HTLV-1 gp46 mosaic
Description
Definition and Composition
HTLV-1 gp46 mosaic is a synthetic protein combining immunodominant regions of the HTLV-1 envelope glycoprotein gp46. This recombinant antigen is engineered to enhance detection sensitivity by integrating multiple epitopes critical for antibody recognition . Key features include:
-
Amino Acid Regions: Combines residues 162–214 and 242–257 (or alternative regions like 374–400/190–207 in other constructs) .
-
Molecular Weight: ~34.2 kDa when expressed in E. coli with a C-terminal hexahistidine tag .
-
Purity: >90% purity via SDS-PAGE, stabilized in phosphate buffer (pH 7.5) .
Diagnostic Use
Therapeutic Research
-
Neutralization Studies: Anti-gp46 antibodies block syncytium formation (cell-cell fusion) and reduce viral entry .
-
ADCC Activity: Monoclonal antibodies (e.g., hu-LAT-27) enhance NK cell-mediated killing of HTLV-1-infected cells .
Critical Observations:
-
Antibody Correlation: Anti-gp46 IgG levels directly correlate with neutralization titers (r = 0.72–0.85, P < 0.001) .
-
Protective Role: Higher neutralizing/ADCC-inducing antibodies in asymptomatic carriers suggest immune control of HTLV-1 .
Future Directions
Product Specs
PSCCTLTVGV SSYHSKPCNP AQPVCSWTLD LLALSADRAL QPPCPNLVSY SSYHATYSLY LFPHWIKKPN RNGGGYYSAS YSDPCSLKCP YLGCQSWTCP YTGAVSSPYW KFQQDVNFTQ EVSHLNINLH FSKCGFPFSL LVDAPGYDPI WFLNTEPSQL PPTAPPLLSH SNLDHILEPS IPWKSKLLTL VQLTLQSTNY TCIVCIDRAS LSTWHVLYSP NVSVPSPSST PLLYPSLALP APHLTLPFNW THCFDPQIQA IVSSPCHNSL ILPPFSLSPV PTLGSRSRRA.
Q&A
What is HTLV-1 gp46 and what is its functional significance?
HTLV-1 gp46 is a surface envelope glycoprotein that mediates viral attachment and entry into host cells. It contains functional domains associated with inhibition of syncytium formation, cell-cell transmission, and antibody production . The protein plays a critical role in determining viral tropism by interacting with specific cellular receptors including glucose transporter-1 (GLUT-1) and heparan sulfate proteoglycans (HSPGs) . The "mosaic" term refers to a constructed version of gp46 that combines elements or epitopes from different viral variants to create a recombinant protein for research or vaccine development purposes .
Methodologically, studying gp46 function typically involves:
-
Molecular cloning and expression of recombinant proteins
-
Cell binding assays to determine receptor interactions
-
Syncytium inhibition assays to evaluate viral entry
-
Antibody neutralization studies to identify immunogenic epitopes
How genetically stable is the HTLV-1 gp46 gene across populations?
Research indicates HTLV-1 gp46 exhibits remarkable genetic stability compared to envelope proteins of other retroviruses. Studies from Brazilian Amazonia found the aA (Transcontinental Cosmopolitan) genotype demonstrated an extremely low mutation rate of approximately 1.83 × 10^-4 mutations per site per year . The nucleotide diversity in this population ranged from 0.00% to 2.0%, confirming the conservative nature of this region .
To study gp46 genetic stability, researchers employ:
-
Phylogenetic analysis using Bayesian Inference
-
Amplification and sequencing of gp46 from clinical isolates
-
Calculation of nucleotide diversity and substitution rates
-
Mapping of mutations to functional domains
What cell receptors does HTLV-1 gp46 interact with and how does this influence tropism?
HTLV-1 gp46 primarily interacts with two cellular receptors: glucose transporter-1 (GLUT-1) and heparan sulfate proteoglycans (HSPGs). These interactions determine the cellular tropism of the virus:
| Receptor | Expression | Viral Preference | Methodology for Study |
|---|---|---|---|
| HSPGs | Higher on CD4+ T cells | HTLV-1 preferentially infects | Cell surface expression analysis, binding assays |
| GLUT-1 | Higher on CD8+ T cells | HTLV-2 preferentially infects | Receptor overexpression, viral entry assays |
Binding studies with HTLV-1/HTLV-2 SU recombinants have demonstrated that the C-terminal portion of HTLV-1 SU is responsible for preferential binding to CD4+ T cells expressing high levels of HSPGs . Experimentally, transfection studies have shown that overexpression of GLUT-1 in CD4+ T cells increases HTLV-2 entry, while expression of HSPGs on CD8+ T cells increases entry of HTLV-1 .
What methodologies are most effective for analyzing HTLV-1 gp46 genetic variations in clinical samples?
Effective analysis of HTLV-1 gp46 genetic variations requires a multi-step methodological approach:
-
Sample preparation:
-
Isolation of peripheral blood mononuclear cells (PBMCs)
-
DNA extraction using phenol-chloroform or commercial kits
-
PCR amplification with primers flanking the gp46 region
-
-
Sequencing strategies:
-
Direct Sanger sequencing for predominant variants
-
Next-generation sequencing for detecting minor variants
-
Single-genome amplification to avoid recombination artifacts
-
-
Bioinformatic analysis:
-
Sequence alignment against reference sequences
-
Phylogenetic analysis using Bayesian methods
-
Identification of selection pressure signatures
-
Mapping mutations to functional domains
-
This approach has successfully identified clinically significant mutations such as the N93D amino acid substitution, which appears exclusively in symptomatic cases . Researchers should carefully select methods that minimize PCR bias and provide sufficient depth to detect minor variants.
