The polyomaviruses WUPyV and KIPyV: a retrospective quantitative analysis in patients undergoing hematopoietic stem cell transplantation

  • Nasim Motamedi1Email author,

    Affiliated with

    • Helga Mairhofer1,

      Affiliated with

      • Hans Nitschko1,

        Affiliated with

        • Gundula Jäger1 and

          Affiliated with

          • Ulrich H Koszinowski1

            Affiliated with

            Virology Journal20129:209

            DOI: 10.1186/1743-422X-9-209

            Received: 14 September 2011

            Accepted: 13 September 2012

            Published: 18 September 2012



            The polyomaviruses WUPyV and KIPyV have been detected in various sample types including feces indicating pathogenicity in the gastrointestinal (GI) system. However, quantitative viral load data from other simultaneously collected sample types are missing. As a consequence, primary replication in the GI system cannot be differentiated from swallowed virus from the respiratory tract.

            Here we present a retrospective quantitative longitudinal analysis in simultaneously harvested specimens from different organ sites of patients undergoing hematopoietic stem cell transplantation (HSCT). This allows the definition of sample types where deoxyribonucleic acid (DNA) detection can be expected and, as a consequence, the identification of their primary replication site.


            Viral DNA loads from 37 patients undergoing HSCT were quantified in respiratory tract secretions (RTS), stool and urine samples as well as in leukocytes (n = 449). Leukocyte-associated virus could not be found. WUPyV was found in feces, RTS and urine samples of an infant, while KIPyV was repeatedly detected in RTS and stool samples of 4 adult patients.

            RTS and stool samples were matched to determine the viral load difference showing a mean difference of 2.3 log copies/ml (p < 0.001).


            The data collected in this study suggest that virus detection in the GI tract results from swallowed virus from the respiratory tract (RT). We conclude that shedding from the RT should be ruled out before viral DNA detection in the feces can be correlated to GI symptoms.


            WU polyomavirus KI polyomavirus Gastrointestinal Tract Respiratory system Urine Hematopoietic Stem Cell Transplantation Immunocompromised Host Viral Load



            In 1971, the first human pathogenic polyomaviruses (PyV) BKV and JCV were discovered in severely immunosuppressed patients [1, 2]. Since then, BKV and JCV have been detected in various sample types from different organ systems including urine specimens, serum samples and leukocytes, which seem to form the vehicle for virus spread [36].

            The two polyomaviruses WU polyomavirus (WUPyV) and KI polyomavirus (KIPyV) were first described in 2007 [7, 8]. Recent findings imply that primary contact occurs during childhood resulting in a persistent infection [911]. They have mainly been detected in respiratory tract (RT) secretions (RTS) but also in stool samples [7, 1217], raising the question of a causal connection to gastrointestinal (GI) symptoms [1316, 18]. So far, however, no clear association between virus detection and specific symptoms could be shown. Like previously described for BKV/JCV, an association between the appearance of WUPyV/KIPyV and immunosuppression – especially with hematopoietic stem cell transplantation (HSCT) - has repeatedly been observed [9, 13, 14, 19]. In analogy to findings of BKV and JCV in leukocytes [36], a hematologic reservoir is also suspected for WUPyV and KIPyV [16].

            To elucidate the tissue tropism of these viruses many studies followed a cross-sectional design. Such studies, however, have not revealed significantly different prevalence rates for patients and control groups [20, 21]. Hence, as seen for BKV/JCV, quantitative assignment of viral loads could be indicative for clinically relevant viral replication [22]. This theory is supported by a recent study reporting higher KIPyV loads in RTS of patients undergoing HSCT than of the control group [20].

            As mentioned, WUPyV/KIPyV DNA has been detected in stool samples. However, a common challenge when detecting viral DNA in the GI tract is the differentiation between possibly pathogenic primary replication and secondary shedding due to swallowed virus [23]. This problem can only be addressed by longitudinal viral DNA quantification in different simultaneously collected sample types.

            Therefore, we performed this retrospective analysis to provide quantitative viral load data in different specimens of patients undergoing HSCT. Furthermore, we address the question of genuine viral replication in the gastrointestinal tract as opposed to detection of viral DNA by polymerase chain reaction (PCR) due to secondary shedding from the respiratory system.

