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At least 19 recordsLinked to original sources

Replication of molluscum contagiosum virus.

Molluscum contagiosum virus (MCV) infects preadolescent children and sexually active adults, frequently causing a disfiguring cutaneous disease in immunosuppressed HIV-infected individuals. The development of an efficacious treatment regime has been hampered by the failure to replicate the virus in the laboratory. Here we report the first demonstration of MCV replication in an experimental system. In human foreskin grafts to athymic mice, MCV induced morphological changes which were indistinguishable from patient biopsies and included the development and migration of molluscum bodies containing mature virions to the epidermal surface.

Animals↗

Molecular cloning of a novel CC chemokine, interleukin-11 receptor alpha-locus chemokine (ILC), which is located on chromosome 9p13 and a potential homologue of a CC chemokine encoded by molluscum contagiosum virus.

Molluscum contagiosum virus (MCV) encodes a CC chemokine MC148R which is likely to have been acquired from the host. By a homology search employing MC148R as a probe, we have identified a novel CC chemokine whose gene exists next to the IL-11 receptor alpha (IL-11Ralpha) gene in both humans and mice. Thus, this chemokine maps to chromosome 9p13 in humans where IL-11Ralpha has been assigned. We term this novel chemokine IL-11Ralpha-locus chemokine (ILC). ILC has the highest homology to MC148R among the known human CC chemokines. Furthermore, ILC is strongly and selectively expressed in the skin where infection of MCV also takes place. Thus, ILC is likely to be the original chemokine of MC148R.

Amino Acid Sequence↗

Characterization of early gene transcripts of molluscum contagiosum virus.

Molluscum contagiosum virus (MCV), a member of the family Poxviridae, replicates well in vivo but cannot be propagated in cell culture. The coding capacity of the MCV genome was previously determined by DNA nucleotide sequence analysis. The objective of the present study was to establish experimental systems for the identification and characterization of early MCV gene transcripts. MCV mRNA was obtained in three ways: (1) MCV early mRNA was synthesized in vitro using permeabilized virions, (2) MCV mRNA was extracted from MCV-infected skin tissue, and (3) MCV mRNA was extracted from MCV-infected human embryonic fibroblasts. RNA/DNA hybridization experiments showed significant early transcriptional activity in two parts of the MCV genome. Transcripts of 11 early MCV genes located in these parts of the genome, including two subunits of the MCV DNA-dependent RNA polymerase (mc077R and mc079R), the MCV poly(A)+ polymerase gene (mc076R), and the MCV MHC class I homolog (mc080R), were detected in reverse transcription-polymerase chain reaction experiments. Total RNA obtained from MCV-infected skin tissue was used to confirm these results. Three MCV early transcripts, mc002L, mc004.1L, and mc005L, produced distinct bands on rapid amplification of their 3' ends (3' RACE). The 5' mapping of transcription start sites of MCV open reading frames (ORFs) mc002L, mc004.1L, mc005L, and mc148R revealed that the MCV RNA polymerase transcription start sites are consistently located between 11 and 13 nucleotides downstream of the early MCV consensus promoter signal. When cDNA from both 5' and 3' mapping experiments was analyzed, MCV ORFs mc004. 1L and mc005L were found to be transcribed as a single bicistronic mRNA. The transcript from MCV ORF mc066L, encoding a glutathione peroxidase, was detected in in vitro synthesized MCV mRNA as well as in total RNA from MCV-infected human embryonic fibroblasts and MCV-infected skin. This indicates that despite the lack of an early MCV consensus promoter signal immediately proximal to the start codon, this particular gene is transcribed early during MCV infection.

Base Sequence↗

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.

Animals↗

Strategy for identifying the gene encoding the DNA polymerase of molluscum contagiosum virus type 1.

