Detection of in vivo hepatitis B virus surface antigen mutations-A comparison of four routine screening assays.

An important requirement for a state-of-the-art hepatitis B surface antigen (HBsAg) screening assay is reliable detection of mutated HBsAg. Currently, there is a striking shortage of data regarding the detection rates of in vivo HBsAg mutations for these clinically important assays. Therefore, we compared the detection rates of four commercial HBsAg screening assays using a global cohort of 1553 patients from four continents with known HBV genotypes. These samples, which represent the broadest spectrum of known and novel HBsAg major hydrophilic region (MHR) mutations to date, were analyzed for the presence of HBsAg using the Roche Elecsys® HBsAg II Qualitative, Siemens ADVIA Centaur XP HBsAg II, Abbott Architect HBsAg Qualitative II and DiaSorin Liaison® HBsAg Qualitative assays, respectively. Of the 1553 samples, 1391 samples could be sequenced; of these, 1013 (72.8%) carried at least one of the 345 currently known amino acid substitutions (distinct HBsAg mutation) in the HBsAg MHR. All 1553 patient samples were positive for HBsAg using the Elecsys® HBsAg II Qual assay, with a sensitivity (95% confidence interval) of 99.94% (99.64%-100%), followed by the Abbott Architect 99.81% (99.44%-99.96%), Siemens ADVIA 99.81% (99.44%-99.96%) and DiaSorin Liaison® 99.36% (98.82%-99.69%) assays, respectively. Our results indicate that the Elecsys® HBsAg II Qual assay exhibits the highest sensitivity among the commercial HBsAg screening assays, and demonstrate that its capacity to detect HBV infection is not compromised by HBsAg MHR mutants.

Interleukin-12 requires initial CD80-mediated T-cell activation to support immune responses toward human breast and ovarian carcinoma.

One possible reason for the poor immunogenicity of tumors is the induction of peripheral tolerance by tumor cells that fail to deliver costimulatory signals. Furthermore, T cells stimulated with wild-type tumor cells often fail to secrete cytokines. The present study has been undertaken to identify cytokines that cooperate with CD80 in T-cell activation in vitro toward human breast and ovarian carcinoma cell lines. Tumor cell-mediated T-lymphocyte activation was analyzed directly in allogeneic mixed lymphocyte/tumor cell cultures as proliferation and effector functions were assessed in cytotoxic T-cell assays. Interleukin-7 (IL-7) amplified the proliferative response toward CD80-transfected breast and ovarian carcinomas and stimulated predominantly CD4+ T lymphocytes. IL-12 represses the proliferative response of naive T cells but cooperates with CD80-mediated activation during secondary stimulations. In long-term T-cell cultures, IL-12 synergizes with CD80 expression to stimulate cytolytic CD8+ T-cell lines, which recognize a breast carcinoma line in a human histocompatibility leukocyte antigen-restricted manner. These studies illustrate that costimulation is necessary for tumor cells to function as alloantigen-presenting cells. Furthermore, when added after the priming of T cells with CD80-transfected tumor cells, IL-12 could be helpful in propagating sufficient T-cell numbers to be used in adoptive transfers during cellular immunotherapy.

Potential of CD80-transfected human breast carcinoma cells to induce peptide-specific T lymphocytes in an allogeneic human histocompatibility leukocyte antigens (HLA)-A2.1+-matched situation.

Allogeneic human histocompatibility leukocyte antigen (HLA)-matched tumor cell lines that have been made immunogenic by the transfer of genes encoding for costimulatory molecules such as CD80 are considered to be potential vaccines for the induction of systemic immune reactions in cancer patients. We used a human HLA-A2.1+ CD80-transfected breast carcinoma cell line (KS-CD80) and investigated in vitro the efficiency at which antigen (Ag)-specific responses were induced following the stimulation of allogeneic HLA-A2.1-matched T lymphocytes. The influenza matrix protein M1 was used as a model Ag. It was either endogenously expressed or exogenously loaded as a peptide (matrix protein), and the frequency of the generated specific T cells was determined. The expression of CD80 in KS cells was required for an effective activation and expansion of Ag-specific T cells. This response was augmented following the pretreatment of KS-CD80 cells with interferon-gamma and tumor necrosis factor-alpha. Interleukin-4 (IL-4), IL-7, and IL-12 further increased T-cell expansion. IL-7 was best at supporting the generation of T cells with Ag specificity. This investigation demonstrates that allogeneic CD80+ tumor cells can induce Ag-specific, HLA-restricted T lymphocytes at a high frequency. Our study supports the use of allogeneic cell lines for the induction of specific T-cell responses in tumor patients.

Plasmin abrogates alpha v beta 5-mediated adhesion of a human keratinocyte cell line (HaCaT) to vitronectin.

At cellular surfaces, urokinase-type plasminogen activator (uPA) is bound to a specific receptor (uPA-R). When bound to this receptor, uPA activates plasminogen, which is derived from plasma or the interstitial fluids. Thus, plasmin is provided for proteolysis of pericellular proteinaceous substrates. Here we demonstrate by immunocytology and laser scan microscopy that in the human keratinocyte cell line HaCaT uPA-R and uPA are localized together with the integrin alpha v beta 5 in focal contacts. Via the integrin alpha v beta 5, HaCaT cells adhere to vitronectin in a RGD-dependent manner. Plasmin interfered with the alpha v beta 5-mediated keratinocyte adhesion to vitronectin, most likely via cleavage of vitronectin and destruction of its cell binding function. Our findings demonstrate that plasmin, when generated by the uPA-dependent cell surface-associated pathway of plasminogen activation, can abrogate the cell-binding function of vitronectin and can thus disturb the adhesive interaction with this matrix molecule. In focal contacts molecules are assembled that are crucial for adhesion to vitronectin (i.e., the integrin alpha v beta 5), as well as for the generation of plasmin (i.e., uPA-R and uPA), which can negatively influence the binding interaction. We suggest that the plasmin-mediated abrogation of the interaction between the integrin alpha v beta 5 and vitronectin is a pathway of negative regulation; the codistribution of uPA-R/uPA and alpha v beta 5 in focal contacts may restrict this process to areas of cell/matrix contact.

Binding and activation of plasminogen at the surface of human keratinocytes.

Plasmin is thought to be involved in the pericellular proteolysis of the human epidermis under physiological and pathological conditions. Plasmin is provided by activation of the proenzyme plasminogen. We have explored in vitro whether plasminogen is bound and activated at the keratinocyte surface, a possible mechanism for providing plasmin in the pericellular space. Plasminogen and plasmin could be eluted from the surface of keratinocytes grown in serum-containing medium. When plasminogen was added to cultured keratinocytes it was activated by cell-associated urokinase-type plasminogen activator. The activation required plasminogen binding to the cell surface. Plasminogen binding by keratinocytes was saturable and proceeded in a time- and concentration-dependent manner. Surface-bound plasmin was rapidly displaced from the surface into the culture supernatant. When compared to plasmin in solution surface-bound plasmin was relatively protected from interaction with the specific inhibitor alpha 2-antiplasmin. Addition of exogenous plasmin or plasmin generation by the keratinocyte-associated plasminogen activators was ensued by the detachment of adherent keratinocytes in culture. Along the same line, plasmin counteracted keratinocyte adhesion to fibrin-coated but not to collagen-coated culture plates. The findings indicate that plasmin may be generated in the pericellular space of keratinocytes and may interfere with the adhesion to particular extracellular substrates.