Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs) are synthetic nucleic acid analogs conjugated to cell-penetrating peptides, which enable intracellular delivery and subsequent access to RNA targets. Upon binding to targeted RNAs through Watson-Crick base pairing, PPMOs act through steric blockage to interfere with cellular RNA processing. This technology offers the opportunity to control gene expression within biological systems in a highly targeted manner. Here, we demonstrate the use of a PPMO to block the translation of the Vibrio coralliilyticus zinc metalloprotease VcpA, which has been determined to cause disease in larval Magallana gigas. This work is intended to provide proof of concept for the use of PPMOs to address vibriosis in oyster aquaculture, an industry-threatening problem for which traditional antibiotics are an unsuitable tool.
Within pure V. coralliilyticus cultures propagated in a minimal growth medium, we have determined that an 11-base PPMO targeted to the translation start site on VcpA-encoding messenger RNA has the capacity to reduce proteolytic activity of culture supernatants in a concentration-dependent manner without influencing the viability of treated cultures. Work to examine the effect of PPMO treatment of V. coralliilyticus cultures upon the health of M. gigas larvae exposed to culture supernatants is ongoing.