Monoclonal antibodies to influenza A virus FM1 (H1N1) proteins require individual conditions for optimal reactivity in binding assays.

The physical environments for optimal display of individual antigenic determinant sites on influenza A/FM/1/47 virus, with preference of its haemagglutinin, were established with monoclonal antibodies based on an enzyme-linked binding assay (ELISA). Comparisons were made with requirements of serum-derived antibodies to form immune complexes. Two-coating buffers revealed profound differences in their inherent capacities to provide antigenic reactivity; this activity became further altered when, after adsorption, the antigens were briefly exposed to either methanol or formaldehyde. Ionic strength started to become restrictive on formation of immune complexes above 0.2 M NaC1. The binding of the monoclonal antibodies to the haemagglutinin was charge-dependent. The form of its presentation, located on the viral surface or as an isolated component, further modified the pH-requirements for its optimal display in antigenic reactivity. The binding of serum-derived antibodies differed markedly and showed a dependence neither on the charge nor on the structural form of the haemagglutinin. Pretreatment of the haemagglutinin on the viral surface with small concentrations (0.025-0.05%) of Triton X-100, sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB), strongly changes the accessibility of its determinant sites, while deoxycholate (DOC) and octyl-beta-D-glucoside (OG) were not effective at the same concentrations. None of these detergents, however, altered the binding properties of the isolated component. Instead, some of them even improved its capacity to form immune complexes.