Novel expression of coat proteins from thermophilic bacteriophage IN93 and evaluation for assembly into virus-like particles

Virus-like particles (VLPs) have the potential to be used as display platforms to develop vaccines against infectious and non-infectious agents. However, most VLPs used as vaccine display platforms are derived from viruses that infect humans; unfortunately, most humans already have pre-existing antibodies against these platforms and thus, the immunogenicity of these vaccines may be compromised. VLP platforms derived from viruses that infect bacteria (bacteriophages), especially bacteriophages that infect bacteria, which do not colonize humans are less likely to have pre-existing antibodies against the platforms in the human population. In this study, we assessed whether two putative coat proteins (ORF13 and ORF14) derived from a thermophilic bacteriophage (phi IN93) can be expressed and purified from a mesophilic bacterium such as E. coli. We also assessed whether expressed coat proteins can assemble to form VLPs. Truncated versions of ORF13 and ORF14 were successfully co-expressed in bacteria; the co-expressed truncated proteins formed oval structures that look like VLPs, but their sizes were less than those of an authentic phi IN93 virus.