Recombinant African swine fever virus Protein MGF 360-10L (Ken-033)

What is the role of MGF 360-10L in ASFV pathogenesis?

MGF 360-10L functions as a crucial virulence factor in African swine fever virus (ASFV) pathogenesis by specifically inhibiting the host's innate immune response. The protein significantly inhibits interferon (IFN)-β-triggered STAT1/2 promoter activation and the production of downstream IFN-stimulated genes (ISGs), which are essential components of the antiviral response .

Mechanistically, MGF 360-10L primarily targets Janus kinase 1 (JAK1) and mediates its degradation in a dose-dependent manner, disrupting the JAK-STAT signaling pathway critical for antiviral defense. The protein also mediates K48-linked ubiquitination of JAK1 at specific lysine residues (K245 and K269) by recruiting the E3 ubiquitin ligase HERC5 (HECT and RLD domain-containing E3 ubiquitin protein ligase 5) . This targeted degradation of JAK1 represents a sophisticated viral evasion strategy that contributes significantly to ASFV pathogenicity.

How can researchers produce recombinant MGF 360-10L protein for experimental studies?

For experimental studies, researchers can produce recombinant MGF 360-10L protein using prokaryotic expression systems. The standard methodology involves:

• Gene synthesis or cloning of the MGF 360-10L sequence (amino acids 1-356) from reference isolates such as Pig/Kenya/KEN-50/1950 (Ken-033)

• Subcloning into an appropriate expression vector with histidine or other affinity tags

• Transformation into E. coli expression strains optimized for protein production

• Induction of protein expression using IPTG or other inducers

• Cell lysis and protein purification using affinity chromatography

• Quality control through SDS-PAGE and Western blotting

• Endotoxin removal for immunological studies

• Functional validation through in vitro assays measuring JAK-STAT pathway inhibition

For optimal results, researchers should consider codon optimization for E. coli expression and evaluate protein solubility during purification procedures, as viral proteins can often form inclusion bodies requiring denaturation and refolding protocols.

What detection and quantification methods are appropriate for studying MGF 360-10L expression during ASFV infection?

To study MGF 360-10L expression during ASFV infection, researchers can employ several complementary approaches:

mRNA detection and quantification:

• RT-qPCR using MGF 360-10L-specific primers for transcript quantification

• RNAseq for transcriptomic profiling and relative expression analysis

Protein detection and quantification:

• Western blotting using antibodies against MGF 360-10L or epitope tags in recombinant viruses

• Immunofluorescence microscopy to visualize subcellular localization

• Immunoprecipitation to study protein-protein interactions

For viral mutant analysis:

• PCR and Sanger sequencing for confirming gene deletion or modification

• qPCR for viral genome quantification in samples from infected animals or cell cultures

• Hemadsorption assays (HAD50) for viral titer determination in infected cells

When analyzing clinical samples, it's essential to use OIE-listed ASFV-specific qPCR with appropriate internal controls to ensure reliable detection and quantification .

How does MGF 360-10L interact with the host ubiquitin-proteasome system to degrade JAK1?

MGF 360-10L employs a sophisticated mechanism to exploit the host's ubiquitin-proteasome system for immune evasion. Recent studies have revealed the precise molecular interactions:

• Target recognition: MGF 360-10L directly interacts with JAK1, a key component of the IFN signaling pathway

• Recruitment of E3 ligase: The viral protein specifically recruits HERC5 (HECT and RLD domain-containing E3 ubiquitin protein ligase 5) to form a protein complex with JAK1

• K48-linked ubiquitination: This complex mediates K48-linked polyubiquitination of JAK1 specifically at lysine residues 245 and 269

• Proteasomal degradation: The ubiquitinated JAK1 is subsequently recognized and degraded via the 26S proteasome pathway

This mechanism explains why MGF 360-10L expression increases JAK1 ubiquitination in both overexpression systems (HEK293T cells) and during viral infection (ASFV-10L-GFP in PAMs). Importantly, deletion mutants (ASFV-Δ10L) show significantly reduced ability to induce JAK1 ubiquitination compared to wild-type or reconstructed viruses .

Researchers investigating this interaction should design experiments that:

• Use proteasome inhibitors (e.g., MG132) to confirm the degradation pathway

• Employ site-directed mutagenesis of JAK1 K245 and K269 to validate ubiquitination sites

• Perform co-immunoprecipitation studies to confirm the MGF 360-10L-HERC5-JAK1 complex formation

• Use RNAi to knockdown HERC5 and assess effects on JAK1 degradation during infection

What are the potential applications of MGF 360-10L deletion mutants in vaccine development?

