Demonstration of virus particles in human genital warts.

WHILE the pathology and virology of human skin warts have received considerable attention in the last few years, little work has been done to establish the relationship of genital warts to warts in general, or even to establish if these lesions are of viral origin. The viral aetiology of the human skin wart (verruca vulgaris, plana, and plantaris) is now well established. By use of the electron microscope, particles having the morphology of viruses have been shown in thin sections and by the shadow cast and negativestaining techniques. The virus particles appear spherical and have a diameter of 550 A in shadow cast and negatively-stained preparations (Strauss, Shaw, Bunting and Melnick, 1949; Williams, Howatson and Almeida, 1961), but appear smaller in thin sections owing to dehydration and fixing processes (Bunting, 1953). Particles with similar morphology have been found in the skin and mucosal warts of rabbits, dogs, and cattle (Crawford and Crawford, 1963); these are, however, antigenically distinct from each other and from human skin wart virus (Le Bouvier, Sussman and Crawford, 1966). There is no evidence as yet of antigenic diversity between the viruses found in different clinical types of skin wart in man. In skin warts, virus particles are found in the nuclei of the outer layers of the stratum spinosum, in the stratum granulosum, and in aggregates in the stratum corneum. As in the Shope papilloma (Stone, Shope, and Moore, 1959), the virus first appears in association with the nucleolus of the affected cell, and particles increase in number as the cell moves outward in the epidermis. Eventually virus particles can occupy the whole nucleus, often appearing in pseudocrystalline arrays in the keratin. Rupture of the nuclear membrane may occasionally release some particles, but otherwise virus does not appear in the cytoplasm (Charles, 1960; Almeida, Howatson and Williams, 1962).