Positive effects of porcine IL-2 and IL-4 on virus-specific immune responses induced by the porcine reproductive and respiratory syndrome virus (PRRSV) ORF5 DNA vaccine in swine

pGM-CSF as an adjuvant in DNA vaccination against SARS-CoV-2

The emergence of SARS-CoV-2 presents a significant global public health dilemma. Vaccination has long been recognized as the most effective means of preventing the spread of infectious diseases. DNA vaccines have attracted attention due to their safety profile, cost-effectiveness, and ease of production. This study aims to assess the efficacy of plasmid-encoding GM-CSF (pGM-CSF) as an adjuvant to augment the specific humoral and cellular immune response elicited by DNA vaccines based on the receptor-binding domain (RBD) antigen. Compared to the use of plasmid-encoded RBD (pRBD) alone, mice that were immunized with a combination of pRBD and pGM-CSF exhibited significantly elevated levels of RBD-specific antibody titers in serum, BALF, and nasal wash. Furthermore, these mice generated more potent neutralization antibodies against both the wild-type and Omicron pseudovirus, as well as the ancestral virus. In addition, pGM-CSF enhanced pRBD-induced CD4+ and CD8+ T cell responses and promoted central memory T cells storage in the spleen. At the same time, tissue-resident memory T (Trm) cells in the lung also increased significantly, and higher levels of specific responses were maintained 60 days post the final immunization. pGM-CSF may play an adjuvant role by promoting antigen expression, immune cells recruitment and GC B cell responses. In conclusion, pGM-CSF may be an effective adjuvant candidate for the DNA vaccines against SARS-CoV-2.

Prevention and control of chicken coccidiosis construction of recombinant Lactococcus lactis expressing chicken IL-4 and IL-2 fusion protein and its immune synergistic effect on chicken coccidia live vaccine

Intestinal mucosa injury and loss of weight gain are unavoidable while using live vaccine strain to prevent chicken coccidiosis. In this study, recombinant Lactococcus lactis NZ3900/pNZ8149-IL-4-IL-2, expressing the fusion protein of chicken IL-4 and IL-2, was constructed using food-grade NICE expression system, trying to develop a possible oral immune adjuvant to enhance the immune effect of the live vaccine against chicken coccidiosis and minimize its adverse effects. Chickens were given different doses of recombinant L. lactis together with the live vaccine, then experimently attacked with coccidia virulent strains. Results showed that weight gains of co-immunization groups, given both 1 × 10⁹ or 1 × 10¹⁰ CFU recombinant L. lactis and the live vaccine, were significantly higher than the vaccine-only group (P<0.05), while intestinal lesion scores of duodenum, jejunum, and cecum were significantly lower than the vaccine-only group (P<0.05), so was the oocyst shedding. The anticoccidial indexes (ACI) of the co-immunized groups given 1 × 10⁹ and 1 × 10¹⁰ CFU recombinant L. lactis were 187.85 and 193.33, respectively, higher than 174.61 of the vaccine-only group. In addition, chickens in co-immunization groups gained more body weight than the vaccine-only group before being challenged with the virulent strains (P<0.05). All the results indicated that the constructed recombinant L. lactis NZ3900/ pNZ8149-IL-4-IL-2 exhibited an immune synergistic function to coccidiosis live vaccine, and could alleviate its adverse effect affecting weight gain. The application of the recombinant L. lactis showed the potency to lift the anticoccidial efficiency of the live vaccine from a medium level to a high level.

PDZK1 upregulates nitric oxide production through the PI3K/ERK2 pathway to inhibit porcine circovirus type 2 replication

Porcine circovirus type 2 (PCV2) is the causative agent of porcine circovirus-associated disease. Changes in host cell gene expression are induced by PCV2 infection. Here, we showed that porcine PDZ Domain-Containing 1 (PDZK1) expression was enhanced during PCV2 infection and that overexpression of PDZK1 inhibited the expression of PCV2 Cap protein. PCV2 genomic DNA copy number and viral titers were decreased in PDZK1-overexpressing PK-15B6 cells. PDZK1 knockdown enhanced the replication of PCV2. Overexpression of PDZK1 activated the phosphoinositide 3-kinase (PI3K)/ERK2 signaling pathway to enhance nitric oxide (NO) levels, while PDZK1 knockdown had the opposite effects. A PI3K inhibitor (LY294002) and a NO synthase inhibitor (L-NAME hydrochloride) decreased the activity of PDZK1 in restricting PCV2 replication. ERK2 knockdown enhanced the proliferation of PCV2 by decreasing levels of NO. Levels of interleukin (IL)- 4 mRNA were reduced in PDZK1 knockdown and ERK2 knockdown PK-15B6 cells. Increased IL-4 mRNA levels were unable to decrease NO production in PDZK1-overexpressing cells. Thus, we conclude that PDZK1 affected PCV2 replication by regulating NO production via PI3K/ERK2 signaling. PDZK1 affected IL-4 expression through the PI3K/ERK2 pathway, but PDZK1 modulation of PCV2 replication occurred independently of IL-4. Our results contribute to understanding the biological functions of PDZK1 and provide a theoretical basis for the pathogenic mechanisms of PCV2.