MGF 360-10L deletion mutants represent promising candidates for attenuated ASFV vaccine development, though significant challenges remain. The research considerations include:

Advantages of MGF 360-10L deletion approach:

• Deletion significantly reduces viral virulence in pigs

• Deleted strains show impaired replication compared to wild-type virus

• Deletion results in enhanced expression of IFN-stimulated genes, potentially improving immune response

• Infected animals survive without showing typical ASF clinical signs

Experimental Challenges:

• Single MGF 360-10L deletion may not provide sufficient attenuation for safe vaccination

• Combined deletions (e.g., MGF 360-10L and MGF505-7R) show greater attenuation but may still fail to provide protection against parent strain challenge

Research Design Considerations:

• Evaluate multiple gene deletion combinations to optimize attenuation/immunogenicity balance

• Measure immune response parameters (antibody production, T-cell activation)

• Conduct challenge studies with heterologous ASFV strains

• Assess virus shedding and transmission potential of attenuated strains

• Monitor genetic stability of deletion mutants over multiple passages

A significant finding from recent research shows that while a double deletion mutant (ASFV-Δ10L/Δ7R) significantly reduced virulence in pigs with all animals surviving the observation period without clinical signs, it failed to induce protective immunity against challenge with the parent strain . RNA-seq analysis revealed that despite upregulated expression of innate immune factors compared to wild-type infection, this response was insufficient to provide protection .

How can phylogenetic analysis of MGF 360-10L sequences contribute to ASFV molecular epidemiology?

MGF 360-10L sequences provide valuable genetic markers for ASFV molecular epidemiology due to their variability across different isolates. Methodological approaches include:

• Sequence acquisition and alignment:

  • PCR amplification and Sanger sequencing of the MGF 360-10L locus from field isolates

  • Multiple sequence alignment of orthologous genes using amino acid-based alignment followed by back-conversion to nucleotide alignment

  • Manual curation to ensure coding sequences remain in frame

• Phylogenetic analysis:

  • Maximum likelihood phylogenetic tree construction based on MGF 360-10L sequences

  • Calculation of non-synonymous (dN) and synonymous (dS) substitution rates using the Nei & Gojobori model

  • Likelihood ratio tests (LRT) of selection pressures acting on individual sites using PAML with site-specific models

• Geographical tracing:

  • Identification of MGF 360-10L sequence signatures unique to specific geographical regions

  • Tracking of viral spread patterns based on genetic variations

This approach offers several advantages for outbreak investigation:

• MGF 360-10L shows sufficient sequence variation to discriminate between isolates from different geographical regions

• Analysis of selection pressure on MGF genes provides insights into virus adaptation to new hosts and environments

• Phylogenetic data can help identify the source of new outbreaks and trace transmission chains

For comprehensive molecular epidemiology, researchers should combine MGF 360-10L analysis with sequencing of other variable regions (such as MGF-505-9R and I267L) to improve resolution power .

What cell culture systems are optimal for studying MGF 360-10L function?

For studying MGF 360-10L function, researchers should consider multiple cell systems depending on their specific research objectives:

Primary cells:

• Porcine alveolar macrophages (PAMs): The gold standard for ASFV studies as they represent natural target cells for the virus. PAMs support productive replication of field isolates and are ideal for studying MGF 360-10L in the context of authentic virus-host interactions .

• Peripheral blood monocytes: Can be differentiated into macrophages and provide an alternative when PAMs are unavailable.

Cell lines:

• HEK293T cells: Useful for protein overexpression studies, particularly for investigating protein-protein interactions and ubiquitination studies involving MGF 360-10L .

• Vero cells: Support growth of some adapted ASFV strains and can be used for virus production.

Experimental approaches based on cell system:

• For PAMs:

  • Infection with wild-type ASFV and MGF 360-10L deletion mutants

  • Measurement of viral replication by HAD50 assays

  • Analysis of IFN-stimulated gene expression by RT-qPCR

  • Protein-protein interaction studies via co-immunoprecipitation

• For HEK293T cells:

  • Transfection with MGF 360-10L expression constructs

  • Dual-luciferase reporter assays for STAT1/2 promoter activation

  • Ubiquitination assays to study JAK1 modification

  • Protein stability assays using cycloheximide chase

The choice between these systems should be guided by experimental objectives, with PAMs providing the most physiologically relevant context but presenting greater technical challenges compared to established cell lines.

What are the key considerations for designing gene deletion experiments targeting MGF 360-10L?

