Immunoglobulin G subclasses in antibody responses to St. Louis encephalitis virus infections.

The aim of this study was to recognize the specific antiviral response patterns of IgG1, IgG2, IgG3 and IgG4 subclasses, elicited during St. Louis encephalitis virus (SLEV) infection in humans. Eighty-five samples of human sera from 44 patients with SLEV infection were obtained between days 1 and 365 or later, after onset of the disease. These samples were processed by immunofluorescence assay for detection of IgG1-, IgG2-, IgG3- and IgG4-specific antibodies. We demonstrate the presence of all isotypes of IgG for more than a year in patients infected with SLEV. However; isotype IgG1 was present at the highest titers, with a peak between days 8 and 30 after onset of the disease.