Type 2 Porcine Reproductive And Respiratory Syndrome Virus Research Articles

Infection dynamics and incidence of wild-type porcine reproductive and respiratory syndrome virus in growing pig herds in the U.S. Midwest.

Porcine reproductive and respiratory syndrome virus (PRRSV) infections greatly impact the health and productivity of growing pigs. The introduction and persistence of wild-type PRRSV (WT-PRRSV) strains in growing pig populations is poorly understood. In an observational prospective cohort study, we monitored and surveyed 63 wean-to-finish (WTF) herds across 10 companies located in medium to high pig dense areas in the U.S. Midwest. All herds received weaned pigs from PRRSV-negative or positive-stable breeding herds. Herds were monitored monthly using oral fluids collected following a fixed spatial sampling regime and samples were tested by PRRSV ELISA, RT-PCR and ORF5 sequencing. In most (90%) of the herds, pigs were vaccinated with PRRSV modified-live vaccines either at processing, weaning or shortly after weaning. Wild type PRRSV (WT-PRRSV) infections were defined by the criterion of having more than 2% nucleotide differences in the ORF-5 region compared with reference vaccine strain sequences. Wild type PRRSV was detected in 42% of the herds with infections being more prevalent in the mid to late growing period, with a mean of 20 weeks post placement. Nineteen distinct WT-PRRSV were identified in seven out of 10 production companies with an average of 3 distinct WT-PRRSV strains per company. Vaccinated WTF herds with and without WT-PRRSV detection were compared to each other showing different PCR and ELISA infection patterns. Close-out mortality in vaccinated herds with WT-PRRSV was numerically higher (6.5%) than mortality in those sites where WT-PRRSV was not detected (5.0%) (p=0.07). Mortality was also higher (10.5%) when WT-PRRSV was detected earlier at eight weeks post-placement compared to late finishing at 20 and 25 weeks post-placement, 2.9% and 4.5% respectively (p=0.017). Overall, this study sheds light on WT-PRRSV infection dynamics in vaccinated populations of growing pigs, reinforces the importance of biosecurity practices in this phase of production and calls for better understanding of risk factors associated with PRRSV introductions in growing pig sites.

Differential innate immune response of endometrial cells to porcine reproductive and respiratory syndrome virus type 1 versus type 2.

Modification of cellular and immunological events due to porcine reproductive and respiratory syndrome virus (PRRSV) infection is associated with pathogenesis in lungs. PRRSV also causes female reproductive dysfunction and persistent infection which can spread to fetus, stillbirth, and offspring. In this study, changes in cellular and innate immune responses to PRRSV type 1 or type 2 infection, including expression of PRRSV mediators, mRNA expression of Toll-like receptors (TLRs) and cytokine, and cytokine secretion, were examined in primary porcine glandular endometrial cells (PGE). Cell infectivity as observed by cytopathic effect (CPE), PRRSV nucleocapsid proteins, and viral nucleic acids was detected as early as two days post-infection (2 dpi) and persisted until 6 dpi. A higher percentage of CPE and PRRSV-positive cells were observed in type 2 infections. PRRSV mediator proteins, CD151, CD163, sialoadhesin (Sn), integrin and vimentin, were upregulated following type 1 and type 2 infection. CD151, CD163 and Sn were upregulated by type 2. In both PRRSV types, mRNA expression of TLR1 and TLR6 was upregulated. However, TLR3 was upregulated by type 1, but TLR4 and TLR8 mRNA and protein were downregulated by type 2 only. Interleukin (IL)-1β, IL-6 and tumor necrotic factor (TNF)-α were upregulated by type 2, but IL-8 was upregulated by type 1. Both PRRSV type 1 and 2 stimulated IL-6 but suppressed TNF-α secretion. In addition, IL-1β secretion was suppressed only by type 2. These findings reveal an important mechanism underlying the strategy of PRRSV infection in the endometrium and associated with the viral persistence.

