The natural compound Sanggenon C inhibits PRRSV infection by regulating the TRAF2/NF-κB signalling pathway

The commercial PRRSV attenuated vaccine can be a potentially effective live trivalent vaccine vector

PRRSV is an immunosuppressive virus that is prone to secondary infection by other viral and microbial pathogens, exacerbating its harm to pigs. The development of multivalent vaccines that can prevent and control multiple pathogens is of great significance for the pig industry. In order to evaluate the potential of commercial PRRSV vaccines as the viral vectors for the trivalent vaccine, this study first embedded mCherry or EGFP genes for fluorescent proteins into the infectious clone of the HP-PRRSV MLV vaccine strain GD to construct a recombinant strain. Furthermore, we constructed a recombinant PRRSV strain, rPRRSV-mCherry-EGFP, that expresses both EGFP and mCherry proteins simultaneously and evaluated the stability and immunogenicity of the exogenous proteins. The results showed that MARC-145 cells infected with rPRRSV-mCherry-EGFP could simultaneously express both EGFP and mCherry exogenous proteins, and the number of EGFP and mCherry positive cells increased with virus infection, providing more fluorescent tool options for virus visualization and high-throughput screening of anti-PRRSV drugs. More importantly, the recombinant rPRRSV-mCherry-EGFP can be passaged in MARC-145 cells for at least 10 generations. It can induce piglets to produce antibodies against PRRSV, EGFP, and mCherry, indicating that the embedded two exogenous genes can also induce good immune responses. Our research suggests that using the infectious clone of a commercial HP-PRRSV-attenuated vaccine as a vector and embedding immune genes of two other pathogens to construct a recombinant strain may be an effective attempt to achieve cross-protection against three pathogens, providing an important research basis for the design of trivalent vaccines. KEY POINTS: • A recombinant PRRSV that expressed two foreign proteins was constructed. • The recombinant PRRSV could induce antibodies against PRRSV, EGFP, and mCherry. • PRRSV MLV strain had the potential to be used as a viral vector for triple vaccines.

Inflammation and cancer cell survival: TRAF2 as a key player

TNF receptor-associated factor 2 (TRAF2) plays a crucial role in both physiological and pathological processes. It takes part in the regulation of cell survival and death, tissue regeneration, development, endoplasmic reticulum stress response, autophagy, homeostasis of the epithelial barrier and regulation of adaptive and innate immunity. Initially identified for its interaction with TNF receptor 2 (TNFR2), TRAF2 contains a TRAF domain that enables homo- and hetero-oligomerization, allowing it to interact with multiple receptors and signaling molecules. While best known for mediating TNFR1 and TNFR2 signaling, TRAF2 also modulates other receptor pathways, including MAPK, NF-κB, and Wnt/β-catenin cascades. By regulating NF-κB-inducing kinase (NIK), TRAF2 is a key activator of the alternative NF-κB pathway, linking it to inflammatory diseases, immune dysfunction, and tumorigenesis. In the innate immune system, TRAF2 influences macrophage differentiation, activation, and survival and stimulates natural killer cell cytotoxicity. In the adaptive immune system, it represses effector B- and T-cell activity while sustaining regulatory T-cell function, thus promoting immune suppression. The lack of fine-tuning of TRAF2 activity leads to excessive NF-kB activation, driving chronic inflammation and autoimmunity. Although TRAF2 can act as a tumor suppressor, it is predominantly described as a tumor promoter, as its expression has been correlated with increased metastatic potential and poorer prognosis in several types of cancer. Targeting TRAF2 or TRAF2-dependent signaling pathways might represent a promising anti-cancer therapeutic strategy.

Baicalein inhibits PRRSV through direct binding, targeting EGFR, and enhancing immune response

