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Published on: October 9, 2021
Mapping of the complement C9 binding domain on Trichinella spiralis paramyosin
1Department of Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China. zhuxping@ccmu.edu.cn.
Background:
Trichinellosis is an important foodborne zoonosis that is distributed worldwide. Trichinella spiralis may evade host complement-mediated attack by expressing complement inhibitory proteins, such as paramyosin (Pmy). Previous studies have shown that Trichinella spiralis paramyosin (Ts-Pmy) is able to bind to the human complement component C9 to inhibit the complement activation and protect the parasite from complement-mediated attack. Further determination of the complement-binding domain on Ts-pmy will enable us to better understand the Ts-Pmy's biofunction in the immune evasion and provide feasible approach to develop epitope-based subunit vaccine against trichinellosis.
Methods:
The complement C9 binding region on Ts-Pmy was determined by expression of overlapped fragments of Ts-Pmy and their binding activities to C9. The exact binding site was further narrowed-down to a 14-amino acid peptide at C-terminus using synthesized peptides with different size of amino acid sequence. The C9 complement-binding of the 14-amino acid peptide and its interference in the C9 polymerization and the complement-mediated lysis of rabbit erythrocytes was investigated.
Results:
The protein interaction between human C9 and native Ts-Pmy was further confirmed by immunoprecipitation with T. spiralis lysates. The fragmental expression and C9 binding assays identified that the binding region of Ts-Pmy to C9 is located within 831-885 of Ts-Pmy C-terminus. The exact binding site on Ts-Pmy to C9 was narrowed down to 14 amino acid residues (⁸⁶⁶Val-⁸⁷⁹Met) by using different sizes of synthesized peptides. In the presence of the synthesized 14-amino acid peptide, human C9 polymerization and the hemolytic activity of the human complement was inhibited.
Conclusions:
Our results revealed the precise molecular basis for T. spiralis to produce Ts-Pmy as an immunomodulator to evade the attack of the host complement system as a survival mechanism.
Insights
Trichinella spiralis uses paramyosin (Pmy) to evade host defenses by binding complement C9. Researchers pinpointed a 14-amino acid peptide responsible for this interaction, crucial for parasite survival.
Area of Science:
- Immunology
- Parasitology
- Molecular Biology
Background:
- Trichinellosis is a global foodborne zoonosis caused by Trichinella spiralis.
- Trichinella spiralis evades host immunity by expressing complement inhibitory proteins like paramyosin (Pmy).
- Trichinella spiralis paramyosin (Ts-Pmy) binds human complement component C9, inhibiting complement activation and parasite destruction.
Purpose of the Study:
- To determine the complement-binding domain on Ts-Pmy.
- To elucidate the mechanism of Ts-Pmy's immune evasion.
- To identify targets for vaccine development against trichinellosis.
Main Methods:
- Expression of overlapping Ts-Pmy fragments to identify C9 binding regions.
- Synthesis of peptides to pinpoint the exact C9 binding site.
- Assays to investigate the effect of the binding peptide on C9 polymerization and complement-mediated lysis.
Main Results:
- The C9 binding region on Ts-Pmy was localized to its C-terminus (residues 831-885).
- A 14-amino acid peptide (Val⁸⁶⁶-Met⁸⁷⁹) was identified as the precise binding site for C9.
- This peptide inhibited human C9 polymerization and complement-mediated erythrocyte lysis.
Conclusions:
- The study reveals the molecular basis of Ts-Pmy's immunomodulatory function in evading host complement.
- Ts-Pmy's interaction with C9 is a key survival mechanism for Trichinella spiralis.
- The identified peptide represents a potential target for anti-trichinellosis vaccine strategies.
