Suprabasal Overexpression of the hsRPB7 Gene in Psoriatic Epidermis as Identified by a Reverse Transcriptase-Polymerase Chain Reaction Differential Display Model Comparing Psoriasis Plaque Tissue with Peritonsillar Mucosa

Efalizumab (Raptiva^TM) is an immunomodulating recombinant humanized IgG1 monoclonal antibody that binds to CD11a, the α-subunit of leukocyte function antigen-1 (LFA-1). By blocking the binding of LFA-1 to ICAM-1, efalizumab inhibits the adhesion of leukocytes to other cell types and interferes with the migration of T lymphocytes to sites of inflammation (including psoriatic skin plaques). Analysis of the response in patients treated with efalizumab to date shows that distinct groups of responders and nonresponders to the drug exist. It would therefore be of great practical value to be able to predict which patients are most likely to respond to treatment, by identifying key parameters in the mechanism of action of efalizumab. Detailed investigation and detection of multiple epitopes in microcompartments of skin tissue has until recently been restricted by the available technology. However, the newly developed technique of Multi-Epitope Ligand Cartography (MELC) robot technology combines proteomics and biomathematical tools to visualize protein networks at the cellular and subcellular levels in situ, and to decipher cell functions. The MELC technique, which is outlined in this paper, was used to help characterize the binding of efalizumab to affected and unaffected psoriatic skin as compared to normal control skin under ex vivomodel conditions. Efalizumab was labeled with fluorescein isothiocyanate and integrated into a MELC library of more than 40 antibodies. These antibodies were selected for their potential to detect epitopes which may be indicative of (a) various cell types, (b) structural components of the extracellular matrix, or (c) the processes of cell proliferation, activation and adhesion. Efalizumab bound to CD11a in affected psoriatic skin by a factor 15× and 32× higher than in unaffected psoriatic skin and normal control skin, respectively. CD11a and the efalizumab binding site were primarily expressed in the extravascular dermis, whereas CD54 (ICAM-1) as its ligand was most prevalent in the dermal vessels. T lymphocytes (for which the markers were CD3, CD8, CD4, and CD45R0) were the major cellular targets of efalizumab. In contrast, NK cells were only a minor target of efalizumab. Our study demonstrated that efalizumab represents a treatment for psoriasis that primarily targets memory CD4+ and CD8+ T cells and has a high specificity for psoriatic disease activity. Moreover, we hereby introduce the novel principle of a biological drug-binding biochip assay being especially useful for the future monitoring of psoriatic skin lesions under efalizumab treatment conditions.

Section: Discussionmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 82%

The CD11a Binding Site of Efalizumab in Psoriatic Skin Tissue as Analyzed by Multi-Epitope Ligand Cartography Robot Technology

Bonnekoh

Böckelmann

Pommer

et al. 2006

“…Additionally, presumptive autoantigen cross-reactivities be-tween the cutaneous and synovial compartments would render a pathogenetic link to psoriatic arthritis [8]. Missing autoantigen expression in certain organs like the buccal oral mucosa would explain why these tissues are not affected by the psoriatic autoimmune process [9]. It is an object of current controversial debates if such human leukocyte antigen-restricted autoantigens are recognized by CD4+ or CD8+ lymphocytes [3,10,11].…”

Section: Introductionmentioning

confidence: 99%

Interferon-γ-Dependent in vitro Model for the Putative Keratin 17 Autoimmune Loop in Psoriasis: Exploration of Pharmaco- and Gene-Therapeutic Effects

Böckelmann

Horn

Gollnick

et al. 2004

In 1999, A.S. Gudmundsdottir et al. have envisaged an epitope on keratin 17 (K17) as a putative psoriasis major autoantigen recognized by T cells. In a HaCaT keratinocyte model, we now demonstrate that IFN-γ and to a less extent also TNF-α and TGF-α are able to induce K17 protein expression, in contrast to IL-1α, IL-1β, IL-6, IL-8 and IL-18. This supports our hypothesis of an existing proinflammatory cytokine/K17 autoimmune loop as a presumptive positive feedback mechanism driving psoriasis etiopathogenesis. K17 overexpression was now found to also coincide with suppression of keratinocyte proliferation, e.g. induced by NF-kappa B inhibitors (Bay 11-7082 and Bay 11-7085), and thereby correlated hyperapoptosis to be encountered in psoriatic epidermis. Acitretin as an established antipsoriatic drug and the tyrosine kinase inhibitor imatinib decreased, whereas hydrocortisone as well as dexamethasone increased the IFN-γ-induced K17 overexpression. The latter might be another mechanism explaining the well-known rebound phenomena after abrupt withdrawal of corticosteroids in psoriasis treatment. Finally, we defined a K17-directed and effective antisense oligodesoxynucleotide which may hold promise for future gene-therapeutic approaches in psoriasis.

“…Moreover, presumptive autoantigen cross-reactivities between the cutaneous and synovial compartments would render a plausible causative link to psoriatic arthritis. On the other hand, missing constitutive and inflammation-dependent expression of psoriasis-relevant autoantigens in certain organs like the buccal oral mucosa would explain why these tissues are not affected by the psoriatic autoimmune process [8]. It is still a matter of debate if such putatively expressed HLArestricted autoantigens are recognized by CD4 + or CD8 + lymphocytes [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Dithranol and Dimethylfumarate Suppress the Interferon-γ-Induced Up-Regulation of Cytokeratin 17 as a Putative Psoriasis Autoantigen in vitro

Bonnekoh

Böckelmann²,

Ambach³

et al. 2001

In psoriasis an etiopathogenetic vicious circle has been hypothesized in which disease manifestation is triggered by skin-specific autoantigen structures. Autoreactive T cells are supposed to mediate inflammation and hyperproliferation in the epidermopapillary compartment, positively feeding back the expression and accessibility of decisive antigen structures. Recently an epitope within cytokeratin 17 (K17) has been described as such a putative psoriasis autoantigen, which is moreover known to be up-regulated under the influence of proinflammatory interferon-γ (IFN-γ), which is abundantly detected in psoriatic plaques. The present study proposes an in vitro model for this presumptive IFN-γ/K17 autoimmune loop, i.e. the incubation of hyperproliferative human HaCaT keratinocytes with 25 U IFN-γ/ml for 72 h. This treatment led to a significant up-regulation of K17 protein expression (≧300%) measured by flow immunocytometry as compared to the untreated control (100%, p ≤ 0.05). Preincubation with a subcytotoxic and antiproliferative dithranol concentration as low as 0.3 µM for 2 h prior to the IFN-γ exposure resulted in a K17 expression that was significantly lower than the IFN-γ-induced K17 expression reference level. The IFN-γ-induced K17 expression was also significantly lowered by coincubation with a subcytotoxic and nonantiproliferative concentration of 3 µM dimethylfumarate. The data indicate for dithranol and dimethylfumarate that a part of their antipsoriatic mode of action may be related to a direct down-regulation of putative psoriasis autoantigen structures.