Efficacy of Fostera® PRRS modified live virus (MLV) vaccination strategy against a Thai highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) infection

Development of a Ferritin Protein Nanoparticle Vaccine with PRRSV GP5 Protein

Porcine reproductive and respiratory syndrome virus (PRRSV) presents a significant threat to the global swine industry. The development of highly effective subunit nanovaccines is a promising strategy for preventing PRRSV variant infections. In this study, two different types of ferritin (Ft) nanovaccines targeting the major glycoprotein GP5, named GP5m-Ft and (Bp-IVp)3-Ft, were constructed and evaluated as vaccine candidates for PRRSV. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) demonstrated that both purified GP5m-Ft and (Bp-IVp)3-Ft proteins could self-assemble into nanospheres. A comparison of the immunogenicity of GP5m-Ft and (Bp-IVp)3-Ft with an inactivated PRRSV vaccine in BALB/c mice revealed that mice immunized with GP5m-Ft exhibited the highest ELISA antibody levels, neutralizing antibody titers, the lymphocyte proliferation index, and IFN-γ levels. Furthermore, vaccination with the GP5m-Ft nanoparticle effectively protected piglets against a highly pathogenic PRRSV challenge. These findings suggest that GP5m-Ft is a promising vaccine candidate for controlling PRRS.

Research Progress on the Development of Porcine Reproductive and Respiratory Syndrome Vaccines

Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious disease in the pig industry, but its pathogenesis is not yet fully understood. The disease is caused by the PRRS virus (PRRSV), which primarily infects porcine alveolar macrophages and disrupts the immune system. Unfortunately, there is no specific drug to cure PRRS, so vaccination is crucial for controlling the disease. There are various types of single and combined vaccines available, including live, inactivated, subunit, DNA, and vector vaccines. Among them, live vaccines provide better protection, but cross-protection is weak. Inactivated vaccines are safe but have poor immune efficacy. Subunit vaccines can be used in the third trimester of pregnancy, and DNA vaccines can enhance the protective effect of live vaccines. However, vector vaccines only confer partial protection and have not been widely used in practice. A PRRS vaccine that meets new-generation international standards is still needed. This manuscript provides a comprehensive review of the advantages, disadvantages, and applicability of live-attenuated, inactivated, subunit, live vector, DNA, gene-deletion, synthetic peptide, virus-like particle, and other types of vaccines for the prevention and control of PRRS. The aim is to provide a theoretical basis for vaccine research and development.

Development of a Nanobody-Based Competitive Enzyme-Linked Immunosorbent Assay for Efficiently and Specifically Detecting Antibodies against Genotype 2 Porcine Reproductive and Respiratory Syndrome Viruses

Porcine reproductive and respiratory syndrome virus (PRRSV) infection causes considerable economic loss to the global pig industry. Efficient detection assay is very important for the prevention of the virus infection. Nanobodies are the advantages of small molecular weight, simple genetic engineering, and low production cost for promising diagnostic application. In this study, to develop a nanobody-based competitive ELISA (cELISA) for specifically detecting antibodies against PRRSV, three nanobodies against PRRSV-N protein were screened by camel immunization, library construction, and phage display. Subsequently, a recombinant HEK293S cell line stably secreting nanobody-horseradish peroxidase (HRP) fusion protein against PRRSV-N protein was successfully constructed using the lentivirus transduction assay. Using the cell lines, the fusion protein was easily produced. Then, a novel cELISA was developed using the nanobody-HRP fusion protein for detecting antibodies against PRRSV in pig sera, exhibiting a cut-off value of 23.19% and good sensitivity, specificity, and reproducibility. Importantly, the cELISA specifically detect anti-genotype 2 PRRSV antibodies. The cELISA showed more sensitive than the commercial IDEXX ELISA kit by detecting the sequential sera from the challenged pigs. The compliance rate of cELISA with the commercial IDEXX ELISA kit was 96.4%. In addition, the commercial IDEXX ELISA kit can be combined with the developed cELISA for the differential detection of antibodies against genotype 1 and 2 PRRSV in pig sera. Collectively, the developed nanobody-based cELISA showed advantages of simple operation and low production cost and can be as an assay for epidemiological investigation of genotype 2 PRRSV infection in pigs and evaluation after vaccination.

