Epidermodysplasia verruciformis (EV) is characterized by an abnormal genetic susceptibility to a group of related human papillomavirus (HPV) genotypes, including the oncogenic HPV5 and HPV8. The mode of transmission of these viruses remains unknown. In view of the rare incidence of EV, we had a unique opportunity to perform a virologic study of the amniotic fluid and placenta from an EV patient infected with HPV5, HPV8, several other EV HPV, and HPV3. The child was born by cesarean section and the amniotic fluid specimen was taken prior to rupture of membranes. Analysis of the amniotic fluid and placenta specimens by a nested polymerase chain reaction method, using degenerate EV HPV primers or type-specific HPV primers, disclosed the presence of the variants of EV HPV5, HPV8, HPV24, and HPV36, and of HPV3 detected in the skin lesions of the patient. HPV5, HPV8, HPV24, and HPV3 were also detected in the placenta. No viral sequences were detected in peripheral blood mononuclear cells collected 2 y and 6 mo before cesarean section, rendering an hematogenous transmission unlikely. The same HPV variants were also detected in cervical scrapes taken from the patient, which may suggest an ascending infection of the placenta. This first report of the detection of EV HPV in amniotic fluid, placenta, and cervical scrapes from an EV patient renders vertical transmission of EV HPV likely.

Thrombospondin-1 (TSP-1) is an adhesive glycoprotein which, when secreted from alpha-granules of activated platelets, can bind to the cell surface and participate in platelet aggregate formation. In this study, we show that thrombin activation leads to the rapid and specific association of a large amount of secreted alpha-granular TSP-1 with the actin cytoskeleton. This cytoskeletal association of TSP-1 was correlated with platelet secretion, but not aggregation, and was inhibited by cytochalasin D, an inhibitor of actin polymerization. Association of TSP-1 with the actin cytoskeleton was mediated by membrane receptors, as shown by using MAII, a TSP-1-specific monoclonal antibody that inhibited both TSP-1 surface binding to activated platelets and cytoskeletal association. TSP-1 and its potential membrane receptors, e.g. alphaIIbbeta3 integrin, CD36 and CD47, concomitantly associated with the actin cytoskeleton. However, studies on platelets from a patient with type I Glanzmann's thrombasthenia lacking alphaIIbbeta3 and another with barely detectable CD36 showed normal TSP-1 surface expression and association with the actin cytoskeleton. Likewise, no involvement of CD47 in TSP-1 association with the actin cytoskeleton could be inferred from experiments with control platelets using the function-blocking anti-CD47 antibody B6H12. Finally, assembly of signalling complexes, as observed through translocation of tyrosine-phosphorylated proteins and kinases to the actin cytoskeleton, was found to occur in concert with cytoskeletal association of TSP-1, in control platelets as well as in thrombasthenic and CD36-deficient platelets. Our results imply a role for the actin cytoskeleton in the membrane-surface expression process of TSP-1 molecules and suggest a possible coupling of TSP-1 receptors to signalling events occurring independently of alphaIIbbeta3 or CD36. These results provide new insights into the link between surface-bound TSP-1 and the contractile actin microfilament system which may promote platelet aggregate cohesion.