Poliovirus – A pathogen threatening the function of transplanted kidneys

The polyomaviruses are widely distributed in nature, and the human population is threatened by three different viruses: the BK virus (BKV), the JC virus (JCV), and the simian virus (SV40), which was first recognized in the context of the polio vaccine in the late 1950s. These viruses can cause various health problems, but in many cases, the infection remains hidden without causing serious symptoms.

Infection with polyomaviruses can occur early in childhood, and according to epidemiological data, virtually everyone has encountered these viruses by adulthood. JCV was first isolated in 1971, while the discovery of BKV also occurred around this time. The viruses generally enter the body through the respiratory tract or via blood transfusions, and epidemiological data suggest that 60-80% of the adult population in the United States is seropositive.

The impact of polyomaviruses on transplant recipients is particularly concerning, as the viruses can reactivate following transplantation, especially due to immunosuppressive treatments. The consequences of viral infection can be severe, making appropriate screening essential for diagnosis and the initiation of treatment.

Polyomaviruses and their Infection Mechanism

Polyomaviruses, including BK and JC viruses, attack kidney and nervous system cells. JCV was first isolated from the brain tissue of a patient suffering from multifocal encephalopathy, while BKV was discovered in a patient who had undergone kidney transplantation. The infection is usually asymptomatic, but the viruses can remain dormant in the kidneys and reactivate during organ transplantation.

BK or JC virus can be detected in the urine of 10-60% of transplant recipients, which can lead to serious complications. Typical symptoms include elevated serum creatinine levels, which may indicate declining kidney function. Ultrasound examinations may reveal hydronephrosis or ureteral stricture, while biopsy samples may show inflammatory changes indicative of viral reactivation.

A biopsy is essential for establishing a diagnosis, allowing for the differentiation of polyomaviruses from other viruses, such as cytomegalovirus. Electron microscopy can assist in identifying pathogens, as polyomavirus particles are smaller than those of similar viruses.

Treatment and Challenges of Polyomavirus Infection

Currently, there is no specific therapy available for the treatment of polyomavirus infection. There is no convincing evidence regarding the effectiveness of human immunoglobulins used by clinicians. Reducing immunosuppression may help mitigate the spread of infection, but this approach also carries the risk of organ rejection.

In certain cases, the use of a drug called Cidofovir has successfully saved transplanted kidneys, but viral infections often exacerbate the situation, especially in patients with chronic kidney disease. The diagnosis of PVAN (polyomavirus-associated nephropathy) plays a key role in urine cytological examination, which allows for monitoring of viral activity.

The medical community is continuously working to improve diagnostic methods, including the development of polymerase chain reaction (PCR) techniques that can aid in early diagnosis and tracking treatment responses. The reliability of PCR tests is crucial for monitoring viral load, but false-negative results can occur due to genetic variations.

Monitoring Polyomaviruses in Organ Transplantations

Screening for polyomaviruses during organ transplantations is essential to prevent infection between donor and recipient. Transplant committees follow strict protocols when selecting donors, as defined by appropriate regulations. Documentation must be submitted by the transplanting physician to the relevant authorities within eight days following the procedure.

After establishing a diagnosis of polyomavirus infection, the treatment strategy includes reducing immunosuppression and, if necessary, antiviral medication. Continuous monitoring is important for transplanted patients, as viral infections can recur at any time and increase the risk of organ rejection.

Current research aims to expand knowledge about polyomaviruses and improve treatment options. Researchers are seeking new techniques and therapeutic approaches to monitor viral activity, with the goal of developing more effective methods for treating the disease and preserving the health of transplant recipients in the future.