Molluscum contagiosum virus (MCV) is a member of the family Poxviridae and pathogenic to humans. MCV causes benign epidermal tumors mainly in children and young adults and is a common pathogen in immunecompromised individuals. The viral DNA polymerase is the essential enzyme involved in the replication of the genome of DNA viruses. The identification and characterization of the gene encoding the DNA polymerase of molluscum contagiosum virus type 1 (MCV-1) was carried out by PCR technology and nucleotide sequence analysis. Computer-aided analysis of known amino acid sequences of DNA polymerases from two members of the poxvirus family revealed a high amino acid sequence homology of about 49.7% as detected between the DNA polymerases of vaccinia virus (genus Orthopoxvirus) and fowlpoxvirus (genus Avipoxvirus). Specific oligonucleotide primers were designed and synthesized according to the distinct conserved regions of amino acid sequences of the DNA polymerases in which the codon usage of the MCV-1 genome was considered. Using this technology a 228 bp DNA fragment was amplified and used as hybridization probe for identifying the corresponding gene of the MCV-1 genome. It was found that the PCR product was able to hybridize to the BamHI MCV-1 DNA fragment G (9.2 kbp, 0.284 to 0.332 map units). The nucleotide sequence of this particular region of the MCV-1 genome (7267 bp) between map coordinates 0.284 and 0.315 was determined. The analysis of the DNA sequences revealed the presence of 22 open reading frames (ORFs-1 to -22). ORF-13 (3012 bp; nucleotide positions 6624 to 3612) codes for a putative protein of a predicted size of 115 kDa (1004 aa) which shows 40.1% identity and 35% similarity to the amino acid sequences of the DNA polymerases of vaccinia, variola, and fowlpoxvirus. In addition significant homologies (30% to 55%) were found between the amino acid sequences of the ORFs 3, -5, -9, and -14 and the amino acid sequences of the E6R, E8R, E10R, and a 7.3 kDa protein of vaccinia and variola virus, respectively. Comparative analysis of the genomic positions of the loci of the detected viral genes including the DNA polymerases of MCV-1, vaccinia, and variola virus revealed a similar gene organization and arrangement.

Amino Acid Sequence↗

Characterisation by restriction mapping of three subtypes of molluscum contagiosum virus.

DNA from Molluscum contagiosum virus (MCV) isolates was analysed by restriction endonuclease digestion, identifying three virus subtypes. The structural features of MCV DNA are typical of poxviral DNA. Physical maps of cleavage sites for BamHI, CIaI, and HindIII were constructed for single isolates of each subtype. These differ extensively, indicating the independence of the three subtypes. However, they are closely related, as determined by molecular hybridisation and nucleotide sequence analysis, and their genomes are essentially colinear. There is marked geographical variation in the relative incidence of MCV I and II, whilst MCV III is uniformly rare.

Adolescent↗

Two major antigenic polypeptides of molluscum contagiosum virus.

A library of molluscum contagiosum virus (MCV) transferred into the cowpox vector expression system was screened with 12 sera from molluscum patients. Two recombinant proteins of 70 and 34 kDa were detected by immunoblotting and mapped to the open-reading frames MC133L and MC084L, respectively. Consensus sites were found between the C-terminus of the 70-kDa MCV protein and the 14-kDa fusion protein of vaccinia and variola virus, and between the 34-kDa MCV protein and the 37.5-kDa viral membrane-associated protein of vaccinia and variola virus. Rabbit antisera against these two proteins were prepared. An immunofluorescence study demonstrated that the 70- and 34-kDa proteins were predominantly expressed on the surface of recombinant virus-infected HeLa cells, indicating the potential to be inserted into the membrane. On immunoelectron microscopy, antiserum against 70-kDa protein showed significant labeling of the MCV membrane, while the antiserum against 34-kDa protein failed to do so.

Amino Acid Sequence↗

Immune-defense molecules of molluscum contagiosum virus, a human poxvirus.

Molluscum contagiosum virus encodes more than 150 proteins including some involved in host interactions that might contribute to prolonged viral replication in the skin. These include homologs of a selenocysteine-containing glutathione peroxidase, a death effector domain protein, a chemokine, a major histocompatibility complex class I molecule and an interleukin-18-binding protein.

