Analysis of the genome of molluscum contagiosum virus by restriction endonuclease analysis and molecular cloning

Comprehensive analysis of 66 complete molluscum contagiosum virus (MOCV) genomes: characterization and functional annotation of 47 novel complete MOCV genomes, including the first genome of MOCV genotype 3, and a proposal for harmonized MOCV genotyping indexing

IMPORTANCE

Four molluscum contagiosum virus (MOCV) genotypes (MOCV1-4) and four subtype variants were partially characterized using restriction enzyme profiling in the 1980s/1990s, but complete genome sequences of only MOCV1 and MOCV2 are available. The evolutionary pathways whereby genotypes/subtype variants with unavailable sequences emerged and whether all MOCVs can be detected using current diagnostic approaches remain unclear. We fully characterized 47 novel complete MOCV genomes, including the first complete MOCV3 genome, expanding the number of fully characterized genomes to 66. For reliably classifying the novel non-MOCV1/2 genomes, we developed and validated a framework for matching sequence-derived restriction maps with those defining MOCV subtypes in pioneering studies. Six phylogenetic subgroups (PG1-6) were identified, PG5 representing a novel MOCV2 subtype. The phylogenetic subgroups diverged from the prototype lineages following large-scale recombination events and hinted at partial sequence content of MOCV4 and direction of recombinant transfer in the events spawning PG5 and yet undetected MOCV1vb variant.

British Association for Sexual Health and HIV national guideline for the management of Genital Molluscum in adults (2021)

This guideline offers recommendations on diagnosis, treatment regimens and health promotion principles needed for the effective management of genital molluscum, including management of the initial presentation and recurrences. The Primary focus of the guideline is on infection which affects the genital area and has a sexual mode of transmission. This is an update to the guideline previously published in this journal in 2014.

Characterization of a Complete Genome Sequence of Molluscum Contagiosum Virus from an Adult Woman in Australia

The complete genome sequence of molluscum contagiosum virus 1 (MOCV1) isolate NT2017 was sequenced from a tissue sample from an Australian woman. The genome consisted of 185,655 bp encoding 169 predicted open reading frames. Phylogenetically, isolate NT2017 was most closely related to an MOCV1 strain from Slovenia.

The complete genome sequence of molluscum contagiosum virus 1 (MOCV1) isolate NT2017 was sequenced from a tissue sample from an Australian woman. The genome consisted of 185,655 bp encoding 169 predicted open reading frames. Phylogenetically, isolate NT2017 was most closely related to an MOCV1 strain from Slovenia.

New Insights into the Evolutionary and Genomic Landscape of Molluscum Contagiosum Virus (MCV) based on Nine MCV1 and Six MCV2 Complete Genome Sequences

Molluscum contagiosum virus (MCV) is the sole member of the Molluscipoxvirus genus and the causative agent of molluscum contagiosum (MC), a common skin disease. Although it is an important and frequent human pathogen, its genetic landscape and evolutionary history remain largely unknown. In this study, ten novel complete MCV genome sequences of the two most common MCV genotypes were determined (five MCV1 and five MCV2 sequences) and analyzed together with all MCV complete genomes previously deposited in freely accessible sequence repositories (four MCV1 and a single MCV2). In comparison to MCV1, a higher degree of nucleotide sequence conservation was observed among MCV2 genomes. Large-scale recombination events were identified in two newly assembled MCV1 genomes and one MCV2 genome. One recombination event was located in a newly identified recombinant region of the viral genome, and all previously described recombinant regions were re-identified in at least one novel MCV genome. MCV genes comprising the identified recombinant segments have been previously associated with viral interference with host T-cell and NK-cell immune responses. In conclusion, the two most common MCV genotypes emerged along divergent evolutionary pathways from a common ancestor, and the differences in the heterogeneity of MCV1 and MCV2 populations may be attributed to the strictness of the constraints imposed by the host immune response.