Evaluation of Four Commercial Vaccines for the Protection of Piglets against the Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus (hp-PRRSV) QH-08 Strain

Vaccination is the best way to prevent economic losses from highly pathogenic porcine reproductive and respiratory syndrome virus (hp-PRRSV) disease. However, the commercially available vaccines need to periodically evaluate their efficacy against infections caused by new hp-PRRSV variants. Therefore, the objective of this study was to evaluate the efficacy of four (two modified live vaccines (MLV) and two inactivated) PRRSV commercial vaccines in piglets challenged with QH-08 and to estimate the genetic distance of the vaccine strains from recently isolated (QH-08) filed strain. Randomly, piglets (n = 5) allocated in groups 1–4 were immunized with Ingelvac PRRS MLV, CH-1a, JXA1, and JXA1-RMLV vaccines, whereas the infected and non-infected control piglets in groups 5 and 6 (n = 3), respectively, were subjected to PBS. Results indicated that JXA1 and JXA1-R MLV vaccines showed complete protection, but Ingelvac PRRS MLV and CH-1α vaccines revealed partial protection against the QH-08 PRRSV challenge. Similarly, vaccinated and challenged pigs showed lower macroscopic and microscopic lesions than the pigs in group 5. Our findings demonstrated a new insight that the variation in ORF1a and 1b coding sequence could significantly affect PRRSV vaccines efficacy. In conclusion, QH-08 is a good candidate for the design and development of an innovative PRRSV vaccine that ultimately helps in the control and prevention strategies.

Commercial PRRS Modified-Live Virus Vaccines

Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) presents one of the challenging viral pathogens in the global pork industry. PRRS is characterized by two distinct clinical presentations; reproductive failure in breeding animals (gilts, sows, and boars), and respiratory disease in growing pigs. PRRSV is further divided into two species: PRRSV-1 (formerly known as the European genotype 1) and PRRSV-2 (formerly known as the North American genotype 2). A PRRSV-2 modified-live virus (MLV) vaccine was first introduced in North America in 1994, and, six years later, a PRRSV-1 MLV vaccine was also introduced in Europe. Since then, MLV vaccination is the principal strategy used to control PRRSV infection. Despite the fact that MLV vaccines have shown some efficacy, they were problematic as the efficacy of vaccine was often unpredictable and depended highly on the field virus. This paper focused on the efficacy of commercially available MLV vaccines at a global level based on respiratory disease in growing pigs, and maternal and paternal reproductive failure in breeding animals.

Mir-331-3p Inhibits PRRSV-2 Replication and Lung Injury by Targeting PRRSV-2 ORF1b and Porcine TNF-α

Porcine reproductive and respiratory syndrome (PRRS) caused by a single-stranded RNA virus (PRRSV) is a highly infectious respiratory disease and leads to huge economic losses to the swine industry worldwide. To investigate the role of miRNAs in the infection and lung injury induced by PRRSV, the differentially expressed miRNAs (DE-miRs) were isolated from PRRSV-2 infected/mock-infected PAMs of Meishan, Landrace, Pietrain, and Qingping pigs at 9, 36, and 60 hpi. Mir-331-3p was the only common DE-miR in each set of miRNA expression profile at 36 hpi. Mir-210 was one of 7 common DE-miRs between PRRSV infected and mock-infected PAMs of Meishan, Pietrain, and Qingping pigs at 60 hpi. Mir-331-3p/mir-210 could target PRRSV-2 ORF1b, bind and downregulate porcine TNF-α/STAT1 expression, and inhibit PRRSV-2 replication, respectively. Furthermore, STAT1 and TNF-α could mediate the transcriptional activation of MCP-1, VCAM-1, and ICAM-1. STAT1 could also upregulate the expression of TNF-α by binding to its promoter region. In vivo, pEGFP-N1-mir-331-3p could significantly reduce viral replication and pathological changes in PRRSV-2 infected piglets. Taken together, Mir-331-3p/mir-210 have significant roles in the infection and lung injury caused by PRRSV-2, and they may be promising therapeutic targets for PRRS and lung injury/inflammation.

