Respiratory viral infections drive different lung cytokine profiles in pigs

Porcine cis-acting lnc-CAST positively regulates CXCL8 expression through histone H3K27ac

The chemokine CXCL8, also known as the neutrophil chemotactic factor, plays a crucial role in mediating inflammatory responses and managing cellular immune reactions during viral infections. Porcine reproductive and respiratory syndrome virus (PRRSV) primarily infects pulmonary alveolar macrophages (PAMs), leading to acute pulmonary infections. In this study, we explored a novel long non-coding RNA (lncRNA), termed lnc-CAST, situated within the Cxcl8 gene locus. This lncRNA was found to be highly expressed in porcine macrophages. We observed that both lnc-CAST and CXCL8 were significantly upregulated in PAMs following PRRSV infection, and after treatments with lipopolysaccharide (LPS) or lipoteichoic acid (LTA). Furthermore, we noticed a concurrent upregulation of lnc-CAST and CXCL8 expression in lungs of PRRSV-infected pigs. We then determined that lnc-CAST positively influenced CXCL8 expression in PAMs. Overexpression of lnc-CAST led to an increase in CXCL8 production, which in turn enhanced the migration of epithelial cells and the recruitment of neutrophils. Conversely, inhibiting lnc-CAST expression resulted in reduced CXCL8 production in PAMs, leading to decreased migration levels of epithelial cells and neutrophils. From a mechanistic perspective, we found that lnc-CAST, localized in the nucleus, facilitated the enrichment of histone H3K27ac in CXCL8 promoter region, thereby stimulating CXCL8 transcription in a cis-regulatory manner. In conclusion, our study underscores the pivotal critical role of lnc-CAST in regulating CXCL8 production, offering valuable insights into chemokine regulation and lung damage during PRRSV infection.

Highly pathogenic PRRSV upregulates IL-13 production through nonstructural protein 9-mediated inhibition of N6-methyladenosine demethylase FTO

Porcine reproductive and respiratory syndrome virus (PRRSV), a highly infectious virus, causes severe losses in the swine industry by regulating the inflammatory response, inducing tissue damage, suppressing the innate immune response, and promoting persistent infection in hosts. Interleukin-13 (IL-13) is a cytokine that plays a critical role in regulating immune responses and inflammation, particularly in immune-related disorders, certain types of cancer, and numerous bacterial and viral infections; however, the underlying mechanisms of IL-13 regulation during PRRSV infection are not well understood. In this study, we demonstrated that PRRSV infection elevates IL-13 levels in porcine alveolar macrophages. PRRSV enhances m6A-methylated RNA levels while reducing the expression of fat mass and obesity associated protein (FTO, an m6A demethylase), thereby augmenting IL-13 production. PRRSV nonstructural protein 9 (nsp9) was a key factor for this modulation. Furthermore, we found that the residues Asp567, Tyr586, Leu593, and Asp595 were essential for nsp9 to induce IL-13 production via attenuation of FTO expression. These insights delineate PRRSV nsp9's role in FTO-mediated IL-13 release, advancing our understanding of PRRSV's impact on host immune and inflammatory responses.

DUSP1 mRNA modulation during porcine circovirus type 2 and porcine reproductive and respiratory syndrome virus co-infection regulates viruses replication

The effects of porcine circovirus type 2b (PCV2b) and porcine reproductive and respiratory syndrome virus (PRRSV) co-infection in epithelial cells of the swine respiratory tract is unknown. In the present study, the newborn pig trachea cell line NPTr-CD163, which is permissive to both viruses, was persistently infected with PCV2b and then with PRRSV. Viral replication, cell viability, cytokines' mRNA expression, and modulation of cellular genes expression were evaluated in infected cells. In NPTr-CD163 co-infection model, PCV2b replication was enhanced while PRRSV replication was suppressed. Cell viability was significantly decreased during PCV2b single infection and co-infection compared to mock-infected and PRRSV single infected cells. However, no difference was observed in cell viability between PCV2b and PCV2b/PRRSV infected cells. The IL6, IL8 and IL10 mRNA expression was significantly higher in co-infected cells compared to PCV2b and PRRSV single infected cells. Moreover, the IFN-α/β expression was significantly reduced in co-infected cells compared to PCV2b infected cells whereas it remained higher compared to PRRSV infected cells. The differential gene expression analysis revealed that the mRNA expression level of the cellular gene DUSP1 was significantly higher in all PRRSV infection models compared to PCV2b single infected cells. Knockdown of DUSP1 expression in co-infected cells significantly reduced PCV2b replication, suggesting a role for DUSP1 in PCV2b/PRRSV pathogenesis.