Development of a Multiplex Crystal Digital RT-PCR for Differential Detection of Classical, Highly Pathogenic, and NADC30-like Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV) type 1 (European genotype) and PRRSV type 2 (North American genotype) are prevalent all over the world. Nowadays, the North American genotype PRRSV (NA-PRRSV) has been widely circulating in China and has caused huge economic losses to the pig industry. In recent years, classical PRRSV (C-PRRSV), highly pathogenic PRRSV (HP-PRRSV), and NADC30-like PRRSV (NL-PRRSV) have been the most common circulating strains in China. In order to accurately differentiate the circulating strains of NA-PRRSV, three pairs of specific primers and corresponding probes were designed for the Nsp2 region of C-PRRSV, HP-PRRSV, and NL-PRRSV. After optimizing the annealing temperature, primer concentration, and probe concentration, a multiplex real-time quantitative RT-PCR (qRT-PCR) and a multiplex Crystal digital RT-PCR (cdRT-PCR) for the differential detection of C-PRRSV, HP-PRRSV, and NL-PRRSV were developed. The results showed that the two assays illustrated high sensitivity, with a limit of detection (LOD) of 3.20 × 100 copies/μL for the multiplex qRT-PCR and 3.20 × 10-1 copies/μL for the multiplex cdRT-PCR. Both assays specifically detected the targeted viruses, without cross-reaction with other swine viruses, and indicated excellent repeatability, with coefficients of variation (CVs) of less than 1.26% for the multiplex qRT-PCR and 2.68% for the multiplex cdRT-PCR. Then, a total of 320 clinical samples were used to evaluate the application of these assays, and the positive rates of C-PRRSV, HP-PRRSV, and NL-PRRSV by the multiplex qRT-PCR were 1.88%, 21.56%, and 9.69%, respectively, while the positive rates by the multiplex cdRT-PCR were 2.19%, 25.31%, and 11.56%, respectively. The high sensitivity, strong specificity, excellent repeatability, and reliability of these assays indicate that they could provide useful tools for the simultaneous and differential detection of the circulating strains of C-PRRSV, HP-PRRSV, and NL-PRRSV in the field.

Molecular characterization of porcine reproductive and respiratory syndrome virus (PRRSv) identified from slaughtered pigs in northern Uganda

BackgroundA cross sectional study was conducted to detect and characterize species of porcine reproductive and respiratory syndrome virus (PRRSv) identified from slaughtered pigs in Lira district, northern Uganda. The study was conducted from March to September 2019 in three selected slaughter slabs. Pigs brought for slaughter were randomly sampled. At necropsy, lungs were extracted from the thoracic cavity and examined for pneumonic lesions. Seventy-three (73) pigs with gross lung lesions were sampled, from which one hundred and one (101) tissue samples were taken. A real-time reverse transcriptase PCR (RT-qPCR) was used to characterize PRRSv species.ResultsA total of 20 samples tested positive for PRRSv. The respective prevalence of PRRSv type 1 and type 2 were 24.65% (n = 18) and 2.73% (n = 2) respectively. Of the pigs sampled (n = 73), only two pigs, 2.73% (n = 2) tested positive to both species. The likelihood of PRRSv detection decreased with pig age, but increased with gross pneumonic pathology.ConclusionsThis study demonstrated dual circulation of both species in northern Uganda. The association between PRRSv and lung pathology suggests that it may be an important cause of lung disease in pigs in Uganda and hence loss of production. This calls for further investigations on potential economic impacts of PRRSv on pig productivity. These findings contribute to discussions about the need of surveillance and possible vaccination strategies against PRRSv in Uganda.

Porcine reproductive and respiratory syndrome virus induces tight junction barrier dysfunction and cell death in porcine glandular endometrial epithelial cells

