HCMV infection of EC, placental macrophages and fibroblasts, properties of potential value in a prophylactic vaccine.

Stimulating surface molecules, Th1-polarizing cytokines, proven trafficking--a new protocol for the generation of clinical-grade dendritic cells.

BACKGROUND AIMS: Dendritic cells (DC) have been vigorously investigated as an immunological basis for therapeutic vaccination against cancer and infections, even among patients after allogeneic stem cell transplantation. METHODS: Effective induction of cell-mediated immunity strongly depends on the ability of DC to (i) migrate to the draining lymphoid organs mediated by chemokine receptors, (ii) prime T cells through high expression of costimulatory molecules and major histocompatibility complexes and (iii) secret Th1-polarizing cytokines such as Interleukin-12 (IL-12). However, there is no protocol to generate fully matured and functional DC according to methodical requirements of current good manufacturing practice (CGMP) guidelines. RESULTS: We established a protocol conforming to CGMP standards that permits the generation of fully matured and functional DC on the basis of cell culture in adherence bags with the use of serum-free media with a maturation cocktail, containing tumor necrosis factor-alpha/Interferon-alpha/polyinosinic:polycytidylic acid. Our DC superiorly display three critical features for an effective induction of cell-mediated immunity without evidence of exhaustion, along with its ability to prime infectious or tumor-specific T cells in a short-term cell culture. CONCLUSIONS: Our newly developed protocol offers an attractive method to produce fully matured Th1-polarizing DC with proven migratory and stimulatory capacity for any clinical application according to CGMP standards.

Uptake of antigens from modified vaccinia Ankara virus-infected leukocytes enhances the immunostimulatory capacity of dendritic cells.

BACKGROUND AIMS: Modified vaccinia Ankara (MVA) is a promising vaccine vector for infectious diseases and malignancies. It is fundamental to ascertain its tropism in human leukocyte populations and immunostimulatory mechanisms for application in immunotherapy. METHODS: Human peripheral blood mononuclear cells (PBMC) and leukocyte subpopulations [monocyte-derived dendritic cells (DC), monocytes and B cells] were infected with MVA in order to evaluate their infection rate, changes in surface markers, cytokine expression and apoptosis. RESULTS: Monocytes, DC and B cells were most susceptible to MVA infection, followed by natural killer (NK) cells. Monocytes were activated strongly, with upregulation of co-stimulatory molecules, major histocompatibility complex (MHC) molecules and chemokine (C-C motif) receptor (CCR7), while immature DC showed partial activation and B cells were inhibited. Furthermore, expression of chemokine (C-X-C motif) ligand (CXCL10), tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-12p70 was enhanced but IL-1ß and IL-10 were stable or even downregulated. MVA induced a high apoptosis rate of antigen-presenting cells (APC). Nevertheless, incubation of MVA-infected leukocytes with uninfected immature DC (iDC) led to complete maturation of the DC. Subsequently, the matured DC were able to stimulate cytomegalovirus (CMV)-immediate early protein (IE1)-specific T cells. CONCLUSIONS: MVA induces a T-helper (Th)-1-polarizing cytokine expression in APC. Furthermore, incubation of MVA-infected leukocytes with uninfected iDC leads to complete maturation of the DC and may be the basis for cross-presentation of MVA-encoded antigens. Thus this approach seems to be an ideal model for further studies with MVA-encoded viral antigens regarding immunotherapy and vaccination strategies.

Hepatitis C virus core protein impairs in vitro priming of specific T cell responses by dendritic cells and hepatocytes.

BACKGROUND/AIMS: Hepatitis C virus leads to chronic hepatitis in the majority of infected individuals. The mechanism of viral persistence is not completely understood. Hepatitis C virus core protein is produced within hepatocytes and is secreted during HCV infection. Our study characterizes the effects of core protein on T cell priming in mice. METHODS: We used a system of antigen-specific in vitro priming of CD4(+) and CD8(+) T cells by myeloid dendritic cells, hepatoma cells or primary hepatocytes. Core protein was either added to the cultures or expressed by antigen-presenting cells. RESULTS: Antigen-presenting cells treated with core protein showed reduced surface expression of major histocompatibility molecules. Myeloid dendritic cells showed also reduced expression of costimulatory molecules. CD4(+) and CD8(+) T cells primed by these cells showed defects in activation, proliferation, and cytokine production. Importantly, CD4(+) and also CD8(+) T cells primed in the presence of core protein showed an increase in interleukin-10 production resembling the phenotype of regulatory T cells. CONCLUSIONS: Hepatitis C virus core protein inhibits priming of antigen-specific CD4(+) and CD8(+) T cell responses by downregulation of major histocompatibility molecules and costimulatory molecules on antigen-presenting cells and induces development of IL-10-producing T cells.

Tissue inhibitor of metalloproteinases-1 promotes liver metastasis by induction of hepatocyte growth factor signaling.

Balanced expression of proteases and their inhibitors is one prerequisite of tissue homeostasis. Metastatic spread of tumor cells through the organism depends on proteolytic activity and is the death determinant for cancer patients. Paradoxically, increased expression of tissue inhibitor of metalloproteinases-1 (TIMP-1), a natural inhibitor of several endometalloproteinases, including matrix metalloproteinases and a disintegrin and metalloproteinase-10 (ADAM-10), in cancer patients is negatively correlated with their survival, although TIMP-1 itself inhibits invasion of some tumor cells. Here, we show that elevated stromal expression of TIMP-1 promotes liver metastasis in two independent tumor models by inducing the hepatocyte growth factor (HGF) signaling pathway and expression of several metastasis-associated genes, including HGF and HGF-activating proteases, in the liver. We also found in an in vitro assay that suppression of ADAM-10 is in principle able to prevent shedding of cMet, which may be one explanation for the increase of cell-associated HGF receptor cMet in livers with elevated TIMP-1. Similar TIMP-1-associated changes in gene expression were detected in livers of patients with metastatic colorectal cancer. The newly identified role of TIMP-1 to create a prometastatic niche may also explain the TIMP-1 paradoxon.