Plasmids expressing porcine interferon gamma up-regulate pro-inflammatory cytokine and co-stimulatory molecule expression which are suppressed by porcine reproductive and respiratory syndrome virus

Type I and II interferons, transcription factors and major histocompatibility complexes were enhanced by knocking down the PRRSV-induced transforming growth factor beta in monocytes co-cultured with peripheral blood lymphocytes

The innate and adaptive immune responses elicited by porcine reproductive and respiratory syndrome virus (PRRSV) infection are known to be poor. This study investigates the impact of PRRSV-induced transforming growth factor beta 1 (TGFβ1) on the expressions of type I and II interferons (IFNs), transcription factors, major histocompatibility complexes (MHC), anti-inflammatory and pro-inflammatory cytokines in PRRSV-infected co-cultures of monocytes and peripheral blood lymphocytes (PBL). Phosphorothioate-modified antisense oligodeoxynucleotide (AS ODN) specific to the AUG region of porcine TGFβ1 mRNA was synthesized and successfully knocked down TGFβ1 mRNA expression and protein translation. Monocytes transfected with TGFβAS1 ODN, then simultaneously co-cultured with PBL and inoculated with either classical PRRSV-2 (cPRRSV-2) or highly pathogenic PRRSV-2 (HP-PRRSV-2) showed a significant reduction in TGFβ1 mRNA expression and a significant increase in the mRNA expressions of IFNα, IFNγ, MHC-I, MHC-II, signal transducer and activator of transcription 1 (STAT1), and STAT2. Additionally, transfection of TGFβAS1 ODN in the monocyte and PBL co-culture inoculated with cPRRSV-2 significantly increased the mRNA expression of interleukin-12p40 (IL-12p40). PRRSV-2 RNA copy numbers were significantly reduced in monocytes and PBL co-culture transfected with TGFβAS1 ODN compared to the untransfected control. The yields of PRRSV-2 RNA copy numbers in PRRSV-2-inoculated monocytes and PBL co-culture were sustained and reduced by porcine TGFβ1 (rTGFβ1) and recombinant porcine IFNα (rIFNα), respectively. These findings highlight the strategy employed by PRRSV to suppress the innate immune response through the induction of TGFβ expression. The inclusion of TGFβ as a parameter for future PRRSV vaccine and vaccine adjuvant candidates is recommended.

Silence of TGF-β1 gene expression reduces prrsv replication and potentiates immunity of immune cells of tibetan pig

•

Knockdown of TGF-β1 gene expression by shRNA inhibited PRRSV replication in pig immune cells and increased the viability of infected cells.

•

Silencing TGF-β1 gene expression by shRNA enhanced the antiviral immunity and reduced PRRSV yield in the infected cells.

•

Silence of TGF-β1 gene expression by shRNA can facilitate the control of PRRSV infection in pigs.

Transforming growth factor beta 1 (TGF-β1) was of importance in the pathogenesis of porcine reproductive and respiratory syndrome virus (PRRSV). To determine whether knockdown of TGF-β1 gene expression could facilitate the control of PRRSV infection, specific sequences for expressing shRNA targeted to porcine TGF-β1 gene were synthesized and cloned into pSilencer 3.1-H1 neovector. Then they were used to transfect peripheral blood mononuclear cells of Tibetan pig (Tp-PBMCs) followed by PRRSV inoculation. The positive recombinant plasmids were screened for inhibition of TGF-β1 gene expression by real-time quantitative RT-PCR. Conversely, the mRNA level of PRRSV in shRNA treated Tp-PBMCs dramatically decreased, and there were significant increases of the transcription of immune genes, such as interleukin-2 (IL-2), interleukin-4 (IL-4), interferon-alpha (IFN-α), interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), toll-like receptor 3 (TLR3), toll-like receptor 7 (TLR7), Myeloid differentiation primary response gene (88) (MyD88), and interleukin-27p28 (IL-27p28). However, the expressions of IL-8 and IL-10 genes significantly reduced in comparison to the control infected cells. In addition, transfection with the shRNA plasmids significantly elevated the viability of immune cells. Therefore the knockdown of TGF-β1 gene expression by shRNA not only inhibits the replication of PRRSV but also improves immune responsiveness following viral infection, suggesting a novel way to facilitate the control of PRRSV infection in pigs.

Co-administration of saponin quil A and PRRSV-1 modified-live virus vaccine up-regulates gene expression of type I interferon-regulated gene, type I and II interferon, and inflammatory cytokines and reduces viremia in response to PRRSV-2 challenge

