Current and prospective control strategies of influenza A virus in swine

A systematic review on the incidence of influenza viruses in wastewater matrices: Implications for public health

Influenza viruses pose a significant public health threat, necessitating comprehensive surveillance strategies to enhance early detection and preventive measures. This systematic review investigates the incidence of influenza viruses in wastewater matrices, aiming to elucidate the potential implications for public health. The study synthesizes existing literature, employing rigorous inclusion criteria to identify relevant studies conducted globally. The essence of the problem lies in the gaps of traditional surveillance methods, which often rely on clinical data and may underestimate the true prevalence of influenza within communities. Wastewater-based epidemiology offers a novel approach to supplementing these conventional methods, providing a broader and more representative assessment of viral circulation. This review systematically examines the methodologies employed in the selected studies, including virus concentration techniques and molecular detection methods, to establish a standardized framework for future research. Our findings reveal a consistent presence of influenza viruses in diverse wastewater matrices across different geographic locations and seasons. Recommendations for future research include the standardization of sampling protocols, improvement of virus concentration methods, and the integration of wastewater surveillance into existing public health frameworks. In conclusion, this systematic review contributes to the understanding of influenza dynamics in wastewater matrices, offering valuable insights for public health practitioners and policymakers. Implementation of wastewater surveillance alongside traditional methods can enhance the resilience of public health systems and better prepare communities for the challenges posed by influenza outbreaks.

Oocyte electroporation prior to in vitro fertilization is an efficient method to generate single, double, and multiple knockout porcine embryos of interest in biomedicine and animal production

Genetically modified pigs play a critical role in mimicking human diseases, xenotransplantation, and the development of pigs resistant to viral diseases. The use of programmable endonucleases, including the CRISPR/Cas9 system, has revolutionized the generation of genetically modified pigs. This study evaluates the efficiency of electroporation of oocytes prior to fertilization in generating edited gene embryos for different models. For single gene editing, phospholipase C zeta (PLC ζ) and fused in sarcoma (FUS) genes were used, and the concentration of sgRNA and Cas9 complexes was optimized. The results showed that increasing the concentration resulted in higher mutation rates without affecting the blastocyst rate. Electroporation produced double knockouts for the TPC1/TPC2 genes with high efficiency (79 %). In addition, resistance to viral diseases such as PRRS and swine influenza was achieved by electroporation, allowing the generation of double knockout embryo pigs (63 %). The study also demonstrated the potential for multiple gene editing in a single step using electroporation, which is relevant for xenotransplantation. The technique resulted in the simultaneous mutation of 5 genes (GGTA1, B4GALNT2, pseudo B4GALNT2, CMAH and GHR). Overall, electroporation proved to be an efficient and versatile method to generate genetically modified embryonic pigs, offering significant advances in biomedical and agricultural research, xenotransplantation, and disease resistance. Electroporation led to the processing of numerous oocytes in a single session using less expensive equipment. We confirmed the generation of gene-edited porcine embryos for single, double, or quintuple genes simultaneously without altering embryo development to the blastocyst stage. The results provide valuable insights into the optimization of gene editing protocols for different models, opening new avenues for research and applications in this field.

Assessment of Immune Responses to a Trivalent Pichinde Virus-Vectored Vaccine Expressing Hemagglutinin Genes from Three Co-Circulating Influenza A Virus Subtypes in Pigs

Pichinde virus (PICV) can infect several animal species and has been developed as a safe and effective vaccine vector. Our previous study showed that pigs vaccinated with a recombinant PICV-vectored vaccine expressing the hemagglutinin (HA) gene of an H3N2 influenza A virus of swine (IAV-S) developed virus-neutralizing antibodies and were protected against infection by the homologous H3N2 strain. The objective of the current study was to evaluate the immunogenicity and protective efficacy of a trivalent PICV-vectored vaccine expressing HA antigens from the three co-circulating IAV-S subtypes: H1N1, H1N2, and H3N2. Pigs immunized with the trivalent PICV vaccine developed virus-neutralizing (VN) and hemagglutination inhibition (HI) antibodies against all three matching IAV-S. Following challenge infection with the H1N1 strain, five of the six pigs vaccinated with the trivalent vaccine had no evidence of IAV-S RNA genomes in nasal swabs and bronchoalveolar lavage fluid, while all non-vaccinated control pigs showed high number of copies of IAV-S genomic RNA in these two types of samples. Overall, our results demonstrate that the trivalent PICV-vectored vaccine elicits antibody responses against the three targeted IAV-S strains and provides protection against homologous virus challenges in pigs. Therefore, PICV exhibits the potential to be explored as a viral vector for delivering multiple vaccine antigens in swine.