Molluscum contagiosum virus infection

Molluscum contagiosum virus is an important human skin pathogen: it can cause disfigurement and suffering in children, in adults it is less common and often sexually transmitted. Extensive and persistent skin infection with the virus can indicate underlying immunodeficiency. Traditional ablative therapies have not been compared directly with newer immune-modulating and specific antiviral therapies. Advances in research raise the prospect of new approaches to treatment informed by the biology of the virus; in human skin, the infection is localised in the epidermal layers, where it induces a typical, complex hyperproliferative lesion with an abundance of virus particles but a conspicuous absence of immune effectors. Functional studies of the viral genome have revealed effects on cellular pathways involved in the cell cycle, innate immunity, inflammation, and cell death. Extensive lesions caused by molluscum contagiosum can occur in patients with DOCK8 deficiency-a genetic disorder affecting migration of dendritic and specialised T cells in skin. Sudden disappearance of lesions is the consequence of a vigorous immune response in healthy people. Further study of the unique features of infection with molluscum contagiosum virus could give fundamental insight into the nature of skin immunity.

Rapid detection and typing of Molluscum contagiosum virus by FRET-based real-time PCR

A fluorescence resonance energy transfer (FRET)-based real-time PCR (RT-PCR) was developed for very sensitive and specific detection of Molluscum contagiosum virus (MCV), as well as reliable differentiation of the two MCV subtype genetic lineages, MCV1 and MCV2, in a single reaction. The assay employs modified primers specific for the viral MC021L gene and uses two novel FRET hybridization probes to detect polymorphisms specific for each of the two subtypes. The sensitivity of the assay at a 95% detection level for both MCV subtypes was 3.3 DNA copies/reaction and the dynamic range was nine orders of magnitude, discriminating 10-10(9) viral genome equivalents/reaction. Post-amplification probe-specific dissociation analysis differentiated the two viral subtypes reliably in all tested concentrations. Testing of 43 tissue specimens clinically diagnosed as MCV lesions showed complete agreement with the results obtained with previously described MCV specific MC080R Taqman RT-PCR and MC021L whole gene sequencing. The novel assay is simple, robust and easy to perform, and may be of great value for clinical and epidemiological studies of MCV infections and related conditions.

Congenital molluscum contagiosum: report of four cases and review of the literature

Molluscum contagiosum is a viral infection of the skin and mucous membranes that is caused by infection with the molluscum contagiosum virus. Molluscum contagiosum can be acquired from skin to skin contact which may be during play, in a swimming pool, or through sexual contact. Sexually acquired molluscum is rare in younger children, but becomes quite common during adolescence and young adulthood, after the sexual debut. It has been long known that the human papillomavirus, which causes genital warts, i.e., condyloma accuminatum, can be vertically transmitted through an infected genital tract. Children may not manifest condyloma lesions for a few years. The entity of congenital molluscum has been debated in the literature and only three cases of suspected congenital molluscum have been reported. We report on four more infants with congenital molluscum, two children with congenital lesions, and two children with onset of lesions at 6 weeks of age. Two children had single cutaneous lesions on the extremities and two had lesions of the scalp consistent with the site of cervical pressure. Congenital molluscum appears to be a more common entity than previously reported. Vertical transmission of molluscum should be considered for all infantile cases of molluscum.

Identification and genotyping of molluscum contagiosum virus from genital swab samples by real-time PCR and Pyrosequencing

BACKGROUND

Laboratory diagnosis of molluscum contagiosum virus (MCV) is important as lesions can be confused with those caused by Cryptococcus neoformans, herpes simplex virus, human papillomavirus, and varicella-zoster virus.

OBJECTIVES

To develop a rapid method for identifying patients infected with MCV via swab sampling.

STUDY DESIGN

Two dual-labeled probe real-time PCR assays, one homologous to the p43K gene and one to the MC080R gene, were designed. The p43K PCR was designed to be used in conjunction with Pyrosequencing for confirmation of PCR products and discrimination between MCV1 and MCV2.

RESULTS

Both PCR assays were optimized with respect to reaction components, thermocycling parameters, and primer and probe concentrations. The specificities of both PCR assays were confirmed by non-amplification of 38 known human pathogens. Sensitivity assays demonstrated detection of as few as 10 copies per reaction. Testing 703 swabs, concordance between the two real-time PCR assays was 99.9%. Under the developed conditions, Pyrosequencing of the p43K PCR product was capable of providing enough nucleotide sequence to definitively differentiate MCV1 and MCV2.

CONCLUSIONS

These real-time PCR assays can be used for the rapid, sensitive, and specific detection of MCV and, when combined with Pyrosequencing, can further discriminate between MCV1 and MCV2.

