Anti-Chikungunya E2 Protein [Clone CHK152] — Purified in vivo GOLD™ Functional Grade

Clone CHK152 is primarily used in vivo in mice for protecting against Chikungunya virus (CHIKV)-induced mortality, disease, and viremia. The antibody functions as a potent neutralizer of CHIKV by targeting the viral E2 protein, thereby blocking viral fusion and preventing infection.

Key in vivo applications in mice include:

• Prophylactic and therapeutic protection: CHK152 provides significant protection against death and disease when administered before or shortly after CHIKV infection. Administered as monotherapy, it fully prevents lethality when given shortly before or after viral challenge in susceptible mouse models (e.g., Ifnar^−/−^ mice).
• Reduction of disease severity: Infected mice treated with CHK152 show reduced musculoskeletal symptoms and lower levels of footpad swelling, which is a marker of CHIKV-induced arthritis and tissue inflammation.
• Limiting viral replication: The antibody reduces viremia (virus in the blood) to undetectable levels.
• Use in combination therapies: CHK152 is frequently combined with other neutralizing antibodies (e.g., CHK-166 or CHK-102) to prevent the emergence of viral escape mutants and to extend the effective treatment window. Combination therapy is more effective at preventing mortality and resistance than CHK152 alone, particularly when treatment is initiated at later times post-infection.
• Mechanistic studies: Different engineered variants of CHK152 (including chimeric and aglycosylated forms) are used to assess the role of Fc-mediated effector functions in protection, demonstrating that both antigen binding and Fc effector functions contribute to in vivo efficacy.

Typical endpoints in these mouse studies include:

• Survival/mortality rates after lethal CHIKV challenge
• Clinical scores of disease (e.g., footpad swelling)
• Viral titers in blood and tissues

In summary, clone CHK152 is a gold-standard tool for modeling antibody-mediated protection, therapy, and resistance mechanisms for Chikungunya virus infection in mice.

Other antibodies most commonly used with CHK152 in the literature are CHK-102, CHK-166, and CHK-263, typically in combination for enhanced neutralization and protection against Chikungunya virus (CHIKV) infection.

These monoclonal antibodies target different epitopes on the viral E1 and E2 surface glycoproteins:

• CHK-102: Frequently paired with CHK-152 in combination therapy studies to broaden protection and reduce escape mutant risk. Its epitope is largely distinct from that of CHK-152.
• CHK-166: Used in conjunction with CHK-152; it too binds a distinct site, sometimes on the E1 protein, complementing the action of CHK-152.
• CHK-263: Occasionally combined with CHK-152 or other neutralizing antibodies in research to compare efficacy and resistance profiles.

In laboratory assays, these antibodies are applied together to:

• Assess epitope accessibility and cooperative or competitive binding using ELISA and structural studies.
• Evaluate synergy or additive effects in vitro and in vivo protection models.
• Study escape mutants and resistance development under antibody pressure.

Other proteins briefly mentioned in broader literature for CHIKV research include:

• E1 and E2 viral structural proteins: Principal antigens targeted by the above neutralizing antibodies.
• Chimeric and Fc-effector modified versions of CHK152 (e.g., ch-CHK152, CHK152 N297Q) are used to dissect antibody functional mechanisms and receptor interactions.

In summary, CHK-102, CHK-166, and CHK-263 are the most commonly referenced antibodies in combination with CHK-152 for both mechanistic studies and therapeutic applications in CHIKV literature.

Key Findings on Clone CHK152 (Anti-Chikungunya Virus E2 Monoclonal Antibody)

Highly Protective In Vivo
CHK-152 is a monoclonal antibody (MAb) targeting the E2 glycoprotein of Chikungunya virus (CHIKV) that has demonstrated strong protective effects in mouse models, significantly reducing mortality and disease severity caused by CHIKV infection. Its protective activity is not only due to direct virus neutralization but also involves effector functions mediated by Fc-γ receptors. Even when modified to lack Fc-γ receptor binding (aglycosyl variant), CHK-152 retained high affinity for the viral antigen and neutralizing activity in cell culture, though this modification reduced its in vivo protective efficacy, highlighting the importance of Fc-mediated effector functions for maximal protection.

Mechanism of Neutralization and Fusion Blockade
CHK-152 blocks CHIKV infection by inhibiting viral membrane fusion, likely through steric hindrance at the viral surface, which reduces the virus’s ability to interact with host cell membranes at neutral pH. This mechanism is distinct from some other neutralizing antibodies and contributes to its potency as a therapeutic candidate.