            Material and methods

            A retrospective analysis for the prevalence of WUPyV and KIPyV in HSCT-patients was performed with a total of 449 clinical samples from 37 HSCT-patients. These patients were routinely screened for viral pathogens throughout HSCT-therapy, which comprised WUPyV and KIPyV as well as EBV, CMV, HHV6 and Adenovirus. In case of a clinical suspicion, further PCR testing was performed for HSV, Norovirus, Rotavirus, Parvovirus B19, Influenza virus and Parainfluenza virus.

            The study was conducted in accordance with the Declaration of Helsinki. All patients gave informed consent to virological surveillance, collection and publication of data. Approval was waived by the ethics committee of the Ludwig-Maximilians-University.

            Assays were carried out according to standard detection techniques of the accredited laboratory for virological diagnostics of the Max von Pettenkofer-Institute.

            The study comprised RTS (throat washes, bronchoaleveolar lavages, endotracheal suctions), stool and urine samples and leukocytes. Samples were stored at 4°C and nucleic acid was extracted within 24 h with the High Pure Viral Nucleic Acid Kit (Roche Applied Biosystems). Leukocytes were adjusted to a cell number of 20,000 cells/assay. Quantitative real time-PCR was performed as previously described [24] as an in house test with slightly modified primers: 5’-TTGGATGAAAATGGCATTGG-3’, 5’-AACCCTTCTTTGTCTAAARTGTAGCC-3’; Probes: WU: 5’-FAM-CATAACTTGTGCTGACCTTTTGGGAGTTAAC-BHQ1-3’, KI: 5’-HEX-ACATTACTTGTGCAGATATGCTTGGAACAGC-BHQ1-’3 (ELLA Biotech GmbH, Martinsried, Germany). Positive control plasmids for WUPyV and KIPyV were kindly provided by Benedikt Weißbrich (University of Würzburg, Germany).

            The sensitivity threshold of the assay with a detection probability of 90% was 7 copies/20,000 cells for leukocytes and was 350 copies/ml for RTS, stool and urine samples, corresponding to 2.54 log copies/ml.

            RTS and stool samples that tested positive were matched to define the mean difference between viral loads in RTS and stool samples.

            Our statistical inference regarding the differences in log viral loads was based on a two-sided paired t test. A p value < 0.05 was regarded as significant.


            Initial analysis

            During the initial analysis, 19 out of 208 specimens taken from 37 patients tested positive for WUPyV or KIPyV. Positive results could be assigned to 5 patients (total number of samples from these 5 patients: 64) (Table1). KIPyV was detectable in RTS and stool samples from 4 adult patients, whereas WUPyV was found in RTS, stool and urine samples of an infant.
            Table 1

            Characteristics of the 5 hematopoietic stem cell transplantation (HSCT) patients presenting WUPyV or KIPyV



            Transplant type


            Antiviral therapy

            Co-infecting viruses in RTS

            Co-infecting viruses in stool

            Co-infecting viruses in further samples

            KIPyV (adult patients)


            Double Cord-Blood- Transplantation

            Chronic (skin, gut - max. IV°)

            Cidofovir (days +121 to +272)

            HHV6, HSV


            HHV6 (leukocytes), BKV, HHV6 (urine)



            Allogeneic PBSCT

            Chronic ( skin, gut - max. IV°)

            Cidofovir, Ribavirin ( days +118 to +176)

            EBV, HHV6, HSV

            Adenovirus, EBV

            EBV, HHV6, Adenovirus (leukocytes)



            Allogeneic BMT

            Acute (skin - max. II°)

            Foscarnet ( days +19 to +55), Cidofovir ( days +55 to +138)

            HHV6, EBV


            EBV (leukocytes)



            Allogeneic PBSCT

            Acute (gut - max. III°)




            HHV6, EBV (leukocytes)

            WUPyV (infant)


            Allogeneic PBSCT

            Chronic (pre-PBSCT: skin, gut, hematopoietic system - max. III°)

            Cidofovir ( days +17 to +58)

            HHV6, Adenovirus, HHV7, HSV

            Norovirus, Adenovirus, HHV6

            HHV6 (urine)

            Clinical data summary for the HSCT patients that tested positive for WUPyV and KIPyV including detected co-infecting viruses throughout the observation period and antiviral therapy; Antiviral therapy: all patients received prophylactic Acyclovir therapy. Further antiviral therapy is depicted with time-points (day 0: day of HSCT). Co-infecting viruses in RTS, stool and further samples in order of detection frequency. GvHD: Graft versus Host Disease; RTS: respiratory tract samples, PBSCT: peripheral blood stem cell transplantation.