An overview of sexually transmitted diseases. Part III. Sexually transmitted diseases in HIV-infected patients

The HIV epidemic has dramatically altered the field of sexually transmitted diseases (STDs). HIV infection is unique among sexually transmitted diseases because it can modify the clinical presentation and features of other STDs. Conversely, other STDs can affect the transmission of HIV. This review is the third part of a series that has provided a general overview of STDs. In this article, genital ulcer diseases (genital herpes, syphilis, chancroid, lymphogranuloma venereum, and granuloma inguinale), human papillomavirus infection (anogenital warts and subclinical infections), molluscum contagiosum, human herpesvirus 8 infection, viral hepatitis, and ectoparasitic infestations (scabies and pediculosis pubis) are discussed as they occur in HIV-infected hosts. Additional features as they relate to HIV-infected patients, such as epidemiology and transmission, are discussed when applicable.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should improve their understanding of sexually transmitted diseases in the HIV-infected host.

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.

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.

Close relationship between equine and human molluscum contagiosum virus demonstrated by in situ hybridisation

To determine whether the virus responsible for human molluscum contagiosum (MCV) is the causal agent of a similar disease in horses, in situ hybridisations using cloned fragments of human MCV DNA labelled with digoxigenin were carried out on formalin-fixed biopsy sections of lesions from two horses with molluscum contagiosum-like skin lesions. In both instances there was evidence of specific hybridisation of the labelled probe to target DNA in the sections under high stringency conditions, identified by the development of a deep blue-purple stain in the cytoplasm of cells in the stratum spinosum and stratum granulosum of the lesions and the absence of non-specific hybridisation in adjacent non-lesional areas of the epidermis. These results indicate that on the basis of very close homology of their viral DNA sequences, the causative virus of equine molluscum contagiosum is either identical with, or very closely related to, its human equivalent.

Chemokine homolog of molluscum contagiosum virus: sequence conservation and expression

An analysis of the complete Molluscum contagiosum virus (MCV-1) genome sequence revealed a 104-amino-acid open reading frame (MC148R) that is structurally related to the beta (CC) family of chemokines. The predicted MCV chemokine homolog (MCCH) has a deletion in the NH2-terminal activation domain, suggesting the absence of chemoattractant activity. The principal objectives of the present study were to determine whether: (i) MCCH is conserved in independent isolates of MCV-1 and MCV-2; (ii) MCCH mRNA is expressed in vivo; and (iii) the MCCH protein is secreted from mammalian cells. The nucleotide sequence of the MCCH gene locus was determined for 27 isolates of MCV-1 and 2 of MCV-2 obtained from 29 MCV-infected individuals. In each case, the characteristic CC sequence, the NH2-terminal deletion, and the length of the open reading frame were conserved, although there were some, mostly conservative, amino acid substitutions. Since MCV cannot be propagated in cell culture, mRNA was synthesized in vitro by the early transcription apparatus in purified MCV virions. MCCH RNA was amplified by RT-PCR; the sequence included the complete open reading frame and extended 40 to 50 nucleotides past the first poxviral termination signal (TTTTTNT). Similar RT-PCR results were obtained using total cellular RNA derived from MCV-infected tissue specimens. Finally, the MCCH open reading frame was expressed in a vaccinia virus vector and the predicted size polypeptide was secreted into the medium, as determined by Western blotting. Taken together, our data support the prediction that MCV expresses a secreted chemokine homolog that could antagonize the inflammatory response in vivo.

Identification and typing of molluscum contagiosum virus in clinical specimens by polymerase chain reaction

A polymerase chain reaction (PCR) which enables the detection of molluscum contagiosum virus (MCV) genomes in either fresh or formalin-fixed clinical specimens is described. The primers used were designed to amplify a 167 bp region of the 3.8 kbp HindIII fragment K of the MCV 1 genome. The ability of this PCR to detect three common MCV types (1, 1v and 2) in clinical specimens was confirmed using frozen extracts from 75 molluscum lesions, and digests of single sections of 11 formalin-fixed, paraffin-embedded lesions; all of which had been previously typed by Southern hybridisation. In addition, 2 specimens previously negative by hybridisation were shown to be positive for MCV DNA by PCR. Confirmation of the identity of the PCR products and distinction between the two major MCV types (MCV 1/1v versus MCV 2) was achieved by comparison of the results of cleavage with the restriction endonucleases Hhal and Sacl. Sequencing of the PCR products revealed complete homology between MCV 1 and 1v, but minor nucleotide variations between MCV 1/1v and MCV 2 were identified. As well as providing a highly sensitive means of diagnosis, the technique may also prove useful for investigations into the pathogenesis, epidemiology and natural history of molluscum contagiosum infection.