Humans↗

A random DNA sequencing, computer-based approach for the generation of a gene map of molluscum contagiosum virus.

The genome of Molluscum contagiosum virus (MCV) has a high G + C content, which largely differs from those of vaccinia virus (VAC) and other characterized poxviruses. This has precluded the use of DNA hybridization for the identification of MCV genes and the further establishment of the virus genetic map. To circumvent this problem, we have partially sequenced clones containing virus restriction endonuclease fragments, which were derived by either single or double-digestion of genomic DNA from the subtype I of MCV. The DNA sequences were translated and used to search protein data bases. This analysis resulted in the finding of high-scoring matches to data base entries, including forty-five VAC genes. In addition, MCV-specific sequences that encoded protein domains of known function (i.e. DNA J domain) were found. The locations of MCV clones were inferred from the presumed colinearity of both MCV and VAC genomes, and further confirmed by PCR technology. The data presented here led to the construction of a partial genetic map of MCVI, which revealed that the order and orientation of a large number of MCV genes were equivalent to those of their VAC homologues. The conserved gene arrangement was apparently disrupted in the terminal regions, where MCV sequences showing homologies with the VAC counterparts were not found.

Base Composition↗

Detection of Molluscum contagiosum virus (MCV) subtype I as a single dominant virus subtype in Molluscum lesions from a Turkish population.

BACKGROUND: Molluscum contagiosum has a worldwide occurrence and its primary mode of transmission is via direct human contact including sexual means. The aim of the study was to implement a polymerase chain reaction-based assay for detection and subtyping of Molluscum contagiosum virus (MCV) in skin lesions diagnosed with molluscum contagiosum in a large regional teaching hospital in Turkey. METHODS: For this purpose, a total of 61 patients were included in the study. Randomly selected single lesion from each patient was used to extract DNA material and a specific PCR reaction amplifying 393-bp- and 575-bp-long regions from MCV genome was used in the detection. Subtyping was carried out by digestion of the amplified 575-bp product with restriction endonuclease enzyme BamHI. Both amplified and restriction enzyme digested products visualized on agarose gel electrophoresis. RESULTS: All 61 molluscum cases (100%) included in the study contained MCV genetic material as demonstrated by the presence of 393- and 575-bp-long PCR amplified products. Restriction enzyme BamHI digestion of the 575-bp-long amplicon indicated that the infecting subtype in all the cases (100%) was MCV subtype I. CONCLUSIONS: Results of this study demonstrate that subtype I is the only infecting strain dominant in our region. Because the only consecutive molluscum patients admitted to our hospital were included in the study, our data do not rule out the possibility that other genotypes might be present in the Turkish population. However, it is not unreasonable to conclude that similar trends exist in the rest of the country. Results also show that a molecular-based diagnostic assay would be feasible in cases where diagnosis was deemed necessary.

Adolescent↗

Some biological and physical properties of molluscum contagiosum virus propagated in cell culture.

Molluscum contagiosum virus propagated in FL cells of human amnion origin has a one-step growth cycle time of 12 to 14 h. The appearance and exponential increase of intracellular virus preceded the release of extracellular virus by approximately 2 h. Demonstration of comparable titers of extracellular and intracellular virus at the end of the replication cycle indicated that a substantial amount of virus remained associated with cells exhibiting cytopathogenic changes. Mean buoyant density values of virus in sucrose ranged from 1.275 to 1.278 g/cm3, but in CsCl the virus banded at densities at 1.325 to 1.340 and 1.261 to 1.281 g/cm3. Although virus infectivity was not affected by high concentrations of CsCl, it was found by polyacrylamide gel electrophoresis that the salt removed several nonglycosylated polypeptides with estimated molecular weights of 15,000 to 60,000. This suggested that the high-density band (1.325 to 1.340) may reflect the loss of these structural components. The half-life of virus infectivity was approximately 26.5 h at 26 degrees C and 11.2 h at 37 degrees C. Although the virus was rapidly inactivated at 50 degrees C, it could be stabilized at this temperature by the presence of 1.0 M MgCl2. Virus did not agglutinate newborn chick, adult chicken, or type "0" human erythrocytes. Virus infectivity was found to be sensitive to acid pH but resistant to treatment with diethyl ether or chloroform. The replication of molluscum virus in FL cells was not inhibited by 5-iodo-2'-deoxyuridine, 5-bromo-2'-deoxyuridine, or cytosine arabinonucleoside in noncytotoxic concentrations of 200 to 400 mug/ml, but greater than 99% reduction in the yield of herpes simplex virus or vaccinia virus in FL cells was obtained with 200 mug of these compounds per ml. Guanidinium chloride in concentrations of 100 to 200 mug/ml reduced molluscum virus yields by more than 99.9%.