Epitope and Neutralization Escape Mutants
Epitope mapping revealed that CHK-152 primarily targets a region involving residue D59 in the E2 protein. Neutralization escape mutants selected under CHK-152 pressure consistently acquired a D59N mutation in E2. In rare cases, a secondary mutation (A89E) was also observed, but the D59N change was dominant both in vitro and in vivo.
Importantly, CHK-152 escape mutants remained sensitive to neutralization by other MAbs (e.g., CHK-102, CHK-166, CHK-263), indicating non-overlapping epitopes. Conversely, escape mutants selected under other MAbs (e.g., CHK-166, which targets E1-K61) remained sensitive to CHK-152, supporting the value of combination antibody therapy to prevent viral escape.

Combination Therapy and Resistance
Administration of CHK-152 as a single agent led to the rapid emergence of neutralization escape variants, primarily via the D59N mutation. However, combination therapy (e.g., CHK-152 plus CHK-166) prevented the emergence of escape mutants in both mice and nonhuman primates, underscoring the necessity of using antibody cocktails to treat CHIKV infection. In rhesus macaques, combination therapy with CHK-152 and CHK-166 reduced viral spread and infection in distant tissues, with no detectable escape mutants in residual viral RNA.

Fitness of Escape Variants
Engineered escape variants (e.g., E2-D59N) retained viral fitness in cell culture and mosquito vectors, with no reversion to wild-type sequences observed. Surprisingly, these mutants caused less severe clinical disease in mice, with decreased musculoskeletal symptoms and prolonged survival in immunocompromised models, albeit without a reduction in infectivity. Competition studies showed no fitness cost for the double mutant (E1-K61T E2-D59N) compared to wild-type virus, suggesting these escape variants could persist in nature if selected.

Conservation of Targeted Residues
The residues involved in CHK-152 escape (notably E2-D59) are nearly 100% conserved across historical and circulating CHIKV strains, making them attractive targets for therapeutic antibodies and highlighting the barrier to natural escape.

Summary Table: Major Properties and Findings for CHK-152

Conclusion

CHK-152 is a potent, E2-targeting monoclonal antibody with demonstrated efficacy in animal models of CHIKV infection. Its therapeutic potential is maximized in combination with other MAbs to prevent viral escape, and the targeted epitope is highly conserved, reducing the likelihood of natural resistance. Escape mutants, while retaining fitness, are clinically attenuated, which may have implications for viral evolution under antibody pressure.

Dosing regimens of clone CHK152 vary widely depending on the mouse model used, including differences in dose amounts, timing (prophylaxis or treatment), and whether CHK152 is given as monotherapy or in combination therapy.

Key variations in dosing regimens:

• Mouse Model Susceptibility:

  • Highly immunocompromised mice (such as Ifnar–/– and Rag1–/–) often receive higher or more frequent doses, and combinations of antibodies are used to prevent viral resistance and extend the therapeutic window.
  • Wild-type C57BL/6 mice usually receive lower doses and are tested for both prophylactic and therapeutic efficacy.

• Dose Amounts:

  • Typical doses for Ifnar–/– mice range from 10 to 250 µg of CHK152 per mouse, depending on whether it is administered alone or in combination.
  • Combination therapy often uses 100–500 µg total antibody, such as 50–250 µg each of CHK152 and a second monoclonal antibody (e.g., CHK-102 or CHK-166), especially when dosing is later after infection to maximize protection.
  • Wild-type mice may receive 10–250 µg per antibody in single or combination doses, particularly in studies of joint pathology and viremia.

• Timing (Prophylaxis vs. Treatment):

  • Prophylactic administration typically occurs 1 day before infection and is shown to fully protect mice at doses as low as 10 µg in some models.
  • Therapeutic administration occurs after infection, with efficacy depending on how late the antibody is given. Combinations can provide protection when administered up to 48–60 hours post-infection, but protection fails if delayed to 72 hours after infection in highly susceptible mice.

• Monotherapy vs. Combination Therapy:

  • Monotherapy with CHK152 is protective at early or lower doses, but viral escape mutations may arise, especially in immunocompromised mice.
  • Combination therapy (e.g., CHK152 + CHK166, CHK152 + CHK102) increases efficacy, prevents resistance, and allows for later therapeutic intervention and higher survival rates.

Example dosing regimens across mouse models:

Additional considerations:

• No standard regimen applies across all models; dosing is tailored to individual study designs and animal vulnerability.
• Humanized CHK152 (hu-CHK-152) retains efficacy and similar dosing approaches in both immunocompromised and WT mice.

Summary:
The dosing regimens for clone CHK152 are highly dependent on mouse model type, immune status, infection timing, and whether monotherapy or combination therapy is used. Dose ranges typically span 10–250 µg per mouse, with combinations preferred for later-stage or therapeutic applications in immunocompromised mice to maximize survival and minimize resistance.