dur3-1 Antibody

What is DUR31 in Candida albicans and why is it significant?

DUR31 (orf19.6656) is a novel transporter in Candida albicans that has been identified as having no human homologue, making it a potentially valuable target for antifungal therapies. This gene has been incorrectly annotated in some databases, where it has been named DUR3 based on sequence similarities to Saccharomyces cerevisiae DUR3, creating a nomenclature conflict as orf19.781 has also been designated as DUR3 . Sequence analysis has confirmed that orf19.781 is actually the major urea transporter in C. albicans, while DUR31 (orf19.6656) plays more diverse roles in pathogenicity .

The significance of DUR31 lies in its multifunctional role during various stages of candidiasis. Research has demonstrated that deletion of DUR31 results in significantly reduced pathogenicity, impacting multiple infection stages including epithelial damage, endothelial damage, and immune evasion . This makes it an important target for understanding fungal virulence mechanisms and potentially developing novel antifungal strategies.

How does DUR31 contribute to different stages of Candida infection?

DUR31 contributes to multiple critical stages of Candida albicans infection:

• Oral Epithelial Damage: DUR31 is exclusively upregulated during oral infection and is required for damage to oral epithelial cells .

• Endothelial Cell Damage: During systemic infections, DUR31 is required for C. albicans to damage endothelial cells. Studies show that a dur31Δ/Δ mutant caused 83% less damage compared to wild type after 15 hours of infection and 35% less damage after 24 hours .

• Immune Evasion: DUR31 is necessary for survival when exposed to neutrophils. While 73.6% of wild type cells survived neutrophil exposure, only 43.2% of dur31Δ/Δ cells remained viable under the same conditions .

• Hyphal Formation: Although DUR31 is not required for initiating hyphal formation in liquid media, it is necessary for continued development of multicellular filamentous structures such as colonies. The dur31Δ/Δ mutant forms aberrant colonies lacking the peripheral, invasive filaments observed in wild type strains .

• Antimicrobial Peptide Resistance: Interestingly, deletion of DUR31 appears to increase resistance to the antimicrobial peptide histatin 5, suggesting DUR31 may function as an importer of this peptide .

What phenotypes are associated with DUR31 deletion in Candida albicans?

Deletion of DUR31 results in multiple phenotypic changes:

The dur31Δ/Δ mutant shows normal growth in the presence of reactive oxygen species but exhibits increased sensitivity to cell wall stress, which may partially explain its higher susceptibility to killing by neutrophils .

What are the molecular mechanisms by which DUR31 mediates host cell damage?

The molecular mechanisms by which DUR31 mediates host cell damage are not fully elucidated, but several aspects have been uncovered:

The relationship between these functions and the direct mechanism of epithelial and endothelial cell damage requires further investigation, particularly to understand if DUR31 transports specific molecules that directly mediate host cell damage.

How does DUR31 contribute to immune evasion strategies in Candida albicans?

DUR31 contributes to immune evasion in Candida albicans through multiple mechanisms:

What is the relationship between DUR31 and histatin 5 susceptibility?

The relationship between DUR31 and histatin 5 susceptibility is intriguing and somewhat counterintuitive:

• Histatin 5 Resistance: The dur31Δ/Δ mutant exhibits increased resistance to histatin 5 compared to wild type and complemented strains, suggesting that DUR31 normally makes C. albicans more susceptible to this antimicrobial peptide .

• Reduced Uptake: Using FITC-labeled histatin 5, researchers observed that fewer dur31Δ/Δ mutant cells internalized the peptide compared to wild type and complemented strains. This indicates that DUR31 likely functions as an importer of histatin 5 .

• Clinical Relevance: This relationship has interesting implications for specific clinical scenarios. For example, in HIV patients with oral candidiasis who have low histatin 5 levels, the function of DUR31 may be particularly relevant. The researchers postulated that DUR31 might function in the absence of histatin 5 in such clinical contexts .