Functional characterization of the C---C chemokine-like molecules encoded by molluscum contagiosum virus types 1 and 2

Many viruses have evolved mechanisms for evading the host immune system by synthesizing proteins that interfere with the normal immune response. The poxviruses are among the most accomplished at deceiving their hosts' immune systems. The nucleotide sequence of the genome of the human cutaneous poxvirus, molluscum contagiosum virus (MCV) type 1, was recently reported to contain a region that resembles a human chemokine. We have cloned and expressed the chemokine-like genes from MCV type 1 and the closely related MCV type 2 to determine a potential role for these proteins in the viral life cycle. In monocyte chemotaxis assays, the viral proteins have no chemotactic activity but both viral proteins block the chemotactic response to the human chemokine, macrophage inflammatory protein (MIP)-1alpha. Like MIP-1alpha, both viral proteins also inhibit the growth of human hematopoietic progenitor cells, but the viral proteins are more potent in this activity than the human chemokine. These viral chemokines antagonize the chemotactic activity of human chemokines and have an inhibitory effect on human hematopoietic progenitor cells. We hypothesize that the inhibition of chemotaxis is an immune evasion function of these proteins during molluscum contagiosum virus infection. The significance of hematopoietic progenitor cell inhibition in viral pathogenesis is uncertain.

The genome of molluscum contagiosum virus: analysis and comparison with other poxviruses

Analysis of the molluscum contagiosum virus (MCV) genome revealed that it encodes approximately 182 proteins, 105 of which have direct counterparts in orthopoxviruses (OPV). The corresponding OPV proteins comprise those known to be essential for replication as well as many that are still uncharacterized, including 2 of less than 60 amino acids that had not been previously noted. The OPV proteins most highly conserved in MCV are involved in transcription; the least conserved include membrane glycoproteins. Twenty of the MCV proteins with OPV counterparts also have cellular homologs and additional MCV proteins have conserved functional motifs. Of the 77 predicted MCV proteins without OPV counterparts, 10 have similarity to other MCV proteins and/or distant similarity to proteins of other poxviruses and 16 have cellular homologs including some predicted to antagonize host defenses. Clustering poxvirus proteins by sequence similarity revealed 3 unique MCV gene families and 8 families that are conserved in MCV and OPV. Two unique families contain putative membrane receptors; the third includes 2 proteins, each containing 2 DED apoptosis signal transduction domains. Additional families with conserved patterns of cysteines and putative redox active centers were identified. Promoters, transcription termination signals, and DNA concatemer resolution sequences are highly conserved in MCV and OPV. Phylogenetic analysis suggested that MCV, OPV, and leporipoxviruses radiated from a common poxvirus ancestor after the divergence of avipoxviruses. Despite the acquisition of unique genes for host interactions and changes in GC content, the physical order and regulation of essential ancestral poxvirus genes have been largely conserved in MCV and OPV.

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.

Detection and typing of molluscum contagiosum virus in skin lesions by using a simple lysis method and polymerase chain reaction

A polymerase chain reaction (PCR) assay for the rapid detection and typing of molluscum contagiosum virus (MCV) was developed. The target DNA was a 393 base pair (bp) segment, which is present in the coding region of the MCV p43K gene product. Release of MCV DNA from skin lesions was performed by using a simple procedure that provided suitable template DNA for amplification, and allowed detection of MCV directly in clinical material. The PCR yielded a unique 393 bp product when MCV DNA was used as template. This product was not shown with DNA from other viruses and bacterial pathogens causing skin diseases. The specific PCR product was obtained with individual lesions from all patients clinically diagnosed with MCV infection, whereas no products were detected with skin samples from healthy individuals. Sequencing of this PCR product allowed determination of the virus subtype on the basis of previously described nucleotide differences between subtypes MCVI and MCVII. To avoid the sequencing process, a second PCR assay was developed, in which the target DNA sequence included a MCVI-specific recognition site for the restriction endonuclease BamHI. This PCR assay yielded a unique 575 bp product with lesions from either MCVI- or MCVII-infected patients. However, only the MCVI-derived product was susceptible to BamHI digestion, which generated two fragments of 291 and 284 bp, respectively. Amplification of specific MCV DNA sequences from single, individual lesions provides a sensitive and reliable method for laboratory diagnosis and molecular epidemiology studies of molluscum contagiosum.

