Primary response against cytomegalovirus during antiviral prophylaxis with valganciclovir,in solid organ transplant recipients

Antiviral prophylaxis has proved successful for prevention of cytomegalovirus (CMV) disease in solid organ transplant (SOT) patients; though emerging data suggest that antiviral agents interfere with immunity, and may inhibit immune priming. In this context, we investigated levels and phenotype of primary CMV‐specific immune responses that developed during antiviral prophylaxis in a cohort of CMV seronegative recipients (R^?) of a SOT from a seropositive donor (D⁺). We longitudinally monitored CMV viral load, antibodies and levels of the negative immuno‐modulator IL‐10. PBMC were stimulated with CMV‐specific peptide libraries to measure CD137 activation marker on CMV‐specific T‐cells and levels of PD‐1 receptor, which is over expressed on exhausted T‐cells. Unexpectedly, the majority (13/18) of D⁺R^? patients who developed a primary CMV response showed early post‐transplant CMV‐specific responses, though levels of PD‐1 on CMV‐specific T‐cells remained elevated throughout prophylaxis. A strong inverse association was found between levels of plasma IL‐10 and CMV‐specific cellular immune responses. Our study suggests that during prophylaxis, subclinical CMV infection might have occurred in the D⁺R^? patients, and primary CMV‐specific responses were detected early post‐transplant when levels of plasma IL‐10 were low. Extended prophylaxis or antiviral treatment did not appear to suppress CMV‐specific antibodies or T‐cells, which, however, showed exhaustion phenotypes.     

Cytomegalovirus‐Responsive CD8+ T Cells Expand After Solid Organ Transplantation in the Absence of CMV Disease

Cytomegalovirus (CMV) is a major cause of morbidity and mortality in solid organ transplant recipients. Approximately 60% of adults are CMV seropositive, indicating previous exposure. Following resolution of the primary infection, CMV remains in a latent state. Reactivation is controlled by memory T cells in healthy individuals; transplant recipients have reduced memory T cell function due to chronic immunosuppressive therapies. In this study, CD8⁺ T cell responses to CMV polypeptides immediate‐early‐1 and pp65 were analyzed in 16 CMV‐seropositive kidney and heart transplant recipients longitudinally pretransplantation and posttransplantation. All patients received standard of care maintenance immunosuppression, antiviral prophylaxis, and CMV viral load monitoring, with approximately half receiving T cell–depleting induction therapy. The frequency of CMV‐responsive CD8⁺ T cells, defined by the production of effector molecules in response to CMV peptides, increased during the course of 1 year posttransplantation. The increase commenced after the completion of antiviral prophylaxis, and these T cells tended to be terminally differentiated effector cells. Based on this small cohort, these data suggest that even in the absence of disease, antigenic exposure may continually shape the CMV‐responsive T cell population posttransplantation.     

The use of CMVIg rescue therapy in cardiothoracic transplantation: A single‐center experience over 6 years (2011‐2017)

Cytomegalovirus (CMV) is the most important infectious agent in solid organ transplant recipients and has a major impact on morbidity and mortality. Most cases are well managed with antiviral agents, but CMV hyperimmune globulin (CMVIg) can be used alongside antiviral therapy for prophylaxis in high‐risk thoracic organ recipients and to treat life‐threatening CMV infection or disease. CMVIg may also improve antiviral host defences when genetic resistance to antivirals or unwanted side effects occur. In this single‐center, retrospective study, we reviewed the CMVIg use to supplement antiviral therapy as a “rescue therapy” in cardiothoracic transplant recipients. These comprised 12 single lung, 11 double lung, and 12 heart transplant recipients. Patients received a median of 2 doses of CMVIg, most often in combination with ganciclovir or valganciclovir, and reduced immunosuppression. One week after rescue therapy was initiated, CMV DNA levels were significantly reduced, and after four weeks, CMV DNA was undetectable in 73% patients. Only one patient died as a result of CMV‐related disease. No significant adverse effects were observed. We conclude that CMVIg rescue therapy is safe, well tolerated, and effective at controlling viral replication in cardiothoracic transplant recipients.     

