Prevention of Cognitive Decline in Alzheimer's Disease by Ingested Interferon Alpha

Inflammatory mechanisms contribute to neurodegeneration in AD. Acute phase proteins such as the antichymotrypsin (a1ACT), pro-inflammatory cytokines IL-6 and IL-1, and activated microglial cells are all associated with neuritic plaques. a1ACT levels are elevated in AD, correlate with cognitive decline and serve as a biological marker of intervention. a1ACT is intimately associated with the 42-AA b peptide (Ab) in filamentous amyloid deposits and stimulates the polymerization of Ab into amyloid filaments. IL-6 is found in AD cortices prior to the onset of neuritic change, serum and stimulated PMNC IL-6 levels are higher in AD, and may induce b-amyloid protein deposition. Microglia, CNS resident inflammatory cells, produce IL-6 within the adult human brain, are IL-1a +, and are a prominent component of the neuritic plaque. Because the pathogenesis of AD appears in part immune mediated, we propose testing directly in humans whether ingested IFN-a can ameliorate AD. Because there is no good model for inflammation in animal models of AD, we will directly determine in humans 1) if 3,000 or 30,000 IU hrIFN-a inhibits the natural history rate of cognitive decline in mild to moderate AD using neuropsychological instruments as primary and secondary outcome measures that 2) correlates with inhibition of acute phase reactants and pro-inflammatory IL-6. If this novel anti-inflammatory agent inhibits the natural history rate of cognitive decline in AD in this pilot phase II trial, this would provide the preliminary data to submit a phase III clinical trial.

IFNs administered by the oral route show a systemic effect. Oral IFN-a caused neutropenia in mice. In contrast to their i.p. administration, oral IFN-a did not result in the presence of detectable levels of IFNs in the blood. Circulating specific antibody to IFN blocked the neutropenic effects of i.p. IFN, but did not block the neutropenic effects of the oral IFNs (2). Therefore, we examined the expression of antiviral MxA message, a type 1 IFN-specific induced signal, as a sensitive marker for type 1 IFN interaction with lymphoid cells in the gut-associated lymphoid tissue (GALT) using semi-quantitative RT-PCR on splenocytes from mice and PMNC from man after IFN-a ingestion. Both mice and man demonstrated inducible levels of Mx mRNA after ingesting IFN-a. Murine spleen T cells and CD8+ T cells also demonstrated upregulation of Mx mRNA. Therefore, ingested IFN-a acts via established pathways of type 1 IFN signalling (3). Elevated levels of activated T cells, mainly of the CD8+ (cytotoxic/suppressor) phenotype, are found in AD brains in contact with microglial cells (4). Interestingly, peripheral CD8+ T cells are depleted in AD patients (5). Lymphocytes bearing T helper and T cytotoxic/suppressor cell antigens are found in hippocampus and temporal cortex in AD (6,7). The data above suggest that lymphocytes are part of inflammation in AD, and potential immunomodulatory T and CD8+ T cells that contact ingested non-absorbed IFN in the GALT could migrate to the brain and decrease inflammation.