Porcine reproductive and respiratory syndrome virus (PRRSV) is a devastating virus which suppresses the expression of type I and II interferons (IFNs) as well as several pro-inflammatory cytokines. Our previous study reported that saponin quil A had a potential to up-regulate the expression of type I IFN-regulated genes and type I and II IFNs in porcine peripheral blood mononuclear cells (PBMC) inoculated with PRRSV. The present study evaluated the immunostimulatory effect of quil A on potentiating cross protective immunity of PRRSV-1 modified-live virus (MLV) vaccine against PRRSV-2 challenge. Twenty-four 4-week-old PRRSV-seronegative pigs were divided into four groups of six pigs. Group 1 and group 2 pigs were vaccinated with PRRSV-1 MLV vaccine at 0 dpv (day post vaccination), and additionally group 2 pigs were injected intramuscularly with quil A at -1, 0, 1 dpv. Group 3 pigs were injected with PRRSV-1 MLV vaccine solvent at 0 dpv and served as challenge control, while group 4 pigs served as strict control. Group 1-3 pigs were challenged intranasally with PRRSV-2 at 28 dpv and immune and clinical parameters were observed from 0 until 49 dpv. Group 1 pigs showed significantly reduced PRRSV viremia, number of viremic pigs, and clinical scores, and significantly improved average daily weight gain (ADWG), compared to group 3 pigs. Group 2 pigs showed significantly increased mRNA expressions of interferon regulatory factor 3, 2'-5'-oligoadenylatesynthetase 1, osteopontin, IFNα, IFNβ, IFNγ, interleukin-2 (IL-2), IL-13 and tumor necrosis factor alpha, compared to group 1 pigs. The animals demonstrated significantly reduced PRRSV viremia and number of viremic pigs, but did not demonstrate any further improved PRRSV-specific antibody levels, neutralizing antibody titers, rectal temperature, clinical scores, and ADWG as compared to group 1 pigs. Our findings suggest that quil A up-regulates type I IFN-regulated gene, type I and II IFNs, and inflammatory cytokine expressions which may contribute to further reducing PRRSV viremia and number of viremic pigs which were conferred by PRRSV-1 MLV vaccine. Our findings also suggest that quil A may serve as an effective immunostimulator for potentiating cell-mediated immune defense to PRRSV.

Nasal delivery of chitosan/alginate nanoparticle encapsulated bee (Apis mellifera) venom promotes antibody production and viral clearance during porcine reproductive and respiratory syndrome virus infection by modulating T cell related responses

In this study, we administered specially developed chitosan/alginate nanoparticle encapsulated BV (CH/AL-BV) which has slow-releasing properties and mucosal adhesiveness to pig via nasal route and evaluate whether it can facilitate systemic immune response and improve clearance of porcine reproductive and respiratory syndrome virus (PRRSV). The CH/AL-BV-administered group with PRRSV vaccination showed significantly enhanced Th1-related responses including a high population of CD4⁺ T lymphocyte and cytokine mRNA levels including interferon-gamma (IFN-γ) and interleukin (IL)-12 and increased PRRSV-specific IgG levels. In the PRRSV challenge experiment, the CH/AL-BV group showed a significant decrease of viral burden in the sera and tissues (lung and bronchial lymph node) and mild interstitial pneumonia signs on both lung gross examination and microscopic evaluation with high levels of PRRSV-specific IgG and viral neutralizing antibody. CH/AL-BV also effectively induced not only Th1-related immune responses including increase in portion of CD4⁺ T lymphocyte, cytokines (IFN-γ and IL-12), and transcriptional factors (STAT4 and T-bet), but also stimulated IFN-γ-secreting cell families such as CD4⁺ T lymphocytes and Th/memory cells. Interestingly, the CH/AL-BV group showed decrease in PRRSV-specific immune-suppressive actions, including the T regulatory cell population and its related cytokines (IL-10 and TGF-β) and transcriptional factors (STAT5 and Foxp3). Therefore, nasal-delivered CH/AL-BV may effectively induce non-specific immune stimulating actions, particularly those related to Th1 responses and viral clearance activities against PRRSV infection. Based on these results, CH/AL-BV could be a promising strategy for overcoming the disadvantages of classical PRRSV vaccination and can be applied as a preventive agent against PRRSV and other viral diseases, particularly those with immune-suppressive characteristics.

Saponin Quil A up-regulates type I interferon-regulated gene and type I and II interferon expressions which are suppressed by porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) suppresses innate immune response following infection of myeloid antigen-presenting cells. Poor innate immune response results in weak and delayed PRRSV-specific adaptive immunity, and facilitates PRRSV replication, pathogenesis, and persistent infection. Numerous efforts have been made to enhance the effective innate and adaptive immune defenses to PRRSV, however, only a few attempts have so far elicited satisfactory results. The present study aims to evaluate in vitro the potential of saponin quil A to enhance the expression of type I interferon (IFN)-regulated gene, type I and II IFNs, and pro-inflammatory cytokines in PRRSV-inoculated peripheral blood mononuclear cells (PBMC). Naïve PBMC from four PRRSV-seronegative pigs were inoculated with PRRSV and subsequently stimulated with quil A in the absence or presence of either polyinosinic:polycytidylic acid (poly IC) or lipopolysaccharide (LPS). The mRNA expression levels of myxovirus resistance 1 (Mx1), interferon regulatory factor 3 (IRF3), IRF7, 2'-5'-oligoadenylatesynthetase 1 (OAS1), stimulator of interferon genes (STING), osteopontin (OPN), IFNα, IFNβ, IFNγ, interleukin-2 (IL-2), IL-10, IL-13, tumor necrosis factor alpha (TNFα), and transforming growth factor beta (TGFβ) were evaluated by real-time PCR. Compared with uninoculated PBMC, PRRSV significantly suppressed expression of all immune parameters except IL-2, IL-10, IL-13, and TGFβ. When compared with PRRSV-inoculated PBMC, stimulation with quil A significantly enhanced Mx1, IRF3, IRF7, OAS1, STING, IFNβ, and IFNγ mRNA expressions, and significantly reduced TGFβ mRNA expression. Our findings thus suggest that quil A has a potential to up-regulate the expression of type I IFN-regulated gene and type I and II IFNs which are suppressed by PRRSV. Therefore, it may serve as an effective immunostimulator for potentiating the innate immune defense to PRRSV.