Reproductive failure caused by porcine reproductive and respiratory syndrome virus (PRRSV) is characterized by embryonic death and weak-born piglets and is associated with placental cell apoptosis and impairment of endometrial integrity. Here, we aimed to determine whether endometrial epithelial barrier function and viability were altered following PRRSV type 1 or type 2 infection. PRRSV inoculation was examined at the apical or basolateral side of porcine glandular endometrial epithelial cell cultures isolated from 4- to 6-month-old PRRSV-free herd gilts (n = 7 pigs). On the apical side, four days postinfection (4 dpi) with type 2 PRRSV, transepithelial electrical resistance decreased by 31% ± 5%, and paracellular permeability to fluorescein isothiocyanate-dextran (4 kDa) increased by 10-fold as compared with the mock and type 1 infection. Real-time polymerase chain reaction results revealed that both PRRSV types upregulated the mRNA expression of the barrier builder tight junction protein (TJ) Cldn5, but downregulated pore-forming TJ Cldn7. Additionally, the expression of other TJ genes, i.e., Cldn3 and Cldn8, was differentially increased by PRRSV type 1 and that of zonula occludens-1 was increased by PRRSV type 2. MTT assays indicated an increase in porcine glandular endometrial epithelial cell culture at 2–6 dpi following type 2 infection. Analysis of apoptosis using Annexin/propidium iodide staining combined with flow cytometry showed that the percentage of viable cells decreased, accompanied by a significantly higher dead cell population following PRRSV type 2 infection at 2–4 dpi. PRRSV type 1 infection also induced dead cells (>4%) at 2 dpi; however, the cell population recovered at 4 dpi. In conclusion, PRRSV type 2 infection caused more severe TJ barrier dysfunction and reduced cell viability compared with PRRSV type 1 infection in the porcine endometrium. Impairment in the membrane integrity of the maternal glandular endometrium may be the underlying mechanism of PRRSV-induced reproductive failure in pregnant sows.

A Molecular and Epidemiological Description of a Severe Porcine Reproductive and Respiratory Syndrome Outbreak in a Commercial Swine Production System in Russia.

Porcine reproductive and respiratory syndrome (PRRS) is an economically devastating disease of swine in many parts of the world. Porcine reproductive and respiratory syndrome virus (PRRSV) type 1 is endemic in Europe, and prevalence of the subtypes differ spatially. In this study, we investigated a severe PRRS outbreak reported in 30 farms located in eastern Russia that belong to a large swine production company in the region that was also experiencing a pseudorabies outbreak in the system. Data included 28 ORF5 sequences from samples across 18 of the 25 infected sites, reverse transcriptase real-time polymerase chain reaction (RT-qPCR) results from diagnostic testing, reports of clinical signs, and animal movement records. We observed that the outbreak was due to two distinct variants of wildtype PRRSV type 1 subtype 1 with an average genetic distance of 15%. Results suggest that the wildtype PRRSV variants were introduced into the region around 2019, before affecting this production system (i.e., sow farms, nurseries, and finisher farms). Clinical signs did not differ between the variants, but they did differ by stage of pig production. Biosecurity lapses, including movement of animals from infected farms contributed to disease spread.

Phylogenetically Distinct Near-Complete Genome Sequences of Porcine Reproductive and Respiratory Syndrome Virus Type 2 Variants from Four Distinct Disease Outbreaks at U.S. Swine Farms over the Past 6 Years.

ABSTRACTPorcine reproductive and respiratory syndrome virus (PRRSV) continues to mutate, causing disruptive PRRS outbreaks in farms that lead to reproductive failure and respiratory disease-associated mortality. We present four new PRRSV type 2 variants in the United States belonging to four distinct orf5 sublineages within lineage 1.

Susceptibility of immortalized porcine kidney macrophages to porcine reproductive and respiratory syndrome virus-2 infection

Porcine reproductive and respiratory syndrome virus (PRRSV) displays restricted tropism to porcine alveolar macrophages in nature. Meanwhile, non-porcine cell lines derived from African green monkey kidney cell lines are permissive to PRRSV, resulting in their widespread use in PRRSV research. Furthermore, genetically modified cell lines expressing receptors targeted by PRRSV have been established. We previously established porcine immortalized kidney-derived macrophages (IPKMs) that maintained typical macrophage function. In the present study, we demonstrated the advantages of IPKMs for PRRSV research. IPKMs expressed receptors for PRRSV such as CD163 and CD169. The efficiency of virus isolation from field biological samples was higher for IPKMs than for MARC-145 cells. Five different clusters of North American type PRRSV were propagated in IPKMs. Four field strains continuously produced progeny viruses during 10 continuous passages. The efficiency of virus isolation from field biological samples and continuous progeny virus production in the sequential passages using IPKMs indicated that these cells are good vessels for PRRSV research.

Porcine Reproductive and Respiratory Syndrome Virus Antagonizes PCSK9's Antiviral Effect via Nsp11 Endoribonuclease Activity.

