Subtype IV of the BK polyomavirus is prevalent in East Asia

Abstract

BK polyomavirus (BKV) is ubiquitous in human populations, infecting children asymptomatically and then persisting in the kidney. Using either serological or genotyping methods, BKV isolates have been classified into four subtypes (I-IV), with subtype I mainly detected in all countries studied so far. To elucidate the subtype of BKV prevalent in East Asia, we examined BKV-positive urine samples collected from immunocompetent elderly patients in Mongolia, Northeast China, Northwest China, Southeast China, Southwest China, Vietnam and Japan. The 287-bp typing region of the viral genome in each of these samples was PCR-amplified and sequenced, and a phylogenetic tree was constructed. According to the tree, BKV isolates in East Asia were unambiguously classified into subtype I or IV (subtypes II and III were not detected). In Japan, subtype I was mainly detected and subtype IV was rare, whereas in the other regions subtype IV was detected frequently, at rates ranging from 24 to 100%. Thus, East Asia (excluding Japan) is a region in which subtype-IV BKV is prevalent, a finding that requires the view of the geographic distribution of BKV subtypes to be revised. Furthermore, we present evidence that the immunological states of urine donors do not affect the pattern of BKV subtypes.

Age-Related Urinary Excretion of BK Polyomavirus by Nonimmunocompromised Individuals

“…Since it has been shown that JCV has coevolved with human populations (24), we recently started a series of studies to elucidate relationships between BKV lineages and human populations (3,9,25). In some of these studies, we used BKV DNA from urine samples collected from nonimmunocompromised individuals.…”

Distribution patterns of BK polyomavirus (BKV) subtypes and subgroups in American, European and Asian populations suggest co-migration of BKV and the human race

“…Two American populations in North-east USA and southern California, two European populations in Finland and Ireland/England, and two Asian populations in Japan and China were examined in this study. The population in North-east USA is described in this study, whilst the other populations have been described previously Chen et al, 2006;Suzuki et al, 2002;Takasaka et al, 2004). The population in North-east USA consisted of three groups with different clinical status: healthy volunteers, non-immunosuppressed patients and immunosuppressed renal transplant (RT) patients (Table 1).…”

Evolution of four BK virus subtypes

“…Even taking the 95% highest posterior density intervals into account, the time scale provided using this calibration point clearly dates the evolution and divergence of BKVs (2.2 Myr ago) far prior to the appearance and radiation of modern humans (0.195 Myr ago;McDougall et al, 2005), and does not offer an explanation for the observed relationships between BKV lineages and human populations (Zheng et al, 2007). There are several reports on the prevalence of BKV subtypes and subgroups (Agostini et al, 1995;Baksh et al, 2001;Chen et al, 2006;Di Taranto et al, 1997;Ikegaya et al, 2006;Jin et al, 1993aJin et al, , 1995Krumbholz et al, 2006;Takasaka et al, 2004), and the data indicate a complex regional distribution pattern. An even earlier timescale for BKV evolution was obtained by Nishimoto et al (2006).…”

“…Furthermore, there is evidence that BKV infection is a prominent risk factor for bladder carcinoma in immunocompetent individuals (Weinreb et al, 2006). The regional distribution of the BKV subtypes has been established in several studies (Agostini et al, 1995; Baksh et al, 2001; Chen et al, 2006;Di Taranto et al, 1997;Ikegaya et al, 2006;Jin et al, 1993aJin et al, , 1995Krumbholz et al, 2006;Takasaka et al, 2004). Subtype I is most prevalent, followed by subtype IV, with subtypes II and III occurring less frequently.…”