Hypervolemic infusion of Lumbricus terrestris erythrocruorin purified by tangential-flow filtration.

Background: The hemoglobin of the earthworm Lumbricus terrestris (also known as erythrocruorin, or LtEc) is a naturally occurring high-molecular-weight protein assembly (3.6 MDa) that is extremely stable, resistant to oxidation, and transports oxygen similarly to human whole blood. Therefore, LtEc may serve as an alternative to donated human red blood cells. However, a suitable purification process must be developed to produce highly pure LtEc on a large scale that can be evaluated in an animal model to determine the safety and efficacy of LtEc.

Study Design And Methods: We used tangential-flow filtration (TFF), an easily scalable and affordable technique, to produce highly pure LtEc from earthworms. The purity, yield, methemoglobin level, viscosity, colloid osmotic pressure, O(2) binding equilibria, and ligand-binding kinetics of the purified LtEc were measured in vitro. The purified LtEc product was then evaluated in hamsters using a hypervolemic infusion model to establish its basic biocompatibility and detect any changes in microcirculatory and systemic variables.

Results: TFF was able to produce LtEc with high purity and yield (5-10 g/1000 worms). The purified LtEc product did not elicit hypertension or vasoconstriction when infused into hamsters.

Conclusion: LtEc may be easily purified and safely transfused into hamsters in small amounts (0.5-1.5 g/dL final concentration in blood) without any noticeable side effects. Therefore, LtEc may serve as a very promising oxygen carrier for use in transfusion medicine.