A prospective longitudinal analysis of cytomegalovirus (CMV)‐specific CD4+ and CD8+ T cells in kidney allograft recipients at risk of CMV infection

Cytomegalovirus (CMV)‐specific cellular immunity is essential in controlling CMV infection after transplantation. We investigated whether CMV‐specific T cell levels predict CMV DNAemia after kidney transplantation. Using cytokine‐flow cytometry, we enumerated interferon‐γ producing CMV‐specific CD4+ and CD8+ T cells at serial time points among CMV‐mismatched (D+/R?) and seropositive (R+) kidney recipients who received 3 months of valganciclovir prophylaxis. Among 44 patients, eight (18%) developed CMV DNAemia at a mean (±SD) time of 151 (±33) days after transplantation, including two (5%) with CMV syndrome and three (7%) with tissue‐invasive CMV disease. Cox proportional hazards regression analysis showed that CMV mismatch (D+/R?) status (HR: 13, 95% CI: 1.6–106.4; P = 0.02) and diabetes mellitus (HR: 5.6; 95%CI: 1.1–27.9; P = 0.03) were significantly associated with CMV DNAemia. In contrast, the percentage or change‐over‐time in CMV‐specific CD4+ [pp65 (P = 0.45), or CMV lysate (P = 0.22)] and CD8+ [pp65 (P = 0.43), or IE‐1 (P = 0.37)] T cells were not significantly associated with CMV DNAemia. CMV‐specific T cell assays have limited clinical utility among CMV R+ kidney recipients who received valganciclovir prophylaxis. On the other hand, the clinical utility of CMV‐specific T cell assays will need to be assessed in a larger cohort of CMV D+/R? kidney recipients who remain at high‐risk of delayed‐onset CMV disease.     

Linking CMV Serostatus to Episodes of CMV Reactivation Following Lung Transplantation by Measuring CMV-Specific CD8+ T-Cell Immunity

CMV-specific immunity was assessed in a longitudinal cohort of 39 lung transplant recipients (LTR) who were followed prospectively from the time of transplant using a novel assay. At the time of surveillance bronchoscopy, CMV-specific CD8⁺ T-cell responses were assessed in the peripheral blood, using the QuantiFERON^®-CMV assay, which measures IFN-γ-secreting T cells following stimulation with CMV peptides. In total, 297 samples were collected from 39 LTR (CMV D+/R−, n = 8; D+/R+, n = 18; D−/R+, n = 6; D−/R−, n = 7). CMV-specific T-cell immunity was not detected in any of the CMV D−/R− LTR. In CMV seropositive LTR levels of CMV immunity were lowest early posttransplant and increased thereafter. While levels of CMV-specific immunity varied between LTR, measurements at any one time point did not predict episodes of CMV reactivation. In CMV mismatched (D+/R−) LTR, primary CMV immunity was not observed during the period of antiviral prophylaxis, but typically developed during episodes of CMV reactivation. Measuring CMV-specific CD8⁺ T-cell function with the QuantiFERON^®-CMV assay provides insights into the interrelationship between CMV immunity and CMV reactivation in individual LTR. A better understanding of these dynamics may allow the opportunity to individualize antiviral prophylaxis in the future.     

The risk of cytomegalovirus recurrence after kidney transplantation

Recurrent cytomegalovirus (CMV) infections commonly occur after kidney transplantation. We studied the impact of secondary prophylaxis and other factors on the risk of CMV recurrence. All kidney transplant recipients between 2004 and 2009 in our institution were analyzed (N = 254). Patients with CMV infection were included (N = 62). CMV infections were diagnosed with quantitative PCR. CMV D+/R- recipients received 6 months valganciclovir prophylaxis, after which DNAemia was monitored. After treatment, secondary prophylaxis with valganciclovir was given at the clinician's discretion for 2-26 weeks and CMV DNAemia was monitored. Altogether 43 reactivations and 19 primary infections occurred. Antiviral treatment with valganciclovir or ganciclovir was given to 45 patients; 34/62 (55%) patients received secondary prophylaxis for mean 62 days (range 14-180 days). CMV recurrence occurred in 14/43 (33%) seropositive patients and in 4/19 (21%) patients after primary infection. In logistic regression, delayed graft function (OR 3.4) and high viral load (>100 000 copies/ml) at initial diagnosis (OR 5.9) predicted recurrence. Use or length of secondary prophylaxis, CMV serostatus, level of immunosuppression, HLA mismatch, antiviral treatment, or time to clearance of viremia during treatment did not predict recurrence of CMV. CMV recurrences occur commonly despite secondary prophylaxis. High viral load at diagnosis predicted the risk of recurrent CMV infection.     

