Recombinant African swine fever virus Protein MGF 110-11L (War-021)

What is the molecular structure of recombinant ASFV MGF 110-11L protein?

Recombinant ASFV MGF 110-11L protein (War-021) is derived from the African swine fever virus isolate Warthog/Namibia/Wart80/1980 and can be expressed in E. coli expression systems . The protein features highly conserved central cysteine-rich domains with a distinctive C-(X)2-C-(X)2-C motif that resembles thioredoxin motifs found in lumenal ER thioreductase enzymes . This structural characteristic suggests the protein functions in oxidizing environments such as the endoplasmic reticulum lumen. The cysteine motif shares homology with bovine posterior pituitary peptides, indicating potential disulfide bond formation capabilities .

Where does MGF 110-11L localize within infected cells?

MGF 110-11L, like other MGF 110 family proteins, contains C-terminal ER retention motifs that direct its localization within the cell's secretory pathway. While some MGF 110 family members (such as pY118L) contain the classical KDEL ER retention sequence, others (like pXP124L) contain a homologous KEDL motif . The retention of MGF 110 proteins in the ER and associated compartments is likely functionally significant for viral replication. Research suggests these proteins may facilitate recruitment of ER cisternae into virus assembly sites, as immunogold electron microscopy has shown pXP124L localizing to assembling virions and membranous material within cytoplasmic virus factories .

How conserved is MGF 110-11L across different ASFV isolates?

MGF 110-11L shows conservation patterns similar to other MGF 110 family members. Analysis of the related MGF-110-9L protein demonstrated high conservation across African, European, and Caribbean pathogenic virus isolates, with only a few isolates featuring a truncated C-terminus . The MGF 110 family as a whole shows varying degrees of conservation, with MGF 110-1L being the only member present in all ASFV isolates . Serial passaging of ASFV in tissue culture often causes the loss of members of the MGF 110 family, suggesting possible adaptation mechanisms .

What is the role of MGF 110-11L in ASFV pathogenesis and virulence?

Recent gene deletion studies have revealed valuable insights into MGF 110-11L's role in virulence. When the MGF 110-11L gene was deleted using CRISPR/Cas9 technology from the Lv17/WB/Rie1 strain, the resulting mutant virus showed reduced pathogenicity compared to the parental strain, while still inducing immunity in vaccinated animals . This finding suggests MGF 110-11L contributes to ASFV virulence. Interestingly, the functions of MGF 110 family members appear to differ, as deletion of MGF 110-9L similarly resulted in partial attenuation, while deletion of MGF 110-1L did not affect virulence . These comparative results highlight the unique contributions of individual MGF 110 genes to ASFV's pathogenic properties.

How does MGF 110-11L interact with host cellular machinery?

MGF 110-11L, like other MGF 110 family proteins, likely interacts with components of the host endoplasmic reticulum and secretory pathway. The protein's structural features suggest potential roles in protein folding or disulfide bond regulation in the ER, similar to the functions of ER resident proteins with similar motifs such as ERp57, protein disulfide isomerase (PDI), and Ero1-Lα . Some MGF 110 family members may affect the ER's capacity to synthesize proteins involved in cytokine production or antigen presentation, potentially modulating host immune responses . Additionally, the presence of these proteins in the ER could influence the trafficking of resident TGN proteins, affecting cellular secretory functions .

What are the temporal expression dynamics of MGF 110-11L during ASFV infection?

While specific data on MGF 110-11L expression kinetics is limited in the provided search results, related MGF 110 family members like MGF-110-9L show early expression patterns during viral replication. Studies of MGF-110-9L demonstrated mRNA expression patterns similar to the early viral protein p30, with expression detectable from approximately 3 hours post-infection (h.p.i.) . This contrasts with late viral proteins like p72, which appears around 10 h.p.i. The early expression timing suggests MGF 110 proteins may be involved in establishing favorable conditions for viral replication rather than in later assembly processes. Members of MGF 110 are highly expressed at both mRNA and protein levels during infection with various ASFV isolates, including BA71V and OURT88/3 .

How can recombinant MGF 110-11L protein be effectively expressed and purified?

Recombinant ASFV MGF 110-11L protein can be efficiently expressed in E. coli expression systems as demonstrated with the War-021 variant (Uniprot ID: P0C9J2) . For optimal expression, researchers should consider the following methodology:

• Clone the MGF 110-11L gene sequence into an appropriate prokaryotic expression vector

• Transform the vector into E. coli expression strain optimized for recombinant protein production

• Induce protein expression under controlled conditions

• Perform cell lysis and initial purification through affinity chromatography

• Conduct secondary purification steps (e.g., ion exchange, size exclusion chromatography)

• Verify protein identity through Western blotting and mass spectrometry

• Assess protein folding and functionality through activity assays

Careful attention should be paid to solubility, as the hydrophobic signal sequences and cysteine-rich domains may affect proper folding in bacterial systems.

What CRISPR/Cas9 design strategies are effective for MGF 110-11L gene deletion studies?

