Early host cell-Molluscum contagiosum virus interactions

Selective inhibition of nuclear steroid receptor function by a protein from a human tumorigenic poxvirus

The poxvirus molluscum contagiosum (MC) has a worldwide distribution and its prevalence is on the rise. Here we report that the MCV MC013L protein inhibits glucocorticoid and vitamin D, but not retinoid or estrogen, nuclear receptor transactivation. A direct interaction of MC013L with glucocorticoid and vitamin D receptor is supported by yeast two-hybrid, GST pull-down, and far Western blot analyses. Glucocorticoids act as potent inhibitors of keratinocyte proliferation, while vitamin D and retinoids promote and block terminal differentiation, respectively. Therefore, MC013L may promote efficient virus replication by blocking the differentiation of infected keratinocytes. MC013L may be the first member of a new class of poxvirus proteins that directly modulate nuclear receptor-mediated transcription.

Recent advances in molluscum contagiosum virus research

Molluscum contagiosum virus (MCV) and variola virus (VAR) are the only two poxviruses that are specific for man. MCV causes skin tumors in humans and primarily in children and immunocompromised individuals. MCV is unable to replicate in tissue culture cells or animals. Recently, the DNA sequence of the 190 kbp MCV genome was reported by Senkevich et al. MCV was predicted to encode 163 proteins of which 103 were clearly related to those of smallpox virus. In contrast, it was found that MCV lacks 83 genes of VAR, including those involved in the suppression of the host response to infection, nucleotide biosynthesis, and cell proliferation. However, MCV possesses 59 genes predicted to code for novel proteins including MHC-class I, chemokine and glutathione peroxidase homologs not found in other poxviruses. The MCV genomic data allow the investigation of novel host defense mechanisms and provide new possibilities for the development of therapeutics for treatment and prevention of the MCV infection.

Rapid cold fixation of tissue samples by microwave irradiation for use in electron microscopy

A cold microwave irradiation procedure was developed to fix rapidly and stain various tissues and monolayers for electron microscopy. Because microwave stimulation always produces some heat, melting ice was used to maintain the temperature of the tissue samples, the fixative, and the staining solution at 0 to 4 degrees C. The low temperature also reduced vapour formation, thus minimizing the risk of explosion. The microwave method shortened the total time of fixation and dehydration from the usual 3 h required by the conventional method to 65 min. After microwave fixation, the ultrastructural details of membranes and subcellular structures were excellent.

Immunocompetent cells and epithelial cell modifications in molluscum contagiosum

We studied lesions of molluscum contagiosum with a panel of monoclonal antibodies to determine the phenotype of infiltrating cells and antigen modifications of infected keratinocytes. Our data indicate (1) a complete lack of immunocompetent cells in the viral lesions, and simultaneously a loss of B2-microglobulin reactivity by molluscum bodies, a cellular activation of EGF and transferrin receptors and expression of CD36 antigen of these bodies; (2) a moderate infiltrate of activated T cells and monocytes in the underlying epidermis; (3) an increase of Langerhans cell density and a CD36 expression by the surface of upper layer keratinocytes in the perilesional epidermis.

Molluscum contagiosum of the oral mucosa

A case of molluscum contagiosum involving the buccal mucosa is reported. A review of the literature disclosed only two documented cases of this tumor with oral involvement, emphasizing its rare occurrence in the oral cavity.

Structural polypeptides of molluscum contagiosum virus: their variability in various isolates and location within the virion

The structural polypeptides of molluscum contagiosum virus (MCV) obtained from the skin lesions of patients were examined by SDS-polyacrylamide gel electrophoresis. At least 40 polypedtides from purified virions were detected on SDS-polyacrylamide gel by a highly sensitive silver stain. Two of the structural polypeptides of the nine isolates were different in their migration rate in SDS-polyacrylamide gel. Following controlled degradation virions the two variable polypeptides were shown to be located in the surface or subsurface layers.

GAp junctions in skin tumors of molluscum contagiosum

Thin section, tracer, and freeze-fracture experiments demonstrate that the infection caused by molluscum contagiosum virus implies alterations of cellular contacts in the epidermis, never before observed in cutaneous viroses. These changes are basically represented by a distinctive variation in particle packing of gap junctions, a greater proliferation of these junctions and the presence of a high amount of intracytoplasmic gap junctions. Skin tumors caused by molluscum contagiosum virus appear to be a convenient model to study the morphological and topological variations as well as the turnover of gap junctions in the epidermis.

Demonstration of giant and anular nexus in the psoriatic epidermis

In the psoriatic skin, nexus were most prominent in the upper layers of the viable epidermis, using the Alcian blue-Lanthanum technique. There, they reached double and manifold the length (giant nexus) of those in normal epidermis. According to the villous transformation of the epidermal cell surface in psoriasis, the nexus showed a great variation in their shape. Undulating nexus were seen beside invagination--and anular nexus. On ther other hand, nexus were lacking in the deepest layers of the psoriatic epidermis in contrast to normal epidermis. From these findings it seems that the intercellular communication by specialized low resistant junctions is reduced in the deepest layers of the psoriatic epidermis. In the upper epidermal layers, however, the extensive formation and the variable configuration of the nexus express a high synthetic activity and a well developed intercellular information in these areas of the psoriatic epidermis.