Following Universal Prophylaxis with Intravenous Ganciclovir and Cytomegalovirus Immune Globulin, Valganciclovir is Safe and Effective for Prevention of CMV Infection Following Lung Transplantation

We prospectively determined the safety and efficacy of valganciclovir for prevention of cytomegalovirus (CMV) in at-risk (donor positive/recipient negative [D+/R-] or R+) lung transplant recipients. We also determined the length of prophylaxis required to significantly decrease both CMV infection and disease. Consecutive lung transplant recipients surviving >30 days (n = 90) received combination prophylaxis with intravenous (i.v.) ganciclovir (GCV) 5 mg/kg/day and cytomegalovirus immune globulin (CMV-IVIG) followed by valganciclovir (450 mg twice-daily) to complete 180, 270 or 365 days of prophylaxis. This group was compared to a historical group (n = 140) who received high-dose oral acyclovir following i.v. GCV and CMV-IVIG. CMV disease was significantly lower in patients receiving valganciclovir compared to acyclovir (2.2% vs. 20%; p < 0.0001). Freedom from CMV infection and disease was significantly greater (p < 0.02) in patients receiving 180, 270 or 365 days of prophylaxis (90%, 95% and 90%, respectively) compared to those receiving 100-179 days (64%) or < 100 days (59%). No patient receiving valganciclovir died during the study. Following prophylaxis with i.v. GCV and CMV-IVIG, valganciclovir is safe and effective for prevention of CMV infection and disease in at-risk lung transplant recipients. The required length of prophylaxis was at least 180 days.     

Cytomegalovirus prevention strategies in seropositive kidney transplant recipients: an insight into current clinical practice

There is notable heterogeneity in the implementation of cytomegalovirus (CMV) prevention practices among CMV‐seropositive (R+) kidney transplant (KT) recipients. In this prospective observational study, we included 387 CMV R+ KT recipients from 25 Spanish centers. Prevention strategies (antiviral prophylaxis or preemptive therapy) were applied according to institutional protocols at each site. The impact on the 12‐month incidence of CMV disease was assessed by Cox regression. Asymptomatic CMV infection, acute rejection, graft function, non‐CMV infection, graft loss, and all‐cause mortality were also analyzed (secondary outcomes). Models were adjusted for a propensity score (PS) analysis for receiving antiviral prophylaxis. Overall, 190 patients (49.1%) received preemptive therapy, 185 (47.8%) antiviral prophylaxis, and 12 (3.1%) no specific intervention. Twelve‐month cumulative incidences of CMV disease and asymptomatic infection were 3.6% and 39.3%, respectively. Patients on prophylaxis had lower incidence of CMV disease [PS‐adjusted HR (aHR): 0.10; 95% confidence interval (CI): 0.01–0.79] and asymptomatic infection (aHR: 0.46; 95% CI: 0.29–0.72) than those managed preemptively, with no significant differences according to the duration of prophylaxis. All cases of CMV disease in the prophylaxis group occurred after prophylaxis discontinuation. There were no differences in any of the secondary outcomes. In conclusion, antiviral prophylaxis was associated with a lower occurrence of CMV disease in CMV R+ KT recipients, although such benefit should be balanced with the risk of late‐onset disease.     

Primary CMV Infections Are Common in Kidney Transplant Recipients After 6 Months Valganciclovir Prophylaxis

Prolonging cytomegalovirus (CMV) prophylaxis in CMV seronegative recipients of a kidney from CMV seropositive donor (D+/R–) may reduce the incidence of late infections. We analyzed late‐onset primary CMV infections after 6 months valganciclovir prophylaxis. Data from all CMV D+/R– kidney transplant recipients between January 2004 and December 2008 at our center were analyzed. Patients with a functioning graft at 6 months after transplantation who received 6 months of valganciclovir prophylaxis 900 mg once daily were included (N = 127). CMV was diagnosed with quantitative PCR. Prophylaxis was completed in 119 patients. Prophylaxis was stopped at 3–5 months due to leukopenia or gastrointestinal side effects in eight patients. Late‐onset primary CMV infection developed in 47/127 (37%) patients median 244 days after transplantation (range 150–655) and median 67 days after the cessation of prophylaxis (range 1–475). Four infections were asymptomatic. In others, symptoms included fever (N = 28), gastrointestinal symptoms (nausea, vomiting, diarrhea) (N = 24), respiratory tract symptoms (N = 12), and hepatopathy (N = 6). Median peak viral load was 13500 copies/mL (range 400–2 831 000). Recurrent CMV infection developed in 9/47 (19%) patients. No significant risk factors for CMV infection were identified. Symptomatic primary CMV infections were commonly detected also after prolonged valganciclovir prophylaxis.     