            In these 5 patients, viral loads were defined over time in another 241 samples from different organ sites (RTS, stool, leukocytes, urine; total: 305 samples) (Figure 1 2). All patients had a period of diarrhea during HSCT which coincided with detection of WUPyV/KIPyV, but also with mucositis and Graft versus Host Disease (GvHD – stages were defined according to Glucksberg et al. [25]) of the gut and detection of co-infecting pathogenic viruses (Table1). Thus, primary and possibly pathogenic replication in the gastrointestinal tract needed to be differentiated from secondary shedding events from the RT. For this purpose, RTS and stool specimens collected with a maximum time difference of 24 hours were matched in pairs (n = 34) and viral load differences were defined. A significant mean viral load difference of 2.3 log copies/ml was determined between these 2 sample types (p < 0.001).
            Figure 1

            Courses of KIPyV load in respiratory tract samples and stool samples in 4 adult patients. Quantitative Real Time-PCR was performed to determine viral loads (copies/ml) in different specimens before and after hematopoietic stem cell transplantation (HSCT). The 90% sensitivity threshold was at 350 copies/ml corresponding to 2.54 log copies/ml indicated by the horizontal dotted line. The bold line represents day 0 of HSCT; the dashed vertical line shows time point of neutrophil granulocyte engraftment. Please note that most samples were collected after HSCT. RTS: respiratory tract secretion.

            Figure 2

            Courses of WUPyV viral load in respiratory tract samples, stool and urine samples in infant patient 5. Quantitative Real Time-PCR was performed to determine viral loads (copies/ml) in different specimens before and after hematopoietic stem cell transplantation (HSCT). The 90% sensitivity threshold was at 350 copies/ml corresponding to 2.54 log copies/ml indicated by the horizontal dotted line. The bold line represents day 0 of HSCT; the dashed vertical line shows time point of neutrophil granulocyte engraftment. RTS: respiratory tract secretion.

            Repeated testing of leukocytes showed neither KIPyV nor WUPyV. Leukocyte-associated viremia was therefore not seen in these patients despite simultaneous detection of high viral titers in other specimens and the severe immunosuppression throughout HSCT-therapy.

            A pediatric patient presented WUPyV in feces and RTS as well as in urine samples (Figure2). Previous studies indicate that primary infection with WUPyV/KIPyV occurs during childhood [911]. Thus, this could have been a case of primary infection for WUPyV which led to virus detection in the urine with lower viral loads than in RTS and stool samples.

            KIPyV was not detectable in urine samples at any time point.

            Prophylactic therapy with Acyclovir was routinely performed for all patients under HSCT. Further antiviral therapy is depicted in Table1. All patients presented HHV6, among other co-infecting viruses (Table1).

            Patients 1 and 2 had chronic Graft versus Host Disease (maximum WHO stage 4) until the end of the observation period that was treated with high doses of various immunosuppressants including Infliximab. Patient 1 developed a BKV-associated hemorrhagic cystitis. For this reason and for the HHV6-infection (Table1), antiviral therapy with Cidofovir was initiated on day +121 and lasted till the end of observation. While he could not clear BKV throughout the course of analysis, he did clear KIPyV (Figure1).

            Patient 2 was treated with Cidofovir and Ribavirin from day +118 to +176. From day +71 to +99 he had received 5 doses of Infliximab. The first time-point of virus detection was at day +82, followed by a steady decline and clearing of KIPyV until day + 246 (Figure1).

            Patient 3 was treated with Foscarnet and Cidofovir for HHV6 and EBV (Table1) from day +55 to +138. Clearing of virus coincided with antiviral treatment and neutrophil engraftment.

            Patient 4 did not receive further antiviral therapy and cleared the virus after a viral load peak of 6.1 log copies/ml 21 days after neutrophil engraftment.