CRISPR/Cas9-mediated homologous recombination has been successfully employed to generate MGF 110-11L deletion mutants. The following methodology has proven effective :

• Design a recombination cassette containing:

  • Left homologous arm (~1100 bp)

  • Reporter gene (e.g., eGFP) under control of a viral promoter (e.g., p72)

  • Right homologous arm (~1100 bp)

• Assemble the cassette into an appropriate transfer plasmid (e.g., pUC19)

• Design guide RNAs (gRNAs) targeting sequences flanking the MGF 110-11L gene

• Infect macrophages (e.g., porcine alveolar macrophages) with the parent virus strain

• Transfect infected cells with the transfer plasmid and gRNA plasmids using appropriate transfection reagents

• Incubate transfected cells and collect virus progeny

• Screen for recombinant viruses expressing the reporter gene

• Isolate and verify the deletion mutant through PCR and sequencing

This approach facilitates precise deletion of the target gene while minimizing off-target effects .

How can researchers effectively compare functional differences between MGF 110 family members?

To systematically compare functional differences between MGF 110 family members, researchers should consider a multi-faceted experimental approach:

• Sequence and phylogenetic analysis:

  • Perform comparative sequence analysis of all MGF 110 family members

  • Identify conserved motifs and divergent regions

  • Construct phylogenetic trees to establish evolutionary relationships

• Expression profiling:

  • Quantify temporal expression patterns of different MGF 110 genes during infection

  • Compare mRNA and protein expression levels across multiple viral isolates

  • Identify correlations between expression patterns and virus virulence

• Subcellular localization studies:

  • Create fluorescently tagged versions of each MGF 110 protein

  • Perform co-localization studies with markers for different cellular compartments

  • Identify unique or shared localization patterns

• Gene deletion studies:

  • Generate single and combined deletion mutants for MGF 110 genes

  • Assess the effects on viral replication in vitro and virulence in vivo

  • Identify complementation patterns between family members

• Host interaction analysis:

  • Use immunoprecipitation followed by mass spectrometry to identify host binding partners

  • Compare interactomes between different MGF 110 proteins

  • Validate key interactions through functional assays

This systematic approach would help delineate both overlapping and unique functions of MGF 110 family members in ASFV biology and pathogenesis .

How can MGF 110-11L be utilized in ASFV vaccine development?

MGF 110-11L modifications show promising applications in ASFV vaccine development. The deletion of MGF 110-11L using CRISPR/Cas9 from virulent strains has produced mutants with reduced pathogenicity while maintaining immunogenicity . Key methodological considerations for utilizing MGF 110-11L in vaccine development include:

• Rational attenuation approach:

  • Delete MGF 110-11L from naturally occurring attenuated strains to further reduce virulence

  • Combine MGF 110-11L deletion with modifications to other virulence factors

  • Assess safety through dose escalation studies in target species

• Immunogenicity evaluation:

  • Measure antibody responses to key protective antigens

  • Assess T-cell responses to determine cell-mediated immunity

  • Challenge vaccinated animals with virulent strains to determine protection efficacy

• Stability assessment:

  • Verify genetic stability of the deletion over multiple passages

  • Ensure consistent attenuation phenotype across production batches

  • Monitor for potential compensatory mutations in related genes

Deletion mutants targeting MGF 110-11L could serve as potentially safer live-attenuated vaccine candidates by removing genes with "unique and uncharted characteristics" while maintaining protective immunogenicity .

What experimental approaches can reveal the molecular mechanisms of MGF 110-11L in ER reorganization?

Understanding how MGF 110-11L affects ER morphology and function requires sophisticated experimental approaches:

• High-resolution imaging techniques:

  • Implement super-resolution microscopy to visualize ER morphological changes

  • Use transmission electron microscopy to observe ultrastructural alterations

  • Apply correlative light and electron microscopy to link protein localization with structural changes

• Biochemical analysis of ER functions:

  • Measure protein folding capacity using reporter substrates

  • Assess ER stress responses through XBP1 splicing and ATF6 cleavage assays

  • Quantify calcium homeostasis using fluorescent calcium indicators

• Proteomics approaches:

  • Perform differential proteomics on isolated ER fractions from infected versus uninfected cells

  • Identify changes in ER resident protein composition and post-translational modifications

  • Map protein interaction networks altered by MGF 110-11L expression

• Live-cell dynamics:

  • Track ER membrane dynamics using fluorescent markers

  • Measure protein mobility within the ER using FRAP (Fluorescence Recovery After Photobleaching)

  • Monitor trafficking between ER and other compartments using cargo reporters

Since MGF 110 proteins may facilitate recruitment of ER cisternae into virus assembly sites, these approaches would help elucidate the molecular mechanisms behind this process and potentially identify targets for therapeutic intervention .

How do comparative studies between attenuated and virulent ASFV strains inform MGF 110-11L function?