Porcine reproductive and respiratory syndrome virus (PRRSV) presents significant economic challenges to the global pork industry due to its ability to mutate rapidly. The current commercial vaccines have limited effectiveness, and there are strict restrictions on the use of antiviral chemical drugs. Therefore, it is urgent to identify new strategies for preventing and controlling PRRSV infections. Baicalein, a flavonoid derived from Scutellaria baicalensis, has gained attention for its potential antiviral properties. However, there is little information about the effects and mechanisms of baicalein in relation to PRRSV. In this study, a network pharmacology analysis identified seven potential targets of baicalein against PRRSV, with the epidermal growth factor receptor (EGFR) emerging as the core target. The results of molecular docking and dynamics (MD) simulations confirmed that baicalein has a high binding affinity for EGFR, with a measured value of - 7.935 kcal/mol. Additionally, both in vitro (EC50 = 10.20 μg/mL) and in vivo (2.41 mg/kg) experiments were conducted to assess the effectiveness of baicalein against PRRSV. Notably, baicalein was found to inhibit various stages of the PRRSV replication cycle and could directly bind to PRRSV in vitro. Baicalein inhibited the entry of PRRSV by blocking EGFR phosphorylation and the downstream PI3K-AKT signaling pathway. This was confirmed by a decrease in the expression of p-EGFR/EGFR, p-AKT/AKT, PI3K, and SRC following treatment with baicalein. Additionally, baicalein significantly enhanced the immune response in piglets infected with PRRSV. In conclusion, this study suggests that baicalein may be a promising pharmaceutical candidate for preventing and controlling PRRS, offering new insights into the antiviral potential of Chinese herbal medicine.

Mechanism of PRRSV infection and antiviral role of polyphenols

Porcine reproductive and respiratory syndrome (PRRS) is associated with the endemic outbreak of fever, anorexia, and abortion in pregnant sows, resulting in an enormous economic impact on the global swine industry. Current mainstream prophylactic agents and therapies have been developed to prevent PRRSV infection; however, they have limited efficacy. Therefore, there is an urgent need to develop novel antiviral strategies to prevent PRRSV infection and transmission. The identification of new PRRSV entry mediators, such as MYH9 and HSPA8; viral apoptotic mimicry; and TIM-induced macropinocytosis, to facilitate infection has led to a novel molecular understanding of the PRRSV infection mechanism, which can be utilized in the development of prophylactic agents and therapies for PRRSV infection. Polyphenols, complex chemical molecules with abundant biological activities derived from microorganisms and plants, have demonstrated great potential for controlling PRRSV infection via different mechanisms. To explore new possibilities for treating PRRSV infection with polyphenols, this review focuses on summarizing the pathogenesis of PRRSV, reviewing the potential antiviral mechanisms of polyphenols against PRRSV, and addressing the challenges associated with the widespread use of polyphenols.

Inhibition Effect of STING Agonist SR717 on PRRSV Replication

The porcine reproductive and respiratory syndrome virus (PRRSV) belongs to the Arteriviridae family and is a single-stranded, positively stranded RNA virus. The currently available PRRSV vaccines are mainly inactivated and attenuated vaccines, yet none of the commercial vaccines can provide comprehensive, long-lasting, and effective protection against PRRSV. SR717 is a pyridazine-3-carboxamide compound, which is commonly used as a non-nucleoside STING agonist with antitumor and antiviral activities. Nevertheless, there is no evidence that SR717 has any antiviral effects against PRRSV. In this study, a dose-dependent inhibitory effect of SR717 was observed against numerous strains of PRRSV using qRT-PCR, IFA, and WB methods. Furthermore, SR717 was found to stimulate the production of anti-viral molecules and trigger the activation of the signaling cascade known as the stimulator of interferon genes (STING) pathway, which contributed to hindering the reproduction of viruses by a certain margin. Collectively, these results indicate that SR717 is capable of inhibiting PRRSV infection in vitro and may have potential as an antiviral drug against PRRSV.

Natural compound Sanggenon C inhibits porcine reproductive and respiratory syndrome virus replication in piglets

Porcine reproductive and respiratory syndrome virus is one of the main pathogens threatening the global pig industry, and there is still a lack of effective therapeutic drugs. Sanggenon C is a flavanone Diels-Alder adduct compound extracted from the root bark of the mulberry genus, which has blood pressure-reducing, anti-atherosclerotic, anti-oxidative, and anti-inflammatory effects. In our previous study, Sanggenon C was confirmed to significantly inhibit PRRSV replication in vitro. However, its antiviral potential to inhibit PRRSV infection in vivo has not been evaluated in piglets. Here, the antiviral effect of Sanggenon C was evaluated in PRRSV-challenged piglets based on assessments of rectal temperature, viral load, pathological changes of lung tissue and secretion of inflammatory cytokines. The results showed that Sanggenon C treatment relieved the clinical symptoms, reduced the viral loads in the lungs and bloods, alleviated the pathological damage of lung tissue, decreased the secretion of inflammatory cytokines, and shorten the excretion time of virus from the oral and nasal secretions and feces of piglets after PRRSV infection. The results indicated that Sanggenon C is a promising anti-PRRSV drug, which provides a new strategy for the prevention and control of PRRS in clinical practice.