When designing gene deletion experiments targeting MGF 360-10L, researchers should consider several methodological factors to ensure successful outcomes:

Vector design considerations:

• Homologous recombination arms: Include 500-1000 bp homologous sequences flanking the MGF 360-10L gene

• Selection markers: Incorporate fluorescent reporter genes (e.g., GFP) for efficient identification of recombinant viruses

• Verification elements: Design PCR primer binding sites for confirming deletion

Experimental workflow:

• Vector construction:

  • PCR amplification of homologous regions

  • Assembly into a recombination vector with selection markers

  • Verification by sequencing

• Virus generation:

  • Transfection of vector into ASFV-infected cells (typically PAMs)

  • Identification of recombinant viruses by fluorescence microscopy

  • Plaque purification through limiting dilution

• Verification methods:

  • PCR confirmation of MGF 360-10L deletion

  • Sanger sequencing of junction regions

  • Western blot to confirm absence of MGF 360-10L protein

  • Next-generation sequencing to verify genomic integrity

• Functional characterization:

  • Growth kinetics compared to parental virus

  • Analysis of IFN response gene expression

  • JAK1 degradation and ubiquitination assays

  • In vivo virulence assessment

Potential pitfalls and solutions:

• Difficulty in isolating viable deletion mutants if the gene is essential
  Solution: Consider conditional deletion approaches or complementing cell lines

• Genomic instability of recombinant viruses
  Solution: Perform extensive passage stability testing

• Secondary mutations affecting phenotype
  Solution: Generate revertant viruses to confirm phenotype is due to target gene deletion

Studies combining MGF 360-10L deletion with other genes (e.g., MGF505-7R) have shown enhanced attenuation, suggesting potential synergistic effects that should be considered in experimental design .

How should researchers design RNA sequencing experiments to study host response to MGF 360-10L deletion mutants?

RNA sequencing experiments to study host responses to MGF 360-10L deletion mutants require careful planning:

Experimental design framework:

• Cell/tissue selection:

  • Primary porcine alveolar macrophages (PAMs) for in vitro studies

  • Multiple tissues (spleen, lymph nodes, liver) from infected animals for in vivo studies

• Treatment groups:

  • Mock-infected controls

  • Wild-type ASFV infection

  • MGF 360-10L deletion mutant infection

  • Complemented mutant (for validation)

• Time points:

  • Early (4-8 hours post-infection): Capture immediate innate immune responses

  • Intermediate (24 hours): Assess viral replication impact

  • Late (48-72 hours): Evaluate adaptive immune activation

• Sample preparation:

  • Total RNA extraction with verification of RNA integrity (RIN > 8)

  • rRNA depletion or poly(A) selection depending on research focus

  • Library preparation with unique molecular identifiers to control for PCR bias

  • Paired-end sequencing with sufficient depth (>30 million reads per sample)

• Bioinformatic analysis pipeline:

  • Quality control and adapter trimming

  • Alignment to both host and viral genomes

  • Differential expression analysis between treatment groups

  • Pathway enrichment analysis focusing on immune pathways

  • Integration with proteomics data when available

Key considerations for data interpretation:

Recent RNA-seq analyses comparing recombinant ASFV-Δ10L/Δ7R to parental strains revealed that while the mutant induced higher expression of natural immune factors, this response was insufficient to provide immune protection . When designing similar experiments, researchers should:

• Focus on JAK-STAT pathway components and IFN-stimulated genes

• Analyze temporal dynamics of immune response genes

• Look for signatures of effective vs. ineffective immune responses

• Consider both magnitude and timing of differential gene expression

• Validate key findings using RT-qPCR and protein-level assays

This approach will provide insights into why certain attenuated strains fail to confer protection despite reduced virulence, informing future vaccine development strategies.

How does MGF 360-10L function compare with other ASFV immune evasion proteins?

ASFV encodes multiple immune evasion proteins that target different aspects of host immunity. Comparing MGF 360-10L with other viral proteins reveals both unique and overlapping mechanisms:

Methodological approaches for comparative analysis:

• Protein interaction studies:

  • Comparative proteomics to identify binding partners

  • Co-immunoprecipitation followed by mass spectrometry

  • Yeast two-hybrid screening

• Pathway inhibition assays:

  • Luciferase reporter systems for different immune pathways

  • Phosphorylation status of pathway components

  • Transcriptional profiling of pathway-specific genes

• Deletion mutant phenotyping:

  • Single vs. multiple gene deletions

  • In vitro growth kinetics

  • In vivo virulence and immune response

What are the evolutionary patterns and selection pressures acting on MGF 360-10L across different ASFV isolates?

