Identification of monoclonal antibody defined epitopes on human leukocyte antigens utilizing phage display peptide libraries

Summary Utilizing phage display peptide libraries, we have identified and mapped the antigenic determinants recognized by mouse monoclonal antibodies (mAb) on two sets of immunologically important molecules, HLA class I and class II antigens. Anti-HLA class I mAb TP25.99 recognizes a conformational and a linear determinant on distinct regions of the HLA class I α3 domain. Anti-HLA class I mAb HO-4 recognizes a conformational determinant on the α2 domain of HLA-A2 and A28 allospecificities. Anti-HLA-DR1,-DR4,-DR6,-DR8,-DR9 mAb SM/549 recognizes a conformational determinant on the β chain of HLA class II antigens. These results indicate the versatility of phage display peptide libraries to characterize antigenic determinants recognized by anti-HLA mAb.     

Altered cytokine production after human herpes virus type 6 infection.

Several strategies allow viruses to elude the surveillance of the immune system and to establish persistent infection in the host. One of such mechanisms is the immunosuppression caused by the direct infection and functional impairment of immune cells. Human Herpes virus type 6 (HHV-6) is a typical immunosuppressive agent, as suggested by its tropism for both CD4+ and CD8+ T cells, B cells, monocytes/macrophages, megakaryocytes and NK cells. In this study the production of IL-10 and IL-12 by peripheral blood mononuclear cells (PBMC) was evaluated during HHV-6 infection "in vitro". Our results demonstrate that HHV-6 up-regulates IL-10 production by PBMC. Furthermore, our data suggest that rhIFN gamma addition counteracts the effect of HHV-6 in promoting IL-10 release. To gain more insight into the role of IFN gamma, anti-IFN gamma monoclonal antibodies were added to PBMC stimulated with LPS. Neutralization of endogenous IFN gamma upregulated IL-10 release. Furthermore, HHV-6 infection inhibited IFN gamma release induced by LPS in PBMC. No basal production of IL-12 was found in PBMC. Moreover, HHV-6 infection did not induce IL-12 release by PBMC. On the contrary, IL-12 was detected in the supernatants of PBMC treated with LPS with or without rhIFN gamma. In these experimental conditions the further addition of HHV-6 markedly impaired IL-12 production. Moreover, the neutralization of IL-10 resulted in a significant up-regulation of IL-12. Finally our data suggest that the immunodysregulation induced by HHV-6 could be accounted for by a shift from a Th-1 to a Th-2 type cytokine profile.     

Monitoring Azospirillum-wheat interactions using the gfp and gusA genes constitutively expressed from a new broad-host range vector

To monitor the colonization of wheat roots by Azospirillum brasilense, we constructed several plasmids based on the pBBR1 replicon expressing the gfp and gusA genes constitutively. Both genes were placed under control of the gentamycin resistance gene promoter resulting in high levels of expression in Escherichia coli and A. brasilense. The constructed plasmids were stably maintained in A. brasilense strains even in the absence of selective pressure. The colonization of wheat plants grown under controlled conditions in sterilized vermiculite by A. brasilense strain FP2 (a Sp7-derivative) transconjugants containing these plasmids was monitored. Bacteria expressing GFP were easily observed in fresh plant material by fluorescence microscopy. Cell aggregates and single bacteria were visualized on the surfaces of young root zones, such as roots hairs and lateral roots. Large cellular clumps were observed at the points of lateral root emergence or at intercellular spaces of root epidermal cells 30 days after inoculation. Although we failed to detected bacteria in internal cortical and xylem tissues of wheat roots, the initial stage of endophytic colonization by A. brasilense may involve the sites detected in this work.     