Pretransplant Interferon‐γ Secretion by CMV‐Specific CD8+ T Cells Informs the Risk of CMV Replication After Transplantation

In this prospective study we analyzed pretransplant interferon‐γ secretion by cytomegalovirus (CMV)‐specific CD8+ T cells to assess its possible utility in determining the risk of CMV replication after solid organ transplantation. A total of 113 lung and kidney transplant patients were enrolled in the study but only 55 were evaluable. All CMV‐seronegative recipients were pretransplant “nonreactive” (IFNγ <0.2 IU/mL) (11/11), whereas 30/44 (68.2%) CMV‐seropositive (R+) recipients were “reactive” (IFNγ ≥0.2 IU/mL) and 14/44 (31.8%) were “nonreactive”. In the R(+) “nonreactive” group, 7/14 (50%) developed posttransplant CMV replication, whereas the virus replicated only in 4/30 (13.3%) of the R(+) “reactive” patients (p = 0.021). According to the best multivariate model, pretransplant “nonreactive” recipients receiving an organ from a CMV‐seropositive donor had a 10‐fold increased risk of CMV replication compared to pretransplant “reactive” recipients (adjusted OR 10.49, 95% CI 1.88–58.46). This model displayed good discrimination ability (AUC 0.80) and calibration (Hosmer–Lemeshow test, p = 0.92). Negative and positive predictive values were 83.7% and 75%, respectively. The accuracy of the model was 82%. Therefore, assessment of interferon‐γ secretion by cytomegalovirus (CMV)‐specific CD8+ T cells prior to transplantation is useful in informing the risk of posttransplant CMV replication in solid organ transplant patients.     

Clinical validation of a novel enzyme‐linked immunosorbent spot assay‐based in vitro diagnostic assay to monitor cytomegalovirus‐specific cell‐mediated immunity in kidney transplant recipients: a multicenter,longitudinal, prospective,observational study

Impaired cytomegalovirus (CMV)‐specific cell‐mediated immunity (CMV‐CMI) is a major cause of CMV reactivation and associated complications in solid‐organ transplantation. Reliably assessing CMV‐CMI is desirable to individually adjust antiviral and immunosuppressive therapy. This study aimed to evaluate the suitability of T‐Track^® CMV, a novel IFN‐γ ELISpot assay based on the stimulation of peripheral blood mononuclear cells with pp65 and IE‐I CMV proteins, to monitor CMV‐CMI following kidney transplantation. A prospective longitudinal multicenter study was conducted in 86 intermediate‐risk renal transplant recipients. CMV‐CMI, CMV viral load, and clinical complications were monitored over 6 months post‐transplantation. Ninety‐five percent and 88–92% ELISpot assays were positive pre‐ and post‐transplantation, respectively. CMV‐specific response was reduced following immunosuppressive treatment and increased in patients with graft rejection, indicating the ability of the ELISpot assay to monitor patients' immunosuppressive state. Interestingly, median pp65‐specific response was ninefold higher in patients with self‐clearing viral load compared to antivirally treated patients prior to first viral load detection (P < 0.001), suggesting that reactivity to pp65 represents a potential immunocompetence marker. Altogether, T‐Track^® CMV is a highly sensitive IFN‐γ ELISpot assay, suitable for the immunomonitoring of CMV‐seropositive renal transplant recipients, and with a potential use for the risk assessment of CMV‐related clinical complications (ClinicalTrials.gov Identifier: NCT02083042).     