            Patient 5 presented WUPyV among various co-infecting viruses. For an adenoviral infection, he was treated with Cidofovir from day +17 to +58, which coincides with clearing of the virus from the urine, but not in RTS or stool samples.


            In this retrospective longitudinal study, a total of 449 samples (RTS, stool, urine, leukocytes) from 37 HSCT-patients were quantitatively analyzed for the polyomaviruses WUPyV and KIPyV. KIPyV was found in RTS and stool samples of four adult patients, while an infant presented WUPyV in RTS and stool samples as well as in urine.

            Recent studies raised the question of a causal connection between WUPyV/KIPyV detection in the stool and the appearance of GI symptoms [1316, 18]. In this study, viral loads in RTS and stool samples correlated consistently. A mean viral load difference of 2.3 log copies/ml (p < 0.001) between respiratory and stool samples was observed. This suggests the RT as the primary site of replication with virus detection in feces resulting from swallowed virus. We conclude that, when screening for WUPyV or KIPyV in stool samples to define associated symptoms, respiratory secretions should be simultaneously analyzed to rule out viral shedding from the respiratory tract.

            These polyomaviruses were repeatedly detected in all 5 patients and viral load courses could be quantified. Clearing of KIPyV coincided with Cidofovir therapy in patients with severe immunosuppressive therapy due to high-grade GvHD and with immune reconstitution as determined by neutrophil granulocyte engraftment in patients with moderate immunosuppressive therapy, respectively. Cidofovir is a treatment option for BKV [4], and might therefore have antiviral activity on related viruses, such as WUPyV or KIPyV. Therefore, more studies are needed to exclude or to specify a possible impact of this substance and to further define factors associated with viral replication taking into account clinical symptoms as well as medication and immune status.



            We wish to thank Alexander Crispin for the great support in statistical analysis, Benedikt Weißbrich for kindly providing us with control plasmids for WUPyV and KIPyV and Josef Eberle for critical reading of the manuscript.

            Authors’ Affiliations

            Max von Pettenkofer-Institute, Ludwig-Maximilians-University, Department of Virology