Seroprevalence of Swine Influenza A Virus (swIAV) Infections in Commercial Farrow-to-Finish Pig Farms in Greece

Swine influenza is a highly contagious respiratory disease caused by influenza A virus infection. Pigs play an important role in the overall epidemiology of influenza because of their ability to transmit influenza viruses of avian and human origin, which plays a potential role in the emergence of zoonotic strains with pandemic potential. The aim of our study was to assess the seroprevalence of Swine Influenza Viruses (swIAVs) in commercial pig farms in Greece. A total of 1416 blood samples were collected from breeding animals (gilts and sows) and pigs aged 3 weeks to market age from 40 different swIAV vaccinated and unvaccinated commercial farrow-to-finish pig farms. For the detection of anti-SIV antibodies, sera were analyzed using an indirect ELISA kit CIVTEST SUIS INFLUENZA®, Hipra (Amer, Spain). Of the total 1416 animals tested, 498 were seropositive, indicating that the virus circulates in both vaccinated (54% seroprevalence) and unvaccinated Greek pig farms (23% seroprevalence). In addition, maternally derived antibody (MDA) levels were lower in pigs at 4 and 7 weeks of age in unvaccinated farms than in vaccinated farms. In conclusion, our results underscore the importance of vaccination as an effective tool for the prevention of swIAV infections in commercial farrow-to-finish pig farms.

Genetic diversification patterns in swine influenza A virus (H1N2) in vaccinated and nonvaccinated animals

Influenza A viruses (IAVs) are characterized by having a segmented genome, low proofreading polymerases, and a wide host range. Consequently, IAVs are constantly evolving in nature causing a threat to animal and human health. In 2009 a new human pandemic IAV strain arose in Mexico because of a reassortment between two strains previously circulating in pigs; Eurasian "avian-like" (EA) swine H1N1 and "human-like" H1N2, highlighting the importance of swine as adaptation host of avian to human IAVs. Nowadays, although of limited use, a trivalent vaccine, which include in its formulation H1N1, H3N2, and, H1N2 swine IAV (SIAV) subtypes, is one of the most applied strategies to reduce SIAV circulation in farms. Protection provided by vaccines is not complete, allowing virus circulation, potentially favoring viral evolution. The evolutionary dynamics of SIAV quasispecies were studied in samples collected at different times from 8 vaccinated and 8 nonvaccinated pigs, challenged with H1N2 SIAV. In total, 32 SIAV genomes were sequenced by next-generation sequencing, and subsequent variant-calling genomic analysis was carried out. Herein, a total of 364 de novo single nucleotide variants (SNV) were found along all genetic segments in both experimental groups. The nonsynonymous substitutions proportion found was greater in vaccinated animals suggesting that H1N2 SIAV was under positive selection in this scenario. The impact of each substitution with an allele frequency greater than 5% was hypothesized according to previous literature, particularly in the surface glycoproteins hemagglutinin and neuraminidase. The H1N2 SIAV quasispecies evolution capacity was evidenced, observing different evolutionary trends in vaccinated and nonvaccinated animals.

Protein sequence features of H1N1 swine influenza A viruses detected on commercial swine farms in Serbia

Introduction

Swine influenza A viruses (swIAVs) are characterised by high mutation rates and zoonotic and pandemic potential. In order to draw conclusions about virulence in swine and pathogenicity to humans, we examined the existence of molecular markers and accessory proteins, cross-reactivity with vaccine strains, and resistance to antiviral drugs in five strains of H1N1 swIAVs.

Material and Methods

Amino acid (AA) sequences of five previously genetically characterised swIAVs were analysed in MEGA 7.0 software and the Influenza Research Database.

Results

Amino acid analysis revealed three virus strains with 590S/591R polymorphism and T271A substitution within basic polymerase 2 (PB2) AA chains, which cause enhanced virus replication in mammalian cells. The other two strains possessed D701N and R251K substitutions within PB2 and synthesised PB1-F2 protein, which are the factors of increased polymerase activity and virulence in swine. All strains synthesised PB1-N40, PA-N155, PA-N182, and PA-X proteins responsible for enhanced replication in mammalian cells and downregulation of the immune response of the host. Mutations detected within haemagglutinin antigenic sites imply the antigenic drift of the five analysed viruses in relation to the vaccine strains. All viruses show susceptibility to neuraminidase inhibitors and baloxavir marboxil, which is important in situations of incidental human infections.

