COMPARISON OF MONOCLONAL-ANTIBODIES AND POLYMERASE CHAIN-REACTION ASSAYS FOR THE TYPING OF ISOLATES BELONGING TO THE D-SEROTYPES AND M-SEROTYPES OF PLUM POX POTYVIRUS

Plum pox potyvirus (PPV) isolates may be divided into four groups sepa rated by serological, molecular, and epidemiological differences. Mono clonal antibodies specific for the two major groups of isolates, repre sented by the D and M serotypes of the virus, have been obtained. Poly merase chain reaction (PCR)-based assays allowing the direct detection and differentiation of PPV isolates have also been developed. We now report on a large-scale comparison of these two typing approaches. The results obtained show an overall excellent correlation between the re sults obtained in indirect double-antibody sandwich enzyme-linked immu nosorbent assay using PPV-D- and PPV-M-specific monoclonal antibodies and those derived from either specific PCR assays or restriction fragm ent length polymorphism analysis of PCR fragments. Without exception, all isolates reacting positively with the PPV-M-specific monoclonal an tibody were found to belong to the M serotype using the PCR-based assa ys, while 51 out of 53 isolates recognized by the D-specific monoclona l antibodies belonged to the D serotype according to the PCR typing re sults. However, failure to react with a specific monoclonal antibody d id not prove as effective a predictor of the serotype of the isolate a nalyzed. In a few cases, the results obtained with the various techniq ues diverged, indicating low level variability of the epitopes recogni zed by the serotype-specific monoclonal antibodies. Isolates belonging to the two minor groups of PPV (El Amar and Cherry) also gave diverge nt results, indicating that the current typing assays are not suited f or the analysis of such isolates.