MGF 360-10L shows distinct evolutionary patterns reflecting its importance in ASFV pathogenesis:

Selection pressure analysis:

Evolutionary studies applying likelihood ratio tests (LRT) of selection pressures on ASFV genes have identified sites under positive selection in MGF gene families . For MGF 360-10L:

• Diversifying selection: Certain amino acid positions show elevated non-synonymous to synonymous substitution ratios (dN/dS > 1), indicating positive selection

• Structural correlations: Positively selected sites often map to predicted secondary structures that may interact with host factors

• Genotype associations: Selection patterns differ between ASFV genotypes, suggesting adaptation to different host environments

Comparative genomic approaches:

When studying MGF 360-10L evolution, researchers should:

• Perform multiple sequence alignment of orthologous genes across ASFV isolates

• Calculate population prevalence frequencies and pairwise amino acid divergence

• Map variable regions to protein functional domains

• Compare with other MGF family members to identify paralogue-specific patterns

Phylogenetic utility:

MGF 360-10L sequences have proven valuable for phylogenetic analysis of ASFV isolates, allowing researchers to track virus spread and evolution . The gene shows sufficient variability to differentiate isolates from different geographical regions, making it useful for molecular epidemiology studies.

A maximum likelihood phylogenetic tree based on MGF 360-10L sequences can distinguish between isolates from different regions, as demonstrated in studies of ASFV isolates from the Kaliningrad region of Russia between 2017 and 2019 . This approach complements whole-genome sequencing for examining evolutionary changes in ASFV.

How does the recombinant MGF 360-10L protein from the Kenya/KEN-50/1950 isolate differ from contemporary ASFV strains?

The recombinant MGF 360-10L protein derived from the historical Kenya/KEN-50/1950 isolate (Ken-033) differs from contemporary ASFV strains in several important aspects:

Sequence variation analysis:

• Amino acid substitutions: Comparative sequence analysis between historical Ken-033 and contemporary isolates (particularly Genotype II viruses circulating in Europe and Asia) reveals specific substitutions that may affect protein function

• Functional domains: Variations typically cluster in regions corresponding to host interaction interfaces

• Conservation level: The core functional regions mediating JAK1 targeting remain highly conserved, suggesting functional constraints on these domains

Functional comparisons:

When studying functional differences between historical and contemporary MGF 360-10L proteins, researchers should:

• Compare JAK1 binding affinity using co-immunoprecipitation assays

• Assess relative efficiency of JAK1 degradation in cellular assays

• Measure impact on IFN-stimulated gene expression

• Evaluate contribution to virulence in experimental infections

Experimental considerations:

The recombinant MGF 360-10L protein from Kenya/KEN-50/1950 produced in E. coli systems (as described in commercial sources ) represents a valuable tool for comparative studies. Researchers can use this protein to:

• Generate antibodies recognizing conserved epitopes across ASFV strains

• Perform structure-function analyses through site-directed mutagenesis

• Develop screening assays for inhibitors targeting conserved functional domains

• Create reference materials for quantitative assays

Understanding these differences is particularly important for vaccine development efforts, as historical isolates like Ken-033 have been used as the basis for attenuated vaccine candidates. The functional conservation or divergence of immune evasion proteins like MGF 360-10L between historical and contemporary strains will impact cross-protection efficacy.

What are the recommended protocols for studying protein-protein interactions involving MGF 360-10L?

To study protein-protein interactions involving MGF 360-10L, researchers should employ multiple complementary approaches:

Co-immunoprecipitation (Co-IP):

• Cell-based approach:

  • Express tagged MGF 360-10L in HEK293T cells or infect PAMs with ASFV

  • Lyse cells under non-denaturing conditions

  • Immunoprecipitate with anti-tag antibodies or specific MGF 360-10L antibodies

  • Analyze by Western blot for interacting partners (JAK1, HERC5)

• Recombinant protein approach:

  • Express and purify recombinant MGF 360-10L with affinity tags

  • Incubate with cell lysates containing potential interacting partners

  • Pull down complexes and analyze by mass spectrometry

Proximity Ligation Assay (PLA):

• Visualize protein interactions in situ with single-molecule sensitivity

• Particularly valuable for confirming MGF 360-10L-JAK1 interactions in infected cells

Bimolecular Fluorescence Complementation (BiFC):

• Fuse potential interacting proteins to complementary fragments of fluorescent proteins

• Interaction brings fragments together, restoring fluorescence

• Useful for confirming interactions and determining subcellular localization

Yeast Two-Hybrid (Y2H) Screening:

• Screen for novel interaction partners using MGF 360-10L as bait

• Validate hits using methods above

Pull-down assays for ubiquitination studies:

• Express HA-tagged ubiquitin along with MGF 360-10L in cells

• Treat with proteasome inhibitor (MG132)

• Immunoprecipitate JAK1 and blot for HA to detect ubiquitination

• Use ubiquitin mutants (K48R, K63R) to determine linkage type

Studies have successfully employed these approaches to demonstrate that MGF 360-10L mediates JAK1 degradation by recruiting the E3 ubiquitin ligase HERC5, leading to K48-linked polyubiquitination of JAK1 at lysine residues 245 and 269 .

