Human polyomavirus 9 infection in kidney transplant patients

Abstract

Several human polyomaviruses of unknown prevalence and pathogenicity have been identified, including human polyomavirus 9 (HPyV9). To determine rates of HPyV9 infection among immunosuppressed patients, we screened serum samples from 101 kidney transplant patients in the Netherlands for HPyV9 DNA and seroreactivity. A total of 21 patients had positive results for HPyV9 DNA; positivity rates peaked at 3 months after transplantation, but the highest viral loads were measured just after transplantation. During 18 months of follow-up, HPyV9 seroprevalence increased from 33% to 46% among transplant patients; seroprevalence remained stable at ≈30% in a control group of healthy blood donors in whom no HPyV9 DNA was detected. Further analysis revealed an association between detection of HPyV9 and detection of BK polyomavirus but not of cytomegalovirus. Our data indicate that HPyV9 infection is frequent in kidney transplant patients, but the nature of infection-endogenous or donor-derived-and pathogenic potential of this virus remain unknown.

Keywords: BK polyomavirus; BKPyV; HPyV9; immunocompromised host; immunosuppression; kidney transplant; kidney transplantation; kidney-pancreas transplant; polyomavirus; transplant; viruses.

Figure 1

Human polyomavirus 9 (HPyV9) DNA positivity and mean DNA viral load in transplant patients over time, the Netherlands. Bars indicate percentage of HPyV9-positive patients; line indicates DNA load. Time points are shown as described in Table 2. Pre, pretransplant (baseline).

Figure 2

Human polyomavirus 9 (HPyV9) seropositivity and seroreactivity in samples from transplant patients and healthy blood donor controls collected 1 year apart, the Netherlands. Black bars, baseline samples; white bars, follow-up samples (Table 2). Values below bars indicate no. persons positive/total no. tested. A) Seropositivity percentages for transplant patients and controls; B) seroreactivity levels for transplant patients and controls; C) seropositivity percentages for kidney transplant and kidney–pancreas transplant patients; D) seroreactivity levels for kidney transplant and kidney–pancreas transplant patients. MFI, median fluorescent intensity. *Borderline significant (0.05

Figure 3

Kaplan-Meier curves showing proportional increase of human polyomavirus 9 (HPyV9) DNA–positive and seropositive transplant patients during 12-month follow-up, the Netherlands. A) Cumulative HPyV9 DNA positivity (viremia) for transplant patients who were seronegative (gray) or seropositive (black) at baseline. B) Cumulative HPyV9 seropositivity for transplant patients who were nonviremic (gray) or viremic (black) at baseline.

Figure 4

Association between human polyomavirus 9 (HPyV9), BK polyomavirus (BKPyV), and cytomegalovirus (CMV) infection among transplant patients, the Netherlands. A) Percentage of HPyV9 DNA–positive samples among samples that tested negative (white bars) or positive (black bars) for BKPyV and CMV DNA; B) percentage of HPyV9 viremic patients among BKPyV- and CMV-nonviremic (white bars) and viremic (gray bars) patients; C) percentage of HPyV9 DNA–positive samples by measured BKPyV load within the same sample: low, <10³ copies/mL (white bars) or high, >10³ copies/mL (black bars). Values below bars indicate no. persons positive/total no. tested. *Significant (p<0.05 by χ² test).