Metacyclic Trypanosoma vivax possess a surface coat

Area of Science:

• Parasitology
• Molecular Biology
• Entomology

Background:

• Trypanosoma vivax is a protozoan parasite transmitted by tsetse flies.
• Metacyclic trypanosomes are the infective stage transmitted to mammalian hosts.
• The presence and timing of the surface coat acquisition in T. vivax metacyclics were previously debated.

Purpose of the Study:

• To investigate the presence and ultrastructure of metacyclic Trypanosoma vivax within the tsetse fly vector.
• To determine when T. vivax metacyclics acquire their surface coat in relation to transmission.
• To understand the functional implications of the T. vivax surface coat in the context of antigenic variation.

Main Methods:

• Tsetse flies infected with Trypanosoma vivax were dissected.
• Proboscides of infected flies were extensively searched for metacyclic trypanosomes.
• A specialized process was used to examine single, extruded, metacyclic trypanosomes.
• Electron microscopy was employed to visualize the surface coat of metacyclic T. vivax.

Main Results:

• Coated metacyclic Trypanosoma vivax were identified in the hypopharynges of infected tsetse flies.
• Metacyclic T. vivax were extruded in low numbers upon probing by the tsetse fly.
• Electron microscopic evidence demonstrated that metacyclic T. vivax acquire a surface coat prior to host contact, contradicting earlier findings.
• The surface coat plays a role in the antigenic variation of T. vivax.

Conclusions:

• Metacyclic Trypanosoma vivax are coated within the tsetse fly vector before transmission.
• The acquisition of a surface coat by metacyclic T. vivax is an early event, preceding mammalian host infection.
• The surface coat of T. vivax is functionally analogous to that of other tsetse-transmitted trypanosomes, likely mediating antigenic variation.