Conclusion

The detection of virulence markers and accessory proteins in the analysed viruses suggests their higher propensity for replication in mammalian cells, increased virulence, and potential for transmission to humans, and implies compromised efficacy of influenza vaccines.

An Orf-Virus (ORFV)-Based Vector Expressing a Consensus H1 Hemagglutinin Provides Protection against Diverse Swine Influenza Viruses

Influenza A viruses (IAV-S) belonging to the H1 subtype are endemic in swine worldwide. Antigenic drift and antigenic shift lead to a substantial antigenic diversity in circulating IAV-S strains. As a result, the most commonly used vaccines based on whole inactivated viruses (WIVs) provide low protection against divergent H1 strains due to the mismatch between the vaccine virus strain and the circulating one. Here, a consensus coding sequence of the full-length of HA from H1 subtype was generated in silico after alignment of the sequences from IAV-S isolates obtained from public databases and was delivered to pigs using the Orf virus (ORFV) vector platform. The immunogenicity and protective efficacy of the resulting ORFVΔ121conH1 recombinant virus were evaluated against divergent IAV-S strains in piglets. Virus shedding after intranasal/intratracheal challenge with two IAV-S strains was assessed by real-time RT-PCR and virus titration. Viral genome copies and infectious virus load were reduced in nasal secretions of immunized animals. Flow cytometry analysis showed that the frequency of T helper/memory cells, as well as cytotoxic T lymphocytes (CTLs), were significantly higher in the peripheral blood mononuclear cells (PBMCs) of the vaccinated groups compared to unvaccinated animals when they were challenged with a pandemic strain of IAV H1N1 (CA/09). Interestingly, the percentage of T cells was higher in the bronchoalveolar lavage of vaccinated animals in relation to unvaccinated animals in the groups challenged with a H1N1 from the gamma clade (OH/07). In summary, delivery of the consensus HA from the H1 IAV-S subtype by the parapoxvirus ORFV vector decreased shedding of infectious virus and viral load of IAV-S in nasal secretions and induced cellular protective immunity against divergent influenza viruses in swine.

Evaluation of early single dose vaccination on swine influenza A virus transmission in piglets: From experimental data to mechanistic modelling

Swine influenza A virus (swIAV) is a major pathogen affecting pigs with a huge economic impact and potentially zoonotic. Epidemiological studies in endemically infected farms permitted to identify critical factors favoring on-farm persistence, among which maternally-derived antibodies (MDAs). Vaccination is commonly practiced in breeding herds and might be used for immunization of growing pigs at weaning. Althoughinterference between MDAs and vaccination was reported in young piglets, its impact on swIAV transmission was not yet quantified. To this aim, this study reports on a transmission experiment in piglets with or without MDAs, vaccinated with a single dose injection at four weeks of age, and challenged 17 days post-vaccination. To transpose small-scale experiments to real-life situation, estimated parameters were used in a simulation tool to assess their influence at the herd level. Based on a thorough follow-up of the infection chain during the experiment, the transmission of the swIAV challenge strain was highly dependent on the MDA status of the pigs when vaccinated. MDA-positive vaccinated animals showed a direct transmission rate 3.6-fold higher than the one obtained in vaccinated animals without MDAs, estimated to 1.2. Vaccination nevertheless reduced significantly the contribution of airborne transmission when compared with previous estimates obtained in unvaccinated animals. The integration of parameter estimates in a large-scale simulation model, representing a typical farrow-to-finish pig herd, evidenced an extended persistence of viral spread when vaccination of sows and single dose vaccination of piglets was hypothesized. When extinction was quasi-systematic at year 5 post-introduction in the absence of sow vaccination but with single dose early vaccination of piglets, the extinction probability fell down to 33% when batch-to-batch vaccination was implemented both in breeding herd and weaned piglets. These results shed light on a potential adverse effect of single dose vaccination in MDA-positive piglets, which might lead to longer persistence of the SwIAV at the herd level.

