BacMam Expressing Highly Glycosylated Porcine Interferon Alpha Induces Robust Antiviral and Adjuvant Effects against Foot-and-Mouth Disease Virus in Pigs

Prophylactic treatment with PEGylated bovine IFNλ3 effectively bridges the gap in vaccine-induced immunity against FMD in cattle

Foot-and-mouth disease (FMD) is a vesicular disease of cloven-hoofed animals with devastating economic implications. The current FMD vaccine, routinely used in enzootic countries, requires at least 7 days to induce protection. However, FMD vaccination is typically not recommended for use in non-enzootic areas, underscoring the need to develop new fast-acting therapies for FMD control during outbreaks. Interferons (IFNs) are among the immune system's first line of defense against viral infections. Bovine type III IFN delivered by a replication defective adenovirus (Ad) vector has effectively blocked FMD in cattle. However, the limited duration of protection-usually only 1-3 days post-treatment (dpt)-diminishes its utility as a field therapeutic. Here, we test whether polyethylene glycosylation (PEGylation) of recombinant bovine IFNλ3 (PEGboIFNλ3) can extend the duration of IFN-induced prevention of FMDV infection in both vaccinated and unvaccinated cattle. We treated groups of heifers with PEGboIFNλ3 alone or in combination with an adenovirus-based FMD O1Manisa vaccine (Adt-O1M) at either 3 or 5 days prior to challenge with homologous wild type FMDV. We found that pre-treatment with PEGboIFNλ3 was highly effective at preventing clinical FMD when administered at either time point, with or without co-administration of Adt-O1M vaccine. PEGboIFNλ3 protein was detectable systemically for >10 days and antiviral activity for 4 days following administration. Furthermore, in combination with Adt-O1M vaccine, we observed a strong induction of FMDV-specific IFNγ+ T cell response, demonstrating its adjuvanticity when co-administered with a vaccine. Our results demonstrate the promise of this modified IFN as a pre-exposure prophylactic therapy for use in emergency outbreak scenarios.

Porcine interferon-α linked to the porcine IgG-Fc induces prolonged and broad-spectrum antiviral effects against foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is an economically important disease, and the FMD virus (FMDV) can spread rapidly in susceptible animals. FMD is usually controlled through vaccination. However, commercial FMD vaccines are only effective 4-7 days after vaccination. Furthermore, FMDV comprises seven serotypes and various topotypes, and these aspects should be considered when selecting a vaccine. Antiviral agents could provide rapid and broad protection against FMDV. Therefore, this study aimed to develop a fusion protein of consensus porcine interferon-α and Fc portion of porcine antibody IgG (poIFN-α-Fc) using a baculovirus expression system to develop a novel antiviral agent against FMDV. We measured the antiviral effects of the poIFN-α-Fc protein against FMDV and the enhanced duration in vitro and in vivo. The broad-spectrum antiviral effects were tested against seven FMDV serotypes, porcine reproductive and respiratory syndrome virus (PRRSV), and bovine enterovirus (BEV). Furthermore, the early protective effects and neutralizing antibody levels were tested by co-injecting poIFN-α-Fc and an FMD-inactivated vaccine into mice or pigs. Sustained antiviral effects in pig sera and mice were observed, and pigs injected with a combination of the poIFN-α-Fc and an inactivated FMD vaccine were protected against FMDV in a dose-dependent manner at 2- and 4-days post-vaccination. In addition, combined with the inactivated FMD vaccine, poIFN-α-Fc increased the neutralizing antibody levels in mice. Therefore, poIFN-α-Fc is a potential broad-spectrum antiviral and adjuvant candidate that can be used with inactivated FMD vaccines to protect pigs against FMDV.

Interferon alpha and beta receptor 1 knockout in human embryonic kidney 293 cells enhances the production efficiency of proteins or adenoviral vectors related to type I interferons

Human embryonic kidney (HEK) 293 cells are widely used in protein and viral vector production owing to their high transfection efficiency, rapid growth, and suspension growth capability. Given their antiviral, anticancer, and immune-enhancing effects, type I interferons (IFNs) have been used to prevent and treat human and animal diseases. However, the binding of type I IFNs to the IFN-α and-β receptor (IFNAR) stimulates the expression of IFN-stimulated genes (ISGs). This phenomenon induces an antiviral state and promotes apoptosis in cells, thereby impeding protein or viral vector production. In this study, we generated an IFNAR subtype 1 knockout (KO) HEK 293 suspension (IFNAR-KO) cell line by using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) technology. Upon treatment with human IFN-α, the IFNAR-KO cells showed a constant expression of ISGs, including 2'-5'-oligoadenylate synthetase 1 (OAS1), myxovirus resistance 1 (Mx1), protein kinase RNA-activated (PKR), and IFN-induced transmembrane protein 1 (IFITM1), when compared with the wild-type HEK 293 (WT) cells, wherein the ISGs were significantly upregulated. As a result, the titer of recombinant adenovirus expressing porcine IFN-α was significantly higher in the IFNAR-KO cells than in the WT cells. Furthermore, the IFNAR-KO cells continuously produced higher amounts of IFN-α protein than the WT cells. Thus, the CRISPR-Cas9-mediated IFNAR1 KO cell line can improve the production efficiency of proteins or viral vectors related to IFNs. The novel cell line may be used for producing vaccines and elucidating the type I IFN signaling pathway in cells.

