Functional identification of Annexin B1 and Annexin B2 from Cysticercus cellulosae and their mechanism in plasma membrane repair

TL;DR

This study identifies Annexin B1 and B2 in Cysticercus cellulosae and shows they help the parasite avoid the host's immune system by preventing blood clotting and repairing cell membranes.

Contribution

This is the first discovery of an invertebrate annexin facilitating plasma membrane repair, offering new ideas for controlling cysticercosis.

Findings

Annexin B1 and B2 are expressed on the surface of Cysticercus cellulosae and in digestive glands.

These proteins prolong coagulation time and bind phosphatidylserine, possibly inhibiting coagulation.

Transfection with B1 and B2 genes reduces plasma membrane repair time, suggesting roles in immune evasion.

Abstract

Cysticercosis is a severe foodborne zoonotic parasitosis infected by the metacestode larvae of Taenia solium. However, its invasion mechanism is still not clear, which might provide the important evidence for treatment or vaccine. It was reported the annexin involved in the physiological and pathological functions of Cysticercus cellulosae. However, the regulatory mechanisms and roles of annexin B1 and annexin B2 in the invasion and immune escape of Cysticercus cellulosae have not been fully explored.

The annexin was acquired by cloning in prokaryotic expression vector, expressed in Escherichia coli, and purified by affinity chromatography. Its expression was determined by immunohistochemistry. The anticoagulant function and its underlying mechanism was verified by the determination of activated partial thromboplastin time, prothrombin time and phospholipid binding activity. The membrane repair function was verified by cell culture, transfection, and laser confocal technology.

Immunohistochemistry results showed the B1 and B2 were mainly expressed on the body surface and the surface of digestive glands of Cysticercus cellulosae. The Blood coagulation results illustrated the B1 and B2 can prolong the time of both exogenous and endogenous coagulation pathways, with B2 having a more significant effect. They tend to bind to phosphatidylserine, possibly interfering with coagulation complex formation and inhibiting the coagulation pathway, and may assist in the worm’s penetration through blood vessels and migration to parasitic sites. The plasma membrane repair test revealed the cells transfected with B1 and B2 genes have a significantly shorter plasma membrane repair time than the control group, suggesting that these proteins may be involved in repairing the worm’s body surface to resist the immune system’s attack when the host immune system attacks.

The Annexin B1 and Annexin B2 of Cysticercus cellulosae possess anticoagulant properties and can assist in membrane repair. Given these functions, it is speculated that they play a crucial role in immune evasion and invasion. However, further experiments are required to provide direct evidence to further validate these speculations.

Cysticercosis is a significant foodborne zoonotic parasitic disease, and it is also a neglected disease. It has excellent immune evasion ability and complex evasion mechanisms (antigen simulation and camouflage, plasma membrane isolation, immunosuppression, etc.), which is one of the important reasons why the disease is still prevalent. This study investigated the possible roles of Cysticercus cellulosae Annexin B1 and Annexin B2 in the invasion of hosts and immune evasion by Cysticercus cellulosae. We found that its coagulation function showed inconsistent effects compared to previous studies. To our knowledge, this is the first discovery of an invertebrate annexin facilitating plasma membrane repair. This has opened up new ideas for the prevention and control of Cysticercus cellulosae, as well as for the development of drug targets. In conclusion, this study provides new perspectives and valuable clues for further elucidation of the invasion mechanism of Cysticercus cellulosae.

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