![]() Proteins abundant in other skin diseases or UV and heat-stressed skin were not abundant in skin invaded by cercariae, suggesting that results did not reflect general stress in the surgically removed skin specimen. Analysis of specific host proteins in skin invaded by cercariae served to highlight both the tissue degradation that facilitates cercarial invasion, and the host defenses that attempt to arrest or retard invasion. Among the proteins released by the parasite larvae were enzymes that degrade host tissue and immune defense molecules and other factors that protect the larvae from host defense mechanisms. In addition, the proteins in human skin that serve as mechanical or biochemical barriers to parasite invasion were also identified. The proteins released by larvae of a parasitic blood fluke as they invade human skin were identified using high-resolution protein identification equipment and software. Understanding the molecular and biochemical mechanisms by which parasites invade their host is key to rational vaccine and drug development. Control skin samples incubated with water for the same period as experimental samples ensured that invasion-related proteins and host protein fragments were not due to nonspecific degeneration of the skin samples. There were, however, abundant immunoglobulins, complement factors, and serine protease inhibitors in skin. While macrophage-derived proteins were present, no mast cell or lymphocyte cytokines were identified. Components of lysed epidermal cells, including desmosome proteins which link cells in the stratum granulosum and stratum spinosum, were identified. Both lysis and apoptosis of epidermal cells took place during cercarial invasion of the epidermis. Components of the schistosome surface tegument, previously identified with immune serum, were also released. Among the abundant proteins secreted by cercariae was the cercarial protease that has been implicated in degradation of host proteins, secreted proteins proposed to mediate immune invasion by larvae, and proteins implicated in protection of parasites against oxidative stress. ![]() The coexistence of proteins released by cercariae and host skin proteins from epidermis and basement membrane confirmed that cercarial tunnels in skin were sampled. Fluid from both control and experimental samples was analyzed by LC/MS/MS using a linear ion trap in “triple play” mode. ![]() Controls were exposed to water used to collect cercariae in an identical manner, and punctured to simulate cercarial tunnels. ![]() Human skin samples were exposed to cercariae for one-half hour to two hours. ![]()
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