HLA-DRB1 is part of the HLA class II beta chain paralogs. The class II molecule is a heterodimer composed of an alpha (DRA) and a beta chain (DRB), both of which are anchored in the membrane. This molecule is crucial in the immune system as it presents peptides from extracellular proteins. Class II molecules are expressed on antigen-presenting cells. The beta chain, approximately 26-28 kDa, is encoded by six exons. Exon one encodes the leader peptide; exons two and three encode the two extracellular domains; exon four encodes the transmembrane domain; and exon five encodes the cytoplasmic tail. The beta chain contains all polymorphisms that determine peptide binding specificities. Hundreds of DRB1 alleles exist, some of which are associated with certain diseases. For instance, DRB1*1302 is associated with the persistence of acute and chronic hepatitis B virus infection. Additionally, this gene has multiple pseudogenes.

Gene and Protein Complex Functionality

HLA-DRB1 facilitates several functions, including MHC class II receptor activity, peptide antigen binding, and signaling receptor binding. It is involved in processes such as the positive regulation of immune response, gene expression regulation, and leukocyte differentiation. This gene’s products are located in the bounding membrane of organelles, on the external side of the plasma membrane, and within the immunological synapse. HLA-DRB1 is part of the MHC class II protein complex and is implicated in various diseases, including asthma, autoimmune diseases, bacterial infectious diseases, eye diseases, and sarcoidosis. It also serves as a biomarker for toxic shock syndrome.

Detailed Function and Structure

The HLA-DRB1 gene encodes a protein essential to the immune system. It is part of the human leukocyte antigen (HLA) complex, which helps the immune system differentiate between the body’s proteins and those of foreign invaders, such as viruses and bacteria. The HLA complex is the human equivalent of the major histocompatibility complex (MHC) found in many species. HLA-DRB1 belongs to the MHC class II group, which encodes cell-surface proteins. These proteins bind to extracellular peptides and display them to the immune system, prompting a response if they are identified as foreign.

The beta chain produced by HLA-DRB1 binds to the alpha chain produced by HLA-DRA, forming the HLA-DR antigen-binding heterodimer. This complex displays foreign peptides to the immune system, triggering an immune response. Each MHC class II gene has numerous variations, enabling the immune system to respond to various foreign invaders. Researchers have identified hundreds of HLA-DRB1 alleles, each designated by a unique number (e.g., HLA-DRB1*04:01).

Allele DRB1*01:01

• Bacillus anthracis pagA/protective antigen, PA: KLPLYISNPNYKVNVYAVT
• HIV-1 gag peptide: FRDYVDRFYKTLRAEQASQE
• HRV-16 capsid proteins:
  • VP1: PRFSLPFLSIASAYYMFYDG
  • VP2: PHQFINLRSNNSATLIVPYV
• IAV external protein HA:
  • PKYVKQNTLKLAT
  • SNGNFIAPEYAYKIVK
• IAV internal proteins M, NP, and PB1:
  • M-derived epitope: GLIYNRMGAVTTEV
• COL4A3: GWISLWKGFSF
• MBP: VHFFKNIVTPRTP

Allele DRB1*03:01

• HRV-16 capsid protein VP2: NEKQPSDDNWLNFDGTLLGN
• Retinal SAG: NRERRGIALDGKIKHE
• Thyroid TG: LSSVVVDPSIRHFDV
• HHV-6B gH/U48 and U85 antigens (no specific peptide sequences provided)
• C. tetani neurotoxin tetX (no specific peptide sequences provided)

Allele DRB1*04:01

• M. tuberculosis esxB/culture filtrate antigen CFP-10: EISTNIRQAGVQYSR
• HRV-16 capsid protein VP2: NEKQPSDDNWLNFDGTLLGN
• Melanoma-associated TYR antigen:
  • QNILLSNAPLGPQFP
  • DYSYLQDSDPDSFQD
• VIM:
  • GVYATR/citSSAVR
  • SAVRAR/citSSVPGVR
• ACAN: VVLLVATEGR/CitVRVNSAYQDK
• COL2A1 (no specific peptide sequences provided)