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogens in the swine industry worldwide. Our previous study had indicated that proprotein convertase subtilisin/kexin type 9 (PCSK9) was a responsive gene in porcine alveolar macrophages (PAMs) upon PRRSV infection. However, whether PCSK9 impacts the PRRSV replication and how the PRRSV modulates host PCSK9 remains elusive. Here, we demonstrated that PCSK9 protein suppressed the replication of both type-1 and type-2 PRRSV species. More specifically, the C-terminal domain of PCSK9 was responsible for the antiviral activity. Besides, we showed that PCSK9 inhibited PRRSV replication by targeting the virus receptor CD163 for degradation through the lysosome. In turn, PRRSV could down-regulate the expression of PCSK9 in both PAMs and MARC-145 cells. By screening the nonstructural proteins (nsps) of PRRSV, we showed that nsp11 could antagonize PCSK9’s antiviral activity. Furthermore, mutagenic analyses of PRRSV nsp11 revealed that the endoribonuclease activity of nsp11 was critical for antagonizing the antiviral effect of PCSK9. Collectively, our data provide further insights into the interaction between PRRSV and the cell host and offer a new potential target for the antiviral therapy of PRRSV.

Genetic signatures of the immune-escaping type 2 porcine reproductive and respiratory syndrome virus in farms with a robust vaccination program

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important porcine viruses worldwide. Recently, severe PRRS outbreaks had occurred in two farms located in eastern and southern Thailand where stringent vaccination had been routinely practiced. Genetic analysis of GP5 identified two highly virulent PRRSVs designated as NA/TH/S001/2015 and NA/TH/E001/2016 from the southern and eastern farms, respectively. Both incidences were the first outbreaks of severe PRRSV since the implementation of the modified live virus (MLV) vaccine, indicating the concurrent emergence of immune-escape viruses. The genetics of the two PRRSV variants, the previous studied sequences from Thailand, and the reference strains were characterized with a focus on the GP5 and NSP2 genes. The results indicated that NA/TH/S001/2015 and NA/TH/E001/2016 shared less than 87% nucleotide similarity to the MLV and PRRSV type 2, lineages 1 and 8.7 (NA), respectively. A comparative analysis of the retrospective GP5 sequences categorized the PRRSVs into five groups based on the clinical outcomes, and both of the novel PRRSV strains were in the same group. Epitope A, T cell epitope, and N-linked glycosylation patterns within GP5 of both PRRSV variants were highly variable and significantly differed from those of MLV. As observed in highly virulent type 2 strains, NA/TH/S001/2015 contained a single amino acid deletion at position 33 in the hypervariable region 1 (HV–1) of GP5. Amino acid analysis of the hypervariable region of NSP2 revealed that NA/TH/E001/2016 had a unique deletion pattern that included two discontinuous deletions: a 127-amino acid deletion from residues 301 to 427 and a single amino acid deletion at position 470. These results indicate the emergence of two novel PRRSV strains and highlight the common genetic characteristics of the immune-escaping PRRSV variants.

Phylogenetics, Genomic Recombination, and NSP2 Polymorphic Patterns of Porcine Reproductive and Respiratory Syndrome Virus in China and the United States in 2014-2018.

