Specific detection of antibodies to different flaviviruses using a new immune complex ELISA.

Immune complex (IC) ELISAs for IgG antibodies to various virus antigens have turned out to be both highly specific and sensitive. During incubation of a labelled antigen with the serum samples, ICs are formed, which bind to microtiter plates coated with rheumatoid factor (RF) IgM. Here, we describe an improved coating of the solid-phase support comparing various Fc-receptor molecules. IC ELISAs were applied to detect human IgG antibodies to the highly virus-specific ED3 domain of West Nile- and tick-borne encephalitis virus envelopes. Compared with other Fc-receptor molecules like RF or C1q, FcγRIIA (CD32) turned out to bind the ICs composed of IgG antibodies and peroxidase-labelled ED3 antigens more efficiently. Due to low background reactions, sera could be tested at a dilution of 1:10. Moreover, using CD32 instead of RF coating, anti-flavivirus antibodies could be detected in various animal species.