• Mechanistic Implications: The findings suggest that histatin 5 may use DUR31 as a "Trojan horse" to enter C. albicans cells, where it can exert its antimicrobial effects. By deleting DUR31, this entry mechanism is compromised, resulting in increased resistance .

This relationship highlights the complex interactions between host defense molecules and fungal transport systems, and suggests that DUR31 may have evolved primarily for other functions (such as nutrient acquisition) but has been co-opted by the human host's antimicrobial defense system.

How can DUR31 deletion mutants be generated in Candida albicans?

DUR31 deletion mutants can be generated using PCR-based gene disruption techniques. The detailed methodology as described in the research includes:

• Background Strain Selection: Use an appropriate auxotrophic strain such as BWP17 (Arg-, His-, and Ura-auxotrophic) as the background .

• Disruption Cassette Generation:

  • Create PCR-amplified ARG4 and HIS1 disruption cassettes flanked by approximately 104 base pairs of target homology region.

  • Use primers DUR31-FG and DUR31-RG with plasmids pFA-ARG4 and pFA-HIS1 as templates .

• Sequential Transformation:

  • Perform two sequential transformations using the improved lithium-acetate method.

  • First, transform with one disruption cassette to delete one allele.

  • Then, transform with the second disruption cassette to delete the remaining allele .

• Prototrophic Strain Construction:

  • The resulting Ura-auxotrophic mutant can be rendered prototrophic for uridine.

  • Transform with NcoI-linearized plasmid CIp10, which harbors the URA3 gene.

  • This will stably integrate at the RPS10 locus .

• Verification:

  • Verify correct deletion of both alleles using colony PCR.

  • Use target gene and disruption/integration cassette flanking primers: DUR31-F1, DUR31-R1, ARG4-F1, ARG4-R1, HIS1-F1, HIS1-R1, URA3-F2 and RPF-F1 .

• Complementation (for creating dur31Δ/Δ::DUR31 strain):

  • Amplify the open reading frame of DUR31 including upstream (504 bp) and downstream (460 bp) sequences from wild type genomic DNA.

  • Use HindIII restriction site-containing primers DUR31rec-F1 and DUR31rec-R1.

  • Digest the PCR product with HindIII and purify.

  • Digest plasmid CIp10 with HindIII, dephosphorylate, and gel extract.

  • Ligate the DUR31 insert and CIp10 vector.

  • Transform into E. coli, select on ampicillin-containing medium, and re-isolate the plasmid.

  • Digest with NcoI and transform into the uridine auxotrophic C. albicans dur31Δ/Δ ura- strain.

  • Verify correct integration by PCR using primers RPF-F1 and URA3-F2 .

This methodology ensures complete deletion of both copies of DUR31 in C. albicans, which is diploid, and allows for the creation of a complemented strain to confirm phenotypic specificity.

What assays can be used to measure DUR31-dependent virulence traits?

Several assays can be employed to measure DUR31-dependent virulence traits:

• Endothelial Cell Damage Assay:

  • Grow monolayers of HUVEC endothelial cells.

  • Infect with C. albicans strains (wild type, dur31Δ/Δ, and complemented strains).

  • Co-incubate for 15 or 24 hours.

  • Measure lactate dehydrogenase (LDH) release as an indicator of host cell damage .

• Neutrophil Survival Assay:

  • Isolate human neutrophils.

  • Expose C. albicans strains to neutrophils for three hours.

  • Determine viability by plating on YPD agar and counting colony-forming units (CFUs) .

• Hyphal Formation Assay:

  • Induce hyphal formation in liquid media (e.g., YPD with 10% fetal bovine serum).

  • Observe morphology microscopically.

  • Plate on solid media such as YPS agar to assess colony morphology and invasive filament formation .

• Histatin 5 Susceptibility Assay:

  • Incubate C. albicans strains with various concentrations of histatin 5.

  • Determine survival rates by plating and CFU counting.

  • For uptake studies, use FITC-labeled histatin 5 (30 μM) and visualize internalization using fluorescence microscopy after 15 minutes of incubation at 30°C .

