Mutations within scavenger receptor cysteine-rich (SRCR) protein domain 5 of porcine CD163 involved in infection with porcine reproductive and respiratory syndrome virus (PRRS)

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.

Role of CD163 in PRRSV infection

Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly infectious agent that poses a significant economic threat to the global swine industry. Efficient viral entry relies on interactions with cellular receptors, with CD163-a cysteine-rich scavenger receptor found on porcine alveolar macrophages (PAMs)-playing a critical role. Extensive evidence supports CD163's essential function in PRRSV infection. This review synthesizes current knowledge about CD163's role, examining its structure-function relationship and identifying specific regions crucial for viral entry. We evaluate the established role of CD163 in PRRSV pathogenesis and highlight areas requiring further investigation, along with the potential for targeted therapeutic interventions. Understanding the molecular determinants of CD163's function is vital for developing effective strategies to control PRRSV infection and mitigate its economic impact on swine production. Further research into the PRRSV-CD163 interactions will be crucial for creating novel antiviral strategies.

Intervention strategies targeting virus and host factors against porcine reproductive and respiratory syndrome virus: A systematic review

Porcine reproductive and respiratory syndrome (PRRS) caused by porcine reproductive and respiratory syndrome virus (PRRSV) causes considerable economic losses to the global swine industry every year and seriously hinders the healthy development of this industry. Although tremendous efforts have been made over the past 30 years toward the development of prevention and control strategies against PRRSV infection, to date, treatments with proven efficacy have yet to be available due to our incomplete understanding of the molecular basis and complexity of the infection machinery. This review systematically discusses recent advances in the research and development of anti-PRRSV therapies targeting different stages of the viral life cycle. Furthermore, this review puts forward novel intervention targets and research approaches based on our in-depth exploration of virus-host interactions and the latest biological technologies, which have the potential to complement or transform current anti-PRRSV strategies and become breakthrough points for the control of PRRS in the future.

Deletion of maternal CD163 PSTII-domain-coding exon 13 protects fetuses from infection with porcine reproductive and respiratory syndrome virus (PRRSV)

Following infection of a porcine dam with PRRSV around 90 days of gestation, the virus crosses the placenta and starts to infect fetuses. This can lead to consequences such as abortions, stillbirths, and respiratory issues in newborn piglets. CD163 is an essential cellular viral entry receptor for porcine reproductive and respiratory syndrome virus (PRRSV). CD163 contains nine scavenger receptor cysteine-rich (SRCR) and two proline-serine-threonine (PST) domains. Gene-edited pigs possessing a complete deletion of CD163 are resistant to PRRSV infection. Recently, we demonstrated that pigs harboring a clean deletion of CD163 exon 13 (ΔExon13 CD163 pigs) which encodes the first 12 amino acids of the CD163 PSTII domain were not susceptible to PRRSV infection. In this study, ΔExon13 CD163 (-/-) gilts were bred with wildtype CD163 (+/+) boars producing heterozygous, CD163 (+/-) fetuses. We found that fetuses with a wildtype CD163, recovered between day 103 of gestation or 17 days after the maternal infection with PRRSV, were fully protected from PRRSV in dams containing a clean deletion of CD163 exon 13. These findings suggest a feasible approach for eliminating PRRSV-related reproductive illness, which is a significant cause of economic losses in agriculture.

Role of N-linked glycosylation in porcine reproductive and respiratory syndrome virus (PRRSV) infection