Vaccination against swine influenza in pigs causes different drift evolutionary patterns upon swine influenza virus experimental infection and reduces the likelihood of genomic reassortments

Influenza A viruses (IAVs) can infect a wide variety of bird and mammal species. Their genome is characterized by 8 RNA single stranded segments. The low proofreading activity of their polymerases and the genomic reassortment between different IAVs subtypes allow them to continuously evolve, constituting a constant threat to human and animal health. In 2009, a pandemic of an IAV highlighted the importance of the swine host in IAVs adaptation between humans and birds. The swine population and the incidence of swine IAV is constantly growing. In previous studies, despite vaccination, swine IAV growth and evolution were proven in vaccinated and challenged animals. However, how vaccination can drive the evolutionary dynamics of swine IAV after coinfection with two subtypes is poorly studied. In the present study, vaccinated and nonvaccinated pigs were challenged by direct contact with H1N1 and H3N2 independent swine IAVs seeder pigs. Nasal swab samples were daily recovered and broncho-alveolar lavage fluid (BALF) was also collected at necropsy day from each pig for swine IAV detection and whole genome sequencing. In total, 39 swine IAV whole genome sequences were obtained by next generation sequencing from samples collected from both experimental groups. Subsequently, genomic, and evolutionary analyses were carried out to detect both, genomic reassortments and single nucleotide variants (SNV). Regarding the segments found per sample, the simultaneous presence of segments from both subtypes was much lower in vaccinated animals, indicating that the vaccine reduced the likelihood of genomic reassortment events. In relation to swine IAV intra-host diversity, a total of 239 and 74 SNV were detected within H1N1 and H3N2 subtypes, respectively. Different proportions of synonymous and nonsynonymous substitutions were found, indicating that vaccine may be influencing the main mechanism that shape swine IAV evolution, detecting natural, neutral, and purifying selection in the different analyzed scenarios. SNV were detected along the whole swine IAV genome with important nonsynonymous substitutions on polymerases, surface glycoproteins and nonstructural proteins, which may have an impact on virus replication, immune system escaping and virulence of virus, respectively. The present study further emphasized the vast evolutionary capacity of swine IAV, under natural infection and vaccination pressure scenarios.

Pterostilbene effectively inhibits influenza A virus infection by promoting the type I interferon production

With the prevalence of novel strains and drug-resistant influenza viruses, there is an urgent need to develop effective and low-toxicity anti-influenza therapeutics. Regulation of the type I interferon antiviral response is considered an attractive therapeutic strategy for viral infection. Pterostilbene, a 3,5-dimethoxy analog of resveratrol, is known for its remarkable pharmacological activity. Here, we found that pterostilbene effectively inhibited influenza A virus infection and mainly affected the late stages of viral replication. A mechanistic study showed that the antiviral activity of pterostilbene might promote the induction of antiviral type I interferon and expression of its downstream interferon-stimulated genes during viral infection. The same effect of pterostilbene was also observed in the condition of polyinosinic-polycytidylic acid (poly I:C) transfection. Further study showed that pterostilbene interacted with influenza non-structural 1 (NS1) protein, inhibited ubiquitination mediated degradation of RIG-I and activated the downstream antiviral pathway, orchestrating an antiviral state against influenza virus in the cell. Taken together, pterostilbene could be a promising anti-influenza agent for future antiviral drug exploitation and compounds with similar structures may provide new options for the development of novel inhibitors against influenza A virus (IAV).

Farm management practices, biosecurity and influenza a virus detection in swine farms: a comprehensive study in colombia

Biosecurity protocols (BP) and good management practices are key to reduce the risk of introduction and transmission of infectious diseases into the pig farms. In this observational cross-sectional study, survey data were collected from 176 pig farms with inventories over 100 sows in Colombia. We analyzed a complex survey dataset to explore the structure and identify clustering patterns using Multiple Correspondence Analysis (MCA) of swine farms in Colombia, and estimated its association with Influenza A virus detection. Two principal dimensions contributed to 27.6% of the dataset variation. Farms with highest contribution to dimension 1 were larger farrow-to-finish farms, using self-replacement of gilts and implementing most of the measures evaluated. In contrast, farms with highest contribution to dimension 2 were medium to large farrow-to-finish farms, but implemented biosecurity in a lower degree. Additionally, two farm clusters were identified by Hierarchical Cluster Analysis (HCA), and the odds of influenza A virus detection was statistically different between clusters (OR 7.29, CI: 1.7,66, p = < 0.01). Moreover, after logistic regression analysis, three important variables were associated with higher odds of influenza detection: (1) “location in an area with a high density of pigs”, (2) “farm size”, and (3) “after cleaning and disinfecting, the facilities are allowed to dry before use”. Our results revealed two clustering patterns of swine farms. This systematic analysis of complex survey data identified relationships between biosecurity, husbandry practices and influenza status. This approach helped to identify gaps on biosecurity and key elements for designing successful strategies to prevent and control swine respiratory diseases in the swine industry.