Allele DRB1*04:02

• VIM: Native or citrullinated self-peptides (no specific sequences provided)

Allele DRB1*04:04

• HRV-16 capsid proteins:
  • VP1: HIVMQYMYVPPGAPIPTTRN
  • VP2: RGDSTITSQDVANAVVGYGV
• VIM: SAVRAR/citSSVPGVR

Allele DRB1*04:05

• Tumor-associated antigen WT1: KRYFKLSHLQMHSRKH

Allele DRB1*05:01

• HIV-1 gag peptide: FRDYVDRFYKTLRAEQASQE

Allele DRB1*07:01

• EBV latent antigen EBNA2 peptide: PRSPTVFYNIPPMPLPPSQL
• HRV-16 capsid proteins:
  • VP1: PRFSLPFLSIASAYYMFYDG
  • VP2: VPYVNAVPMDSMVRHNNWSL
• Tumor-associated antigen WT1: MTEYKLVVVGAVGVGKSALTIQLI
• KRAS neoantigen: MTEYKLVVVGAVGVGKSALTIQLI (G12V mutation)

Allele DRB1*11:01

• HIV-1 gag peptide: FRDYVDRFYKTLRAEQASQE
• HRV-16 capsid protein VP2: SDRIIQITRGDSTITSQDVA
• C. tetani neurotoxin tetX (no specific peptide sequences provided)

Allele DRB1*13:01

• HHV-6B antigens (no specific peptide sequences provided)

Allele DRB1*15:01

• HRV-16 capsid protein VP2: SNNSATLIVPYVNAVPMDSM
• MBP: ENPVVHFFKNIVTPR
• Tumor-associated antigen WT1: KRYFKLSHLQMHSRKH

Allele DRB1*15:02

• HIV-1 gag peptide: FRDYVDRFYKTLRAEQASQE
• Tumor-associated antigen WT1: KRYFKLSHLQMHSRKH

This linear peptide is suggested: MTEYKLVVVGAVGVGKSALTIQLI

A study utilized a rapid, high-throughput approach to experimentally measure peptide/HLA thermal stability on a scale needed for analyzing neoantigens from thousands of patients. By combining UV-cleavable peptide/HLA class I complexes with differential scanning fluorimetry, the Tm values of neoantigen complexes were determined. These Tm values were accurate, reproducible, and directly proportional to the complexes’ half-lives. When analyzing known HLA-A2–restricted immunogenic peptides, Tm values correlated more strongly with immunogenicity than algorithm-predicted binding affinities. Using temperature stability information can help select neoantigens for cancer vaccines, focusing on mutated peptides most likely to be expressed on the cell surface.

Tm analysis of HLA-A2 complexes containing immunogenic neoantigen peptides

Poly(ethylene glycol) (PEG), also known as poly(ethylene oxide) (PEO), has long been the polymer of choice in biomedicine, widely recognized for its ability to extend the half-life and reduce the immunogenicity of proteins. While PEG’s biocompatibility, low dispersity, and immune evasion have established it as a standard in biomedicine, it is not without its shortcomings. Notably, the prevalence of anti-PEG antibodies in patients poses a potential hindrance, as does the polyether backbone’s vulnerability to oxidative degradation.

Check LifeTein’s Pegylation Service!

This is where Poly(2-alkyl/aryl-2-oxazoline)s, abbreviated as PAOx, POx, or POZ, step in, offering a promising alternative with higher stability and tunability than PEG. PAOx polymers maintain the critical properties required for biomedical use, such as biocompatibility and “stealth” behavior, but with enhanced functionalization options. The synthesis of PAOx via cationic ring-opening polymerization (CROP) yields polymers with a tertiary amide backbone that interacts minimally with proteins and is largely ignored by the immune system.

PAOx can be tailored at the molecular level to adjust the hydrophilic-hydrophobic balance and control the lower critical solution temperature (LCST), enabling a fine-tuning of physical properties for a range of applications. Notably, some PAOx variants exhibit thermoresponsive behavior, becoming more hydrophobic at higher temperatures—a property leveraged in innovative material design for applications like diagnostics and triggered drug release.