• In Vivo Virulence Assay:

  • Use a mouse model of hematogenously disseminated candidiasis.

  • Intravenously challenge mice with C. albicans strains.

  • Monitor survival over time.

  • Examine fungal burden in organs such as kidneys, liver, and brain .

• Cell Wall Stress Assay:

  • Grow C. albicans strains on media containing cell wall stressors.

  • Assess growth and morphology to determine sensitivity .

These assays provide a comprehensive assessment of DUR31's role in various aspects of C. albicans virulence, from direct host cell interactions to in vivo pathogenicity.

What approaches can be used to develop antibodies against DUR31?

Developing antibodies against DUR31 would require several strategic approaches, especially given its nature as a transmembrane protein:

• Antigen Design Strategies:

  • Identify extracellular epitopes of DUR31 through computational prediction of its membrane topology.

  • Design synthetic peptides corresponding to these extracellular regions.

  • Consider using recombinant fragments of DUR31 that include key extracellular domains.

  • Alternatively, utilize the full-length protein in detergent-solubilized form or reconstituted in nanodiscs or liposomes.

• Antibody Generation Platforms:

  • Traditional hybridoma technology: Immunize mice or rabbits with DUR31 antigens and generate monoclonal antibodies.

  • Phage display: Screen synthetic or natural antibody libraries against DUR31 epitopes.

  • De novo antibody design: Utilize AI-powered platforms similar to those described in search result to design antibodies with specific binding properties to DUR31.

• Validation Techniques:

  • ELISA assays to confirm binding to recombinant DUR31.

  • Western blotting to verify recognition of native DUR31 in C. albicans lysates.

  • Immunofluorescence microscopy to assess binding to DUR31 in intact C. albicans cells.

  • Flow cytometry to quantify binding to the cell surface.

  • Functional assays to determine if antibody binding blocks DUR31 transporter function.

• Optimization Considerations:

  • Affinity maturation to enhance binding specificity and strength.

  • Format engineering (IgG, Fab, scFv) depending on the intended application.

  • Incorporation of detection tags or conjugation to fluorophores for easy visualization.

  • Humanization if therapeutic applications are considered.

Modern AI-powered approaches could significantly enhance antibody design against challenging targets like DUR31. As described in search result , generative AI models can design antibodies with novel binding properties, potentially creating antibodies that specifically target functional epitopes of DUR31 to inhibit its role in virulence .

What in vivo models are appropriate for studying DUR31 function?

Several in vivo models can be used to study DUR31 function in C. albicans:

• Murine Systemic Candidiasis Model:

  • Female BALB/c mice can be challenged intravenously with C. albicans strains (wild type, dur31Δ/Δ, and dur31Δ/Δ::DUR31 complemented strain).

  • Survival can be monitored over time, with the dur31Δ/Δ mutant showing significantly attenuated virulence compared to wild type .

  • This model is particularly relevant for studying DUR31's role in systemic infections, endothelial damage, and immune evasion.

• Organ Burden Assay:

  • Following intravenous infection, mice can be sacrificed at defined time points.

  • Organs such as kidneys, liver, and brain can be harvested, homogenized, and plated to determine fungal burden.

  • This provides quantitative assessment of the mutant's ability to disseminate to and proliferate in various organs.

• Oral Candidiasis Model:

  • Since DUR31 is specifically upregulated during oral infection, a murine oral candidiasis model would be highly relevant.

  • Immunosuppressed mice can be orally infected with C. albicans strains.

  • Tongue tissues can be examined histologically and fungal burden determined.

  • This model allows study of DUR31's role in oral epithelial damage.

• Vaginal Candidiasis Model:

  • Female mice can be estrogen-treated and vaginally infected with C. albicans strains.

  • Lavage samples can be collected to assess fungal burden and inflammatory responses.

  • This model allows assessment of DUR31's role in another clinically relevant mucosal infection.

