Porcine Reproductive and Respiratory Syndrome: Genomic Surveillance and Vaccine Strategies Using Bioinformatics

Introduction

Porcine reproductive and respiratory syndrome (PRRS) remains one of the most economically significant viral diseases affecting global swine production. The causative agent, PRRS virus (PRRSV), is an enveloped, positive-sense single-stranded RNA virus classified within the family Arteriviridae, order Nidovirales. The virus is subdivided into two distinct species: Betaarterivirus europensis (PRRSV-1, formerly European genotype) and Betaarterivirus americense (PRRSV-2, formerly North American genotype). Both species exhibit extensive genetic diversity driven by high mutation rates, recombination events, and selective immune pressure. This genetic heterogeneity complicates disease control and necessitates continuous genomic surveillance coupled with bioinformatics-driven vaccine design.

This article provides a detailed examination of PRRSV molecular biology, genomic surveillance methodologies, and computational approaches for vaccine development. The discussion integrates recent findings on viral protein function, host-pathogen interactions, and diagnostic assay development.

Molecular Virology and Host-Pathogen Interactions

Viral Genome Organization and Protein Functions

The PRRSV genome is approximately 15 kilobases in length and contains at least 10 open reading frames (ORFs). ORF1a and ORF1b encode two large polyproteins, pp1a and pp1ab, which are processed by viral proteases into at least 16 nonstructural proteins (nsps). These nsps are essential for viral replication, transcription, and modulation of host innate immune responses.

Recent structural and functional studies have revealed critical details about several nsps. The Nsp1α leader protease contains a [4Fe-4S] iron-sulfur cluster, a discovery that highlights a novel host-virus interplay mechanism [1]. This cluster is required for the proteolytic activity of Nsp1α and influences its downstream functions, including the suppression of interferon signaling. The presence of a metallocluster in a viral protease represents a potential target for antiviral intervention.

Nonstructural protein 12 (nsp12) has been identified as a key factor in subgenomic RNA synthesis. Adaptive mutations at lysine residues within nsp12 enable the virus to evade host proteasomal degradation, thereby promoting efficient subgenomic RNA transcription [2]. This evasion mechanism underscores the evolutionary arms race between PRRSV and the porcine host cell.

Nonstructural protein 1 (nsp1) interacts with tumor necrosis factor receptor-associated factor 6 (TRAF6) to activate the TAK1/p38/JNK/AP-1 signaling cascade, leading to the induction of interleukin-1β (IL-1β) [3]. This proinflammatory cytokine contributes to the immunopathology observed during PRRSV infection, including fever and respiratory distress.

Autophagy and Metabolic Hijacking

PRRSV exploits host cellular processes to facilitate its replication. The virus hijacks the non-canonical enzymatic function of phosphoglycerate dehydrogenase (PHGDH), a key enzyme in serine biosynthesis, to arrest autophagic flux [4]. By blocking autophagosome-lysosome fusion, the virus creates a protected niche for replication while simultaneously preventing the degradation of viral components. This mechanism represents a convergence of metabolic reprogramming and autophagy inhibition.

Genetic Variability and Recombination

The genetic diversity of PRRSV is driven by the error-prone nature of its RNA-dependent RNA polymerase (RdRp) and by homologous recombination. Recombination events frequently occur between co-circulating strains, generating novel viruses with altered pathogenicity and antigenic profiles. Molecular characterization of field isolates has identified HP-like (highly pathogenic) strains and NADC30-like recombinant strains, each possessing distinct genetic markers associated with virulence [5].

In a study of PRRSV-2 sublineage 1A isolates from commercial pig farms, extensive genetic variability was observed in the ORF5 gene, which encodes the major envelope glycoprotein GP5 [6]. This variability was accompanied by changes in N-glycosylation patterns, which can affect viral neutralization and immune recognition. The presence of multiple N-glycosylation sites on GP5 is a well-characterized mechanism for glycan shielding, a strategy that limits antibody accessibility.