From Snoot to Tail: A Brief Review of Influenza Virus Infection and Immunity in Pigs

Pigs play an important role in influenza A virus (IAV) epidemiology because they support replication of human, avian, and swine origin viruses and act as an IAV reservoir for pigs and other species, including humans. Moreover, novel IAVs with human pandemic potential may be generated in pigs. To minimize the threat of IAVs to human and swine health, it is crucial to understand host defense mechanisms that restrict viral replication and pathology in pigs. In this article, we review IAV strains circulating in the North American swine population, as well as porcine innate and acquired immune responses to IAV, including recent advances achieved through immunological tools developed specifically for swine. Furthermore, we highlight unique aspects of the porcine pulmonary immune system, which warrant consideration when developing vaccines and therapeutics to limit IAV in swine or when using pigs to model human IAV infections.

Secondary Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus (HP-PRRSV2) Infection Augments Inflammatory Responses, Clinical Outcomes, and Pathogen Load in Glaesserella-parasuis-Infected Piglets

Glaesserella parasuis (Gps), Gram-negative bacteria, are a universal respiratory-disease-causing pathogen in swine that colonize the upper respiratory tract. Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus (HP-PRRSV2HP-PRRSV2) and Gps coinfections are epidemics in China, but little is known about the influence of concurrent coinfection on disease severity and inflammatory responses. Herein, we studied the effects of secondary HP-PRRS infection on clinical symptoms, pathological changes, pathogen load, and inflammatory response of Gps coinfection in the upper respiratory tract of piglets. All coinfected piglets (HP-PRRSV2 + Gps) displayed fever and severe lesions in the lungs, while fever was present in only a few animals with a single infection (HP-PRRSV2 or Gps). Additionally, HP-PRRSV2 and Gps loading in nasal swabs and blood and lung tissue samples was significantly increased in the coinfected group. Necropsy data showed that coinfected piglets suffered from severe lung damage and had significantly higher antibody titers of HP-PRRSV2 or Gps than single-infected piglets. Moreover, the serum and lung concentrations of inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8) were also significantly higher in coinfected piglets than in those infected with HP-PRRSV2 or Gps alone. In conclusion, our results show that HP-PRRSV2 promotes the shedding and replication of Gps, and their coinfection in the upper respiratory tract aggravates the clinical symptoms and inflammatory responses, causing lung damage. Therefore, in the unavoidable situation of Gps infection in piglets, necessary measures must be made to prevent and control secondary infection with HP-PRRSV2, which can save huge economic losses to the pork industry.

Repositioned Natural Compounds and Nanoformulations: A Promising Combination to Counteract Cell Damage and Inflammation in Respiratory Viral Infections

Respiratory viral diseases are among the most important causes of disability, morbidity, and death worldwide. Due to the limited efficacy or side effects of many current therapies and the increase in antiviral-resistant viral strains, the need to find new compounds to counteract these infections is growing. Since the development of new drugs is a time-consuming and expensive process, numerous studies have focused on the reuse of commercially available compounds, such as natural molecules with therapeutic properties. This phenomenon is generally called drug repurposing or repositioning and represents a valid emerging strategy in the drug discovery field. Unfortunately, the use of natural compounds in therapy has some limitations, due to their poor kinetic performance and consequently reduced therapeutic effect. The advent of nanotechnology in biomedicine has allowed this limitation to be overcome, showing that natural compounds in nanoform may represent a promising strategy against respiratory viral infections. In this narrative review, the beneficial effects of some promising natural molecules, curcumin, resveratrol, quercetin, and vitamin C, which have been already studied both in native form and in nanoform, against respiratory viral infections are presented and discussed. The review focuses on the ability of these natural compounds, analyzed in in vitro and in vivo studies, to counteract inflammation and cellular damage induced by viral infection and provide scientific evidence of the benefits of nanoformulations in increasing the therapeutic potential of these molecules.