Genetic characterization of a novel recombinant PRRSV2 from lineage 8, 1 and 3 in China with significant variation in replication efficiency and cytopathic effects

There are four major porcine reproductive and respiratory syndrome virus 2 (PRRSV2) lineages circulating in China based on classification system, including lineages 1 (NADC30-like), 3 (QYYZ-like), 5.1 (VR2332-like) and 8 (JXA1-like/CH-1a-Like), which leads to the potential recombination. In the present study, a novel variant of PRRSV2 strain named JS18-3 was isolated from piglets suffering severe breathing difficulties in Jiangsu Province of China in 2018. Full-length genome analysis indicated that JS18-3 shared 86.5%, 87.9%, 84.2%, 82.2% and 86.4% nucleotide similarity with PRRSVs CH-1a, JXA1, VR2332, QYYZ and NADC30, respectively. 4871-6635 of JS18-3 shared the highest identity of 99.3% in nucleotide sequence with HP-PRRSV representative strain JXA1 indicating ongoing evolution to HP-PRRSV. JS18-3 was classified into classical lineage 8 of PRRSV2 based on phylogenetic analysis of complete genome and ORF5. Genomic break points in structural (ORF3) and non-structural (NSP2, NSP3) regions of genomes were detected in recombination analysis. JS18-3 is a recombinant isolate from lineages 8, 1 and 3. Replication enhancement and severe cytopathic effects caused by JS18-3 were observed in Marc-145 cells and porcine alveolar macrophages (PAMs) as compared to JX07, a typical strain of lineage 8. Pathogenicity results indicated that piglets inoculated with JS18-3 presented persistent fever, dyspnoea, serious microscopic lung lesions and lymph node congestion. The study suggests that lineage 8 of PRRSV2 is involved in continuing evolution by genetic recombination and mutation leading to outbreaks in vaccinated pigs in China.

The efficacy and performance impact of Fostera PRRS in a Vietnamese commercial pig farm naturally challenged by a highly pathogenic PRRS virus

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) is characterized by high fever, respiratory distress, and high mortality in pigs of all ages and has severely affected the Vietnam pork industry in recent years. The study was conducted to compare the efficacy, safety, and overall performance of a modified live PRRSV-2 vaccine (Fostera PRRS) to an existing PRRSV modified live vaccine on a farm with a recent history of HP-PRRSV-associated respiratory diseases. A total of 351 pigs were randomly allocated to three treatment groups: (i) vaccinated with Fostera PRRS at 1 day of age (n = 118), (ii) vaccinated with Fostera PRRS (n = 118) at 21 days of age, and (iii) vaccinated with Amervac PRRS (n = 115) at 21 days of age. The Fostera PRRS vaccinated pigs had milder clinical symptoms, lower levels of HP-PRRSV viremia, fewer pathological changes in the lung, and higher body weight gain at the end of the study compared with the Amervac PRRS group. Vaccination of pigs with Fostera PRRS at 1 day of age also significantly reduced viral loads in their blood (P < 0.05) and induced higher anti-PRRSV antibody titers (P < 0.01) compared with pigs vaccinated with Amervac PRRS at 21 days of age. Fostera PRRS vaccination at 1 day of age can be useful in protecting young piglets from early HP-PRRSV infection because the immunized pigs were marketed 20 days earlier than their peers immunized at 21-day old as they reached the target market weight earlier in this study.