How do specific mutations in gp46 correlate with clinical manifestations of HTLV-1 infection?
The relationship between gp46 mutations and clinical outcomes represents a critical area of research. Studies have found that amino acid mutations were present in 66.6% of samples from individuals with signs/symptoms or diseases associated with HTLV-1 (p = 0.0091) . Specifically:
| Mutation | Clinical Association | Discovery Method | Significance |
|---|---|---|---|
| N93D | Invariably associated with symptomatic cases | Sequencing and clinical correlation | Previously undescribed mutation potentially serving as clinical marker |
To investigate these correlations, researchers should:
-
Conduct case-control studies comparing asymptomatic carriers with patients having different manifestations
-
Perform longitudinal studies to monitor mutation emergence and disease progression
-
Use site-directed mutagenesis to evaluate the functional impact of specific mutations
-
Employ statistical methods to establish significant associations between genetic and clinical parameters
What approaches are most effective for developing neutralizing antibodies against HTLV-1 gp46?
Development of neutralizing antibodies against HTLV-1 gp46 requires strategic targeting of conserved, functionally critical epitopes. Effective approaches include:
-
Target identification:
-
Epitope mapping of conserved regions
-
Structural analysis to identify surface-exposed domains
-
Focus on regions involved in receptor binding
-
-
Antibody generation methods:
-
Functional screening:
-
Syncytium inhibition assays to evaluate neutralizing capacity
-
Antibody-dependent cellular cytotoxicity (ADCC) assays
-
Cell-to-cell transmission inhibition assessment
-
Notably, studies have shown that levels of neutralizing antibodies, as determined by syncytium inhibition assays, are significantly lower in acute and chronic ATL patients than in asymptomatic carriers, suggesting their protective role . Additionally, antibody development focusing on the proline-rich region of gp46 has yielded monoclonal antibodies that remain on the cell surface rather than being internalized .
What are the challenges in developing an HTLV-1 vaccine based on gp46?
Developing an effective HTLV-1 vaccine based on gp46 faces several significant challenges:
-
Biological obstacles:
-
Cell-to-cell viral transmission may bypass antibody neutralization
-
Establishment of latent infection with minimal viral protein expression
-
Need to induce both humoral and cellular immune responses
-
-
Technical challenges:
-
Production of properly folded recombinant gp46 that presents native epitopes
-
Design of immunogens that elicit broadly neutralizing antibodies
-
Limited appropriate animal models for efficacy testing
-
-
Clinical evaluation difficulties:
-
Low incidence and long latency period complicating trial design
-
Lack of established correlates of protection
-
Need for long-term follow-up to assess efficacy
-
Despite these challenges, the high conservation of gp46 and evidence that HTLV-1 gp46-specific neutralizing and ADCC-inducing antibodies play a protective role make it a promising vaccine target . The development of gp46 mosaic constructs represents one innovative approach to address viral diversity while focusing on conserved epitopes .
What experimental models are most suitable for studying HTLV-1 gp46 function?
Several experimental models provide valuable platforms for investigating HTLV-1 gp46 function:
For studying particle morphology and assembly, cryo-electron tomography has revealed that mature HTLV-1 particles are polymorphic and spherical with polyhedral capsid cores that have at least one curved region contacting the inner face of the viral membrane . This technique, combined with other approaches like scanning transmission electron microscopy (STEM), provides valuable insights into viral structure and assembly.
How does HTLV-1 Gag-gp46 interaction contribute to viral assembly and morphology?
The interaction between HTLV-1 Gag and gp46 during viral assembly represents an important aspect of the viral life cycle with distinct characteristics:
-
Assembly pathway:
-
Morphological characteristics:
-
Experimental approaches:
Understanding these interactions is crucial for developing antivirals targeting assembly and provides insights into the unique biology of HTLV-1 compared to other retroviruses.
Product Science Overview
Human T-lymphotropic virus type 1 (HTLV-I) is a single-stranded RNA retrovirus that primarily infects T-helper cells, leading to conditions such as T-cell leukemia and T-cell lymphoma . The virus activates a subset of T-helper cells known as Th1 cells, resulting in their proliferation and the overproduction of Th1-related cytokines, including interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) . This overproduction suppresses Th2 lymphocytes and reduces Th2 cytokine production, which can impair the host’s immune response to certain infections .
HTLV-I gp46 is a major envelope glycoprotein of the virus and serves as a critical target for neutralizing antibodies and antibody-dependent cellular cytotoxicity (ADCC) . The gp46 protein contains immunodominant regions that are essential for the virus’s ability to infect host cells .
The recombinant HTLV-I gp46 mosaic protein is derived from E. coli and includes the immunodominant regions of the gp46 protein, specifically amino acids 162-214 and 242-257 . This recombinant protein has a molecular weight of approximately 39 kDa as determined by SDS-PAGE . The protein is formulated with 10 mM sodium phosphate (pH 6.0), 0.1% SDS, 1 mM DTT, and 1 mM EDTA .
The recombinant HTLV-I gp46 mosaic protein is primarily used as an antigen in ELISA and Western Blot assays to detect HTLV-I infections . It is highly pure, with a purity level greater than 95% as determined by SDS-PAGE and RP-HPLC . The protein is stable at 4°C for one week but should be stored below -18°C to prevent freeze-thaw cycles .