The Combined Effect of Weaning Stress and Immune Activation during Pig Gestation on Serum Cytokine and Analyte Concentrations

Weaning stress can elicit changes in the metabolic, hormone and immune systems of pigs and interact with prolonged disruptions stemming from maternal immune activation (MIA) during gestation. The present study advances the characterization of the combined effects of weaning stress and MIA on blood chemistry, immune and hormone indicators that inform on the health of pigs. Three-week-old female and male offspring of control gilts or gilts infected with the porcine reproductive and respiratory syndrome virus were allocated to weaned or nursed groups. The anion gap and bilirubin profiles suggest that MIA enhances tolerance to the effects of weaning stress. Interleukin 1 beta and interleukin 2 were highest among weaned MIA females, and cortisol was higher among weaned relative to nursed pigs across sexes. Canonical discriminant analysis demonstrated that weaned and nursed pigs have distinct chemistry profiles, whereas MIA and control pigs have distinct cytokine profiles. The results from this study can guide management practices that recognize the effects of the interaction between MIA and weaning stress on the performance and health of pigs.

Enhanced immunogenicity of foot and mouth disease DNA vaccine delivered by PLGA nanoparticles combined with cytokine adjuvants

Although the immunogenicity of DNA vaccines is nonideal, they are still considered as potential alternative vaccine candidates to conventional vaccines. Various DNA delivery systems, including nanoparticles, have been extensively explored and validated to further enhance the immunogenicity of DNA vaccines. DNA vaccines are considered as alternative vaccine candidates. Various DNA delivery systems, including nanoparticles, have been extensively explored to enhance the immunogenicity of DNA vaccines. In this study, positively charged Poly (D, l-lactide-co-glycolic acid) (PLGA) nanoparticles were generated and characterized as a delivery system for O-serotype foot-and-mouth DNA vaccine. A recombinant plasmid encoding swine interleukin (IL)-18, IL-2, or granulocyte-macrophage colony-stimulating factor (GM-CSF) gene was introduced into the DNA vaccine to further improve its immunogenicity, which was evaluated in a guinea pig model. PLGA-pVAX-VP013/IL-18 elicited significantly (P = 0.0149) higher FMDV-specific antibody levels than naked DNA before the challenge. The level of neutralizing antibodies induced by PLGA-pVAX-VP013/IL-18, PLGA-pVAX-VP013/IL-2, and PLGA-pVAX-VP013/GM-CSF significantly increased compared with that induced by naked DNA (P < 0.0001). The lymphocyte proliferation assay showed that cellular immunity induced by PLGA-pVAX-VP013/IL-18 and PLGA-pVAX-VP013/GM-CSF was dramatically enhanced compared with that induced by the inactivated vaccine. The protection by PLGA-pVAX-VP013/IL-18 was consistent with that by the inactivated vaccine post-challenge and was followed by PLGA-pVAX-VP013/GM-CSF. Therefore, cationic PLGA nanoparticles can deliver DNA vaccines and induce humoral and cellular immune responses. The co-administration of FMD DNA vaccine with IL-18 formulated with PLGA nanoparticles was the optimal strategy to improve the immunogenicity of FMD DNA vaccines.

Cold-inducible RNA-binding protein (CIRBP) promotes porcine reproductive and respiratory syndrome virus (PRRSV)-induced inflammatory response

Porcine reproductive and respiratory syndrome virus (PRRSV) infection causes severe systemic inflammation. Based on transcriptome sequencing data, a new cold-inducible RNA-binding protein (CIRBP) was identified, and its upregulated expression was detected in PRRSV-infected porcine alveolar macrophages (PAMs). However, the immunoregulatoryeffect of CIRBP in PRRSV infection remains unclear. In this study, we found that CIRBP, as an RNA-binging protein, migrates to the cytoplasm from the nucleus and exists in cytoplasmic stress granules under PRRSV infection. In addition, as a new pro-inflammatory factor, the overexpression of CIRBP promotes the expression of inflammatory cytokines and oxidative stress as showing the production of iNOS and ROS in PRRSV-infected cells, which contributes to the inflammatory response via the NF-κB pathway. Our findings suggested that CIRBP is involved in the regulation of PRRSV-induced inflammatory response.