Differential induction of TNFalpha and IL-18 in human peripheral blood mononuclear cells infected with Leishmania major or Leishmania donovani

Several cytokines are involved in the host response to Leishmania. However, the role played by cytokines during infection with different species of Leishmania is not univocal. In this work, the production of tumor necrosis factor alpha (TNFalpha) and interleukin 18 (IL-18) during interaction of human phagocytes with Leishmania major or L. donovani was comparatively investigated. Peripheral blood mononuclear cells (PBMC) and monocytes from healthy donors were used. The release of TNFalpha and IL-18 during infection of cells with different species of Leishmania "in vitro" was evaluated. L. donovani induced in both PBMC and monocytes significantly more TNFalpha and IL-18 with respect to L. major. The amounts of TNFalpha released by PBMC were always significantly higher than those released by monocytes of the same donors.     

Low fasting serum triglyceride level as a precocious marker of autoimmune disorders

The authors recently reported the occurrence of low fasting serum triglyceride (TG) and high free fatty acid (FFA) levels in idiopathic pulmonary fibrosis. TG estimation in diverse groups of patients with autoimmune disease or hyperactive immune response confirmed the occurrence of a similar decrease of TG. In some patients, serum FFA level was also evaluated. TG value in lean and obese patients was compared with that in lean (n = 108) and obese (n = 208) control subjects without autoimmune disease. In patients affected by autoimmune chronic thyroiditis with enhanced concentration of antithyroglobulin antibodies and without thyroidal failure (n = 24), lean and obese patients had reduced TG (-69/%, P < .01 and -52%, P < .0001, respectively). Both lean and obese patients affected by chronic active B or C hepatitis (n = 26), with autoantibodies and without signs of hepatic insufficiency or cirrhosis, presented reduced TG (-57%, P < .01 and -61%, P < .001, respectively). A marked TG decrease (-73%, P < .001) was observed in the lean patients affected by lupus-like syndrome (n = 7). The lean and obese patients with systemic lupus erythematosus or rheumatoid arthritis (n = 11) showed TG decrease (-66%, P < .01 and -55%, P < .05, respectively). In patients affected by anamnestic allergy or atopic dermatitis/asthma (n = 66), both lean and obese, TGs were reduced (-67%, P < .0001 and -62%, P < .001, respectively). In isolated cases of diverse autoimmune diseases (scleroderma, APECED [autoimmune polyendocrinopathy, candidiasis, and ectodermal dystrophy], urticaria or urticarial vasculitis, Reiter or Sjogren syndromes, ulcerative colitis or Crohn's disease, multiple sclerosis or Guillain-Barré syndrome) (n = 14), decreased TG was also observed both in the lean and obese subjects (-59%, P < .01 and -57%, P < .01, respectively). Concerning FFA (n = 69), value in lean patients (n = 22) vs that in lean controls (n = 18) was increased (520 +/- 31 vs 299 +/- 30 mcEq/L, +74%, P < .001), whereas value in obese patients (n = 18) vs that in obese control subjects (n = 11) was decreased (542 +/- 34 vs 774 +/- 62, -30%, P < .01). This opposite behavior of FFA in lean and obese patients needs to be confirmed. Data in this study seem to indicate that low TG value may be a precocious marker of autoimmunity or immune system hyperreactivity.     

Platinum toxicity and gene expression in Xenopus embryos: analysis by FETAX and differential display

Since the level of platinum in the environment is destined to increase, because of its use in vehicle catalytic converters, the toxicity of platinum needs further investigation. In this study, the frog embryo teratogenesis assay-Xenopus (FETAX) was used to compare the embryotoxicity and teratogenicity of two common platinum species, (NH4)2PtCl4 and (NH4)2PtCl6. The uptake rates of the two platinum species were studied, and also their effects on the expression of genes encoding metallothionein and heat-shock protein 70, which are known to be induced by several stress factors. In addition, the differential display technique was used to search for genes that were specifically induced by platinum. A gene for the type I collagen alpha-chain and a novel gene were identified.     

