Bacteriophage M13KE as a nanoparticle platform to display and deliver a pathogenic epitope: Development of an effective porcine epidemic diarrhoea virus vaccine.

Porcine epidemic diarrhoea virus (PEDV) is a porcine enteric coronavirus, outbreaks and epidemics of which have caused huge economic losses to the livestock industry. The disadvantage of existing PEDV vaccines is that the unstable efficacy and high cost limit their widespread use. Therefore, there is an urgent need to develop a recombinant transgenic vaccine candidate for PEDV. In this study, three linear epitopes on the PEDV spike (S) were screened using peptide scanning. The screened epitopes were linked to targeting peptides for lung and intestinal epithelial cells, respectively, and displayed on the M13KE phage to form recombinant phage nanoparticles. Active immunisation experiments showed that a single B-cell epitope delivered by M13KE phage nanoparticles induced the production of specific neutralising antibodies against PEDV in mice. After PEDV stimulation, the immunised mice had significantly higher levels of interferon-γ (IFN-γ) than the control group. Simultaneously, PEDV stimulation caused lymphocyte activation and proliferation in the immunised mice, which is a typical immune response to viral infections. These results suggest that a single linear antigenic epitope delivered by M13KE phage nanoparticles induces significant humoral and cellular immune responses. The constructed recombinant phage nanoparticles are expected to be potential vaccine candidates for PEDV.