Ecological and evolutionary dynamics of multi-strain RNA viruses

Potential interactions among co-circulating viral strains in host populations are often overlooked in the study of virus transmission. However, these interactions probably shape transmission dynamics by influencing host immune responses or altering the relative fitness among co-circulating strains. In this Review, we describe multi-strain dynamics from ecological and evolutionary perspectives, outline scales in which multi-strain dynamics occur and summarize important immunological, phylogenetic and mathematical modelling approaches used to quantify interactions among strains. We also discuss how host-pathogen interactions influence the co-circulation of pathogens. Finally, we highlight outstanding questions and knowledge gaps in the current theory and study of ecological and evolutionary dynamics of multi-strain viruses.

Evolution of Swine Influenza Virus H3N2 in Vaccinated and Nonvaccinated Pigs after Previous Natural H1N1 Infection

Swine influenza viruses (SIV) produce a highly contagious and worldwide distributed disease that can cause important economic losses to the pig industry. Currently, this virus is endemic in farms and, although used limitedly, trivalent vaccine application is the most extended strategy to control SIV. The presence of pre-existing immunity against SIV may modulate the evolutionary dynamic of this virus. To better understand these dynamics, the viral variants generated in vaccinated and nonvaccinated H3N2 challenged pigs after recovery from a natural A(H1N1) pdm09 infection were determined and analyzed. In total, seventeen whole SIV genomes were determined, 6 from vaccinated, and 10 from nonvaccinated animals and their inoculum, by NGS. Herein, 214 de novo substitutions were found along all SIV segments, 44 of them being nonsynonymous ones with an allele frequency greater than 5%. Nonsynonymous substitutions were not found in NP; meanwhile, many of these were allocated in PB2, PB1, and NS1 proteins. Regarding HA and NA proteins, higher nucleotide diversity, proportionally more nonsynonymous substitutions with an allele frequency greater than 5%, and different domain allocations of mutants, were observed in vaccinated animals, indicating different evolutionary dynamics. This study highlights the rapid adaptability of SIV in different environments.

Simulating the Commercial Implementation of Gene-Editing for Influenza A Virus Resistance in Pigs: An Economic and Genetic Analysis

The development of swine Influenza A Virus resistance along with genetic technologies could complement current control measures to help to improve animal welfare standards and the economic efficiency of pig production. We have created a simulation model to assess the genetic and economic implications of various gene-editing methods that could be implemented in a commercial, multi-tiered swine breeding system. Our results demonstrate the length of the gene-editing program was negatively associated with genetic progress in commercial pigs and that the time required to reach fixation of resistance alleles was reduced if the efficiency of gene-editing is greater. The simulations included the resistance conferred in a digenic model, the inclusion of genetic mosaicism in progeny, and the effects of selection accuracy. In all scenarios, the level of mosaicism had a greater effect on the time required to reach resistance allele fixation and the genetic progress of the herd than gene-editing efficiency and zygote survival. The economic analysis highlights that selection accuracy will not affect the duration of gene-editing and the investment required compared to the effects of gene-editing-associated mosaicism and the swine Influenza A Virus control strategy on farms. These modelling results provide novel insights into the economic and genetic implications of targeting two genes in a commercial pig gene-editing program and the effects of selection accuracy and mosaicism.

Live attenuated influenza A virus vaccines with modified NS1 proteins for veterinary use

Influenza A viruses (IAV) spread rapidly and can infect a broad range of avian or mammalian species, having a tremendous impact in human and animal health and the global economy. IAV have evolved to develop efficient mechanisms to counteract innate immune responses, the first host mechanism that restricts IAV infection and replication. One key player in this fight against host-induced innate immune responses is the IAV non-structural 1 (NS1) protein that modulates antiviral responses and virus pathogenicity during infection. In the last decades, the implementation of reverse genetics approaches has allowed to modify the viral genome to design recombinant IAV, providing researchers a powerful platform to develop effective vaccine strategies. Among them, different levels of truncation or deletion of the NS1 protein of multiple IAV strains has resulted in attenuated viruses able to induce robust innate and adaptive immune responses, and high levels of protection against wild-type (WT) forms of IAV in multiple animal species and humans. Moreover, this strategy allows the development of novel assays to distinguish between vaccinated and/or infected animals, also known as Differentiating Infected from Vaccinated Animals (DIVA) strategy. In this review, we briefly discuss the potential of NS1 deficient or truncated IAV as safe, immunogenic and protective live-attenuated influenza vaccines (LAIV) to prevent disease caused by this important animal and human pathogen.