Comparative studies between attenuated and virulent ASFV strains provide crucial insights into MGF 110-11L function through:

• Genomic comparative analysis:

  • Profile the presence/absence of MGF 110-11L across strains with varying virulence

  • Identify natural mutations or truncations in MGF 110-11L sequences

  • Correlate genomic variations with phenotypic differences

• Transcriptomic analysis:

  • Compare MGF 110-11L expression patterns between attenuated and virulent strains

  • Analyze co-expressed gene networks to identify functional associations

  • Identify host response differences triggered by different strains

• Functional reconstitution experiments:

  • Introduce MGF 110-11L from virulent strains into attenuated strains lacking the gene

  • Assess changes in virulence, replication efficiency, and host responses

  • Identify specific domains responsible for virulence-associated functions

Several naturally attenuated ASFV strains lack MGF 110 genes. For example, the Estonia 2014 strain is missing thirteen MGF 110 (-1L-14L) family genes, while the OURT 88/3 strain lacks the MGF 110-4L-7L and -12-13L genes . These natural deletion patterns provide valuable starting points for understanding the contributions of specific MGF 110 family members to virulence and adaptation to different hosts .

What are the major challenges in studying MGF 110-11L protein expression and function?

Researchers face several technical challenges when investigating MGF 110-11L:

• Protein expression obstacles:

  • The cysteine-rich domains may form aberrant disulfide bonds in prokaryotic expression systems

  • Transmembrane or hydrophobic regions can lead to insolubility and aggregation

  • Post-translational modifications present in mammalian cells may be absent in E. coli systems

• Functional redundancy issues:

  • The presence of multiple MGF 110 family members may mask phenotypes in single-gene studies

  • Compensatory mechanisms may activate when individual genes are deleted

  • Cross-reactivity of antibodies between family members can complicate interpretation

• Methodological approaches:

  • Consider eukaryotic expression systems for proteins requiring proper folding and modification

  • Implement combinatorial gene deletion strategies to address redundancy

  • Develop highly specific detection methods to distinguish between family members

  • Create domain-specific mutations rather than complete gene deletions to identify critical functional regions

Since MGF 110 proteins show varying degrees of conservation and some isolates feature truncated versions , careful consideration of the specific viral strain and cell type is essential for interpreting experimental results.

How can researchers distinguish between direct effects of MGF 110-11L and indirect consequences of viral infection?

Distinguishing direct MGF 110-11L effects from general infection consequences requires:

• Isolated expression systems:

  • Express MGF 110-11L alone in relevant cell types without other viral components

  • Create inducible expression systems to control timing and expression levels

  • Compare phenotypes between MGF 110-11L expression and full viral infection

• Comparison with deletion mutants:

  • Perform parallel analyses of wild-type virus and MGF 110-11L deletion mutants

  • Identify phenotypes that differ specifically due to the presence/absence of MGF 110-11L

  • Conduct complementation studies by reintroducing the gene to confirm specificity

• Temporal analysis:

  • Monitor cellular changes in relation to MGF 110-11L expression timing

  • Compare with early-appearing effects versus late infection effects

  • Use time-course experiments with synchronized infection

• Protein-protein interaction studies:

  • Identify direct binding partners of MGF 110-11L using proximity labeling techniques

  • Validate interactions through co-immunoprecipitation and functional assays

  • Map interaction networks to specific cellular pathways

This multi-faceted approach helps separate direct MGF 110-11L functions from general viral effects or consequences of other viral proteins .

How does MGF 110-11L function compare with other multigene family proteins in ASFV?

A systematic comparison reveals distinct functional profiles among ASFV multigene families:

While MGF 360 and 505 family members are better characterized for their roles in evading host type I interferon responses, the MGF 110 family appears more involved in cellular compartment organization and potentially viral morphogenesis . The varying effects of gene deletions within the same family highlight the specialized functions evolved by these paralogs despite their sequence similarities.

What structural and functional homologies exist between MGF 110-11L and host proteins?

MGF 110-11L shares important structural and functional elements with host proteins:

• Thioredoxin-like motifs:

  • MGF 110-11L contains C-(X)2-C sequences resembling thioredoxin motifs found in ER thioreductase enzymes

  • These similarities suggest potential functions in redox regulation or protein folding within the ER

• Metal-binding structures:

  • The C-(X)2-C-(X)2-C sequence resembles iron cluster protein motifs

  • This structural element is also found in Ero1-Lα, involved in disulfide bond formation in the ER

• ER retention signals:

  • While not identical to MGF 110-11L, related family members contain KDEL or KEDL motifs

  • These motifs function similarly to host ER retention signals, controlling protein localization

• Bovine posterior pituitary peptide homology:

  • The cysteine motif shares homology with bovine posterior pituitary peptides

  • This suggests similar disulfide bond formation patterns between viral and host proteins

These homologies indicate MGF 110-11L may have evolved to mimic or manipulate host cellular machinery, particularly within the secretory pathway . Such viral mimicry of host proteins often serves to evade immune detection or hijack cellular processes.