Assessment of the immunogenicity of recombinant porcine reproductive and respiratory syndrome virus-1 (PRRSV-1) soluble Glycosylated Protein 3 (sGP3)

Groups of pigs (n = 3) were primed (day 0) and boosted (day 28) with GP3 delivered either via a self-amplifying RNA (saRNA) vector, on the surface of cobalt porphyrin phospholipid bilayer (CoPoP) adjuvanted liposomes, or adjuvanted with Montanide™ ISA 201 VG (ISA 201). Peripheral blood mononuclear cells (PBMCs) were stimulated with GP3 peptides, and the frequency of interferon-γ (IFN-γ)-secreting cells was assessed by ELISpot assay (IFN-γ S-C/10⁶ cells) (A). Serum was collected weekly and assessed for reactivity against recombinant sGP3 by enzyme-linked immunosorbent assay. Statistical differences between ISA 201 and CoPoP are shown by *P < 0.05 and **P < 0.01, and between ISA 201 and saRNA by #P < 0.05 (B). Endpoint titers for each serum were determined at days 0, 28, and 42; statistical differences between groups are shown by ***P < 0.001 and ****P < 0.0001 (C). Neutralization of PRRSV-1 was determined for each serum at day 56 and compared with a PRRSV-immune pig (PRRSV) and a naïve animal (naïve) (D). Mean data for each group are shown, and error bars represent SD. All statistical differences were determined by two-way ANOVA with Tukey’s multiple-comparison test.