• Zebrafish Larvae Model:

  • Zebrafish larvae provide a transparent system where host-pathogen interactions can be visualized in real-time.

  • C. albicans strains can be fluorescently labeled and injected into zebrafish larvae.

  • Dissemination, phagocyte interactions, and mortality can be monitored.

  • This model is particularly useful for studying immune evasion mechanisms.

• Invertebrate Models:

  • Galleria mellonella (wax moth larvae) and Caenorhabditis elegans can serve as alternative, ethically advantageous models.

  • These models allow high-throughput screening of mutant virulence.

  • While less complex than mammalian systems, they provide valuable initial insights into virulence mechanisms.

These models provide complementary approaches to understand DUR31 function in various infection contexts, from mucosal to systemic candidiasis, and allow for both survival and mechanistic studies.

What are the most promising research directions for DUR31 antibody development?

Based on the available data, several promising research directions for DUR31 antibody development emerge:

• Therapeutic Antibody Development: Given that DUR31 has no human homologue and plays critical roles in multiple stages of candidiasis, antibodies targeting its extracellular domains could potentially inhibit its function and reduce virulence . This approach might be particularly valuable as an adjunct to conventional antifungal therapies.

• Diagnostic Applications: DUR31-specific antibodies could be developed for detection of invasive Candida infections, potentially enabling earlier diagnosis and treatment. The specificity of DUR31 to C. albicans makes it an attractive target for species-specific diagnostics.

• Structural Biology Studies: Antibodies can be valuable tools for crystallography and cryo-EM studies to elucidate the three-dimensional structure of DUR31, which remains largely unknown. Understanding its structure would facilitate rational drug design targeting this transporter.

• Mechanism Investigation: Using antibodies to block specific domains of DUR31 could help elucidate the precise mechanisms by which it contributes to virulence, particularly its roles in host cell damage and immune evasion.

• Combination Strategies: Exploring synergistic effects between DUR31 antibodies and conventional antifungals could lead to more effective therapeutic approaches, especially for drug-resistant strains.

• Nanobody Development: Given the challenges in accessing membrane protein epitopes, developing smaller antibody formats like nanobodies might provide better access to functional domains of DUR31.

The application of AI-powered antibody design approaches, as described in search result , could significantly accelerate these research directions by enabling the rapid generation of diverse, high-affinity antibodies against DUR31 .

How might DUR31 research impact broader understanding of fungal pathogenesis?

Research on DUR31 has significant implications for our broader understanding of fungal pathogenesis:

• Multi-functional Virulence Factors: DUR31 exemplifies how a single protein can influence multiple virulence traits, from host cell damage to immune evasion to stress resistance . This highlights the efficiency with which pathogenic fungi have evolved to maximize the utility of their genome.

• Host-Pathogen Co-evolution: The relationship between DUR31 and histatin 5 illustrates an interesting aspect of host-pathogen co-evolution, where a fungal transporter may have been co-opted by the host immune system as an entry point for antimicrobial peptides . This represents a classic "evolutionary arms race" scenario.

• Microbial Transport Systems in Virulence: DUR31 research emphasizes the importance of membrane transporters in fungal pathogenesis, which have traditionally received less attention than secreted virulence factors. This may encourage more research into how fungi acquire nutrients during infection and how these processes might be targeted therapeutically.

• Novel Antifungal Strategies: By understanding how DUR31 contributes to virulence, researchers can develop new strategies to combat fungal infections, potentially addressing the growing problem of antifungal resistance. Targeting virulence factors rather than essential genes may also reduce selective pressure for resistance development.

• Comparative Pathogenesis: Comparison of DUR31 with transporters in other pathogenic fungi, such as the S. aureus orthologue of E. coli PutP (which is also a virulence factor) , may reveal conserved mechanisms of pathogenesis across diverse microbial species.

• Mucosal Immunity Understanding: Given DUR31's role in oral candidiasis and its interaction with histatin 5, research in this area contributes to our understanding of mucosal immunity against fungi, which differs significantly from systemic antifungal responses.