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type I interferon and treatment for RAType I Inferferon as treatment for RA
Cytokines are heavily present in the disease rheumatoid arthritis (RA), in particular, the inflammatory cytokines: interleukins-1 and -6 (IL-1, IL-6) as well as tumour-necrosis factor-α and the osteoprotegerin ligand (OPGL) [1,2]. These cytokines are recruited to the synovial fluids and tissue and activate these cells, as well as inflaming these regions, causing much of the pain and swelling.
Although more popular therapies against TNF-α are in use, these inhibitors only slow the disease progression, and do not halt it completely, which implies that there are other cytokine pathways that must be involved, and can thus be targeted for therapy. This has led to the study of Type I interferon in the regulation of RA. Type I interferons include IFN-α and IFN-β, whereas Type II interferon is IFN-γ. Studies have looked into IFN-β's ability to control the effects of RA in mice, IFN-β's therapeutic value in human sufferers of RA, as well as IFN-α's ability to treat RA ex vivo in cells from RA sufferers.
In the IFN-α study mentioned above by Wong et al., cells isolated from the synovial fluids and tissue of RA sufferers were treated with IFN-α. It was observed that IFN-α could induce the expression of the IL-1 receptor antagonist and soluble TNF receptor. Both these molecules serve to downregulate the inflammatory effects of IL-1 and TNF, respectively. The IL-1 receptor antagonist serves as a competitor for the IL-1 receptor, meaning the usual IL-1 molecule cannot bind or signal. The soluble TNF receptor binds to TNF and disallows its signalling as well. Osteoprotegerin (OPG), another receptor for the inflammatory cytokine osteoprotegrin ligand (OPGL) was also upregulated in the 24h following IFN-α treatment. In contrast, the levels of inflammatory cytokines themselves were not affected (OPGL, particularly), evidence that the mechanism IFN-α employs is upregulating the receptor antagonists.
In similar studies on mice, treatment with IFN-β secreting fibroblasts was shown to reduce swelling in the paws of the RA mice, and it was noted that NF-κB activity was downregulated (NF-κB is a transcription factor often employed in the transcription of pro-inflammatory cytokines). Likewise, subcutaneous IFN-β treatments in eleven RA patients showed that their immunological RA profile changed (reduction in certain T cells, plasma cells, and IL-6) for the better .
As of this website's creation, there has been no studies to the authors' knowledge on the production of recombinant IFN-β through transgenic plant systems. However a Japanese group, Ohya et al., has been active in expressing IFN-α in potato systems and evaluating the recombinant product's usefulness[5,6]. This group has attempted expressing the cDNA of human IFN-α2b and IFN-α8 in potatoes using the constitutive non-tissue-specific CaMV 35V promoter and transformation by Agrobacterium tumefaciens. In this attempt, both IFN-α entities were successfully expressed in the potato systems, as measured by the presence of mRNA transcripts and translated protein. However, the bioactivity assays used (inhibition of vesicular stomatitis virus) showed that only IFN-α8 was notably active. The investigators theorized that this could be due to differences in cDNA structures, or simply because IFN-α8 is naturally reported to have the highest relative activity among human IFN-α subtypes.
Another study by this group showed that the recombinant IFN-α8 product, when orally administered to mice infected with the bacterium Listeria monocytogenes in the form of transgenic potato extract, was successful in reducing the viral burden of the mice in their liver and spleen. This demonstrates that oral/mucosal administration of IFN-α is successful in having systemic effects. Also, it was shown that lower amounts of the potato extracts were needed than pure IFN-α to obtain the same beneficial results. The authors surmised this was due to a bioencapsulation effect, wherein the recombinant cytokines were protected from degradation by the plant tissues.
These studies are promising. Imagine a system in which RA treatment is delivered orally, through just eating a banana or potato. It has already been shown that these recombinant cytokines are indeed biologically active in vitro and in vivo for mice. However, more research must first be conducted regarding IFN-α in human clinical trials.
references1) E.N. Fish. Personal communication on "Cytokines". February 2006.
2) Wong T, Majchrzak B, Bogoch E, Keystone EC, Fish EN. Therapeutic implications for interferon-alpha in arthritis: a pilot study. J Rheumatol 2003, 30: 934-40.
3) van Holten J, Reedquist K, Sattonet-Roche P, Smeets TJ, Plater-Zyberk C, Vervoordeldonk MJ, Tak PP. Treatment with recombinant interferon-beta reduces inflammation and slows cartilage destruction in the collagen-induced arthritis model of rheumatoid arthritis. Arthritis Res Ther 2004, 6: R239-49. Epub 2004 Mar 23.
4) Smeets TJ, Dayer JM, Kraan MC, Versendaal J, Chicheportiche R, Breedveld FC, Tak PP. The effects of interferon-beta treatment of synovial inflammation and expression of metalloproteinases in patients with rheumatoid arthritis. Arthritis Rheum 2000, 43: 270-4.
5) Ohya K, Matsumura T, Ohashi K, Onuma M, Sugimoto C. Expression of two subtypes of human IFN-alpha in transgenic potato plants. J Interferon Cytokine Res 2001, 21: 595-602.
6) Ohya K, Matsumura T, Itchoda N, Ohashi K, Onuma M, Sugimoto C. Ability of orally administered IFN-alpha-containing transgenic potato extracts to inhibit Listeria monocytogenes Infection. J Interferon Cytokine Res 2005, 25: 459-66.