What are the best approaches for quantifying the effects of MGF 360-10L on interferon-stimulated gene expression?

To quantify the effects of MGF 360-10L on interferon-stimulated gene (ISG) expression, researchers should employ multiple complementary approaches:

RNA-level quantification methods:

• RT-qPCR analysis:

  • Target genes: ISG15, ISG56, MX1, and other key ISGs

  • Experimental design:

    • Compare wild-type ASFV vs. MGF 360-10L deletion mutants

    • Include IFN-β treatment conditions with and without viral infection

    • Use appropriate housekeeping genes (GAPDH, β-actin) as internal controls

  • Data analysis: Apply ΔΔCt method with normalization to mock-infected controls

• Transcriptomics approaches:

  • RNA-seq to assess global ISG expression patterns

  • NanoString technology for targeted analysis of immune response genes

  • Time-course experiments to capture dynamic changes in ISG expression

Protein-level quantification:

• Western blot analysis:

  • Detect ISG protein levels (ISG15, MX1) in cell lysates

  • Measure phosphorylation of STAT1/2 as indicators of pathway activation

  • Quantify results using densitometry with normalization to loading controls

• Flow cytometry:

  • Intracellular staining for ISG proteins

  • Single-cell analysis to assess population heterogeneity in response

  • Multi-parameter analysis to correlate with viral protein expression

Reporter assay systems:

• Luciferase reporter assays:

  • Transfect cells with ISRE-luciferase reporter constructs

  • Co-express increasing amounts of MGF 360-10L

  • Stimulate with IFN-β and measure luminescence

  • Include Renilla luciferase for normalization

Experimental data from published studies demonstrate that overexpression of MGF 360-10L significantly inhibits the mRNA levels of ISG15, ISG56, and MX1 induced by IFN-β, but does not affect GBP1 expression induced by IFN-γ . Similarly, infection with MGF 360-10L deletion mutants (ASFV-Δ10L) significantly increases ISG15 and ISG56 expression compared to wild-type virus , confirming the role of this viral protein in suppressing interferon responses.

What in vivo models are most appropriate for evaluating the role of MGF 360-10L in ASFV pathogenesis?

For evaluating the role of MGF 360-10L in ASFV pathogenesis, several in vivo models can be employed, each with specific advantages and limitations:

Domestic pig models:

The domestic pig (Sus scrofa domesticus) represents the gold standard for ASFV pathogenesis studies, as it is the natural host with direct relevance to field outbreaks.

Experimental design considerations:

• Animal selection:

  • Age: Typically 8-12 week-old pigs

  • Health status: Specific pathogen-free (SPF)

  • Group size: Minimum 5-6 animals per group for statistical power

• Infection protocols:

  • Route: Intramuscular injection (standard) or oronasal (natural)

  • Dose: 10^4 HAD50 is commonly used for MGF 360-10L deletion mutant studies

  • Controls: Include wild-type virus, mock-infected, and when possible, revertant viruses

• Assessment parameters:

  • Clinical monitoring: Temperature, clinical score, food intake

  • Virological parameters: Viremia, viral load in tissues

  • Immunological parameters: Cytokine levels, ISG expression

  • Pathological assessment: Gross and histopathological lesions

Published studies have demonstrated that pigs infected with MGF 360-10L deletion mutants show reduced clinical signs compared to wild-type virus infection . A combined deletion of MGF 360-10L and MGF505-7R resulted in significantly reduced virulence with all animals surviving the observation period without showing ASF-related clinical signs .

Alternative models:

Wild boar:

• Represents another natural host with potentially different disease dynamics

• Useful for transmission studies and wildlife reservoir aspects

Cell-based systems:

• Precision-cut lung slices (PCLS) from pigs

• 3D organoid cultures derived from porcine tissues

• Ex vivo whole blood assays

When designing in vivo experiments, researchers should:

• Consider ethical implications and implement appropriate refinement methods

• Include detailed immunological monitoring to correlate with protection

• Plan for sequential sampling to understand disease progression

• Ensure sufficient statistical power while minimizing animal use

• Include appropriate controls including single gene deletions when studying combination mutants

These approaches provide a comprehensive understanding of how MGF 360-10L contributes to ASFV pathogenesis and can inform rational attenuation strategies for vaccine development.