Porcine reproductive and respiratory syndrome virus vaccine does not fit in classical vaccinology

All vaccines are developed to elicit an effective immune response in vaccinated animals such as innate, humoral and cell mediated response to protect animal health. Quality and intensity of the immune responses are differing by characteristics of the vaccine formulation and nature of the infectious agent. Modified live virus vaccines showed advantages over killed vaccines in terms of rapid immune response, duration of the immunity and better cell mediated protection mechanism. The porcine reproductive and respiratory syndrome virus (PRRSV) is relatively newly emerging (1986 in United States, 1990 in Europe) viral pathogen in pigs and tremendous effort has been made to protect pigs from this economically devastating disease such as developing killed, modified live, recombinant protein based and DNA vaccines. However, only cell culture attenuated virus vaccine is practiced with arguably limited efficacy. The PRRSV vaccine did not clear virus from infected pigs nor prevent re-infection of the virus. The vaccine showed very limited innate immune response, low anamnestic immune response and negligible cell mediated immune response. Despite of the current developed scientific technology, there still remain many questions to solve a most important pig disease worldwide.

Honeybee (Apis mellifera) Venom Reinforces Viral Clearance during the Early Stage of Infection with Porcine Reproductive and Respiratory Syndrome Virus through the Up-Regulation of Th1-Specific Immune Responses

Porcine reproductive and respiratory syndrome (PRRS) is a chronic and immunosuppressive viral disease that is responsible for substantial economic losses for the swine industry. Honeybee venom (HBV) is known to possess several beneficial biological properties, particularly, immunomodulatory effects. Therefore, this study aimed at evaluating the effects of HBV on the immune response and viral clearance during the early stage of infection with porcine reproductive and respiratory syndrome virus (PRRSV) in pigs. HBV was administered via three routes of nasal, neck, and rectal and then the pigs were inoculated with PRRSV intranasally. The CD4⁺/CD8⁺ cell ratio and levels of interferon (IFN)-γ and interleukin (IL)-12 were significantly increased in the HBV-administered healthy pigs via nasal and rectal administration. In experimentally PRRSV-challenged pigs with virus, the viral genome load in the serum, lung, bronchial lymph nodes and tonsil was significantly decreased, as was the severity of interstitial pneumonia, in the nasal and rectal administration group. Furthermore, the levels of Th1 cytokines (IFN-γ and IL-12) were significantly increased, along with up-regulation of pro-inflammatory cytokines (TNF-α and IL-1β) with HBV administration. Thus, HBV administration—especially via the nasal or rectal route—could be a suitable strategy for immune enhancement and prevention of PRRSV infection in pigs.

Development and validation of a harmonized TaqMan-based triplex real-time RT-PCR protocol for the quantitative detection of normalized gene expression profiles of seven porcine cytokines

Dysregulation of cytokine responses plays a major role in the pathogenesis of severe and life-threatening infectious diseases like septicemia or viral hemorrhagic fevers. In pigs, diseases like African and classical swine fever are known to show exaggerated cytokine releases. To study these responses and their impact on disease severity and outcome in detail, reliable, highly specific and sensitive methods are needed. For cytokine research on the molecular level, real-time RT-PCRs have been proven to be suitable. Yet, the currently available and most commonly used SYBR Green I assays or heterogeneous gel-based RT-PCRs for swine show a significant lack of specificity and sensitivity. The latter is however absolutely essential for an accurate quantification of rare cytokine transcripts as well as for detection of small changes in gene expressions. For this reason, a harmonized TaqMan-based triplex real-time RT-PCR protocol for the quantitative detection of normalized gene expression profiles of seven porcine cytokines was designed and validated within the presented study. Cytokines were chosen to represent different immunological pathways and targets known to be involved in the pathogenesis of the above mentioned porcine diseases, namely interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, tumor necrosis factor (TNF)-α and interferon (IFN)-α. Beta-Actin and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) served as reference genes for normalization. For absolute quantification a synthetic standard plasmid was constructed comprising all target cytokines and reference genes within a single molecule allowing the generation of positive control RNA. The standard as well as positive RNAs from samples, and additionally more than 400 clinical samples, which were collected from animal trials, were included in the validation process to assess analytical sensitivity and applicability under routine conditions. The resulting assay allows the reliable assessment of gene expression profiles and provides a broad applicability to any kind of immunological research in swine.