JC virus
Encyclopedia
The JC virus or John Cunningham virus (JCV) is a type of human polyomavirus
Polyomavirus
Polyomavirus is the sole genus of viruses within the family Polyomaviridæ. Murine polyomavirus was the first polyomavirus discovered by Ludwik Gross in 1953. Subsequently, many polyomaviruses have been found to infect birds and mammals...

 (formerly known as papovavirus
Papovavirus
A Papovavirus is any member of the former virus family of Papovaviridae. They are mainly associated with various neoplasms in mammals. The family of Papovaviridae is not longer used in recent taxonomy, but is split into the Papillomaviridae and the Polyomaviridae.The name derives from three...

) and is genetically similar to BK virus
BK virus
The BK virus is a member of the polyomavirus family. Past infection with the BK virus is widespread, but significant consequences of infection are uncommon, with the exception of the immunocompromised and the immunosuppressed.-History:...

 and SV40
SV40
SV40 is an abbreviation for Simian vacuolating virus 40 or Simian virus 40, a polyomavirus that is found in both monkeys and humans...

. It was discovered in 1971 and named using the two initials of a patient with progressive multifocal leukoencephalopathy
Progressive multifocal leukoencephalopathy
Progressive multifocal leukoencephalopathy , also known as progressive multifocal leukoencephalitis, is a rare and usually fatal viral disease that is characterized by progressive damage or inflammation of the white matter of the brain at multiple locations .It occurs almost exclusively in...

 (PML). The virus causes PML and other diseases only in cases of immunodeficiency
Immunodeficiency
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...

, as in AIDS
AIDS
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

 or during treatment with drugs intended to induce a state of immunosuppression
Immunosuppression
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...

 (e.g., organ transplant
Organ transplant
Organ transplantation is the moving of an organ from one body to another or from a donor site on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be...

 patients).

Epidemiology

The virus is very common in the general population, infecting 70 to 90 percent of humans; most people acquire JCV in childhood or adolescence. It is found in high concentrations in urban sewage worldwide, leading some researchers to suspect contaminated water as a typical route of infection.

Minor genetic variations are found consistently in different geographic areas; thus, genetic analysis of JC virus samples has been useful in tracing the history of human migration.

Infection and pathogenesis

The initial site of infection may be the tonsil
Tonsil
Palatine tonsils, occasionally called the faucial tonsils, are the tonsils that can be seen on the left and right sides at the back of the throat....

s, or possibly the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

. The virus then remains latent in the gastrointestinal tract and can also infect the tubular epithelial
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...

 cells in the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

s, where it continues to reproduce, shedding virus
Viral shedding
Viral shedding refers to the successful reproduction, expulsion, and host-cell infection caused by virus progeny. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses may begin to leave the cell by several methods.The term is used...

 particles in the urine.

JCV can cross the blood-brain barrier
Blood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...

 into the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

, where it infects oligodendrocyte
Oligodendrocyte
Oligodendrocytes , or oligodendroglia , are a type of brain cell. They are a variety of neuroglia. Their main function is the insulation of axons in the central nervous system of some vertebrates...

s and astrocyte
Astrocyte
Astrocytes , also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord...

s, possibly through the 5-HT2A
5-HT receptor
The serotonin receptors, also known as 5-hydroxytryptamine receptors or 5-HT receptors, are a group of G protein-coupled receptors and ligand-gated ion channels found in the central and peripheral nervous systems. They mediate both excitatory and inhibitory neurotransmission...

 serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...

 receptor
Receptor (biochemistry)
In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...

. JC viral DNA can be detected in both non-PML affected and PML-affected (see below) brain tissue.

Immunodeficiency or immunosuppression allows JCV to reactivate. In the brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

 it causes the usually fatal progressive multifocal leukoencephalopathy
Progressive multifocal leukoencephalopathy
Progressive multifocal leukoencephalopathy , also known as progressive multifocal leukoencephalitis, is a rare and usually fatal viral disease that is characterized by progressive damage or inflammation of the white matter of the brain at multiple locations .It occurs almost exclusively in...

, or PML, by destroying oligodendrocytes. Whether this represents the reactivation of JCV within the CNS or seeding of newly reactivated JCV via blood or lymphatics is unknown. Several studies since 2000 have suggested that the virus is also linked to colorectal cancer
Colorectal cancer
Colorectal cancer, commonly known as bowel cancer, is a cancer caused by uncontrolled cell growth , in the colon, rectum, or vermiform appendix. Colorectal cancer is clinically distinct from anal cancer, which affects the anus....

, as JCV has been found in malignant colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...

 tumors, but these findings are still controversial.

Drug interactions

Since immunodeficiency causes this virus to progress to PML, immunosuppressants are contraindicative to those infected.

The boxed warning for the drug rituximab
Rituximab
Rituximab, sold under the trade names Rituxan and MabThera, is a chimeric monoclonal antibody against the protein CD20, which is primarily found on the surface of B cells...

 (Rituxan, co-marketed by Genentech BioOncology and Biogen Idec) includes a statement that JC virus infection resulting in progressive multifocal leukoencephalopathy
Progressive multifocal leukoencephalopathy
Progressive multifocal leukoencephalopathy , also known as progressive multifocal leukoencephalitis, is a rare and usually fatal viral disease that is characterized by progressive damage or inflammation of the white matter of the brain at multiple locations .It occurs almost exclusively in...

, and death has been reported in patients treated with the drug.

The boxed warning for the drug natalizumab
Natalizumab
Natalizumab is a humanized monoclonal antibody against the cellular adhesion molecule α4-integrin. Natalizumab is used in the treatment of multiple sclerosis and Crohn's disease. It is co-marketed by Biogen Idec and Élan as Tysabri, and was previously named Antegren. Natalizumab is administered by...

 (Tysabri, marketed by Elan and developed by Biogen Idec) includes a statement that JC virus resulted in progressive multifocal leukoencephalopathy developing in three patients who received natalizumab in clinical trials.

The boxed warning was added on Feb. 19, 2009, for the drug efalizumab
Efalizumab
Efalizumab is a formerly available medication designed to treat autoimmune diseases, origianally marketed to treat psoriasis. As implied by the suffix -zumab, it is a recombinant humanized monoclonal antibody administered once weekly by subcutaneous injection...

 (Raptiva, marketed in the U.S. by Genentech, and marketed in Europe by Swiss drugmaker Merck Serono) includes a statement that JC virus, resulting in progressive multifocal leukoencephalopathy, developed in three patients who received efalizumab in clinical trials. The drug was pulled off the U.S. market because of the association with PML on April 10, 2009.

Treatments

In June 2010, the first case report appeared of a PML patient being successfully treated with mefloquine
Mefloquine
Mefloquine hydrochloride is an orally administered medication used in the prevention and treatment of malaria. Mefloquine was developed in the 1970s at the United States Department of Defense's Walter Reed Army Institute of Research as a synthetic analogue of quinine...

. Mefloquine is an antimalarial drug that can also act against the JC virus. Administration of mefloquine seemed to eliminate the virus from the patient's body and prevented further neurological deterioration.

On November 30, 2010, Cytheris announced that they had eradicated the JC virus from a PML patient, using their human interleukin-7 investigational drug (CYT107) combined with Chimerix's investigational, orally-available lipid conjugate prodrug of Cidofovir (CMX001).

External links

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