Polyomavirus testing

Federal and state regulatory agencies mandate the use of fecal coliforms, E. coli and/or Enterococci as microbial indicators of water quality. However, these traditional indicators of fecal pollution do not adequately assess the specific sources of pollution or the associated health risks.  Many methods have been developed to identify sources of fecal contamination, and this field of study has been collectively termed Microbial Source Tracking (MST).

BCS laboratories uses the presence of human-specific polyomaviruses (HPyVs), (JCV and BKV), as an indicator of human fecal pollution in environmental water.  HPyVs are ubiquitous throughout the human population and serological studies speculate 60-80% of adults harbor antibodies against HPyVs. They are secreted in the urine in high titers and mostly cause asymptomatic infections. Infected individuals shed viruses throughout their life span.

We have developed and optimized a rapid and sensitive method to concentrate and extract DNA of HPyVs from environmental water samples.  Primers specific for the conserved T-antigen of both JCV and BKV are used in a nested PCR reaction to detect HPyVs. The method is able to detect as little as one microliter of raw sewage added to 100-ml of water.

Background on Human Polyomaviruses

The human polyomaviruses (HPyVs), JCV and BKV, have similarly structured genomes that show 75% homology (Hirsch and Steiger, 2003). The prevalence of these viruses in the human population is worldwide (Del Valle et al., 2004, Pavesi, 2005, Stolt et al., 2003).  Serological studies have shown 60-90% of adults harbor antibodies against human polyomaviruses (HPyVs) (Hirsch and Steiger, 2003, Polo et al., 2004).

A symptomless primary infection occurs during childhood (Bofill-Mas et al., 2000, Dorries, 1998); following which, the viruses establish latent infections in the renal tissue and can persist indefinitely (Del Valle et al., 2004, Shah, 1996).  Asymptomatic viruria can occur occasionally or continuously in infected individuals (Arthur et al., 1989, Hogan et al., 1980, Markowitz et al., 1993, Polo et al., 2004, Vanchiere et al., 2005).  Disease is normally associated when the host’s immune system becomes suppressed by conditions such as AIDS (White et al., 2005).

In general, polyomaviruses have a low morbidity, latency, and symptomless reactivation (Hirsch and Steiger, 2003).  Clinically these viruses are known for life long asymptomatic viruria in immunocompetent individuals (Polo et al., 2004).  Approximately one million viral particles can be shed in one milliliter of urine from a healthy individual (Bofill-Mas et al., 2000).

JC virus

The JC virus was first isolated in 1971 from a patient suffering from progressive multifocal leukoencephalopathy (PML) (Padgett et al., 1971); and is now recognized as the pathogenic agent associated with PML (Venter et al., 2004).  Disease caused by the JC virus is limited to individuals with comprised immune systems such as those who have AIDS (Padgett et al., 1971).  More than 10% of AIDS patients are afflicted with PML (Dolei et al., 2000, Berger et al., 1998).  JCV excretion is not contingent on a suppressed immune system and JCV DNA is often found in the urine of healthy individuals (Bofill-Mas et al., 2000, Markowitz et al., 1993).

BK virus

The BK virus was also initially isolated in 1971.  The virus was found in the urine of a male that had undergone a renal transplant (Gardner et al., 1971).  It is now documented that BKV reactivation can lead to interstitial nephritis and urteral stenosis in kidney transplant patients (Hirsch and Steiger, 2003, Polo et al., 2004).  BKV is more readily excreted in immunocompromised patients, including organ transplant patients, HIV patients and pregnant women (Knowles, 2001); however excretion in immunocompetent individuals has been documented (Behzadbehbahani et al., 2004).