The similarity of PAOx structures to natural polypeptides accounts for their biocompatibility and stealth behavior. Studies demonstrate that PAOx-based pharmaceuticals exhibit rapid clearance from the bloodstream and minimal accumulation in the reticuloendothelial system, suggesting a favorable toxicity profile and a promising future in human clinical applications.

The extensive applications of PAOx in drug delivery are diverse and inventive. PAOx can significantly improve drug solubility and bioavailability as excipients in drug formulations. PAOx-based micellar systems exploit the polymer’s amphiphilic nature to achieve high drug loading, which is especially beneficial for cancer therapeutics with low water solubility. Additionally, PAOx-based hydrogels provide versatile platforms for drug delivery and tissue engineering, with potential for injectable applications and for customization through polymer chain functionalization.

The conjugation of drugs and proteins with PAOx—referred to as PAOxylation—has yielded conjugates that often outperform their PEGylated equivalents. For example, PAOx-protein conjugates have demonstrated prolonged efficacy compared to non-conjugated forms and increased cellular uptake.

Advances in PAOx research are ongoing, and applications are expanding to include nanoparticle functionalization. These PAOx-functionalized nanoparticles possess unique characteristics beneficial for imaging and drug delivery, and are “smart” materials that respond to external stimuli.

Given the breadth of possibilities that PAOx polymers offer, the biomedical field stands on the cusp of a new era in which drug delivery and patient care may be significantly enhanced through these versatile materials. With ongoing research and clinical trials, the potential for PAOx to become a leading platform in precision medicine and beyond is becoming increasingly apparent.

In the field of peptide synthesis, linkers play a crucial role by bridging the gap between various molecular entities, thus enabling the creation of complex peptides and proteins with desired functionalities. These linkers are not merely inert spacers; they are carefully selected to impart stability, solubility, and specificity to the resultant molecules. Among the plethora of linkers used, Fmoc-NH-PEG (Polyethylene glycol) derivatives and Aminohexanoic Acid are particularly noteworthy due to their unique properties and applications in both synthetic chemistry and biological studies.

Fmoc-NH-PEG derivatives, such as Fmoc-NH-PEG2-CH2COOH and Fmoc-NH-PEG3-CH2CH2COOH, are widely utilized in peptide synthesis for several reasons. The Fmoc (9-Fluorenylmethyloxycarbonyl) group serves as a temporary protector for amino groups, facilitating the sequential addition of amino acids in a controlled manner. The PEG (Polyethylene glycol) segment, varying in length (e.g., PEG2, PEG3), introduces solubility and flexibility into the peptide chain. This solubility is critical for otherwise insoluble peptides in aqueous or organic solvents, limiting their biological application. Moreover, the flexibility provided by the PEG linker is beneficial for peptides required to adopt specific conformations for binding to proteins or other targets in biological systems.

Aminohexanoic Acid, a simpler linker, offers a hydrophobic chain that can increase the peptide’s overall hydrophobicity, influencing its interaction with biological membranes and other hydrophobic entities within the cell. This property is precious in the delivery of therapeutic peptides, where membrane permeability is a crucial factor.

The application of these linkers extends beyond mere synthesis. In biological studies, they facilitate the exploration of protein-protein interactions, enzyme-substrate relationships, and the mechanisms of action of therapeutic peptides. For instance, a peptide linked with a PEG spacer can be used to probe the active site of an enzyme without undue steric hindrance, enabling researchers to glean insights into enzyme kinetics and substrate specificity. Similarly, in protein function and structure studies, these linkers allow the attachment of fluorescent tags or other probes to peptides without significantly altering their native structure or function, thus enabling real-time tracking of peptide behavior in live cells or in vitro systems.

Furthermore, in therapeutic applications, the use of such linkers can dramatically improve the pharmacokinetic and pharmacodynamic profiles of peptide drugs. By enhancing solubility, reducing degradation by proteases, and modulating interaction with biological targets, these linkers contribute to the efficacy and safety of peptide-based therapies.