Genomic Surveillance Using Bioinformatics

Sequencing Technologies and Data Analysis

Genomic surveillance of PRRSV relies on high-throughput sequencing of viral genomes obtained from clinical samples. Whole-genome sequencing provides the highest resolution for phylogenetic analysis, recombination detection, and identification of emerging variants. Bioinformatics pipelines for PRRSV typically include quality trimming, reference-based or de novo assembly, genome annotation, and variant calling.

Phylogenetic analysis using maximum likelihood or Bayesian methods allows classification of isolates into lineages and sublineages. For PRRSV-2, a standardized lineage classification system based on ORF5 sequences is widely adopted. This system facilitates the tracking of strain movements across regions and production systems.

Recombination Detection

Recombination is a major driver of PRRSV evolution. Computational tools such as RDP4, SimPlot, and GARD are used to identify recombination breakpoints within aligned genome sequences. Detection of recombination requires multiple sequence alignments of closely related strains and statistical testing for incongruent phylogenetic signals. The identification of recombinant strains, such as those derived from NADC30-like and HP-PRRSV parents, is critical for understanding emerging virulence patterns [5].

Molecular Diagnostic Assays

Accurate and rapid detection of PRRSV is essential for surveillance and control. Reverse transcription quantitative PCR (RT-qPCR) remains the gold standard for diagnosis. A recently developed locked nucleic acid (LNA)-based multiplex RT-qPCR assay enables simultaneous differentiation of PRRSV-1, PRRSV-2, and the highly pathogenic L8 lineage of PRRSV-2 [7]. The incorporation of LNA nucleotides increases the melting temperature and specificity of probes, allowing robust discrimination between genetically similar targets. This assay is particularly valuable for regions where multiple PRRSV genotypes co-circulate.

Surveillance Workflow

The following Mermaid diagram illustrates a typical genomic surveillance workflow for PRRSV.

flowchart TD
    A[Clinical Sample Collection], > B[RNA Extraction]
    B, > C[RT-qPCR Screening]
    C, > D{Positive?}
    D, >|No| E[Report Negative]
    D, >|Yes| F[High-Throughput Sequencing]
    F, > G[Quality Control and Assembly]
    G, > H[Genome Annotation]
    H, > I[Phylogenetic Analysis]
    H, > J[Recombination Detection]
    I, > K[Lineage Classification]
    J, > K
    K, > L[Variant Reporting]
    L, > M[Vaccine Strain Matching]

Vaccine Strategies Informed by Bioinformatics

Modified Live Vaccines

Modified live virus (MLV) vaccines are the most widely used intervention against PRRSV. These vaccines are derived from attenuated field strains and provide partial protection against homologous and some heterologous challenges. A recent study demonstrated that vaccination with a PRRSV-1 MLV provided protection against a highly virulent PRRSV-1.1 Spanish strain challenge in piglets [8]. Vaccinated animals showed reduced clinical signs, lower viral loads, and improved growth performance compared to unvaccinated controls. However, MLV vaccines carry inherent risks, including reversion to virulence and recombination with field strains.

Computational Antigen Design

Bioinformatics tools are increasingly applied to design novel vaccine antigens. The nucleocapsid (N) protein of PRRSV is highly conserved and immunogenic, making it a target for vaccine development. A structure-aware generative framework called MolFoundry was developed for the de novo design of candidate binders targeting the PRRSV N protein [9]. This approach uses deep learning models trained on protein-ligand interaction data to generate small molecules or peptides with high binding affinity. Such computational methods can accelerate the discovery of antiviral compounds and vaccine adjuvants.

Reverse Vaccinology and Epitope Prediction

Reverse vaccinology involves the in silico screening of the viral proteome for potential B-cell and T-cell epitopes. For PRRSV, algorithms such as NetMHCpan, BepiPred, and IEDB are used to predict peptide sequences that can elicit protective immune responses. These predictions are based on binding affinity to swine leukocyte antigen (SLA) molecules, which are the porcine equivalents of human MHC. Epitopes that are conserved across multiple PRRSV strains are prioritized to achieve broad coverage.

Antiviral Compounds and Feed Additives

In addition to vaccines, antiviral compounds and feed additives are being explored as adjunctive control measures. Sodium copper chlorophyllin, a chlorophyll derivative, inhibits PRRSV infection through multiple antiviral mechanisms, including direct virucidal activity and interference with viral entry [10]. A novel feed additive was shown to reduce clinical symptoms and modulate the nasal and cecal microbiome in nursery pigs co-challenged with PRRSV and Streptococcus suis [11]. These findings suggest that microbiome modulation may support respiratory health during viral infection.