The Host Protein CAD Regulates the Replication of FMDV through the Function of Pyrimidines' De Novo Synthesis

Foot-and-mouth disease virus (FMDV) is a single-stranded picornavirus that causes economically devastating disease in even-hooved animals. There has been little research on the function of host cells during FMDV infection. We aimed to shed light on key host factors associated with FMDV replication during acute infection. We found that HDAC1 overexpression in host cells induced upregulation of FMDV RNA and protein levels. Activation of the AKT-mammalian target of rapamycin (mTOR) signaling pathway using bpV(HOpic) or SC79 also promoted FMDV replication. Furthermore, short hairpin RNA (shRNA)-induced suppression of carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD), a transcription factor downstream of the AKT-mTOR signaling pathway, resulted in downregulation of FMDV RNA and protein levels. Coimmunoprecipitation assays showed that the ACTase domain of CAD could interact with the FMDV 2C protein, suggesting that the ACTase domain of CAD may be critical in FMDV replication. CAD proteins participate in de novo pyrimidine synthesis. Inhibition of FMDV replication by deletion of the ACTase domain of CAD in host cells could be reversed by supplementation with uracil. These results revealed that the contribution of the CAD ACTase domain to FMDV replication is dependent on de novo pyrimidine synthesis. Our research shows that HDAC1 promotes FMDV replication by regulating de novo pyrimidine synthesis from CAD via the AKT-mTOR signaling pathway. IMPORTANCE Foot-and-mouth disease virus is an animal virus of the Picornaviridae family that seriously harms the development of animal husbandry and foreign trade of related products, and there is still a lack of effective means to control its harm. Replication complexes would generate during FMDV replication to ensure efficient replication cycles. 2C is a common viral protein in the replication complex of Picornaviridae virus, which is thought to be an essential component of membrane rearrangement and viral replication complex formation. The host protein CAD is a key protein in the pyrimidines de novo synthesis. In our research, the interaction of CAD and FMDV 2C was demonstrated in FMDV-infected BHK-21 cells, and it colocalized with 2C in the replication complex. The inhibition of the expression of FMDV 3D protein through interference with CAD and supplementation with exogenous pyrimidines reversed this inhibition, suggesting that FMDV might recruit CAD through the 2C protein to ensure pyrimidine supply during replication. In addition, we also found that FMDV infection decreased the expression of the host protein HDAC1 and ultimately inhibited CAD activity through the AKT-mTOR signaling pathway. These results revealed a unique means of counteracting the virus in BHK-21 cells lacking the interferon (IFN) signaling pathway. In conclusion, our study provides some potential targets for the development of drugs against FMDV.

Recombinant porcine Interferon-α and Interleukin-2 fusion protein (rPoIFNα+IL-2) shows potent anti-pseudorabies virus activity in vitro and in vivo

Pseudorabies virus (PRV) variants have been widely prevalent since 2011, leading to substantial losses to the swine industry. Although PRV can cause cross-species transmission and induce human infection, no drugs can currently prevent PRV infection. Interferons (IFNs) and interleukin-2 (IL-2) are important cytokines that mediate several biological functions including antiviral activity and immune regulation. In this study, we expressed and purified a recombinant porcine IFN-α and IL-2 fusion protein (rPoIFNα+IL-2), which did not show a cytotoxic effect on PK-15 cells. The antiviral activity was evaluated in PK-15 cells using the cytopathic effect inhibition method, and the results indicated that rPoIFNα+IL-2 can inhibit the replication of PRV, with an antiviral activity of approximately 10⁴ U/mL. Moreover, the proliferation of peripheral blood mononuclear cells was enhanced by rPoIFNα+IL-2. Additionally, rPoIFNα+IL-2 substantially increased the expression of IFN-stimulated genes, including IFIT1, ISG15, MX1, and OAS, which are critical for antiviral activity. Furthermore, rPoIFNα+IL-2 alleviated the clinical symptoms and reduced mortality in mice infected with PRV. Simultaneously, rPoIFNα+IL-2 increased the expression levels of IFN-γ and IL-10 and inhibited the expression of IL-1β and IL-6. Additionally, the viral DNA copies in different tissues in the rPoIFNα+IL-2-treated group were lower than those in the untreated group. These findings indicate that rPoIFNα+IL-2 may serve as an antiviral agent for the prevention and treatment of PRV infection and may expand the potential function of IFN antiviral drugs in the future.

Advances in CRISPR-Cas9 for the Baculovirus Vector System: A Systematic Review

The baculovirus expression vector systems (BEVS) have been widely used for the recombinant production of proteins in insect cells and with high insert capacity. However, baculovirus does not replicate in mammalian cells; thus, the BacMam system, a heterogenous expression system that can infect certain mammalian cells, was developed. Since then, the BacMam system has enabled transgene expression via mammalian-specific promoters in human cells, and later, the MultiBacMam system enabled multi-protein expression in mammalian cells. In this review, we will cover the continual development of the BEVS in combination with CRPISPR-Cas technologies to drive genome-editing in mammalian cells. Additionally, we highlight the use of CRISPR-Cas in glycoengineering to potentially produce a new class of glycoprotein medicines in insect cells. Moreover, we anticipate CRISPR-Cas9 to play a crucial role in the development of protein expression systems, gene therapy, and advancing genome engineering applications in the future.