Molluscum contagiosum virus

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Molluscum contagiosum virus
Negatively stained transmission electron micrograph of "Molluscum contagiosum virus" virions
transmission electron micrograph
of Molluscum contagiosum virus virions
Virus classification Edit this classification
(unranked): Virus
Realm: Varidnaviria
Kingdom: Bamfordvirae
Phylum: Nucleocytoviricota
Class: Pokkesviricetes
Order: Chitovirales
Family: Poxviridae
Genus: Molluscipoxvirus
Species:
Molluscum contagiosum virus

Molluscum contagiosum virus (MCV) is a species of

variola virus (cause of smallpox) and monkeypox virus.[3]

The poxvirus family uniquely contains both non-enveloped particles (mature virions), and enveloped particles (extracellular virions).

extracellular envelope. Like other poxviruses, MCV is a DNA virus that replicates in the cytoplasm instead of the nucleus. Because of this, the virus must bring all necessary enzymes for replication with it or encode the enzymes in its genome
.

Structure

The Molluscum contagiosum virus virion is described as oval-shaped and has the dimension of approximately 320 nm × 250 nm × 200 nm. The virus has two distinct infectious particles called the mature virion (MV) and the enveloped virion (EV), which differ in that the EV contains a second outer

cellular membrane. Poxviridae is the only virus family that contains both enveloped and non-enveloped infectious particles. Other structures of the EV and MV virion include the nucleocapsid, core wall, and two lateral bodies.[6] Before the virion is released into the cytosol, the lateral bodies are associated with the virion core through boding interactions. However, during virion release into the cytoplasm, the virion core wall expands and forces the lateral bodies to dissociate. The lateral bodies function to transport one or more vital virion proteins needed for genome replication or expression.[7]

Genome

The genome consists of a linear double-stranded

Vaccinia virus. The inverted terminal sequence of MCV differs from the sequences of others in the poxvirus family because it contains genus-specific host response evasion genes. The genome contains 64% GC bases, and thus encodes a lesser amount of the stop codons UAA, UGA, and UAG compared to other poxviruses. Further gene analysis has shown the MCV genome contains many long and overlapping open reading frames.[8]

Replication cycle

Entry into cell

Molluscum contagiosum virus, similar to all poxviruses, produces two infectious particles: mature virions (MV) and extracellular virions (EV), with the EV differing from the MV in that they possess an extra cellular membrane. To enter the cell, the membrane of MV fuses to the

macropinocytosis. This process is initiated by the presence of phosphatidylserine molecules exposed on the MV cellular membrane.[9] Similarly, the outer membrane of EV fuses to the plasma membrane, specifically glycosaminoglycans, of the host cell and also enters via macropinocytosis. After macropinocytosis, H+ is pumped inside the internalized vacuole containing EV and this acidification breaks down the outer membrane, exposing a MV like particle. For both MV and EV, the cellular membranes then fuse with the vacuole allowing the release of the virus core into the cytosol.[9][10]
The virion is then uncoated, exposing the DNA to commence replication.

Replication and transcription

Molluscum contagiosum virus, like other poxviruses, replicates entirely in the cytoplasm of the host cell. This is a property unique to poxviruses, as all other DNA viruses replicate in the nucleus. Therefore, because the host cell proteins for DNA replication are present inside the nucleus, this virus has to bring or encode for all of the proteins needed for replication.

viral factory' where DNA replication, transcription, and translation all occur sequentially.[citation needed
]

There are three phases of DNA transcription. During the early phase, genes that encode for

structural proteins and enzymes needed for future infection are transcribed and then translated. Gene expression is sequential from early to intermediate to late phase of transcription, and it is temporally regulated.[6]

Assembly and release

The virion cytoplasmic factories serve as the place where mature virions are assembled for future infection. Mature virions are released via

epithelial tissue.[6]