Efficacy evaluation of three modified-live PRRS vaccines against a local strain of highly pathogenic porcine reproductive and respiratory syndrome virus

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) is characterized by high fever and high mortality in pigs of all ages and has severely affected the pork industry of China in the last decades. This study evaluated the differences in protection conferred by of three MLV PRRS vaccines derived from classical PRRSV (C-PRRSV, VR2332) and HP-PRRSV (TJM-F92 and JXA1-R) against the field challenge of HP-PRRSV TP strain (JXA1-R like). Compared to the experiment pigs in control group which were vaccinated with normal saline, the MLV PRRS vaccinated pigs had milder clinical symptoms, fewer pathological changes in the lung, and higher body weight gain at the end of the study. However, piglets vaccinated with VR2332 had higher body temperature, higher viral loads and lower body weight gain when compared with piglets vaccinated with TJM-F92 or JXA1-R vaccines at the end of the study. The results demonstrated that VR2332 vaccine provided a limited cross-protection against the HP-PRRSV TP strain infection, while in contrast the TJM-F92 and JXA1-R vaccines provided more efficacious protection. The findings of this study could serve as a valuable reference guide for the pig producers and veterinarians when considering the choice of which type of MLV PRRS vaccines to protect their pig herds against field challenge by HP-PRRSV TP strain.

Efficacy of a type 2 PRRSV modified live vaccine (PrimePac™ PRRS) against a Thai HP-PRRSV challenge

The Chinese highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) has caused a severe threat to the pig population in Southeast Asian countries. The purpose of this study was to investigate the efficacy of a type 2 PRRSV modified live vaccine (PrimePac™ PRRS, lineage 7) against a Thai HP-PRRSV (10PL01, lineage 8). Three-week-old PRRSV-free pigs were randomly assigned into three groups. Vaccinated challenged group (group 1, n = 16) was immunized with PrimePac™ PRRS vaccine at 3 weeks old. The unvaccinated challenged group (group 2, n = 16) was injected with PBS at 3 weeks old, and unvaccinated unchallenged group (group 3, n = 10) was served as a negative control. At 9 weeks old, all groups, except the negative control group, were challenged with the Thai HP-PRRSV. All pigs were monitored daily during 10 days post-infection (dpi) and were necropsied at 10 and 17 dpi. The results revealed that vaccinated challenged pigs showed significantly lower (p < 0.05) mean rectal temperatures, clinical respiratory scores, lung lesion scores, and levels of virus load in serum and lung tissue compared with the unvaccinated challenged pigs. Moreover, vaccinated challenged pigs exhibited PRRSV-specific serum neutralizing antibodies at the end of the experiment. Our findings indicated that the studied type 2 PRRSV vaccine provided partial protection against the Thai HP-PRRSV infection based on the body temperature, levels of viremia, and the severity of lung lesions. These results demonstrated that partial protection of PrimePac™ PRRS vaccine might be useful for controlling HP-PRRSV infection in the endemic area.

Efficacy of live attenuated porcine reproductive and respiratory syndrome virus 2 strains to protect pigs from challenge with a heterologous Vietnamese PRRSV 2 field strain

Background

Effective vaccines against porcine reproductive and respiratory syndrome virus (PRRSV), especially against highly pathogenic (HP) PRRSV are still missing. The objective of this study was to evaluate the protective efficacy of an experimental live attenuated PRRSV 2 vaccine, composed of two strains, against heterologous challenge with a Vietnamese HP PRRSV 2 field strain. For this reason, 20 PRRSV negative piglets were divided into two groups. The pigs of group 1 were vaccinated with the experimental vaccine, group 2 remained unvaccinated. All study piglets received an intranasal challenge of the HP PRRSV 2 on day 0 of the study (42 days after vaccination). Blood samples were taken on days 7 and 21 after vaccination and on several days after challenge. On day 28 after challenge, all piglets were euthanized and pathologically examined.