Porcine reproductive and respiratory syndrome virus (PRRSV), an important pathogen that affects the pig industry, is a highly genetically diverse RNA virus. However, the phylogenetic and genomic recombination properties of this virus have not been completely elucidated. In this study, comparative analyses of all available genomic sequences of North American (NA)-type PRRSVs (n = 355, including 138 PRRSV genomes sequenced in this study) in China and the United States during 2014-2018 revealed a high frequency of interlineage recombination hot spots in nonstructural protein 9 (NSP9) and the GP2 to GP3 regions. Lineage 1 (L1) PRRSV was found to be susceptible to recombination among PRRSVs both in China and the United States. The recombinant major parent between the 1991-2013 data and the 2014-2018 data showed a trend from complex to simple. The major recombination pattern changed from an L8 to L1 backbone during 2014-2018 for Chinese PRRSVs, whereas L1 was always the major backbone for US PRRSVs. Intralineage recombination hot spots were not as concentrated as interlineage recombination hot spots. In the two main clades with differential diversity in L1, NADC30-like PRRSVs are undergoing a decrease in population genetic diversity, NADC34-like PRRSVs have been relatively stable in population genetic diversity for years. Systematic analyses of insertion and deletion (indel) polymorphisms of NSP2 divided PRRSVs into 25 patterns, which could generate novel references for the classification of PRRSVs. The results of this study contribute to a deeper understanding of the recombination of PRRSVs and indicate the need for coordinated epidemiological investigations among countries.IMPORTANCE Porcine reproductive and respiratory syndrome (PRRS) is one of the most significant swine diseases. However, the phylogenetic and genomic recombination properties of the PRRS virus (PRRSV) have not been completely elucidated. In this study, we systematically compared differences in the lineage distribution, recombination, NSP2 polymorphisms, and evolutionary dynamics between North American (NA)-type PRRSVs in China and in the United States. Strikingly, we found high frequency of interlineage recombination hot spots in nonstructural protein 9 (NSP9) and in the GP2 to GP3 region. Also, intralineage recombination hot spots were scattered across the genome between Chinese and US strains. Furthermore, we proposed novel methods based on NSP2 indel patterns for the classification of PRRSVs. Evolutionary dynamics analysis revealed that NADC30-like PRRSVs are undergoing a decrease in population genetic diversity, suggesting that a dominant population may occur and cause an outbreak. Our findings offer important insights into the recombination of PRRSVs and suggest the need for coordinated international epidemiological investigations.

Efficacy of concurrent vaccination with modified-live PRRSV-1 and PRRSV-2 vaccines against heterologous dual PRRSV-1 and PRRSV-2 challenge in late term pregnancy gilts

The objective of this study was to evaluate the effect of concurrent vaccination with a porcine reproductive and respiratory syndrome virus (PRRSV)-1 modified-live virus (MLV) vaccine and a PRRSV-2 MLV vaccine against a dual heterologous PRRSV-1 and PRRSV-2 challenge in late term pregnancy gilts. Gilts were concurrently administered PRRSV-1 and PRRSV-2 MLV vaccines at 21 days prior to breeding at separate anatomical sites and were inoculated intranasally with both PRRSV types at 93 days of gestation. Vaccinated gilts had a higher number of live-born and weaned pigs, and a decrease in stillbirths compared to the unvaccinated control group following a dual challenge. Concurrent vaccination resulted also in the reduction of both PRRSV-1 and PRRSV-2 viremia which correlated with an increase in the number of PRRSV-1 and PRRSV-2 specific interferon-γ secreting cells (IFN-γ-SC). We believe the T cell responses contributed to the reduction of both PRRSV-1 and PRRSV-2 viremia. The results presented here demonstrate that concurrent vaccination with PRRSV-1 and PRRSV-2 MLV vaccines improves reproductive performance, reduces viremia of PRRSV-1 and PRRSV-2, and induces protective T cell reactions against dual PRRSV-1 and PRRSV-2 challenge in late term pregnancy gilts without local and systemic adverse reactions related to concurrent vaccination.

Macroepidemiological aspects of porcine reproductive and respiratory syndrome virus detection by major United States veterinary diagnostic laboratories over time, age group, and specimen.