Genome sequence of a human tumorigenic poxvirus: prediction of specific host response-evasion genes

Molluscum contagiosum virus (MCV) commonly causes asymptomatic cutaneous neoplasms in children and sexually active adults as well as persistent opportunistic acquired immunodeficiency syndrome (AIDS)-associated disease. Sequencing the 190-kilobase pair genome of MCV has now revealed that the virus potentially encodes 163 proteins, of which 103 have homologs in the smallpox virus. MCV lacks counterparts to 83 genes of the smallpox virus, including those important in suppression of host responses to infection, nucleotide biosynthesis, and cell proliferation. MCV possesses 59 genes that are predicted to encode previously uncharacterized proteins, including major histocompatibility complex class I, chemokine, and glutathione peroxidase homologs, which suggests that there are MCV-specific strategies for coexistence with the human host.

Molecular epidemiologic analysis of Japanese patients with molluscum contagiosum

BACKGROUND

Molluscum contagiosum virus (MCV) causes molluscum contagiosum (MC) in both children and adults. Recent studies have revealed that the DNA of MCV can be classified into two major types by restriction enzyme cleavage patterns; however, the relationship between MCV types and the clinical features has not been fully understood. Our study was conducted to examine whether there are geographic differences in the incidence of MCV types and whether a correlation exists between MCV types and the age, sex, and clinical status of the patients.

METHODS

Specimens were obtained from 171 Japanese patients. The total DNA was extracted and digested with the restriction enzymes, BamH I, Hind III, and Cla I, respectively. Specimens were then electrophoresed in agarose gels. The gels were stained with ethidium bromide and photographs were taken under transillumination.

RESULTS

Six different cleavage patterns were observed; they were classified into two major types, MCV 1 and MCV 2, consisting of two MCV 1-variants, and MCV 2 prototype, and three MCV 2-variants. The ratio of MCV 1 to MCV 2 was 13:1. MCV 1 was commonly detected in children (98%) and adult women (92%). MCV 2 was more frequently isolated from adult men (44%) and from patients with human immunodeficiency virus (HIV) infection (75%).

CONCLUSION

MCV types found in Japanese children and adult women were predominantly MCV 1 and less frequently MCV 2. This pattern is similar to that observed in European countries and Australia, suggesting a high frequency and world-wide distribution of MCV 1. The higher incidence of MCV 2 among adult men and HIV-positive patients may indicate that transmission routes of MCV 1 and MCV 2 is somewhat different, of which the latter may be in part by sexual contact.

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.

Analysis of molluscum contagiosum virus genomes isolated in Japan

The genomes of 477 Japanese strains of molluscum contagiosum virus (MCV) were analyzed using an in-gel digestion method with the restriction enzyme BamHI, and classified into four types, including a newly detected type (MCV type 4). All type 1 (MCV-1) genomes examined so far in Japan showed a common difference from the genome of the MCV-1 prototype (MCV-1p), the type reported to be most prevalent in Europe. The common markers of the variants of MCV-1 were 24-kbp fusion fragments generated by the loss of a BamHI site between the D2 and F fragments of MCV-1p. These variants of MCV-1 were classified into three groups (MCV-1va, MCV-1vb, MCV-1vc), with the variability among them being due to additions and losses of BamHI sites located in the right terminus and around the E and I fragments of MCV-1va. The restriction map of MCV-4 was generated and lined up with those of the other types. Cross-hybridization analysis revealed that the organization of all types of MCV genomes were essentially colinear. Considerable numbers of BamHI restriction sites were conserved between MCV-2 and 4, indicating a close analogy between them. The overall prevalence of MCV, as shown by the ratios of MCV-1 (MCV-1p):MCV-2:MCV-3:MCV-4, was 436(0):13:24:4. Thus, the molecular epidemiology of MCV in Japan is characterized by the absence of the European prototype of MCV-1, the exclusive occurrence and abundance of variants of MCV-1, a greater prevalence of MCV-3 over MCV-2, and the presence of MCV-4.