Results

On days 7 and 21 after vaccination, a PRRSV 2 viraemia was seen in all piglets of group 1 which remained detectable in seven piglets up to 42 days after vaccination. On day 3 after challenge, all piglets from both groups were positive in PRRSV 2 RT-qPCR. From day 7 onwards, viral load and number of PRRSV 2 positive pigs were lower in group 1 than in group 2. All pigs of group 1 seroconverted after PRRSV 2 vaccination. PRRSV antibodies were detected in serum of all study pigs from both groups from day 14 after challenge onwards. In group 2, moderate respiratory symptoms with occasional coughing were seen following the challenge with HP PRRSV 2. Pigs of group 1 remained clinically unaffected. Interstitial pneumonia was found in four piglets of group 1 and in all ten piglets of group 2. Histopathological findings were more severe in group 2.

Conclusions

It was thus concluded that the used PRRSV 2 live experimental vaccine provided protection from clinical disease and marked reduction of histopathological findings and viral load in pigs challenged with a Vietnamese HP PRRSV 2 field strain.

Genotypic diversity of Streptococcus suis strains isolated from humans in Thailand

The purpose of this study is to characterize Streptococcus suis isolates recovered from human infections regarding serotype distribution, genotypic profile, clinical manifestations, and epidemiology. A total of 668 S. suis isolates recovered from human infections in Thailand were characterized based on serotyping by multiplex PCR and co-agglutination, genotypic profiles by multilocus sequence typing, and PCR for virulence-associated genes, as well as review of medical records. Serotype 2 (94.6%) was predominant, followed by serotype 14 (4.5%), 24 (0.45%), 5 (0.3%), and 4 (0.15%). Multilocus sequence typing analyses revealed seven clonal complexes (CC): CC1 (56.43%), CC104 (31.74%), CC233/379 (5.4%), CC25 (4.5%), CC28 (0.9%), CC221/234 (0.6%), CC94 (0.15%), and two singletons. The CC1 group contained serotype 2 and 14 isolates, while CC25, 28, 104, and 233/379 consisted of serotype 2 isolates only. CC221/234 contained serotype 5 and 24 isolates, whereas the single serotype 4 isolate belonged to CC94. Two singletons contained serotype 5 (ST235) and 2 (ST236) isolates. Our data showed that ST1 isolates were more associated with meningitis than those of other STs (p < 0.001). The major route of infection was shown to be close contact with infected pigs or contaminated raw pork-derived products, including occupational exposure and recent consumption of raw pork products. This study revealed a relatively large number of CCs of S. suis causing human infection in Thailand. Among them, CC1 followed by CC104, with serotype 2 isolates, are predominant. Food safety campaigns and public health interventions would be important for controlling the S. suis infection in humans.

Vaccination against porcine reproductive and respiratory syndrome virus (PRRSV) reduces the magnitude and duration of viremia following challenge with a virulent heterologous field strain

Forty PRRS-negative, three week-old weaned pigs were randomized into two groups in separate rooms and inoculated with a modified live PRRS vaccine (Fostera^® PRRS) or control (PBS). Four weeks after vaccination pigs were rehoused in a single room and challenged intranasally and intramuscularly with virulent PRRSV strain NADC20. Timed serum samples were collected and titrated for PRRS virus and anti-PRRS virus antibodies. The study concluded when ≥80% of the pigs in the control group were determined to be virus negative (27days post-challenge). Mean duration of viremia was significantly lower (p=0.0327) for vaccinated pigs compared to non-vaccinated pigs. A significant reduction (p≤0.0053) in mean post-challenge viremia titer was seen in vaccinates compared to non-vaccinates from days 8 through 22 post-challenge. At the individual pig level, no pigs in the vaccinated group had detectible PRRSV in serum at the end of the study (27days post-challenge), while 15% of non-vaccinated pigs remained positive for virus.