In summary, linkers like Fmoc-NH-PEG derivatives and Aminohexanoic Acid are indispensable tools in peptide synthesis and have broad implications in biological research and therapeutic development. Their ability to confer solubility, flexibility, and specific physicochemical properties to peptides opens up vast possibilities for studying and manipulating biological systems at the molecular level. As our understanding of these linkers and their interactions within complex biological matrices deepens, we can expect to see even more innovative applications in the realms of synthetic biology, drug discovery, and beyond.

Fmoc-Glycine	2 Carbons
3-Amino-3-(2-Nitrophenyl) Propanoic Acid (ANP Linker)	3 Carbons
Fmoc-beta-Ala-OH	3 Carbons
4-Aminobutyric Acid (GABA) Fmoc-GABA-OH	4 Carbons
5-Aminovaleric Acid (Ava)	5 Carbons
Aminohexanoic Acid (Ahx)	6 Carbons
mini-PEG or AEEA Fmoc-NH-PEG2-CH2COOH	Length of Bonds: 9
mini-PEG2 or AEEP Fmoc-NH-PEG2-CH2CH2COOH	Length of Bonds: 10
AEEEA Fmoc-NH-PEG3-CH2COOH	Length of Bonds: 12
AEEEP, or PEG3 Fmoc-NH-PEG3-CH2CH2COOH	Length of Bonds: 13
AEEEEP, PEG4 Fmoc-NH-PEG4-CH2CH2COOH	Length of Bonds: 16
AEEEEEP, PEG5 Fmoc-NH-PEG5-CH2CH2COOH	Length of Bonds: 19

 

Materials and Reagents:

1. CPP peptide (e.g., TAT, penetratin, or your chosen CPP)
2. DNA plasmid containing your target gene
3. Transfection reagent (e.g., Lipofectamine, Polyethylenimine [PEI], etc.)
4. Cell culture medium
5. Cells for transfection
6. Sterile phosphate-buffered saline (PBS)
7. Sterile deionized water
8. Sterile microcentrifuge tubes and tips
9. Cell culture dishes or plates
10. Incubator with CO2 control (for maintaining cell cultures)

Protocol:

1. Cell Culture:

   • Prepare and maintain your cell culture in an appropriate culture medium under standard conditions. Cells should be sub-confluent and healthy at the time of transfection.

2. CPP and Plasmid Preparation:

   • Prepare a stock solution of your CPP at 1-10 mM concentration in sterile deionized water.
   • Prepare a stock solution of your DNA plasmid at an appropriate concentration (usually 1-2 µg/µL) in sterile deionized water.

3. Complex Formation:

   • Mix the CPP and DNA plasmid solutions at the desired molar ratio (usually 5:1 to 10:1, CPP:DNA).
   • Incubate the mixture at room temperature for 20-30 minutes to allow for complex formation. This step is crucial for efficient transfection.

4. Transfection:

   • Dilute the CPP-DNA complexes in sterile PBS or serum-free medium to achieve the desired final concentration.
   • Add the diluted complexes dropwise to the cells, ensuring even distribution. Gently rock the culture dish to distribute the complexes evenly.

5. Incubation:

   • Incubate the transfected cells at 37°C in a CO2 incubator for a period of time specified in your experimental design. Typically, this ranges from 4 to 48 hours.

6. Media Change:

   • After the incubation period, replace the transfection medium with a fresh, complete cell culture medium containing serum.

7. Analysis:

   • Depending on your experimental objectives, you can analyze gene expression, protein production, or other relevant endpoints post-transfection at the appropriate time points.

8. Optimization:

   • It is crucial to optimize the CPP-to-DNA ratio, transfection duration, and other parameters based on your specific cell type and experimental requirements.

9. Control Experiments:

   • Include appropriate control experiments, such as cells transfected with plasmid alone, to assess the efficiency and specificity of your transfection.

10. Data Analysis:

• Analyze the results and repeat the transfection experiments with optimized conditions if necessary.

