Extensive antigenic heterogeneity of foot-and-mouth disease virus of serotype C.

The antigenic behavior of 46 field isolates of foot-and-mouth disease virus (FMDV) of serotype C has been studied with a panel of 24 monoclonal antibodies (MAbs) prepared against FMDV C1 or FMDV C3 Indaial. Reactivities were assayed by immunodot, immunoelectrotransfer blot, and neutralization of infectivity. The epitopes recognized by the 10 nonneutralizing MAbs are conserved in all isolates analyzed. In contrast, extreme antigenic heterogeneity is documented with regard to reactivity with 14 MAbs that, on this basis, define at least 12 epitopes involved in neutralization of FMDV of serotype C. The 31 isolates from South America were divided into 17 distinct antigenic groups and the 15 isolates from Europe into 7 groups. Lack of correspondence between antigenic composition and the origin--date and place of isolation--of the viruses was noted in several instances. Antigenic heterogeneity is shown among epidemiologically closely related FMDVs. In most--but not all--cases tested, a good correlation was found between binding of a neutralizing MAb to virions and its ability to neutralize infectivity. It is concluded that variation of epitopes involved in neutralization of FMDV is extensive among subtypes of serotype C and also among individual isolates of one subtype.

Monoclonal antibodies of African swine fever virus: antigenic differences among field virus isolates and viruses passaged in cell culture.

An analysis of the binding properties of a collection of monoclonal antibodies to African swine fever virus particles showed that virus field isolates passaged in porcine macrophages changed antigenically more than a strain of a cell-adapted virus passaged in Vero cells. From seven clones isolated from the spleen of a field-infected pig, we found four clones that had the same antigenic properties, one clone that had large changes in proteins p150 and p27 and small changes in proteins p37 and p14, and two clones that had minor changes in proteins p150 and p27, respectively. An analysis of the binding properties of the monoclonal antibodies to 23 field isolates from Africa, Europe, and America showed that the African isolates differed among themselves more than the European and the American isolates; in this study we found changes in 8 of the 10 virus proteins tested. The most variable proteins in the African isolates were p150, p27, p14, and p12. In contrast to the African isolates, protein p12 from the non-African viruses did not change. The clustering of the field virus isolates in six antigenic homology groups indicated the existence of a complex variety of African swine fever virus serotypes.