Different modulation by live or killed Helicobacter pylori on cytokine production from peripheral blood mononuclear cells

The mechanisms by which H. pylori colonizes and persists within the gastric mucosa are poorly understood. The induction and maintenance of gastric inflammation appear to depend on the complex interaction between a number of cytokines and chemokines. The gastric immune response observed "in vivo", during H. pylori infection, is characterized by a polarization of Th1 cell type that seems to be responsible for gastric pathology. The purpose of this study was to test the direct effect of H. pylori (live or gentamicin-killed) on human PBMC in order to evaluate the "in vitro" Th1-Th2 balance by monitoring IL-18, IFNgamma and IL-10 production. This study demonstrates for the first time that "in vitro" pretreatment with gentamicin-killed H. pylori of PBMC, followed by infection with live bacteria, downregulates the production of inflammatory cytokines such as IL-18 and IFNgamma Our results provide a possible strategy to restore the immunological disorders determined by H. pylori infection.     

An imbalance in antioxidant defense affects cellular function: the pathophysiological consequences of a reduction in antioxidant defense in the glutathione peroxidase-1 (Gpx1) knockout mouse

Aerobic cells are subjected to damaging reactive oxygen species (ROS) as a consequence of oxidative metabolism and/or exposure to environmental toxins. Antioxidants limit this damage, yet peroxidative events occur when oxidant stress increases. This arises due to increased radical formation or decreased antioxidative defenses. The two-step enzymatic antioxidant pathway limits damage to important biomolecules by neutralising superoxides to water. However, an imbalance in this pathway (increased first-step antioxidants relative to second-step antioxidants) has been proposed as etiological in numerous pathologies. This review presents evidence that a shift in favor of hydrogen peroxide and/or lipid peroxides has pathophysiological consequences. The involvement of antioxidant genes in the regulation of redox status, and ultimately cellular homeostasis, is explored in murine transgenic and knockout models. The investigations of Sod1 transgenic cell-lines and mice, as well as Gpx1 knockout mice (both models favor H(2)O(2) accumulation), are presented. Although in most instances accumulation of H(2)O(2) affects cellular function and leads to exacerbated pathology, this is not always the case. This review highlights those instances where, for example, increased Sod1 levels are beneficial, and indicates a role for superoxide radicals in pathogenesis. Studies of Gpx1 knockout mice (an important second-step antioxidant) lead us to conclude that Gpx1 functions as the primary protection against acute oxidative stress, particularly in neuropathological situations such as stroke and cold-induced head trauma, where high levels of ROS occur during reperfusion or in response to injury. In summary, these studies clearly highlight the importance of limiting ROS-induced cellular damage by maintaining a balanced enzymatic antioxidant pathway.     

DNA vaccination strategies for anti-tumour effective gene therapy protocols

After more than 15 years of experimentation, DNA vaccines have become a promising perspective for tumour diseases, and animal models are widely used to study the biological features of human cancer progression and to test the efficacy of vaccination protocols. In recent years, immunisation with naked plasmid DNA encoding tumour-associated antigens or tumour-specific antigens has revealed a number of advantages: antigen-specific DNA vaccination stimulates both cellular and humoral immune responses; multiple or multi-gene vectors encoding several antigens/determinants and immune-modulatory molecules can be delivered as single administration; DNA vaccination does not induce autoimmune disease in normal animals; DNA vaccines based on plasmid vectors can be produced and tested rapidly and economically. However, DNA vaccines have shown low immunogenicity when tested in human clinical trials, and compared with traditional vaccines, they induce weak immune responses. Therefore, the improvement of vaccine efficacy has become a critical goal in the development of effective DNA vaccination protocols for anti-tumour therapy. Several strategies are taken into account for improving the DNA vaccination efficacy, such as antigen optimisation, use of adjuvants and delivery systems like electroporation, co-expression of cytokines and co-stimulatory molecules in the same vector, different vaccination protocols. In this review we discuss how the combination of these approaches may contribute to the development of more effective DNA vaccination protocols for the therapy of lymphoma in a mouse model.