Remember that the effectiveness of CPP-mediated transfection can vary depending on several factors, including the CPP sequence, cell type, and the nature of the plasmid. It’s essential to conduct preliminary experiments and refer to the literature for guidance specific to your research.

Contact LifeTein scientists for the correct CPP for your studies. 

Designing peptide antigens for antibody production is a sophisticated process that leverages computational tools and bioinformatics to identify sequences within proteins that are likely to elicit a robust immune response. This process is crucial for various applications, including the development of diagnostics and therapeutics, and tools in research for understanding protein function and structure.

When used to generate antibodies, the principle behind peptide antigen design is to analyze a protein’s sequence and structure to pinpoint segments that yield particular and robust responses against the target protein. These selected segments should ideally represent exposed and accessible regions of the native protein to ensure the produced antibodies can recognize their target in its natural conformation. This specificity is vital for the antibodies’ effectiveness in diverse applications, from therapeutic interventions to detailed structural and functional studies of proteins.

Several key factors are considered in the antigen design process, including the hydrophobicity/hydrophilicity balance, antigenic domains, and the folding characteristics of the protein. The aim is to recommend the most immunogenic sequences that would likely yield productive interactions with the immune system, leading to the generation of specific antibodies. This consideration is essential for both the effectiveness and the broad applicability of the resulting antibodies in various biological and medical research contexts.

Bioinformatics tools and computational methods, such as molecular dynamics simulations and phage display, play a pivotal role in this process. They allow for the identification of peptide sequences that can act as potent antigens, taking into account factors like molecular recognition in antibody-antigen complexes and the peptides’ structural properties. These tools offer a way to navigate the complex relationship between peptide sequence, structure, and antigenicity, providing a more rational and targeted approach to antigen design.

The applications of peptides designed through these methods are vast and varied. In diagnostics, peptides can be used to generate antibodies that recognize specific disease markers, allowing for precise detection and monitoring of pathological conditions. In therapeutic contexts, antibodies developed against carefully selected peptide antigens can be used to target and neutralize disease-causing agents or pathological processes with high specificity. Furthermore, in research, these antibodies serve as valuable tools for probing the structure and function of proteins, elucidating their roles in biological processes, and investigating the molecular basis of diseases.

The potential downside to focusing on peptide sequences for antibody production is the risk that the chosen sequence may not correspond to an exposed region in the native protein, potentially limiting the utility of the produced antibodies. This challenge underscores the importance of comprehensive analysis and selection strategies that consider the native conformation and context of target proteins.

In summary, the design of peptide antigens for antibody production is a critical and highly technical field that blends computational biology with immunology to produce tools and treatments with far-reaching implications for medicine and research. As bioinformatics tools and techniques continue to advance, so too will the sophistication and effectiveness of peptide-based antigen design, opening new frontiers in the understanding and treatment of diseases.

Check here for more details about the peptide antigen design!

Dot Blot protocol
Dot blot is similar to the Western blot technique. However, the proteins are spotted directly onto the membrane or paper for detecting and analyzing. This is a good technique to estimate protein concentration.

Procedure
1. Prepare the nitrocellulose (NC) membrane.
2. Spot 2 µl of diluted samples onto the NC membrane and let it dry.
3.Blocking: Block the membrane in 1% BSA or non-fat milk in TBST (1 hr, Room Temperature).
4. Primary Antibody: Incubate with the primary antibody in BSA/TBST for 1 hr at RT.
5. Washing: Wash three times with TBST (3 x 5 min).
6.Secondary antibody: Incubate with secondary antibody conjugated with HRP for 1 hr at RT.
7. Washing: Wash three times with TBST (15 min x 1, 5 min x 2), then once with TBS (5 min).
8. Developing: Incubate with ECL reagent for 1 min and expose X-ray film in the darkroom with different lengths of exposure.

Reagents
TBS:
20 mM Tris-HCl
150 mM NaCl
pH 7.5

TBST:
0.05% Tween20 in TBS
BSA/TBST
0.1% BSA in TBST
NC: Nitrocellulose membrane (BIO-RAD)