Enzyme-linked immunosorbent assay for measurement of IgG antibody to Molluscum contagiosum virus and investigation of the serological relationship of the molecular types

An ELISA was developed for measuring levels of IgG antibodies to Molluscum contagiosum virus (MCV) using DNA typed purified virus as antigen. The assay was found to be specific and sensitive for antibodies to MCV as well as being economical in its use of antigen. A close relationship was found between antibody levels to the MCV molecular types 1, 1v and 2 by cross-testing sera on plates coated with the different molecular types of the virus as antigen (P < 0.001).

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.

Clinical and molecular aspects of molluscum contagiosum infection in HIV-1 positive patients

Molluscum contagiosum virus (MCV) lesions from 31 human immunodeficiency type 1 (HIV-1) positive patients and 54 HIV-1 negative adult control patients were examined for the presence and type of MCV DNA by high stringency Southern hybridization using 32P-labelled or digoxigenin-labelled MCV DNA probes. Of the 83 patients whose lesions contained detectable MCV DNA, 77 were infected with a single type of MCV (16 with MCV 1; 29 with MCV 1v; 30 with MCV 2; and 2 with MCV 2v). Five patients had apparent double infections, with hybridization results indicating the presence of various combinations of MCV 1 or 1v and MCV 2 or 2v. When these results were analysed in the light of clinical data no correlations were found between the MCV type(s) detected and the clinical stage of HIV-1 infection; nor between the MCV types and the anatomical site of the lesions or persistence of infection. However, the HIV-1 positive patients were significantly more likely to be infected with MCV types 2 or 2v than were the controls (17/29, 59% versus 15/48, 31%; P less than 0.05). Since a concurrent study of MCV lesions in children aged 15 years or less has shown that the percentage of infections attributable to MCV 2 or 2v is extremely small (3%), this finding suggests that MCV lesions in HIV-1 positive patients are attributable to adult-acquired MCV infection rather than to reactivation of a childhood infection.

Molecular epidemiological study of molluscum contagiosum virus in two urban areas of western Japan by the in-gel endonuclease digestion method

The in-gel endonuclease digestion method was introduced for the molecular epidemiology of molluscum contagiosum virus (MCV). We obtained clear electrophoretic patterns from 90.3% of single lesions. The distribution of MCV types in Western Japan was revealed to be different from that in other countries.

Direct detection of Molluscum contagiosum virus in clinical specimens by in situ hybridization using biotinylated probe

Molluscum contagiosum virus (MCV) is an unclassified poxvirus which has recently become recognized as causing a major sexually transmitted disease. At present no assay is available for specific detection of MCV because the virus cannot be serially propagated in cell culture. Since MCV produces an abortive, limited growth with some cytopathic effect in certain cell lines, we were able to develop an in situ hybridization assay for detection of MCV genome in clinical specimens. Human fetal diploid lung cell monolayers were infected with clinical specimens, and after proper incubation and fixation in paraformaldehyde, hybridization was performed under full stringency conditions with a molecularly cloned biotinylated probe. Only MCV infected cells showed homology to the MCV probe with a purple-brown cytoplasmic staining. Additionally, we have described an in situ hybridization assay for direct detection of MCV genome in formalin-fixed, paraffin-embedded biopsies. Characteristic intracytoplasmic Molluscum bodies (Henderson-Paterson bodies) were detected in stratum spinosum cells of the epidermis. Striking staining similarities have been observed between in situ hybridization and haematoxylin-eosin cytostaining. These procedures are the first successful identification of MCV genome in clinical samples by molecular hybridization, with sensitivity and specificity equal to or greater than electron microscopy.