This project investigates the macroepidemiological aspects of porcine reproductive and respiratory syndrome virus (PRRSV) RNA detection by veterinary diagnostic laboratories (VDLs) for the period 2007 through 2018. Standardized submission data and PRRSV real-time reverse-transcriptase polymerase chain reaction (RT-qPCR) test results from porcine samples were retrieved from four VDLs representing 95% of all swine samples tested in NAHLN laboratories in the US. Anonymized data were retrieved and organized at the case level using SAS (SAS® Version 9.4, SAS® Institute, Inc., Cary, NC) with the use of PROC DATA, PROC MERGE, and PROC SQL scripts. The final aggregated and anonymized dataset comprised of 547,873 unique cases was uploaded to Power Business Intelligence—Power BI® (Microsoft Corporation, Redmond, Washington) to construct dynamic charts. The number of cases tested for PRRSV doubled from 2010 to 2018, with that increase mainly driven by samples typically used for monitoring purposes rather than diagnosis of disease. Apparent seasonal trends for the frequency of PRRSV detection were consistently observed with a higher percentage of positive cases occurring during fall or winter months and lower during summer months, perhaps due to increased testing associated with well-known seasonal occurrence of swine respiratory disease. PRRSV type 2, also known as North American genotype, accounted for 94.76% of all positive cases and was distributed across the US. PRRSV type 1, also known as European genotype, was geographically restricted and accounted for 2.15% of all positive cases. Co-detection of both strains accounted for 3.09% of the positive cases. Both oral fluid and processing fluid samples, had a rapid increase in the number of submissions soon after they were described in 2008 and 2017, respectively, suggesting rapid adoption of these specimens by the US swine industry for PRRSV monitoring in swine populations. As part of this project, a bio-informatics tool defined as Swine Disease Reporting System (SDRS) was developed. This tool has real-time capability to inform the US swine industry on the macroepidemiological aspects of PRRSV detection, and is easily adaptable for other analytes relevant to the swine industry.

The T-Cell Response to Type 2 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV).

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to cause severe reproductive and respiratory pathologies resulting in immense monetary and welfare costs for the swine industry. The vaccines against PRRSV are available; but they struggle with providing protection against the plethora of heterologous PRRSV strains. To improve PRRSV vaccine development, the aim of this study was to provide an in-depth analysis of the crucial heterologous T-cell response to type-2 PRRSV. Following PRRSV modified live virus (MLV) vaccination or infection using one high- or one low-pathogenic PRRSV-strain, this nine-week study evaluated the T-cell response to different PRRSV strains. Our results demonstrate an important role for T cells in this homo- and heterologous response. Specifically, the T-helper cells were the main responders during viremia. Their peak response at 28 dpi correlated with a reduction in viremia, and their homing receptor expression indicated the additional importance for the anti-PRRSV response in the lymphatic and lung tissue. The cytotoxic T lymphocyte (CTL) response was the strongest at the site of infection—the lung and bronchoalveolar lavage. The TCR-γδ T cells were the main responders post viremia and PRRSV induced their expression of the lymph node homing the chemokine receptor, CCR7: This indicates a crucial role for TCR-γδ T cells in the anti-PRRSV response in the lymphatic system.

Sequencing and analysis of complete genome of the attenuated Hanvet1.VN strain used for vaccine production against porcine reproductive and respiratory syndrome

The porcine reproductive and respiratory syndrome virus (PRRSV) attenuated strain Hanvet1.VN has been developed by the Pharmaceutical and Veterinary Material J.S.C (HANVET) by passaging HY-2010 strain on MARC-145 cells for 80 passages and used for PRRS vaccine production. In this study, we sequenced and analyzed the whole genome of the attenuated Hanvet1.VN strain. The total RNA was extracted from the Hanvet1.VN strain, RT-PCR was used for amplification of 15 separate segments of the whole genome. The amplified segments were cloned into the pCR2.1 vector and sequenced by Sanger sequencing. The sequences were analyzed with BioEdit and DNA Star Software. The results showed that, GP5 of the Hanvet1.VN attenuated strain had 100% identity in amino acid (aa) sequences with one of the pathogenic Vietnamese strain isolated in Quang Nam Province and had 98% identity with that of the Chinese 07NM strain. However, the identity of aa sequence of the Hanvet1.VN GP5 was much lower in the comparison with GP5 of VR2332, and it was only 87%. The MP and NP proteins were highly conserved compared with pathogenic strains circulating in Vietnam (07QN) and China (07NM) (99-100%, respectively). The other eight proteins of the Hanvet1.VN strain showed changes from 1.2% in NP1a to 3.9% in GP2 compared with the 07QN strain. However, the aa identity of all Hanvet1.VN proteins were very low when compared with proteins of PRRSV type II strain (North American strain, VR2332), ranged from 86.25% to 97.7%. Our results showed that the Hanvet1.VN attenuated vaccine strain had protective immunogenicity similar to that strain circulating in Vietnam closely related to a strain from China but different from the type II North American strain VR2332. Hence, for importing PRRSV vaccine, especially from American or Europe Countries, antigenic compatibility of the PRRSV vaccine and strains circulating in Vietnam should be concerned in PRRSV vaccine production.