Bromodeoxyuridine↗

Domain structure, intracellular trafficking, and beta2-microglobulin binding of a major histocompatibility complex class I homolog encoded by molluscum contagiosum virus.

The MC80R gene of molluscum contagiosum virus (MCV) type 1 encodes a major histocompatibility complex (MHC) class I homolog that lacks several amino-acid residues critical for peptide binding by MHC molecules, contains an unusually long N-terminal hydrophobic domain possibly derived by triplication of a signal peptide, and has a C-terminal transmembrane domain with two glutamate residues. All of these features were present in the orthologous gene of MCV type 2. The MC80R gene was expressed as two glycosylated polypeptides of Mr 47,000 and 42,000. Pulse-chase experiments indicated that the larger polypeptide was a precursor of the shorter one and that the entire N-terminal domain was slowly removed, consistent with its function as a long signal peptide. The protein was largely sequestered in the endoplasmic reticulum and Golgi membranes, remained endoglycosidase-H sensitive, and was not detected on the cell surface. In addition, a genetically modified form of the MC80R protein lacking the transmembrane and cytoplasmic domains was not secreted. The roles of the MC80R protein domains were investigated by constructing chimera between the viral protein and the MHC class I protein HLA-A2. Expression studies confirmed that the N- and C-terminal hydrophobic regions of the MC80R protein served as signal and transmembrane domains, respectively. The central portion of the MC80R protein, corresponding to the alpha1-alpha3 extracellular domains of HLA-A2, was largely responsible for sequestering the protein in the endoplasmic reticulum or Golgi compartments. The MC80R protein, as well as HLA-A2 chimera with the central region of MC80R, formed stable intracellular complexes with beta2-microglobulin. Complex formation, however, was detected only by overexpression of the MC80R protein or beta2-microglobulin.

Amino Acid Sequence↗

Specimens from a vesicular lesion caused by molluscum contagiosum virus produced a cytopathic effect in cell culture that mimicked that produced by herpes simplex virus.

Infection with molluscum contagiosum virus, a poxvirus, normally has a typical clinical presentation; therefore, laboratory confirmation is infrequently sought and the virus is rarely isolated in culture. As reported herein, viral culture of specimens from atypical lesions may produce an abortive infection in limited cell lines and a cytopathic effect suggestive of herpes simplex virus.

Adolescent↗

Preparation and use of molluscum contagiosum virus from human tissue biopsy specimens.

Molluscum contagiosum virus (MCV) lesions are limited to the human epidermis and can persist for months, showing only weak signs of inflammation. Because a culture system has not yet been created to replicate MCV, this chapter describes how the virus can be isolated from patient specimens. From this material, we describe how MCV is purified and used for infection studies, electron microscopy, viral DNA extraction, and analyses of early mRNA synthesized by in vitro transcription of permeabilized virions. The complete MCV-1 genome has been sequenced, and a redundant MCV genome fragment library of MCV type 1 (available from American Type Culture Collection [ATCC]) is useful for the cloning and study of individual MCV genes.

Biopsy↗