Porcine reproductive and respiratory syndrome (PRRSV) is an enveloped single-stranded positive-sense RNA virus and one of the main pathogens that causes the most significant economical losses in the swine-producing countries. PRRSV is currently divided into two distinct species, PRRSV-1 and PRRSV-2. The PRRSV virion envelope is composed of four glycosylated membrane proteins and three non-glycosylated envelope proteins. Previous work has suggested that PRRSV-linked glycans are critical structural components for virus assembly. In addition, it has been proposed that PRRSV glycans are implicated in the interaction with host cells and critical for virus infection. In contrast, recent findings showed that removal of N-glycans from PRRSV does not influence virus infection of permissive cells. Thus, there are not sufficient evidences to indicate compellingly that N-glycans present in the PRRSV envelope play a direct function in viral infection. To gain insights into the role of N-glycosylation in PRRSV infection, we analysed the specific contribution of the envelope protein-linked N-glycans to infection of permissive cells. For this purpose, we used a novel strategy to modify envelope protein-linked N-glycans that consists of production of monoglycosylated PRRSV and viral glycoproteins with different glycan states. Our results showed that removal or alteration of N-glycans from PRRSV affected virus infection. Specifically, we found that complex N-glycans are required for an efficient infection in cell cultures. Furthermore, we found that presence of high mannose type glycans on PRRSV surface is the minimal requirement for a productive viral infection. Our findings also show that PRRSV-1 and PRRSV-2 have different requirements of N-glycan structure for an optimal infection. In addition, we demonstrated that removal of N-glycans from PRRSV does not affect viral attachment, suggesting that these carbohydrates played a major role in regulating viral entry. In agreement with these findings, by performing immunoprecipitation assays and colocalization experiments, we found that N-glycans present in the viral envelope glycoproteins are not required to bind to the essential viral receptor CD163. Finally, we found that the presence of N-glycans in CD163 is not required for PRRSV infection.

Pigs lacking the SRCR5 domain of CD163 protein demonstrate heritable resistance to the PRRS virus and no changes in animal performance from birth to maturity

Porcine reproductive and respiratory syndrome (PRRS) is one of the world's most persistent viral pig diseases, with a significant economic impact on the pig industry. PRRS affects pigs of all ages, causing late-term abortions and stillbirths in sows, respiratory disease in piglets, and increased susceptibility to secondary bacterial infection with a high mortality rate. PRRS disease is caused by a positive single-stranded RNA PRRS virus (PRRSV), which has a narrow host-cell tropism limited to monocyte-macrophage lineage cells. Several studies demonstrated that the removal of CD163 protein or, as a minimum, its scavenger receptor cysteine-rich domain 5 (SRCR5) precludes the viral genome release, conferring resistance to PRRSV in live animals. Today, very limited information exists about the impact of such edits on animal performance from birth to maturity in pigs. Using CRISPR-Cas9 with dual-guide RNAs and non-homologous end joining (NHEJ), first-generation (E0) pigs were produced with a deletion of exon 7 in the CD163 gene. The selected pigs were bred to produce the next three generations of pigs to establish multiple lines of pigs homozygous for the edited allele, thereby confirming that the CD163 gene with removed exon 7 was stable during multiple breeding cycles. The pigs were evaluated relative to non-edited pigs from birth to maturity, including any potential changes in meat composition and resistance to PRRSV. This study demonstrates that removing the SRCR5 domain from the CD163 protein confers resistance to PRRSV and, relative to unedited pigs, resulted in no detected differences in meat composition and no changes in the growth rate, health, and ability to farrow. Together, these results support the targeted use of gene editing in livestock animals to address significant diseases without adversely impacting the health and well-being of the animals or the food products derived from them.

AGIDB: a versatile database for genotype imputation and variant decoding across species

The high cost of large-scale, high-coverage whole-genome sequencing has limited its application in genomics and genetics research. The common approach has been to impute whole-genome sequence variants obtained from a few individuals for a larger population of interest individually genotyped using SNP chip. An alternative involves low-coverage whole-genome sequencing (lcWGS) of all individuals in the larger population, followed by imputation to sequence resolution. To overcome limitations of processing lcWGS data and meeting specific genotype imputation requirements, we developed AGIDB (https://agidb.pro), a website comprising tools and database with an unprecedented sample size and comprehensive variant decoding for animals. AGIDB integrates whole-genome sequencing and chip data from 17 360 and 174 945 individuals, respectively, across 89 species to identify over one billion variants, totaling a massive 688.57 TB of processed data. AGIDB focuses on integrating multiple genotype imputation scenarios. It also provides user-friendly searching and data analysis modules that enable comprehensive annotation of genetic variants for specific populations. To meet a wide range of research requirements, AGIDB offers downloadable reference panels for each species in addition to its extensive dataset, variant decoding and utility tools. We hope that AGIDB will become a key foundational resource in genetics and breeding, providing robust support to researchers.