Ethical and Regulatory Considerations

The application of advanced biotechnologies to PRRS control raises ethical and regulatory questions. The generation of PRRS-resistant pigs through CRISPR-mediated genome editing has been achieved by disrupting the CD163 receptor, which is essential for viral entry. While biologically successful, this approach raises welfare implications and ethical challenges regarding genetic modification of food animals [12]. Regulatory frameworks for genome-edited livestock vary by jurisdiction and continue to evolve.

Future Directions

The integration of genomic surveillance with computational vaccine design holds promise for more effective PRRS control. Real-time genomic monitoring can identify emerging strains and guide the selection of vaccine seed strains. Machine learning models trained on large genomic datasets may predict antigenic drift and cross-protection profiles. Furthermore, the development of broadly neutralizing antibodies and universal vaccine platforms, such as virus-like particles and replicon vectors, remains an active area of research.

Conclusion

Porcine reproductive and respiratory syndrome virus continues to challenge the swine industry due to its genetic plasticity and complex immunobiology. Genomic surveillance using high-throughput sequencing and bioinformatics provides essential data for tracking viral evolution and informing control strategies. Computational approaches, including structure-based antigen design and epitope prediction, are accelerating the development of next-generation vaccines and antivirals. A multidisciplinary approach that integrates virology, immunology, bioinformatics, and regulatory science is required to achieve sustainable control of PRRS.

References

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[2] Chen Y, Chen Z, Huang L, et al. Adaptive mutations at lysine residues of PRRSV-2 nsp12 enable evasion of host proteasomal degradation to promote subgenomic RNA synthesis. J Virol. 2026. https://pubmed.ncbi.nlm.nih.gov/42267824/

[3] Zhu J, Guo S, Liang A, et al. Highly pathogenic porcine reproductive and respiratory syndrome virus nonstructural protein 1 interacts with TRAF6 to activate the TAK1/p38/JNK/AP-1 signaling and induce IL-1β. J Virol. 2026. https://pubmed.ncbi.nlm.nih.gov/42283627/

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[6] Cotaquispe Nalvarte RY, Legua Barrios M, De la Cruz Vásquez E, et al. Genetic variability, N-glycosylation, and recombination in sublineage 1A of Betaarterivirus americense from commercial pig farms in Lima, 2019. Front Microbiol. 2026. https://pubmed.ncbi.nlm.nih.gov/42232907/

[7] Gyurján I, Sipos-Kozma Z, Ásványi B, et al. Development and validation of an LNA-based multiplex RT-qPCR assay for differentiating Betaarterivirus europensis (PRRSV-1), Betaarterivirus americense (PRRSV-2), and the highly pathogenic L8 lineage of PRRSV-2. Vet J. 2026. https://pubmed.ncbi.nlm.nih.gov/42235629/

[8] Pla H, Simon-Grifé M, Cros S, et al. Vaccination with a PRRSV-1 modified live vaccine provides protection against a highly virulent PRRSV-1.1 Spanish strain challenge in piglets. Virology. 2026. https://pubmed.ncbi.nlm.nih.gov/42259180/

[9] Hao J, Jin W. MolFoundry: A Structure-Aware Generative Framework for De Novo Design of PRRSV Nucleocapsid Candidate Binders. ACS Omega. 2026. https://pubmed.ncbi.nlm.nih.gov/42255597/

[10] Wang X, Zhang J, Rui L, et al. Sodium Copper Chlorophyllin Inhibits Porcine Reproductive and Respiratory Syndrome Virus Infection Through Multiple Antiviral Mechanisms. Transbound Emerg Dis. 2026. https://pubmed.ncbi.nlm.nih.gov/42253323/

[11] Tran HT, Mercado AJ, Lahoti MM, et al. Effects of a novel feed additive on clinical symptoms and the nasal and cecal microbiome in nursery pigs challenged with PRRSV and Streptococcus suis. Transl Anim Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42211862/

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