High-throughput whole genome sequencing of Porcine reproductive and respiratory syndrome virus from cell culture materials and clinical specimens using next-generation sequencing technology

Next-generation sequencing (NGS) technologies have increasingly played crucial roles in biological and medical research, but are not yet in routine use in veterinary diagnostic laboratories. We developed and applied a procedure for high-throughput RNA sequencing of Porcine reproductive and respiratory syndrome virus (PRRSV) from cell culture-derived isolates and clinical specimens. Ten PRRSV isolates with known sequence information, 2 mixtures each with 2 different PRRSV isolates, and 51 clinical specimens (19 sera, 16 lungs, and 16 oral fluids) with various PCR threshold cycle (Ct) values were subjected to nucleic acid extraction, cDNA library preparation (24-plexed), and sequencing. Whole genome sequences were obtained from 10 reference isolates with expected sequences and from sera with a PRRSV real-time reverse transcription PCR Ct ≤ 23.6, lung tissues with Ct ≤ 21, and oral fluids with Ct ≤ 20.6. For mixtures with PRRSV-1 and -2 isolates (57.8% nucleotide identity), NGS was able to distinguish them as well as obtain their respective genome sequences. For mixtures with 2 PRRSV-2 isolates (92.4% nucleotide identity), sequence reads with nucleotide ambiguity at numerous sites were observed, indicating mixed infection; however, individual virus sequences could only be separated when 1 isolate identity and sequence in the mixture is known. The NGS approach described herein offers the prospect of high-throughput sequencing and could be adapted to routine workflows in veterinary diagnostic laboratories, although further improvement of sequencing outcomes from clinical specimens with higher Ct values remains to be investigated.

Rescue and evaluation of a recombinant PRRSV expressing porcine Interleukin-4

BACKGROUND

The current vaccines for porcine reproductive and respiratory syndrome virus (PRRSV) have failed to provide broad protection against infection by various strains of PRRSV. Porcine Interleukin-4 (pIL-4) plays an important role in the regulation of the immune response and has been used previously as an immunological adjuvant. The objective of this study was to construct a recombinant PRRSV expressing pIL-4 and to evaluate the immune response of the recombinant virus in piglets.

METHODS

The pIL-4 gene was inserted in the PRRSV (CH-1R strain) infectious clone by overlap PCR. Indirect immunofluorescence assay (IFA) and Western blotting were used to confirm the recombinant virus. The stability of the recombinant virus was assessed by DNA sequencing and IFA after 15 passages in vitro. Recombinant virus was injected into pigs and efficacy of immune protection was evaluated in comparison with the parental virus.

RESULTS

The recombinant virus (CH-1R/pIL-4) was successfully rescued and shown to have similar growth kinetics as the parental virus. The recombinant virus was stable for 15 passages in cell culture. Pigs vaccinated with CH-1R/pIL-4 produced a similar humoral response to the response elicited by parental virus, but IL-4 level in the supernatant of PBMCs from pigs vaccinated with CH-1R/pIL-4 was significantly higher than the parent virus at 28 days post-immunization (DPI). Flow cytometric (FCM) analysis showed that the percentage of CD4(+)CD8(+) double positive T (DPT) cells in the CH-1R/pIL-4 vaccinated group was significantly higher than the parental virus at 3 and 7 Days Post-Challenge (DPC), and the IL-4 level in the blood significantly increased at 7 DPC. However, the viral load and histopathology did not show significant difference between the two groups.

CONCLUSIONS

A recombinant PRRSV expressing porcine IL-4 was rescued and it remained genetically stable in vitro. The recombinant virus induced higher DPT ratios and IL-4 levels in the blood after HP-PRRSV challenge compared to the parental virus in piglets. However, it did not significantly improve protection efficacy of PRRSV vaccine.

Inactivated and subunit vaccines against porcine reproductive and respiratory syndrome: Current status and future direction

Within a few years of its emergence in the late 1980s, the PRRS virus had spread globally to become the foremost infectious disease concern for the pork industry. Since 1994, modified live-attenuated vaccines against porcine reproductive and respiratory syndrome virus (PRRSV-MLV) have been widely used, but have failed to provide complete protection against emerging and heterologous field strains of the virus. Moreover, like many other MLVs, PRRSV-MLVs have safety concerns including vertical and horizontal transmission of the vaccine virus and several documented incidences of reversion to virulence. Thus, the development of efficacious inactivated vaccines is warranted for the control and eradication of PRRS. Since the early 1990s, researchers have been attempting to develop inactivated PRRSV vaccines, but most of the candidates have failed to elicit protective immunity even against homologous virus challenge. Recent research findings relating to both inactivated and subunit candidate PRRSV vaccines have shown promise, but they need to be pursued further to improve their heterologous efficacy and cost-effectiveness before considering commercialization. In this comprehensive review, we provide information on attempts to develop PRRSV inactivated and subunit vaccines. These includes various virus inactivation strategies, adjuvants, nanoparticle-based vaccine delivery systems, DNA vaccines, and recombinant subunit vaccines produced using baculovirus, plant, and replication-deficient viruses as vector vaccines. Finally, future directions for the development of innovative non-infectious PRRSV vaccines are suggested. Undoubtedly there remains a need for novel PRRSV vaccine strategies targeted to deliver cross-protective, non-infectious vaccines for the control and eradication of PRRS.