Sera from 19 patients with Alzheimer's disease (AD) and 21 control subjects were studied by immunofluorescence and enzyme immunoassay for antibody activity against various viruses and 12 self- and non-self-antigens. Total IgG mean level was significantly higher in the AD group; the IgG level was above 15 g/L in 52.8% of AD patients versus 14.3% of control subjects. Antiviral antibody titers showed no significant differences except for antibodies to herpes simplex virus-1, which were increased in control group. In contrast, autoantibodies were more frequently found in AD patients, and the prevalence of antibodies to spectrin, peroxidase, and thyroglobulin was significantly increased. Thus, in our series, autoimmune but not antiviral responses were heightened in at least 42% of AD patients (versus 9% of the control group) suggesting the existence of two subpopulations in the AD group.

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Hepatitis C virus (HCV), a positive stranded RNA virus, is the main causative agent of post-transfusion and sporadic non-A non-B hepatitis worldwide. Paired samples of plasma and peripheral blood mononuclear cells (PBMC) from 11 patients with chronic hepatitis C treated with alpha-interferon (IFN) were tested, using a single step polymerase chain reaction (PCR), for the presence of HCV RNA. Before treatment, the viral genome was detected in all the plasma samples and 81.8% of PBMC. After 3 months of treatment, HCV RNA was still present in 63.6% of plasma samples but in only 27.3% of PBMC. A good correlation was observed between serum alanine aminotransferase level normalisation and disappearance of the viral genome in plasma. Among the six responder patients, five relapsed shortly after IFN withdrawal; HCV RNA became detectable again, especially in PBMC. These results show the presence of HCV in PBMC from most patients infected chronically. IFN therapy had an inhibitory effect on viral replication in lymphoid cells, but frequent relapses observed after cessation of treatment with IFN suggested persistence of HCV in these cells.