Porcine epidemic diarrhea virus (PEDV) has been prevalent for many years. The viral spike (S) protein is the major target of neutralizing antibodies. However, there is little understanding of the locations of the neutralizing antibody epitopes in the spike structure. Here, we used a polyclonal antibody (pAb) against PEDV and a neutralizing monoclonal antibody (mAb) to isolate escape mutants of PEDV strain LNCT2. Finally, we isolated an escape mutant strain of PEDV, mutant-1B9, but still neutralized by the pAb. Analysis showed two regions deleted in the S protein which allowed mutant-1B9 to escape neutralization by mAb 1B9. These results suggest the deleted amino acids participate in the formation of conformational epitope and provides valuable information for mapping conformational epitopes. Importantly, no PEDV escape mutants were generated by treatment with pAbs, which suggests the potential utility of pAbs or combination therapies based on several mAbs in controlling PEDV infections.
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