Anti-Mouse/Human TYRP1/TRP1 (Clone TA99) – Purified in vivo PLATINUM™ Functional Grade

Common In Vivo Applications of Clone TA-99 in Mice

TA-99 is a monoclonal antibody that specifically binds to tyrosinase-related protein 1 (TYRP1, also known as TRP1 or glycoprotein 75/gp75) and is reactive to both mouse and human antigens. Its in vivo applications in mice are primarily in the context of cancer research, particularly in melanoma models, and in studies of the immune response to antibody-based therapeutics.

Key In Vivo Uses

• Melanoma Tumor Models: TA-99 is frequently used in mouse models of melanoma, especially the B16-F10 cell line, to study antibody-mediated tumor clearance, metastasis, and immunotherapy efficacy. It is often administered intravenously or intraperitoneally to target gp75-expressing tumor cells. For example, in chronic B16-F10 melanoma models, TA-99 (often in IgG1 or IgG2a formats, or as a humanized IgG1 variant) has been employed to assess antibody persistence, anti-tumor activity, and the role of Fc receptors in immune effector function.
• Assessment of Antibody Pharmacokinetics and Immunogenicity: The clone has been used in studies evaluating the pharmacokinetic properties of therapeutic antibodies, particularly those with human constant regions. The development of mouse strains tolerant to human IgG has enabled chronic administration of TA-99-containing antibodies, revealing how antibody persistence and neutralizing immune responses affect therapeutic outcomes.
• Engineering and Testing of Antibody Variants: TA-99 has served as a platform for engineering and testing antibody variants, such as Fc-engineered (e.g., GAALIE) or afucosylated forms, to enhance binding to Fcγ receptors and improve anti-tumor efficacy. These studies help characterize how different Fc modifications influence effector functions and tumor clearance in vivo.
• Bispecific Antibody Development: TA-99 has been utilized in the generation and evaluation of bispecific antibodies (bsAbs), where one arm targets gp75 (via TA-99) and the other engages immune cells, such as T cells, for redirected tumor cell killing.
• Immunological Studies: Although less commonly, TA-99 has been used to demonstrate activation of natural killer (NK) cells and priming of CD8+ T cells, which depend on cytokines like IL-2 for anti-tumor activity.

Representative Experimental Designs

• Metastatic Cancer Studies: Mice are often pretreated with TA-99, then challenged with B16-F10 tumor cells. Lungs are later examined for metastases, with TA-99-treated mice showing reduced metastatic burden compared to controls.
• Antibody Clearance Studies: Serum levels of TA-99 are monitored over time to study the impact of anti-antibody immune responses on therapeutic persistence.
• Effector Cell Studies: In some models, the effect of TA-99 on recruitment and activation of immune effector cells (NK, macrophages, neutrophils) is assessed in tumor microenvironments.

Summary Table: Applications of TA-99 in Mice

Conclusion

The TA-99 antibody is a versatile tool in mouse in vivo studies, especially for interrogating the mechanisms of antibody therapy in melanoma, understanding antibody pharmacokinetics, and developing next-generation immunotherapies with enhanced Fc-mediated effector functions. Its specificity for gp75 makes it particularly valuable for preclinical studies in oncologic research.

Commonly used antibodies or proteins combined with TA-99 in the literature, especially in the context of melanoma research, include:

• DNA vaccines or antigens targeting other melanosomal proteins, especially:

  • gp100 (also known as PMEL or Pmel17): Frequently used in DNA vaccination or peptide immunization studies alongside TA-99, aiming to broaden anti-tumor immune responses against melanoma cells.
  • Trp2 (Tyrosinase-related protein 2): Sometimes included in combination vaccine or immunotherapy regimens.
  • Tyrp1: The direct antigen recognized by TA-99, but also used as a target in DNA vaccines administered in combination with TA-99 antibody for synergy.

• Immunomodulatory antibodies and cytokines:

  • Anti-CD25: Used for regulatory T cell (Treg) depletion, enhancing the effects of TA-99 by reducing immunosuppression in the tumor microenvironment.
  • Agonist antibodies to 4-1BB (CD137): These stimulate T and NK cell activity and have been shown to synergize with TA-99 for greater tumor control.
  • Anti-PD1: Checkpoint blockade antibody, often used in triple or combination regimens with TA-99 to relieve immune inhibition and improve therapeutic responses.
  • IL-2: Recombinant interleukin-2 or antibody-cytokine fusions with TA-99 can boost the activation and proliferation of cytotoxic lymphocytes.
  • Engineered cytokine chimeras (e.g., Neo2/15): Used in place of or in conjunction with natural cytokines to further augment antitumor immunity when combined with TA-99.
  • Toll-like receptor agonists: Serve as adjuvants, inducing robust innate immune activation and amplifying the effects of TA-99.

• Adoptive cell therapies:

  • Adoptive transfer of T cells (CD8+ T cells primed with tumor antigens): Efficacy can be enhanced when combined with TA-99 and vaccine strategies.

Summary of combinations in the literature:

These combinations are designed to enhance both innate and adaptive anti-tumor immune responses, exploit epitope spreading, reduce inhibitory immune cell populations, or leverage immune checkpoint blockade.