            1. Gardner SD, Field AM, Coleman DV, Hulme B: New human papovavirus (B.K.) isolated from urine after renal transplantation. Lancet 1971, 1:1253–1257.PubMedView Article
            2. Padgett BL, Walker DL, ZuRhein GM, Eckroade RJ, Dessel BH: Cultivation of papova-like virus from human brain with progressive multifocal leucoencephalopathy. Lancet 1971, 1:1257–1260.PubMedView Article
            3. Weber T, Major EO: Progressive multifocal leukoencephalopathy: molecular biology, pathogenesis and clinical impact. Intervirology 1997, 40:98–111.PubMedView Article
            4. Ahsan N, Shah KV: Polyomaviruses and human diseases. Adv Exp Med Biol 2006, 577:1–18.PubMedView Article
            5. Major EO, Amemiya K, Tornatore CS, Houff SA, Berger JR: Pathogenesis and molecular biology of progressive multifocal leukoencephalopathy, the JC virus-induced demyelinating disease of the human brain. Clin Microbiol Rev 1992, 5:49–73.PubMed
            6. Dorries K, Vogel E, Gunther S, Czub S: Infection of human polyomaviruses JC and BK in peripheral blood leukocytes from immunocompetent individuals. Virology 1994, 198:59–70.PubMedView Article
            7. Allander T, Andreasson K, Gupta S, Bjerkner A, Bogdanovic G, Persson MA, Dalianis T, Ramqvist T, Andersson B: Identification of a third human polyomavirus. J Virol 2007, 81:4130–4136.PubMedView Article
            8. Gaynor AM, Nissen MD, Whiley DM, Mackay IM, Lambert SB, Wu G, Brennan DC, Storch GA, Sloots TP, Wang D: Identification of a novel polyomavirus from patients with acute respiratory tract infections. PLoS Pathog 2007, 3:e64.PubMedView Article
            9. Abedi Kiasari B, Vallely PJ, Corless CE, Al-Hammadi M, Klapper PE: Age-related pattern of KI and WU polyomavirus infection. J Clin Virol 2008, 43:123–125.PubMedView Article
            10. Nguyen NL, Le BM, Wang D: Serologic evidence of frequent human infection with WU and KI polyomaviruses. Emerg Infect Dis 2009, 15:1199–1205.PubMedView Article
            11. Kean JM, Rao S, Wang M, Garcea RL: Seroepidemiology of human polyomaviruses. PLoS Pathog 2009, 5:e1000363.PubMedView Article
            12. Bergallo M, Terlizzi ME, Astegiano S, Ciotti M, Babakir-Mina M, Perno CF, Cavallo R, Costa C: Real time PCR TaqMan assays for detection of polyomaviruses KIV and WUV in clinical samples. J Virol Methods 2009, 162:69–74.PubMedView Article
            13. Babakir-Mina M, Ciccozzi M, Alteri C, Polchi P, Picardi A, Greco F, Lucarelli G, Arcese W, Perno CF, Ciotti M: Excretion of the novel polyomaviruses KI and WU in the stool of patients with hematological disorders. J Med Virol 2009, 81:1668–1673.PubMedView Article
            14. Mourez T, Bergeron A, Ribaud P, Scieux C, de Latour RP, Tazi A, Socie G, Simon F, LeGoff J: Polyomaviruses KI and WU in immunocompromised patients with respiratory disease. Emerg Infect Dis 2009, 15:107–109.PubMedView Article
            15. Bialasiewicz S, Whiley DM, Lambert SB, Nissen MD, Sloots TP: Detection of BK, JC, WU, or KI polyomaviruses in faecal, urine, blood, cerebrospinal fluid and respiratory samples. J Clin Virol 2009, 45:249–254.PubMedView Article
            16. Babakir-Mina M, Ciccozzi M, Perno CF, Ciotti M: The novel KI, WU, MC polyomaviruses: possible human pathogens? New Microbiol 2011, 34:1–8.PubMed
            17. Mueller A, Simon A, Gillen J, Schildgen V, Tillmann RL, Reiter K, Schildgen O: Polyomaviruses KI and WU in children with respiratory tract infection. Arch Virol 2009, 154:1605–1608.PubMedView Article
            18. Neske F, Blessing K, Prottel A, Ullrich F, Kreth HW, Weissbrich B: Detection of WU polyomavirus DNA by real-time PCR in nasopharyngeal aspirates, serum, and stool samples. J Clin Virol 2009, 44:115–118.PubMedView Article
            19. Debiaggi M, Canducci F, Brerra R, Sampaolo M, Marinozzi MC, Parea M, Arghittu M, Alessandrino EP, Nava S, Nucleo E, et al.: Molecular epidemiology of KI and WU polyomaviruses in infants with acute respiratory disease and in adult hematopoietic stem cell transplant recipients. J Med Virol 2010, 82:153–156.PubMedView Article
            20. Rao S, Garcea RL, Robinson CC, Simoes EA: WU and KI polyomavirus infections in pediatric hematology/oncology patients with acute respiratory tract illness. J Clin Virol 2011, 52:28–32.PubMedView Article
            21. Norja P, Ubillos I, Templeton K, Simmonds P: No evidence for an association between infections with WU and KI polyomaviruses and respiratory disease. J Clin Virol 2007, 40:307–311.PubMedView Article
            22. Jiang M, Abend JR, Johnson SF, Imperiale MJ: The role of polyomaviruses in human disease. Virology 2009, 384:266–273.PubMedView Article
            23. Schildgen O, Muller A, Simon A: Human bocavirus and gastroenteritis. Emerg Infect Dis 2007, 13:1620–1621.PubMedView Article
            24. Lindau C, Tiveljung-Lindell A, Goh S, Ramqvist T, Allander T: A single-tube, real-time PCR assay for detection of the two newly characterized human KI and WU polyomaviruses. J Clin Virol 2009, 44:24–26.PubMedView Article
            25. Glucksberg H, Storb R, Fefer A, Buckner CD, Neiman PE, Clift RA, Lerner KG, Thomas ED: Clinical manifestations of graft-versus-host disease in human recipients of marrow from HL-A-matched sibling donors. Transplantation 1974, 18:295–304.PubMedView Article

            This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://​creativecommons.​org/​licenses/​by/​2.​0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.