Highly pathogenic porcine reproductive and respiratory syndrome virus-induced inflammatory response in porcine pulmonary microvascular endothelial cells and effects of herbal ingredients on main inflammatory molecules

The role of microvascular endothelial cells (MVECs) in viral infection has received increasing attention. Our previous study demonstrated the susceptibility of porcine pulmonary MVECs to highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV), while their responses to the viral infection remain unclear. This study aimed to understand effects of the HP-PRRSV infection on functions of porcine pulmonary MVECs and the intervention effects of Chinese herbal ingredients on them. Highly purified porcine pulmonary MVECs were separated using CD31-immunomagnetic beads and infected with HP-PRRSV JXA1 and HN strain. The virus particles in cells and the ultrastructural pathological changes of cells were revealed by transmission electron microscopy. High-throughput transcriptome sequencing indicated that 104 and 228 genes were differentially expressed at 36 h post-infection, respectively, including many inflammatory molecules such as interleukins, chemokines, and adhesion molecules. The expression kinetics of HP-PRRSV-induced IL-1α, IL-6, IL-8, and VCAM-1 were characterized at the mRNA and protein levels. Luteolin significantly down-regulated HP-PRRSV-induced increase of the four molecules at both levels, and glycyrrhetinic acid and baicalin reduced that of IL-6 and VCAM-1. Our results suggest that porcine pulmonary MVECs play important roles in the inflammatory lung injury caused by HP-PRRSV infection and that herbal ingredients have potential regulatory effects on the HP-PRRSV-induced dysfunction of MVECs.

Porcine respiratory disease complex: Dynamics of polymicrobial infections and management strategies after the introduction of the African swine fever

A few decades ago, porcine respiratory disease complex (PRDC) exerted a major economic impact on the global swine industry, particularly due to the adoption of intensive farming by the latter during the 1980's. Since then, the emerging of porcine reproductive and respiratory syndrome virus (PRRSV) and of porcine circovirus type 2 (PCV2) as major immunosuppressive viruses led to an interaction with other endemic pathogens (e.g., Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, Streptococcus suis, etc.) in swine farms, thereby exacerbating the endemic clinical diseases. We herein, review and discuss various dynamic polymicrobial infections among selected swine pathogens. Traditional biosecurity management strategies through multisite production, parity segregation, batch production, the adoption of all-in all-out production systems, specific vaccination and medication protocols for the prevention and control (or even eradication) of swine diseases are also recommended. After the introduction of the African swine fever (ASF), particularly in Asian countries, new normal management strategies minimizing pig contact by employing automatic feeding systems, artificial intelligence, and robotic farming and reducing the numbers of vaccines are suggested. Re-emergence of existing swine pathogens such as PRRSV or PCV2, or elimination of some pathogens may occur after the ASF-induced depopulation. ASF-associated repopulating strategies are, therefore, essential for the establishment of food security. The "repopulate swine farm" policy and the strict biosecurity management (without the use of ASF vaccines) are, herein, discussed for the sustainable management of small-to-medium pig farms, as these happen to be the most potential sources of an ASF re-occurrence. Finally, the ASF disruption has caused the swine industry to rapidly transform itself. Artificial intelligence and smart farming have gained tremendous attention as promising tools capable of resolving challenges in intensive swine farming and enhancing the farms' productivity and efficiency without compromising the strict biosecurity required during the ongoing ASF era.

Successive Inoculations of Pigs with Porcine Reproductive and Respiratory Syndrome Virus 1 (PRRSV-1) and Swine H1N2 Influenza Virus Suggest a Mutual Interference between the Two Viral Infections