Genetically modified pigs lacking CD163 PSTII-domain-coding exon 13 are completely resistant to PRRSV infection

CD163 expressed on cell surface of porcine alveolar macrophages (PAMs) serves as a cellular entry receptor for porcine reproductive and respiratory syndrome virus (PRRSV). The extracellular portion of CD163 contains nine scavenger receptor cysteine-rich (SRCR) and two proline-serine-threonine (PST) domains. Genomic editing of pigs to remove the entire CD163 or just the SRCR5 domain confers resistance to infection with both PRRSV-1 and PRRSV-2 viruses. By performing a mutational analysis of CD163, previous in vitro infection experiments showed resistance to PRRSV infection following deletion of exon 13 which encodes the first 12 amino acids of the 16 amino acid PSTII domain. These findings predicted that removal of exon 13 can be used as a strategy to produce gene-edited pigs fully resistant to PRRSV infection. In this study, to determine whether the deletion of exon 13 is sufficient to confer resistance of pigs to PRRSV infection, we produced pigs possessing a defined CD163 exon 13 deletion (ΔExon13 pigs) and evaluated their susceptibility to viral infection. Wild type (WT) and CD163 modified pigs, placed in the same room, were infected with PRRSV-2. The modified pigs remained PCR and serologically negative for PRRSV throughout the study; whereas the WT pigs supported PRRSV infection and showed PRRSV related pathology. Importantly, our data also suggested that removal of exon 13 did not affect the main physiological function associated with CD163 in vivo. These results demonstrate that a modification of CD163 through a precise deletion of exon 13 provides a strategy for protection against PRRSV infection.

Genetic background influences pig responses to porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly infectious and economically significant virus that causes respiratory and reproductive diseases in pigs. It results in reduced productivity and increased mortality in pigs, causing substantial economic losses in the industry. Understanding the factors affecting pig responses to PRRSV is crucial to develop effective control strategies. Genetic background has emerged as a significant determinant of susceptibility and resistance to PRRSV in pigs. This review provides an overview of the basic infection process of PRRSV in pigs, associated symptoms, underlying immune mechanisms, and roles of noncoding RNA and alternative splicing in PRRSV infection. Moreover, it emphasized breed-specific variations in these aspects that may have implications for individual treatment options.

Molecular breeding of livestock for disease resistance

Animal infectious diseases pose a significant threat to the global agriculture and biomedicine industries, leading to significant economic losses and public health risks. The emergence and spread of viral infections such as African swine fever virus (ASFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and avian influenza virus (AIV) have highlighted the need for innovative approaches to develop resilient and disease-resistant animal populations. Gene editing technologies, such as CRISPR/Cas9, offer a promising avenue for generating animals with enhanced disease resistance. This review summarizes recent advances in molecular breeding strategies for generating disease-resistant animals, focusing on the development of disease-resistant livestock. We also highlight the potential applications of genome-wide CRISPR/Cas9 library screening and base editors in producing precise gene modified livestock for disease resistance in the future. Overall, gene editing technologies have the potential to revolutionize animal breeding and improve animal health and welfare.

Progress in PRRSV Infection and Adaptive Immune Response Mechanisms

Since its discovery, Porcine reproductive and respiratory syndrome (PRRS) has had a huge impact on the farming industry. The virus that causes PRRS is Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), and because of its genetic diversity and the complexity of the immune response, the eradication of PRRS has been a challenge. To provide scientific references for PRRSV control and vaccine development, this study describes the processes of PRRSV-induced infection and escape, as well as the host adaptive immune response to PRRSV. It also discusses the relationship between PRRSV and the adaptive immune response.

