BK polyomavirus

An article about BK polyomavirus, its characteristics, and its clinical significance

BK polyomavirus (BKPyV) is a member of the Polyomaviridae family, which are small, non-enveloped viruses with circular double-stranded DNA genomes. BKPyV is known for its role in causing disease in immunocompromised individuals, particularly in patients who have undergone kidney transplantation.

Discovery and Nomenclature

BK polyomavirus was first isolated in 1971 from the urine of a renal transplant patient with the initials B.K., hence the name. It is one of several human polyomaviruses, which also include JC virus and Merkel cell polyomavirus.

Virology

BKPyV is a small virus, approximately 40-45 nm in diameter, with a genome of about 5,300 base pairs. The genome encodes several proteins, including the large T antigen, small t antigen, and the capsid proteins VP1, VP2, and VP3. The virus is highly species-specific, infecting only humans.

Epidemiology

BKPyV is widespread in the human population, with seroprevalence rates of 80-90% in adults. Primary infection typically occurs in childhood and is usually asymptomatic. After primary infection, the virus establishes latency in the kidneys and urinary tract.

Pathogenesis

In healthy individuals, BKPyV remains latent and does not cause disease. However, in immunocompromised patients, such as those undergoing kidney transplantation, the virus can reactivate. Reactivation can lead to BK virus nephropathy, a condition that can cause significant kidney damage and is a major cause of graft loss in kidney transplant recipients.

Clinical Manifestations

BK virus nephropathy is characterized by inflammation and damage to the renal tubules, leading to a decline in kidney function. Symptoms may include increased creatinine levels, reduced urine output, and signs of kidney dysfunction. Diagnosis is typically confirmed by kidney biopsy and detection of BKPyV DNA in the urine or blood.

Diagnosis

Diagnosis of BKPyV infection involves detecting viral DNA using polymerase chain reaction (PCR) assays in urine or blood samples. Urine cytology may also reveal "decoy cells," which are indicative of BKPyV infection.

Treatment

There is no specific antiviral treatment for BKPyV. Management involves reducing immunosuppression to allow the immune system to control the virus. In some cases, antiviral agents such as cidofovir or leflunomide may be used, although their efficacy is variable.

Prevention

Preventive strategies focus on monitoring kidney transplant recipients for early signs of BKPyV reactivation and adjusting immunosuppressive therapy accordingly. Regular screening for BKPyV DNA in urine or blood is recommended for high-risk patients.

Also see

• Polyomavirus
• JC virus
• Kidney transplantation
• Immunosuppression
• Viral nephropathy