Porcine reproductive and respiratory syndrome virus (PRRSV) and swine influenza A virus (swIAV) are major pathogens of the porcine respiratory disease complex, but little is known on their interaction in super-infected pigs. In this study, we investigated clinical, virological and immunological outcomes of successive infections with PRRSV-1 and H1N2 swIAV. Twenty-four specific pathogen-free piglets were distributed into four groups and inoculated either with PRRSV at study day (SD) 0, or with swIAV at SD8, or with PRRSV and swIAV one week apart at SD0 and SD8, respectively, or mock-inoculated. In PRRSV/swIAV group, the clinical signs usually observed after swIAV infection were attenuated while higher levels of anti-swIAV antibodies were measured in lungs. Concurrently, PRRSV multiplication in lungs was significantly affected by swIAV infection, whereas the cell-mediated immune response specific to PRRSV was detected earlier in blood, as compared to PRRSV group. Moreover, levels of interferon (IFN)-α measured from SD9 in the blood of super-infected pigs were lower than those measured in the swIAV group, but higher than in the PRRSV group at the same time. Correlation analyses suggested an important role of IFN-α in the two-way interference highlighted between both viral infections.

Identification of sensitive indicators in immune response for leprosy affected patients: An observational clinical study of safety and immunogenicity of influenza vaccine

Cured leprosy patients have special physical conditions, which could pose challenges for safety and immunogenicity after immunization. We performed an observational clinical study aimed to identify the safety and immunogenicity of influenza vaccine in cured leprosy patients. A total of 65 participants from a leprosarium were recruited into leprosy cured group or control group, and received a 0.5 ml dose of the inactivated split-virion trivalent influenza vaccine and a follow-up 28 days proactive observation of any adverse events. Hemagglutination and hemagglutination inhibition test was performed to evaluate serum antibody titer, flow cytometry was conducted to screen of cytokines level. The total rate of reactogenicity was 0.0% [0/41] in leprosy cured group and 37.5% [9/24] in control group. The seroconversion rate for H1N1 was difference between leprosy cured group and control group (41.83% vs 79.17%, P = .0082), but not for H3N2 (34.25% vs 50.00%, P = .4468). At day 0, leprosy cured group have relatively high concentration of interleukin-6, interleukin-10, tumor necrosis factor, interferon-γ, and interleukin-17 compared to control group. The interleukin-2 concentration increased 2 weeks after vaccination compared to pre-vaccination in leprosy cured group, but declined in control group (0.92 pg/ml vs -0.02 pg/ml, P = .0147). Leprosy cured group showed a more rapid down-regulation of interleukin-6 when influenza virus was challenged compared to control group (-144.38 pg/ml vs -11.52 pg/ml, P < .0001). Subgroup analysis revealed that the immunization administration declined interleukin-17 concentration in Tuberculoid type subgroup, but not in Lepromatous type subgroup or control group. Clinically cured leprosy patients are relatively safe for influenza vaccine. Leprosy cured patient have immune deficit in producing antibody. Interleukin-6 and interleukin-17 were 2 sensitive indicators in immune response for leprosy affected patients. The identification of indicators might be help management of leprosy and used as predictive markers in leprosy early symptom monitoring.

Concomitant Swine Influenza A Virus Infection Alters PRRSV1 MLV Viremia in Piglets but Does Not Interfere with Vaccine Protection in Experimental Conditions

Modified-live vaccines (MLVs) against porcine reproductive and respiratory syndrome viruses (PRRSVs) are usually administrated to piglets at weaning when swine influenza A virus (swIAV) infections frequently occur. SwIAV infection induces a strong interferon alpha (IFNa) response and IFNa was shown to abrogate PRRSV2 MLV replication and an inherent immune response. In this study, we evaluated the impacts of swIAV infection on the replication of a PRRSV1 MLV (MLV1), post-vaccine immune responses and post-challenge vaccine efficacy at both the systemic and pulmonary levels. Piglets were either swIAV inoculated and MLV1 vaccinated 6 h apart or singly vaccinated or mock inoculated and mock vaccinated. Four weeks after vaccination, the piglets were challenged with a PRRSV1 field strain. The results showed that swIAV infection delayed MLV1 viremia by six days and post-vaccine seroconversion by four days. After the PRRSV1 challenge, the swIAV enhanced the PRRSV1-specific cell-mediated immunity (CMI) but the PRRSV1 field strain viremia was not better controlled. High IFNa levels that were detected early after swIAV infection could have been responsible for both the inhibition of MLV1 replication and CMI enhancement. Thus, whereas swIAV infection had a negative impact on humoral responses post-vaccination, it did not interfere with the protective effectiveness of the PRRSV MLV1 in our experimental conditions.