Tropism

Molluscum contagiosum virus only infects human

epidermal cells. It is not spread throughout the body, which explains why the virus cannot be transmitted through coughing or sneezing.[12] People have attempted to grow the virus in cell culture to study its molecular properties, but have been largely unsuccessful due to it only infecting epidermal cells.[8]

However, there is evidence that it has the ability to adapt and survive in different types of cells in humans with severely

CMX-001 antiviral agent as a treatment because of her severe molluscum contagiosum symptoms. Before administering the CMX-001 drug, Molluscum contagiosum virus DNA was found in 50% of her plasma samples, whereas DNA was found in 20% of samples after administering the drug. This is the first time molluscum contagiosum DNA was ever detected in the blood of a patient.[13]

Modulation of host cell processes

Several proteins produced mRNA in the intermediate phase of transcription modulate host cell processes to promote an ideal environment for the viral replication and transcription. Molecular analysis has shown that 77 MCV proteins may potentially interfere with host cell processes. However, only 7 MCV proteins have confirmed host cell functions. These proteins include MC007, MC054, MC066, MC132, MC148, MC159, and MC160.[8] The following list will give an overview of how these proteins modulate host cell processes.

Related disease

Molluscum contagiosum

Round, hard, flesh colored bumps that are the symptom of Molluscum contagiosum virus infection.

This is a viral infection of the skin that usually presents in children ages 1–10 and immunocompromised patients.

washing hands, not sharing items, refraining from sexual contact and shaving, and by keeping the bumps clean and covered.[4][12]

Generally, if one has a functioning immune system no treatment is needed and the bumps and virus will go away within 6–12 months of contraction. However, treatment is suggested if the bumps are on the genital area or if the person affected is immunocompromised. In healthy (non-immunocompromised) individuals,

laser therapy, oral therapy, or a topical therapy is suggested to treat the lesions. Cryotherapy involves freezing the lesions with liquid nitrogen, whereas curettage involves piercing the core and scraping the lesion with sterile equipment. Laser therapy involves destroying the lesion with a laser. It is a good idea to not try removing the lesions yourself, as the skin can become infected and the virus can spread to other parts of the body. A commonly prescribed oral medication used to treat the lesions is cimetidine and a topical therapy is Podophyllotoxin cream (0.5%).[12]

People with severely weakened immune systems and molluscum contagiosum may have bumps or lesions that are greater than 15 millimeters and look different from normal. Most typical therapies are ineffective in treating these people. The recommended treatment in this case are therapies that help boost the immune system.[12]

References

  1. PMID 23798852
    .
  2. ^ "Molluscum Contagiosum | Johns Hopkins Medicine Health Library". www.hopkinsmedicine.org. Retrieved 2019-03-10.
  3. ^ a b "Virus Taxonomy: 2018b Release". International Committee on Taxonomy of Viruses (ICTV). February 2019. Retrieved 14 March 2019.
  4. ^ a b c "Molluscum contagiosum - Symptoms and causes". Mayo Clinic. Retrieved 2019-03-05.
  5. ^ Humansandviruses (2015-03-24). "Poxviridae". humansandviruses. Retrieved 2019-03-10.
  6. ^ a b c "Molluscipoxvirus ~ ViralZone page". viralzone.expasy.org. Retrieved 2019-03-11.
  7. PMID 23891003
    .
  8. ^
    PMID 9201214
    .
  9. ^
    PMID 21792173
    .
  10. ^
    ISBN 9780123751560
    .
  11. PMID 23838441
    .
  12. ^ a b c d e f "Molluscum Contagiosum | Poxvirus | CDC". www.cdc.gov. 2019-01-03. Retrieved 2019-03-10.
  13. PMID 22262788
    .
  14. PMID 18701596
    .
  15. PMID 12552001
    .
  16. PMID 9417017
    .
  17. PMID 26041281
    .
  18. PMID 21802105
    .
  19. PMID 22301546
    .
  20. PMID 19158250
    .

External links
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