Transplant. increase or only a slight increase in MxA mRNA levels was detectable after administration of rIFN-2a or (C)IFN, whereas a significant increase (10-fold) in MxA mRNA expression was recorded following administration of LeIFN. The neutralizing antibodies to rIFN-2a cross-react with (C)IFN. Sera from these patients neutralized most but not all of the subtypes present in the natural IFN- (LeIFN) mixture, and no significant increase in neopterin levels was observed after these patients were switched to LeIFN treatment. In summary, the data demonstrate that the problem of neutralizing antibodies still exists and that LeIFN may induce an increase in the level of MxA mRNA expression but not GDC-0084 an increase in neopterin levels in patients who are resistant to treatment with rIFN-2a or (C)IFN. It has been repeatedly reported that antibodies to interferon (IFN) may develop during alpha IFN (IFN-) therapy (2). Of the antibodies that bind to different epitopes of the IFN molecule, some are neutralizing antibodies (NABs), as measured in antiviral neutralization assays. The development of NABs against IFN- has been correlated with a decline in therapeutic efficacy in patients with chronic myelogenous leukemia (39), hairy-cell leukemia (40), carcinoid tumors (33, 36), and chronic hepatitis C (7, 21, 31) treated with IFN- and, more recently, in patients with multiple sclerosis treated with IFN- (26, 27, 37). It has also been observed in patients with severe type II essential mixed cryoglobulinemia (EMC), for whom IFN- is a well-established and widely used therapy (9, 10, 12, 32). Several studies have also demonstrated that second-line therapy with natural human IFN- may be effective in restoring the therapeutic response in patients with chronic hepatitis C (5, 13, 31) and in those with cancer (8, 20, 38, 42) GDC-0084 who relapse following the production of NABs to rIFN-. However, the possibility that switching to alternative IFN- preparations could overcome the NAB-induced fall in the biological and clinical activities of IFN has, so far, rarely been considered. Furthermore, a clear cause-and-effect relationship between NAB production and the reduction in the biological effectiveness of IFN has not been proved conclusively. One possible way of addressing these issues would be to study the effect of circulating antibodies on the pharmacodynamics of IFN in an attempt to establish whether they are capable of reducing the bioavailability and biological activity of the administered IFN-. The aim of the present study was thus to analyze the pharmacodynamic response to recombinant IFN-2a (rIFN-2a) in NAB-seropositive patients with EMC who, after initially responding to treatment with rIFN-2a, demonstrated a subsequent lack GDC-0084 of response. Specifically, the following markers were measured: (i) the expression in peripheral blood mononuclear cells (PBMCs) of the mRNA of a well-known IFN-induced protein, MxA, which is an accepted specific indicator of type I IFN (IFN and ) activity (22) and (ii) the level of expression of neopterin in serum, a marker of macrophage activity, which is a surrogate marker for IFN- bioactivity (25). In addition, the question was addressed Rabbit Polyclonal to EDG4 whether IFN- preparations that are different from rIFN-2a, such as consensus IFN [(C)IFN] and leukocyte IFN (LeIFN), are able to overcome the decreases in the biological effects of IFN that developed concomitantly with the formation of NABs. MATERIALS AND METHODS Patient characteristics. In this study, attention was focused on two patients with type II EMC, in whom treatment with rIFN-2a had failed and who therefore had to start a new cycle of IFN therapy. The clinical courses of these patients who were treated with different types of IFN are described below. (i) Patient 1. Patient 1 is a 62-year-old woman with type II cryoglobulins, purpura, diffuse arthralgia, sicca syndrome, hypertension, moderate anemia, proteinuria (3 g/day), reduced creatinine clearance (34 ml/min), and a histopathological diagnosis of diffuse membranoproliferative glomerulonephritis with deposits of immunoglobulin M, immunoglobulin G, and complement. Tests for hepatitis C virus (HCV) antibodies and for plasma HCV RNA were repeatedly negative. Despite the lack of evidence of HCV infection, the patient was treated with rIFN-2a (Roferon A; Hoffmann-La Roche, Basel, Switzerland) at 3 MU daily for 3 months, followed by 3 MU on alternate days (11). Her response was excellent overall: the cryoglobulins disappeared, as did the clinical symptoms. Some 8 months later, IFN therapy was stopped because of the reappearance of proteinuria that was attributed to IFN nephrotoxicity. The patient’s.
