HYALURONIDASE FROM INFECTIVE ANCYLOSTOMA HOOKWORM LARVAE AND ITS POSSIBLE FUNCTION AS A VIRULENCE FACTOR IN TISSUE INVASION AND IN CUTANEOUS LARVA MIGRANS

During skin penetration, infective hookworm larvae encounter hyaluronic acid as they migrate between epidermal keratinocytes and through the ground substance of the dermis. A hyaluronidase would facilitate passage through the epidermis and dermis during larval invasion. Zoonotic hookworm larvae of the genus Ancylostoma were shown to contain a hyaluronidase activity that migrated on modified sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) hyaluronic acid gels with an apparent M(r) of 49,000. A second form with an M(r) of 87,000 was also identified. The major etiologic agent of cutaneous larva migrans, A. braziliense, was shown to have the greatest enzyme activity, hydrolyzing up to 3.3-mu-g of hyaluronic acid per h per-mu-g of total parasite protein at pH 6.0, whereas A. caninum and A. tubaeforme each had much less enzyme activity. The differences in enzyme activities between species correlated with differences in the intensities of the lytic zones at 49 and 87 kDa on SDS-PAGE hyaluronic acid gels. Hookworm hyaluronidase activity exhibited a broad pH optimum between 6.0 and 8.0 and did not hydrolyze chondroitin sulfate, two features that suggest that the hookworm enzyme is more like the invertebrate leech hyaluronidase than mammalian testicular or lysosomal hyaluronidase. Larvae of A. braziliense were shown to release hyaluronidase than mammalian testicular or lysosomal hyaluronidase. Larvae of A. braziliense were shown to release hyaluronidase activity and degrade radiolabeled hyaluronic acid in vitro. Gold sodium thiomalate was identified as an enzyme inhibitor. The hyaluronidase is the second major virulence factor that we have identified from infective hookworm larvae.