Identification of factors associated with virus level in tonsils of pigs experimentally infected with porcine reproductive and respiratory syndrome virus.

Porcine reproductive and respiratory syndrome (PRRS) is one of the most important global swine diseases from both an economic and animal welfare standpoint. PRRS has plagued the US swine industry for over 25 yr, and containment of PRRS virus (PRRSV) has been unsuccessful to date. The primary phase of PRRS, tracked by serum viremia, typically clears between 21 and 42 d postinfection (dpi) but tonsils are a main site of PRRSV persistence and PRRSV can be detected in tonsils in excess of 150 dpi. Measuring tonsil virus (TV) levels at late stages of infection (6 to 7 wk postinfection) can be used to assess tonsil persistence, as levels of virus in tonsil at this time likely influence how long the virus will remain in the tissue. TV levels were measured on pigs experimentally infected with either the NVSL-97-7895 (NVSL; n = 524) or KS-2006-72109 (KS06; n = 328) PRRSV type 2 isolates across five trials. The objectives of this study were to (i) estimate the heritability of TV levels at 35 or 42 dpi; (ii) identify factors the affect TV level, including serum viremia; (iii) identify genomic regions associated with TV level; and (iv) compare results for the two PRRSV isolates. TV level was lowly heritable for both isolates (NVSL: 0.05 ± 0.06; KS06: 0.11 ± 0.10). Level of TV was phenotypically associated with traits related to viral clearance from serum: pigs with low TV levels had an earlier and faster rate of maximal serum viral clearance, lower total serum viral load, and lower viremia level at 35 or 42 dpi. Although no genomic regions with major effects on TV level were identified, several showed some association (>0.1% of total genetic variance in the NVSL-infected dataset, the KS06-infected dataset, and the combined dataset). These regions contained the genes CCL1, CCL2, CCL8, HS3ST3B1, GALNT10, TCF7, C1QA/B/C, HPSE, G0S2, and CD34, which are involved in viral infiltration or replication, immune cell migration, and viral clearance from tissue. Results were similar between the two PRRSV isolates. In conclusion, selection for viral clearance traits in serum may reduce PRRSV persistence in the tonsil across PRRSV isolates. However, genetic correlations need to be estimated to determine whether this will be successful.

Epidemiological and genetic characteristics of porcine reproductive and respiratory syndrome virus circulating in central and South China in 2016

Porcine reproductive and respiratory syndrome virus (PRRSV) is a leading cause of reproductive failure in sows and respiratory disorders in all ages of pigs; PRRSV is one of the most serious threats to the global pig industry. Continuously monitoring the epidemiological and genetic characteristics of PRRSV epidemic strains is beneficial for PRRSV prevention and control. In this study, we detected PRRSV from different types of porcine samples collected from 257 pig farms in Central (Henan Province) and South China (Fujian, Guangdong, and Guangxi Provinces) in 2016. Of the 1047 samples collected, 530 (50.62%) were positive for PRRSV by RT-PCR. The positive rates of virus detection for each of the geographical regions were higher than 44.25%. These findings suggest that the prevalence of PRRSV continues to be a major problem for the pig industry in China. Phylogenetic analysis showed that PRRSV2 was still the prevalent species in Central and South China, and highly pathogenic PRRSV (HP-PRRSV) was the predominate PRRSV type. However, the emergence and circulation of novel PRRSV strains such as the GM2-like strains and NADC30-like strains is worrisome and should receive more attention. In terms of different geographical regions, HP-PRRSV strains were the predominate PRRSV strains circulating in South China, while both HP-PRRSV strains and NADC30-like strains appeared to be the predominate PRRSV strains in Central China (Henan Province). These findings demonstrate that PRRSV types circulating in different regions in China are some different. In addition, a number of amino acid mutation types including amino acid changes and deletions were observed in both the GP5 and Nsp2 proteins. Our study provides important information on the epidemiological and genetic characteristics of PRRSV strains currently circulating in China.