Direct detection of molluscum contagiosum virus in clinical specimens by dot blot hybridization

A dot blot hybridization protocol was developed for the direct detection of molluscum contagiosum virus (MCV) DNA in clinical specimens submitted for virus isolation. Samples were concentrated by high-speed centrifugation and treated with proteinase K; this was followed by a single phenol-chloroform extraction step. The DNA was denatured, and the entire volume was spotted onto a nitrocellulose membrane. A biotinylated DNA probe specific for the BamHI-C region of MCV type 1 was used for hybridization. Evidence of MCV DNA was visualized by using streptavidin alkaline phosphatase conjugate and 5-bromo-4-chloro-3-indolyl phosphate-nitroblue tetrazolium as the substrate. Results showed that nonspecific hybridization does not occur with herpes simplex virus- or orf virus-infected clinical specimens and that dot blotting is more sensitive and reproducible than electron microscopy.

Characterization of a molluscum contagiosum virus homolog of the vaccinia virus p37K major envelope antigen

We present the first nucleotide sequence data for molluscum contagiosum virus (MCV), an unclassified poxvirus. A 2,276-bp XhoI fragment from a near left-terminal fragment of MCV subtype I (MCVI) and a 1,920-bp XhoI fragment from the corresponding locus of MCV subtype II (MCVII) were sequenced and analyzed for open reading frames (ORFs). A large, complete ORF of 1,167 bp was present in both fragments. The putative polypeptide has a calculated molecular mass of 43 kDa (p43K protein) and was shown to have a high degree of homology to the vaccinia virus p37K major envelope antigen (40% amino acid identity and 22% conservative changes). The nucleotide content of the MCV fragments sequenced was 66% G or C. The codon usage within the gene for p43K reflected this high G + C content, with position 3 of codons being predominantly G or C (82 and 87% for MCVI and MCVII, respectively). The MCV p43K-encoding gene has motifs immediately upstream which are similar to those required for vaccinia virus late gene expression. The location and direction of transcription of the MCV p43K-encoding gene were equivalent to those of the vaccinia virus p37K gene, revealing similarity in genetic organization between MCV and vaccinia virus. Another, incomplete ORF was identified downstream of the p43K-encoding gene in both MCVI and MCVII. The sequence immediately upstream of this ORF overlapped the termination codon of the p43K-encoding gene and contained a motif which had homology to the derived consensus sequence for vaccinia virus early gene promoters.

Stability of molluscum contagiosum virus DNA among 184 patient isolates: evidence for variability of sequences in the terminal inverted repeats

The stability of the Molluscum contagiosum virus Type 1 genome (188 kbp) was studied in 184 DNA isolates from 131 patients. Variability of up to 1.5 kbp at both ends of the genome symmetrically was observed using restriction analysis of the DNA isolates and by Southern Blot experiments using cloned and labeled HindIII terminal DNA fragments of MCV-1 prototype DNA. The variable sequences were mainly confined to the terminal fragments and parts of the MCV-1 terminal repeats. Labeled probes did not detect terminal sequences of MCV Type 2 under the applied stringency. A less marked instability of the central MCV-1 BamHI DNA fragment F was observed within the genome coordinates 0.431 to 0.454 mu. Reiteration of tandem repeats similar to those described for vaccinia virus might explain the variability of the terminal sequences and might be involved in viral replication.

Detection of molluscum contagiosum virus DNA by in situ hybridization

Three in situ hybridization protocols have been modified and used to comparatively examine formalin-fixed, paraffin-embedded tissue for the presence of molluscum contagiosum virus (MCV) DNA. Two cloned MCV 1 DNA fragments, MCV-1-B-D1 and MCV-1-B-F, were labelled with 32P-dCTP or digoxigenin-11-dUTP and used under conditions of high stringency to detect MCV DNA in sections of molluscum lesions. All methods were sensitive and were capable of detecting MCV after a minimum of 18 hours autoradiography (radiolabelled probes) or 3 to 18 hours (digoxigenin-labelled probes). However, one of the isotopic protocols produced less acceptable results in terms of non-specific background signals. A comparison of the DNA hybridization pattern with the underlying histopathological features of the molluscum sections revealed that there was not always a consistent association between the presence of detectable MCV DNA and cells containing the characteristic cytoplasmic inclusion bodies ("molluscum bodies") which are known to contain large numbers of virus particles. Although there is likely to be only limited scope for the application of this technique to diagnosis, it may prove useful for both retrospective and prospective epidemiological surveys. The in situ detection of MCV DNA may also be valuable for investigations into the cell biology of this imperfectly characterized virus.