Identification of New Compounds against PRRSV Infection by Directly Targeting CD163

The porcine reproductive and respiratory syndrome viruses (PRRSV) led to a global panzootic and huge economical losses to the pork industry. PRRSV targets the scavenger receptor CD163 for productive infection. However, currently no effective treatment is available to control the spread of this disease. Using bimolecular fluorescence complementation (BiFC) assays, we screened a set of small molecules potentially targeting the scavenger receptor cysteine-rich domain 5 (SRCR5) of CD163. We found that the assay examining protein-protein interactions (PPI) between PRRSV glycoprotein 4 (GP4) and the CD163-SRCR5 domain mainly identifies compounds that potently inhibit PRRSV infection, while examining the PPI between PRRSV-GP2a and the SRCR5 domain maximized the identification of positive compounds, including additional ones with various antiviral capabilities. These positive compounds significantly inhibited both types 1 and 2 PRRSV infection of porcine alveolar macrophages. We confirmed that the highly active compounds physically bind to the CD163-SRCR5 protein, with dissociation constant (KD) values ranging from 28 to 39 μM. Structure-activity-relationship (SAR) analysis revealed that although both the 3-(morpholinosulfonyl)anilino and benzenesulfonamide moieties in these compounds are critical for the potency to inhibit PRRSV infection, the morpholinosulfonyl group can be replaced by chlorine substituents without significant loss of antiviral potency. Our study established a system for throughput screening of natural or synthetic compounds highly effective on blocking of PRRSV infection and shed light on further SAR modification of these compounds. IMPORTANCE Porcine reproductive and respiratory syndrome virus (PRRSV) causes significant economic losses to the swine industry worldwide. Current vaccines cannot provide cross protection against different strains, and there are no effective treatments available to hamper the spread of this disease. In this study, we identified a group of new small molecules that can inhibit the PRRSV interaction with its specific receptor CD163 and dramatically block the infection of both types 1 and type 2 PRRSVs to host cells. We also demonstrated the physical association of these compounds with the SRCR5 domain of CD163. In addition, molecular docking and structure-activity relationship analyses provided new insights for the CD163/PRRSV glycoprotein interaction and further improvement of these compounds against PRRSV infection.

Recent advances in inhibition of porcine reproductive and respiratory syndrome virus through targeting CD163

Porcine reproductive and respiratory syndrome virus (PRRSV) has plagued the pig industry for more than 30 years and causes great economic losses. At present different commercial vaccines are available but limited tools. Until now at least six potential host factors are identified as the key receptors for PRRSV infection. Among them, CD163 molecule is the most important and critical in PRRSV life cycle responsible for mediating virus uncoating and genome release. It determines the susceptibility of target cells to the virus. Several PRRSV non-permissive cells (such as PK-15, 3D4/21, and BHK-21) are demonstrated to become completely susceptible to PRRSV infection in the presence of expression of porcine CD163 protein. Therefore, CD163 has become the target for the design of novel antiviral molecules disrupting the interaction between CD163 and viral glycoproteins, or the breeding of gene-modified animals against PRRSV infection. In this review, we comprehensively summarize the recent progress in inhibition of PRRSV replication via targeting CD163 receptor. In addition, whether there are other potential molecules interacting with CD163 in the process of uncoating of virus life cycle is also discussed.

Reappraising host cellular factors involved in attachment and entry to develop antiviral strategies against porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRS virus (PRRSV), is a highly contagious disease that brings tremendous economic losses to the global swine industry. As an intracellular obligate pathogen, PRRSV infects specific host cells to complete its replication cycle. PRRSV attachment to and entry into host cells are the first steps to initiate the replication cycle and involve multiple host cellular factors. In this review, we recapitulated recent advances on host cellular factors involved in PRRSV attachment and entry, and reappraised their functions in these two stages, which will deepen the understanding of PRRSV infection and provide insights to develop promising antiviral strategies against the virus.