Preliminary assessment of correlation between T-lymphocyte responses and control of porcine reproductive and respiratory syndrome virus (PRRSV) in piglets born after in-utero infection of a type 2 PRRSV

A preliminary study into the protective mechanisms of adaptive immunity against porcine reproductive and respiratory syndrome virus (PRRSV) in piglets (n = 9) born to a gilt challenged intranasally with a type-2 PRRSV. Immune parameters (neutralizing antibodies, CD3+CD4+, CD3+CD8+, CD3+CD4+CD8+ T-lymphocytes, and PRRSVspecific interferon (IFN)-γ secreting T-lymphocytes) were compared with infection parameters (macro- and microscopic lung lesion, and PRRSV-infected porcine alveolar macrophages (CD172α +PRRSV-N+ PAM) as well as with plasma and lymphoid tissue viral loads. Percentages of three T-lymphocyte phenotypes in 14-days post-birth (dpb) peripheral blood mononuclear cell (PBMC) had significant negative correlations with percentages of CD172α +PRRSV-N+ PAM (p 0.1) with infection parameters. The results indicate that T-lymphocytes contribute to controlling PRRSV replication in young piglets born after in-utero infection.

First-time detection of porcine reproductive and respiratory syndrome virus (PRRSV) infection in Uruguay.

Within the last two decades, several high-impact viruses have emerged in the global swine population, including porcine reproductive and respiratory syndrome virus (PRRSV). In Uruguay, the more recent serological survey for PRRSV and other notifiable diseases such as Aujeszky's disease virus (ADV) and classical swine fever virus (CSFV) dated from year 2000. The main purpose of this study was to update our information on the infection status of PRRSV, ADV and CSFV in Uruguayan pig herds, in order to keep informed about the epidemiological situation of these notifiable infections in the country. For serological testing, a total of 524 swine serum samples collected during the period 2014-2016 were assayed by commercial ELISAs. Our results revealed the (unexpected) presence of PRRSV antibodies in Uruguayan domestic swine herds and confirmed the absence of ADV and CSFV antibodies in all of the assessed samples. Following such initial finding, PRRSV antibodies were further investigated in 23 retrospective samples collected during 2010-2014. Thirteen of these 23 samples resulted seropositive. Subsequently, a molecular detection approach in frozen serum samples was implemented to confirm PRRSV infection, and viral RNA was identified by reverse transcription-nested polymerase chain reaction (RT-nPCR). Fourteen of 86 evaluated 2014-2016 samples resulted positive for viral RNA, while molecular analysis of four retrospective samples also revealed the presence of PRRSV type 2. Viral isolation of selected samples was carried out in porcine alveolar macrophages (PAM) and MARC 145 simian kidney cells, and the virus identity was confirmed by cytopathic effect (CPE) and immunofluorescence assay (IFA) using specific monoclonal antibodies for PRRSV nucleocapsid. Data reported here evidence for the first time the circulation of PRRSV type 2 in Uruguay, and retrospective serology results suggest that the virus has been infecting pigs in this country at least since 2011.

Immunogenicity of recombinant vaccinia virus vaccines co-expressing GP3/GP5 of European PRRSV and Cap protein of PCV2 in pigs.

Porcine reproductive and respiratory syndrome (PRRS) is almost always caused by the North American strain of PRRS virus (PRRSV) in China; the European genotype of PRRSV has emerged in China. The mixed infection of PRRSV and Porcine circovirus type 2 virus (PCV2) are always found in pigs and PRRSV-augmented PCV2 replication and serious clinical symptoms. Current vaccines cannot protect mixed European PRRSV and PCV2 infections. Therefore, the development of a safe and effective new vaccine to prevent and control the mixed infection of European PRRSV and PCV2 is both urgent and necessary. In this study, we developed a recombinant vaccinia vaccine co-expressing the GP3 and GP5 proteins of European PRRSV and the ORF2 protein of PCV2 and evaluated the immunogenicity and its protective effects and its inactivated vaccine in pigs. The recombinant vaccinia vaccine and its inactivated vaccine both elicited significant humoral and cellular immune responses with a higher level of specific antibody responses and T-lymphocyte proliferation than the control group. Furthermore, the pigs inoculated with the recombinant vaccinia vaccine were completely protected against challenge with 105 TCID50 of European PRRSV strain LV. These data suggest that the recombinant vaccinia vaccine is a potential candidate vaccine against European PRRSV and PCV2.