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Imidazole initiates exsheathing of L3 Teladorsagia circumcincta
Simon Brown1, Jennifer D Neale, Magnolia Nava-Tirado
1School of Human Life Sciences, University of Tasmania, Locked Bag 1320, Launceston, Tasmania 7250, Australia. Simon.Brown@utas.edu.au
Abstract:
The infective larvae of Teladorsagia circumcincta have a protective sheath that is lost soon after they reach the rumen of the sheep (the definitive host). Incubation in vitro with 50 mM imidazole caused more than 75% of L3 T. circumcincta to begin exsheathing within 2 hr. The initiation of exsheathing was less likely at pH 6.2 than at pH 7.8. The apparent pKa of this process was 7.08, similar to that for the conversion of imidazolium(+) to imidazole. Both the extent and the initial rate of exsheathing initiation increased with imidazole concentration (the apparent K(1/2) was about 50 mM). The initial rate of exsheathing initiation was stimulated by lactose and maltose, but not by some other carbohydrates, and by propylamine and imidazole acetic acid, but not by histidine.
Insights
Imidazole initiates the exsheathment of infective larvae of Teladorsagia circumcincta (T. circumcincta) in sheep. This process is pH-dependent and influenced by imidazole concentration and specific carbohydrates.
Area of Science:
- Veterinary Parasitology
- Biochemistry
- Molecular Biology
Background:
- Teladorsagia circumcincta infective larvae (L3) possess a protective sheath crucial for survival.
- Sheath loss occurs in the sheep's rumen, facilitating infection.
- Understanding exsheathment mechanisms is key to developing anti-parasitic strategies.
Purpose of the Study:
- To investigate the role of imidazole in initiating the exsheathment of T. circumcincta L3.
- To determine the influence of pH, imidazole concentration, and carbohydrates on this process.
Main Methods:
- In vitro incubation of T. circumcincta L3 with varying concentrations of imidazole.
- pH-dependent exsheathment assays.
- Assessment of carbohydrate and amino acid effects on exsheathment initiation.
Main Results:
- Imidazole (50 mM) induced exsheathment in over 75% of L3 within 2 hours.
- Exsheathment initiation was favored at higher pH (7.8) compared to lower pH (6.2), with an apparent pKa of 7.08.
- Both imidazole concentration (apparent K(1/2) ~50 mM) and specific carbohydrates (lactose, maltose) and amino acids (propylamine, imidazole acetic acid) influenced the rate and extent of exsheathment.
Conclusions:
- Imidazole acts as a trigger for T. circumcincta L3 exsheathment in vitro.
- The exsheathment process is sensitive to pH and imidazole concentration, suggesting a biochemical mechanism.
- Specific carbohydrates and amino acids can modulate imidazole-induced exsheathment, offering potential targets for parasite control.