Molecular epidemiology of Australian isolates of molluscum contagiosum

Molluscum contagiosum lesions obtained from 75 Australian patients, 22 (29%) of whom were HIV positive, were examined by restriction endonuclease analysis and Southern blot hybridisation using radiolabelled and digoxigenin-labelled MCV DNA probes. The isolates were classified (MCV 1, 1v, 2, and 2v) on the basis of these results, which were in turn correlated with the clinical features of each lesion. A total of 44 (59%) of the lesions contained MCV 1 or 1v, 24 (32%) contained MCV 2 or 2v, three (4%) contained multiple MCV types, whereas four (5%) of lesions submitted contained no detectable MCV DNA. The ratio of MCV 1/1v to MCV 2/2v was determined to be approximately 1.75:1. There were substantial differences between the distribution of MCV types 1 and 2 among patients of different age groups, but no significant relationship between MCV type and the sex of the patient was found. MCV 2 was more frequently detected in lesions from anogenital areas and in immunosuppressed (HIV-positive) patients, and MCV 1 was more commonly isolated from skin rather than genital lesions, but neither association was statistically significant. Fragment F (10 kbp) obtained from the genome of MCV 1 was capable of differentiating MCV 1 from MCV 2 when used as a probe in hybridisation experiments with BamHI cut samples and may be useful when small amounts of lesion prevents differentiation by direct visualisation of restriction endonuclease fragments.

Genomic characterization of Molluscum contagiosum virus type 1: identification of the repetitive DNA sequences in the viral genome

The genomes (188 kbp) of the prototype Molluscum contagiosum virus type 1 (MCV-1) and a variant strain (MCV-1v) were characterized by construction of the physical maps of the viral DNA for the restriction enzymes BamHI, ClaI, EcoRI, and HindIII using a defined gene library harboring the DNA sequences of the MCV-1 genome and by DNA-DNA hybridizations. It was found that the genomes of both MCV strains are identical, with the exception of very few changes in the DNA fragmentation patterns of restriction endonuclease BamHI as a consequence of naturally occurring nucleotide exchanges in the genome of the variant strain. Detailed hybridization experiments revealed the existence of repetitive DNA sequences, which are located within the terminal regions of the viral genome at the map coordinates 0 to 0.027 and 0.973 to 1.

Epidemiology of molluscum contagiosum using genetic analysis of the viral DNA

The molecular epidemiology of molluscum contagiosum virus (MCV) infections was investigated by restriction endonuclease analysis of the genomes of 222 separate isolates collected from 147 patients living in Germany (33 patients), Hong Kong (6 patients), and Scotland (108 patients). MCV type 1 (MCV-1) caused 96.6% of the infections, and MCV type 2 (MCV-2) caused 3.4%. However, isolates from four of the 142 MCV-1-infected patients and two of the five MCV-2-infected patients showed minor differences in their DNA restriction patterns because of the loss of a single or very few recognition sites for the enzymes used. No genome variations were detected amongst isolates collected from different sites or on several occasions from individual patients or from closely related patients. Southern blot hybridization revealed a high level of relatedness between MCV-1 and 2. No differences were seen in the appearance or anatomical localization of lesions caused by either virus type. In particular, there was no preferred genital localization for MCV-2 infections.

Molluscum contagiosum virus types in genital and non-genital lesions

The endonuclease digest patterns of viral DNA from 48 genital and 45 non-genital molluscum contagiosum virus (MCV) lesions were examined. The overall ratio of MCVI to MCVII was 3.23:1. There was no predominance of either MCV type in genital lesions. No obvious morphological differences were seen between MCVI and MCVII lesions. MCVII was not found in any patient under 15 years old.

Molluscum contagiosum: characterization of viral DNA and clinical features

Restriction endonuclease analysis of molluscum contagiosum virus DNA revealed two subtypes. In a study of 46 isolates from 41 patients, some with no other disorder and some with atopic dermatitis, the ratio of MCV I isolates to MCV II was 34:12. Multiple clustered lesions removed at the same time from an individual patient yielded only one type of MCV. Lesions induced by MCV I or MCV II were indistinguishable on the basis of size and form. Neither subtype was associated exclusively with lesions at certain sites or with other clinical features. Heterogeneity of DNA restriction endonuclease cleavage patterns amongst isolates of the same subtype was observed, this being greatest for MCV II.