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Viruses share antigenic sites with normal host cell components, a phenomenon known as molecular mimicry. It has long been suggested that viral infections might trigger an autoimmune response by several mechanisms including molecular mimicry. More than 600 antiviral monoclonal antibodies generated against 11 different viruses have been reported to react with 3.5% of cells specific for uninfected mouse organs. The main pathological feature of tropical spastic paraparesis/ human T-lymphotropic virus type I (HTLV-I)-associated myelopathy (TSP/HAM) is a chronic inflammation of the spinal cord characterized by perivascular cuffing of mononuclear cells accompanied by parenchymal lymphocytic infiltration. We detected the presence of autoantibodies against a 98-to 100-kDa protein of in vitro cultured human astrocytes and a 33-to 35-kDa protein from normal human brain in the serum of HTLV-I-seropositive individuals. The two cell proteins exhibited molecular mimicry with HTLV-I gag and tax proteins in TSP/HAM patients, respectively. Furthermore, the location of 33-to 35-kDa protein cross-reaction correlated with the anatomical spinal cord areas (in the rat model) in which axonal damage has been reported in several cases of TSP/HAM patients. Our experimental evidence strongly suggests that the demyelinating process occurring in TSP/ HAM may be mediated by molecular mimicry between domains of some viral proteins and normal cellular targets of the spinal cord sections involved in the neurodegeneration.

The acute and subacute toxicity of the aqueous extract of Salvia scutellarioides (Lamiaceae) was studied in mice and rats. In the acute toxicity test, oral administration of 2g/kg of Salvia scutellarioides produced neither mortality nor changes in behavior or any other physiological activities. In subacute toxicity studies, no mortality was observed when the two doses of 1 or 2g/kgday of aqueous extract of Salvia scutellarioides extract were administered orally for a period of 28 days. In the blood chemistry analysis, no significant changes occurred, including glucose, creatinine, blood urea nitrogen (BUN), aspartate transaminase (AST), alanine transaminase (ALT), potassium, sodium, chloride, calcium, phosphorus, conjugated billirrubin, total billirrubin, total cholesterol, high density lipoprotein (HDL), triglycerides, total protein, albumin, prothrombin time (PT) and thromboplastin partial time (PTT) of both sexes. Hematological analysis showed no differences in any of the parameters examined (WBC count, platelet and hemoglobin estimation) in either the control or treated group of both sexes. The urinalysis was negative for glucose, ketonic bodies, casts, red blood cells, and albumin in the control and treatment groups. There were no significant differences in the body and organ weights between controls and treated animals of both sexes. Pathologically, neither gross abnormalities nor histopathological changes were observed.

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