Intranasal delivery of inactivated PRRSV loaded cationic nanoparticles coupled with enterotoxin subunit B induces PRRSV-specific immune responses in pigs

Abstract

This study was conducted to evaluate the induction of systemic and mucosal immune responses and protective efficacy following the intranasal administration of inactivated porcine reproductive and respiratory syndrome virus (PRRSV) loaded in polylactic acid (PLA) nanoparticles coupled with heat-labile enterotoxin subunit B (LTB) and dimethyldioctadecylammonium bromide (DDA). Here, 42- to 3-week-old PRRSV-free pigs were randomly allocated into 7 groups of 6 pigs each. Two groups represented the negative (nonvaccinated pigs/nonchallenged pigs, NoVacNoChal) and challenge (nonvaccinated/challenged, NoVacChal) controls. The pigs in the other 5 groups, namely, PLA nanoparticles/challenged (blank NPs), LTB-DDA coupled with PLA nanoparticles/challenged (adjuvant-blank NPs), PLA nanoparticles-encapsulating inactivated PRRSV/challenged (KNPs), LTB-DDA coupled with PLA nanoparticles loaded with inactivated PRRSV/challenged pigs (adjuvant-KNPs) and inactivated PRRSV/challenged pigs (inactivated PRRSV), were intranasally vaccinated with previously described vaccines at 0, 7 and 14 days post-vaccination (DPV). Serum and nasal swab samples were collected weekly and assayed by ELISA to detect the presence of IgG and IgA, respectively. Viral neutralizing titer (VNT) in sera, IFN-γ-producing cells and IL-10 secretion in stimulated peripheral blood mononuclear cells (PBMCs) were also measured. The pigs were intranasally challenged with PRRSV-2 at 28 DPV and necropsied at 35 DPV, and then macro- and microscopic lung lesions were evaluated. The results demonstrated that following vaccination, adjuvant-KNP-vaccinated pigs had significantly higher levels of IFN-γ-producing cells, VNT and IgG in sera, and IgA in nasal swab samples and significantly lower IL-10 levels than the other vaccinated groups. Following challenge, the adjuvant-KNP-vaccinated pigs had significantly lower PRRSV RNA and macro- and microscopic lung lesions than the other vaccinated groups. In conclusion, the results of the study demonstrated that adjuvant-KNPs are effective in eliciting immune responses against PRRSV and protecting against PRRSV infections over KNPs and inactivated PRRSV and can be used as an adjuvant for intranasal PRRSV vaccines.

Testable Candidate Immune Correlates of Protection for Porcine Reproductive and Respiratory Syndrome Virus Vaccination

“…With respect to other types of vaccinations hoping to produce a more protective immune response than MLV vaccinations against heterologous challenge, the results are varied. In nursery-age pigs, a novel killed PRRSV-2 plus adjuvant intranasal vaccine induced serum NA detectable 14 dpv with a strong protective effect upon PRRSV-2 challenge 28 dpv and significantly higher NA than other vaccination combinations out to 35 dpv (7 dpc) [ 120 ]. A killed PRRSV-2 vaccination in nursery-age pigs resulted in serum NA 10 dpc for the homologous strain and decreased symptoms in vaccinated pigs [ 121 ].…”

“…We briefly will summarize the available research on anti-PRRSV IgA. With respect to the role of secreted IgA in the humoral immune response and as a CoP, an intranasal vaccine induced anti-PRRSV IgA at 28 dpv and a generally stronger immune response resulting in improved performance upon challenge [ 120 ]. Differently, in our MLV study, vaccination did not result in detectable heterologous anti-PRRSV IgA in nasal swabs at 28 dpv.…”

“…In a study to determine immunogenic CD8 + T-cell epitopes, the CTL response to nsp1a and nsp1b was detected in finishing pigs and sows at 16 and 21 dpc respectively [ 128 ]. In two separate PRRSV-2 vaccination and challenge studies in nursery-age pigs, CD4 + and CD8 + phenotypes were both involved in IFN-γ production and observed 28 dpv [ 120 ] or 10 dpc [ 121 ]. After MLV vaccination with and without adjuvant, Chaikhumwang et al quantified IFN-γ using flow cytometry and found that upon homologous and heterologous challenge, CD4 + IFN-γ + T cells were significantly increased in adjuvant-vaccinated piglets, which aligned with decreased viremia and symptoms [ 120 ].…”

“…In two separate PRRSV-2 vaccination and challenge studies in nursery-age pigs, CD4 + and CD8 + phenotypes were both involved in IFN-γ production and observed 28 dpv [ 120 ] or 10 dpc [ 121 ]. After MLV vaccination with and without adjuvant, Chaikhumwang et al quantified IFN-γ using flow cytometry and found that upon homologous and heterologous challenge, CD4 + IFN-γ + T cells were significantly increased in adjuvant-vaccinated piglets, which aligned with decreased viremia and symptoms [ 120 ]. In summary, though these studies are varied, a few key conclusions can be drawn: the T-cell response upon vaccination includes IFN-γ production and proliferation in both CD4 + and CD8 + T cells and generally appears at 28 dpv while the T-cell response upon PRRSV challenge occurs as quickly as 7–10 dpi.…”

Nanoparticle- and Microparticle-Based Vaccines against Orbiviruses of Veterinary Importance

“…Non-lipidic biodegradable nanocarrier- or microcarrier-based delivery platforms have been also assessed, mainly carbohydrate constructs and dendrimers. The most common polymeric nano- and microparticles are those based on poly(α-hydroxy acids) such as the Food and Drug Administration (FDA) and European Medicine Agency (EMA)-approved poly(lactic-coglycolic acid) (PLGA) or poly(lactic acid) (PLA)-based nanoparticles [ 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. In addition, poly-amino acids, such as poly(γ-glutamic acid) (γ-PGA) [ 40 ], poly(ε-lysine) [ 41 ] or poly(L-arginine) [ 42 ], and polysaccharides such as chitosan, alginate or dextran [ 43 , 44 , 45 , 46 , 47 ], have also been developed.…”