Porcine β-defensin 2 confers enhanced resistance to swine flu infection in transgenic pigs and alleviates swine influenza virus-induced apoptosis possibly through interacting with host SLC25A4

Swine influenza virus (SIV) not only brings about great economic losses on the global pig industry, it also poses a significant threat to the public health for its interspecies transmission capacity. Porcine β-defensin 2 (PBD-2) is a host defense peptide and our previous study has shown that PBD-2 inhibits proliferation of enveloped pseudorabies virus both in vitro and in transgenic (TG) mice. The aim of this study is to investigate the possible anti-SIV ability of PBD-2 in a TG pig model created in our previous study. The in-contact challenge trial demonstrated that overexpression of PBD-2 in pigs could efficiently alleviate SIV-associated clinical signs. The SIV titers quantified by EID₅₀ in lung tissues of infected TG pigs were significantly lower than that of wild-type littermates. In vitro, the cell viability assay revealed that PBD-2 mainly interfered with viral entry and post-infection stages. It was further confirmed that PBD-2 could enter porcine tracheal epithelial cells. The proteins interacting with PBD-2 inside host cells were identified with immunoprecipitation and the pathways involved were analyzed. Results showed that PBD-2 could interact with pro-apoptotic solute carrier family 25 member 4 (SLC25A4), also known as adenine nucleotide translocase 1, and thereby inhibited SIV-induced cell apoptosis. The molecular docking analysis suggested that PBD-2 interacted with porcine SLC25A4 mainly through strong hydrogen binding, with the predicted binding affinity being -13.23 kcal/mol. Altogether, these indicate that PBD-2 protects pigs against SIV infection, which may result from its role as a SLC25A4 blocker to alleviate cell apoptosis, providing a novel therapeutic and prophylactic strategy of using PBD-2 to combat SIV.

[Opportunities and risks of the use of genetic resistances to infectious diseases in pigs - an overview]

Demands for health, performance and welfare in pigs, as well as the desire for consumer protection and reduced antibiotic use, require optimal measures in advance of disease development. This includes, in principle, the use of genetically more resistant lines and breeding animals, whose existence has been proven for a wide range of pathogen-host interactions. In addition, attempts are being made to identify the gene variants responsible for disease resistance in order to force the selection of suitable populations, also using modern biotechnical technics. The present work is intended to provide an overview of the research status achieved in this context and to highlight opportunities and risks for the future.The evaluation of the international literature shows that genetic disease resistance exist in many areas of swine diseases. However, polygenic inheritance, lack of animal models and the influence of environmental factors during evaluation render their implementation in practical breeding programs demanding. This is where modern molecular genetic methods, such as Gene Editing, come into play. Both approaches possess their pros and cons, which are discussed in this paper. The most important infectious diseases in pigs, including general diseases and epizootics, diseases of the respiratory and digestive tract and diseases of the immune system are taken into account.

Stem cell-derived porcine macrophages as a new platform for studying host-pathogen interactions

BACKGROUND

Infectious diseases of farmed and wild animals pose a recurrent threat to food security and human health. The macrophage, a key component of the innate immune system, is the first line of defence against many infectious agents and plays a major role in shaping the adaptive immune response. However, this phagocyte is a target and host for many pathogens. Understanding the molecular basis of interactions between macrophages and pathogens is therefore crucial for the development of effective strategies to combat important infectious diseases.

RESULTS

We explored how porcine pluripotent stem cells (PSCs) can provide a limitless in vitro supply of genetically and experimentally tractable macrophages. Porcine PSC-derived macrophages (PSCdMs) exhibited molecular and functional characteristics of ex vivo primary macrophages and were productively infected by pig pathogens, including porcine reproductive and respiratory syndrome virus (PRRSV) and African swine fever virus (ASFV), two of the most economically important and devastating viruses in pig farming. Moreover, porcine PSCdMs were readily amenable to genetic modification by CRISPR/Cas9 gene editing applied either in parental stem cells or directly in the macrophages by lentiviral vector transduction.

CONCLUSIONS

We show that porcine PSCdMs exhibit key macrophage characteristics, including infection by a range of commercially relevant pig pathogens. In addition, genetic engineering of PSCs and PSCdMs affords new opportunities for functional analysis of macrophage biology in an important livestock species. PSCs and differentiated derivatives should therefore represent a useful and ethical experimental platform to investigate the genetic and molecular basis of host-pathogen interactions in pigs, and also have wider applications in livestock.