Key Findings from Clone TA-99 Citations in Scientific Literature

Clone TA99 is a mouse monoclonal antibody that targets tyrosinase-related protein 1 (TYRP1, TRP1, gp75), a protein involved in melanin biosynthesis and expressed on melanocytes and pigmented melanoma cells. Its utility spans research, diagnostics, and experimental therapeutics, especially in melanoma models.

Immunological and Therapeutic Applications

• Melanoma Research Tool: TA99 is widely used as a marker to detect TYRP1 expression in melanoma and melanocytes, supporting applications in immunocytochemistry, immunohistochemistry, immunoprecipitation, and Western blot.
• Antibody Therapy: Experiments in preclinical melanoma models have demonstrated that unmodified TA99 can reduce tumor growth in mice, particularly in B16 melanoma models. However, its efficacy is limited by immunosuppressive mechanisms in the tumor microenvironment, such as regulatory T cells (Tregs).
• Combination Therapies: Combining TA99 with immune checkpoint blockade or MEK inhibitors significantly enhances anti-tumor activity, suggesting that TA99 may be more effective when paired with agents that modulate the immune response or intracellular signaling pathways. Early elimination of regulatory T cells can impair anti-tumor effects, but later interventions boost TA99 efficacy.
• Intratumoral Cytokine Delivery: Engineering TA99 into immunocytokines (e.g., TA99-IL2) was hypothesized to improve tumor targeting. However, studies found that antigen specificity (i.e., TA99-IL2) did not necessarily result in greater tumor accumulation compared to non-specifically targeted immunocytokines, indicating that factors beyond antigen binding may determine therapeutic distribution and efficacy.
• CAR-T Cell Targeting: TYRP1 (detected by TA99) has been explored as a target for CAR-T cell therapy, indicating its relevance beyond antibody-based approaches.

Technical and Developmental Insights

• Antibody Production: TA99 is produced by hybridoma technology following immunization of mice with human melanoma cells. It is available for research from multiple commercial sources.
• Pharmaceutical Potential: TA99 has been patented for use in therapeutic compositions, suggesting its recognized value in experimental oncology.

Summary Table: Major Findings with TA99

Conclusions

Clone TA99 is a foundational reagent in melanoma research, serving as both a diagnostic tool and a component in experimental immunotherapies. Its efficacy as a therapeutic antibody is context-dependent, benefitting from combination with immune-modulating agents, though antigen specificity alone does not ensure superior tumor targeting in immunocytokine formats. Ongoing research explores TA99’s role in next-generation therapies, including CAR-T cells and combination regimens, highlighting its continued relevance in cancer immunology.

Dosing regimens for clone TA-99 vary considerably across mouse models and experimental objectives, with differences in dose amount, frequency, route of administration, timing relative to tumor inoculation, and combination with other treatments.

Key findings regarding dosing regimens:

• B16 Melanoma Model (C57BL/6 mice):

  • Most common regimens use intraperitoneal (i.p.) injection.
  • Typical doses are 100 μg/mouse or 200 μg/mouse, with dosing on specific days after tumor inoculation (e.g., days 5 and 7, or days 5 and 9).
  • Some protocols use a once-weekly schedule (e.g., 100 μg i.p. once per week starting at day 6 post-tumor inoculation).
  • Combination treatments (e.g., with checkpoint blockade, MEK inhibitor, or Treg cell depletion) may alter the regimen's complexity but often retain the core TA-99 schedule.

• Humanized/Engineered Mouse Strains:

  • Novel knock-in mouse strains with humanized IgG1 or FcγR expression enable extended, chronic dosing—including pre-treatment phases and multiple cycles, unattainable in wild-type mice due to immunogenicity against humanized antibodies.
  • In these models, TA-99 variants (e.g., human IgG1-GAALIE) are administered repeatedly, sometimes in four-dose cycles at designated intervals, allowing for studies of long-term efficacy and immunogenicity.

• Pharmacodynamic and Immunotherapy Studies:

  • In experiments assessing combination therapies (e.g., TA-99 with cytokines such as IL-2 or IFN-α), time points and intervals are meticulously staggered, and blood or tissue samples are collected at several intervals after dosing to assess cytokine/chemokine responses.
  • Regimens may combine TA-99 with other agents given either concurrently or on specified days to coordinate immune activation.

• Tumor Models and Dosing Variation:

  • For B16F10 tumors, regimens often start after tumors reach a measurable size (usually day 6 post-inoculation for established models), with i.p. dosing at set intervals.
  • Some studies use iv or intratumoral delivery for other agents in combination, but TA-99 is almost always administered systemically (i.p. or, more rarely, i.v.).

Comparison Table of Dosing Regimens:

Additional context:

• Route of administration and tumor model species/strain are selected based on antibody immunogenicity, combinatory regimen needs, and experimental goals (e.g., acute response vs. long-term clearance or rechallenge).
• In non-engineered, immunocompetent mice, anti-drug immune responses often limit the number of possible doses.
• Chronic and repeated dosing is primarily feasible in engineered strains with tolerance to human IgG1.
• TA-99 is most frequently studied in melanoma models (especially B16, B16F10), but also in combination with various immunomodulators or in different tumor settings.

Summary:
TA-99 dosing regimens in mouse models are highly contingent upon mouse strain, study aims, and combination therapies. Most wild-type models use 1–2 doses of 100–200 μg i.p., whereas engineered/knock-in strains permit prolonged multidose studies of TA-99 and its Fc-engineered variants.