Anti-Mouse/Rat CD71 [Clone OX-26] — Purified in vivo GOLD™ Functional Grade

OX-26 clone has specific applications and limitations when used in in vivo mouse studies, primarily related to drug delivery and brain targeting research.

Primary Applications

Brain Drug Delivery Research: OX-26 is most commonly used as a targeting vector for drug delivery across the blood-brain barrier (BBB) in experimental models. The antibody exploits the endogenous transferrin transport system by binding to CD71 (transferrin receptor protein 1) expressed on brain capillary endothelial cells. When OX-26 binds to the extracellular domain of CD71, it gets transferred into the blood-brain barrier via this natural transport mechanism.

Conjugated Drug Transport: Researchers use OX-26 to transport conjugated drugs across the BBB in experimental studies. The antibody can be linked to various therapeutic compounds, allowing these drugs to potentially reach brain tissue that would otherwise be inaccessible due to the blood-brain barrier.

Liposomal Drug Delivery: OX-26 has been conjugated to liposomes for targeted drug delivery applications. These OX-26-conjugated liposomes can selectively distribute to brain capillary endothelial cells, potentially allowing for controlled release of liposomal cargo into the brain.

Species-Specific Limitations

Effectiveness Concerns in Mice: Despite its widespread use, research has shown that OX-26 monoclonal antibody is not an effective brain delivery vector in mice. This represents a significant limitation for researchers working with mouse models, as the antibody appears to have reduced efficacy compared to rat models.

Cross-Reactivity: While OX-26 was originally developed for rat studies, it does cross-react with mouse CD71. However, this cross-reactivity does not necessarily translate to equivalent functional effectiveness for drug delivery purposes in mouse models.

Technical Considerations

Target Expression: In mouse studies, OX-26 targets CD71, which is expressed on proliferating cells, reticulocytes, and erythroid precursors. The high expression of CD71 on malignant cells makes it particularly attractive for cancer-related drug delivery applications.

Delivery Mechanism: The antibody functions through receptor-mediated endocytosis, where binding to CD71 triggers internalization of the antibody-drug complex. This mechanism is essential for the therapeutic cargo to reach its intended target.

Given these findings, researchers using mouse models may need to consider alternative approaches or validate the effectiveness of OX-26 in their specific experimental context, particularly when the goal is brain-targeted drug delivery.

There is no specific, publicly available information in the search results regarding the correct storage temperature for a sterile packaged clone labeled "OX-26." The provided results discuss cannabis plant storage broadly, but do not reference OX-26 or sterile-packaged clones specifically.

Without more details about the organism, manufacturer, or product guidelines, it is impossible to provide a definitive storage temperature. For sterile packaged clones—especially in research or biotech contexts—best practices are typically to follow the manufacturer’s instructions or industry-specific protocols for that organism. If the clone is a plant (such as a cannabis clone), general guidelines recommend warm, humid conditions for rooting (70–85°F / 20–30°C with higher humidity), but sterile packaging may require different handling.

For accurate, safe storage, consult the product’s documentation or contact the supplier directly.

Other commonly used antibodies or proteins reported in the literature alongside OX-26 include affinity-engineered OX26 variants, control immunoglobulins (IgG), non-targeting antibodies such as A20.1 (anti-Clostridium difficile toxin B single domain antibody), and chimeric or mutated forms of OX26 for improved pharmacological properties.

Key proteins and antibodies paired with OX-26:

• OX26 affinity variants: Researchers use altered OX26 antibodies with single alanine mutations (e.g., HCDR1 W33A, LCDR3 W96A, and HCDR3 F99A) to study how binding affinity affects BBB transport and intracellular sorting.
• A20.1: This single-domain antibody targeting C. difficile toxin B is used as a negative control in BBB transcytosis experiments, helping distinguish receptor-mediated transport versus non-specific passage.
• Control IgGs (e.g., NiP228): Non-specific immunoglobulins are often co-administered as controls to compare the specificity of OX26's transcytosis and cellular uptake.
• Chimeric OX26 antibodies (e.g., OX-26-CP058): Engineered antibodies with rat constant regions to minimize immunogenicity and regulate effector functions when used in rat models.
• Fc-silenced OX26 mutants (e.g., OX-26-CP079, LALA-PG mutation): Modified OX26 antibodies with mutations in the Fc region prevent ADCC (antibody-dependent cell-mediated cytotoxicity) and CDC (complement-dependent cytotoxicity), allowing safer in vivo studies, especially in models where the wild-type antibody causes reticulocyte toxicity.
• Fusion proteins (e.g., OX26 scFv-streptavidin fusion): OX26 single-chain Fv is fused to streptavidin for versatile biotin-binding applications and targeted delivery through the transferrin receptor.

These antibodies and engineered proteins, often used as controls or in combination, allow experimenters to dissect mechanisms of BBB transport, optimize drug delivery, and reduce adverse immunological effects in animal studies.

Alternative proteins sometimes referenced in literature include transferrin itself, recombinant forms of transferrin receptor, and antibodies targeting related BBB transporters, but these are less frequently paired directly with OX26 compared to the control and engineered variants listed above.

Based on the scientific literature, several key findings emerge regarding OX-26, an antibody that targets the transferrin receptor (TfR) and is used for drug delivery across the blood-brain barrier.

Affinity Engineering and Intracellular Trafficking

The most significant finding relates to how antibody affinity affects intracellular trafficking and transcytosis efficiency. Wild-type OX26 has a binding affinity of 5 nM to the transferrin receptor. However, researchers discovered that lowering the affinity of OX26 through specific mutations dramatically improves its performance for brain drug delivery.

Single alanine substitutions at specific positions (HCDR1 W33A, LCDR3 W96A, and HCDR3 F99A) created variant antibodies with reduced affinities of 76, 108, and 174 nM respectively. These lower-affinity variants showed remarkable improvements in their ability to cross the blood-brain barrier through a process called transcytosis.

Enhanced Blood-Brain Barrier Crossing

The key mechanistic insight is that affinity engineering alone is sufficient to redirect TfR antibody intracellular trafficking away from lysosomes and toward more favorable pathways. Lower-affinity OX26 variants (in the 76-108 nM range) were sorted into high-density subcellular fractions containing markers of early endosomes and recycling endosomes, rather than being degraded in lysosomes.

This redirection of intracellular traffic directly correlated with improved transcytosis efficiency across blood-brain barrier models in laboratory studies. The finding challenges the traditional assumption that higher antibody affinity always leads to better therapeutic outcomes.

Drug Delivery Applications

OX26 has been successfully applied in various brain-targeted drug delivery systems. Researchers have conjugated it with liposomes containing therapeutic compounds like CDP-choline for treating neurological conditions. The OX26-conjugated delivery systems demonstrated improved therapeutic efficacy and maintained suitable physicochemical properties for clinical applications.

Mechanistic Understanding

The studies reveal that monovalent receptor binding is not required for the improved trafficking observed with lower-affinity variants. This suggests that the mechanism involves more complex receptor-mediated endocytosis processes that can be optimized through careful affinity tuning rather than simply maximizing binding strength.

These findings have important implications for developing antibody-based therapeutics for brain diseases, as they demonstrate that optimizing antibody affinity within specific ranges (rather than maximizing it) can significantly enhance drug delivery across the blood-brain barrier.