A Multicenter Study of Valganciclovir Prophylaxis up to Day 120 in CMV-Seropositive Lung Transplant Recipients

Seventy-six cytomegalovirus (CMV)-seropositive lung transplant recipients receiving valganciclovir (900 mg/day) for CMV prophylaxis were compared with a group of 87 patients receiving oral ganciclovir (3000 mg/day). Prophylaxis was administered to day 120 post-transplantation and follow-up was 1 year. In addition, a study was conducted on risk factors for CMV infection/disease. CMV disease incidence was 7.9% and 16.1% for valganciclovir and oral ganciclovir, respectively (p = 0.11). Patients receiving valganciclovir had fewer viral syndromes (2.6% vs. 11.5%, p < 0.05), a similar rate of tissue-invasive disease (5.2% vs. 4.6%, p = ns), longer time-to-onset of CMV infection/disease (197.5 vs. 155.2 days, p < 0.05), and a lower probability of infection/disease while on prophylaxis (1.3% vs. 12.6%, p < 0.01). Nonetheless, leukopenia incidence was higher with valganciclovir (15.8% vs. 2.3%, p < 0.01), as was the need for treatment withdrawal due to adverse effects (11.8% vs. 1.1%, p < 0.01). CMV infection was similar in both groups (32.9% vs. 34.5%). Induction therapy with basiliximab and glucocorticosteroid treatment were independent risk factors for developing CMV infection/disease. In conclusion, valganciclovir prophylaxis results in a low incidence of CMV disease in lung transplant recipients and appears more effective than oral ganciclovir. Despite the comparatively higher incidence of adverse events with valganciclovir, the drug can be considered safe for prophylaxis.     

CMV‐specific T‐cell immunity,viral load,and clinical outcome in seropositive renal transplant recipients: a pilot study

Sund F, Lidehäll A‐K, Claesson K, Foss A, Tötterman TH, Korsgren O, Eriksson B‐M. CMV‐specific T‐cell immunity, viral load, and clinical outcome in seropositive renal transplant recipients: a pilot study.
Clin Transplant 2010: 24: 401–409. © 2009 Wiley Periodicals, Inc. Abstract: Background: Cytomegalovirus (CMV) infection is still the leading opportunistic infection following solid organ transplantation. The aim of this prospective study of renal transplant recipients was to evaluate the dynamics of CMV‐specific T‐cells, viral load, and clinical symptoms of CMV infection. Methods: Levels of tetramer‐selected CD8⁺ T‐cells (TetraCD8), CMV‐specific interferon‐γ producing CD8⁺ T‐cells (IFNγCD8), and CD4⁺ T‐cells (IFNγCD4), measured using major histocompatibility complex‐tetramer and cytokine flow cytometry techniques, and CMV DNA were monitored monthly in 17 CMV‐seropositive patients up to one yr (median 12 months, range 3–12) after transplantation and correlated to clinical outcome. Results: CMV DNAemia was detected in 94% of the patients, but only one patient developed CMV disease. CMV DNAemia >1 million copies/mL was seen in asymptomatic patients. CMV‐specific T‐cells decreased rapidly after transplantation. TetraCD8 and IFNγCD8 regenerated within three months, whereas IFNγCD4 recovery was impaired up to one yr after transplantation. The proportion of IFNγCD4 at two months post‐transplantation as compared with baseline, correlated strongly with the magnitude of the CMV DNAemia. Conclusions: Monitoring the reduction of IFNγCD4 compared with baseline during the first months after transplantation could be considered in predicting risk for high‐grade CMV DNAemia and in deciding strategic approaches for pre‐emptive and prophylactic therapy.     

Delayed-onset primary cytomegalovirus disease after liver transplantation.

Clinical practice guidelines recommend antiviral prophylaxis to cytomegalovirus (CMV) donor-positive/recipient-negative (D+/R-) liver transplant recipients. We assessed the outcome of this strategy by determining the incidence, clinical features, and risk factors of CMV disease among CMV D+/R- liver transplant recipients who received antiviral prophylaxis. Sixty-seven CMV D+/R- liver transplant recipients (mean age+/-standard deviation: 49.5+/-11.4 years; 75% male) received oral ganciclovir [n=9 (13%)] or valganciclovir [n=58 (87%)] prophylaxis for a median duration of 92 days (interquartile range: 91-100). No breakthrough CMV disease was observed during antiviral prophylaxis. However, primary CMV disease was observed in 2%, 25%, 27%, 27%, and 29% of patients at 1, 3, 6, 12, and 24 months, respectively, after antiviral prophylaxis was stopped. The incidence of delayed-onset primary CMV disease was similar between those who received oral ganciclovir and valganciclovir. Nine (47%) patients had CMV syndrome, 8 (42%) had gastrointestinal CMV disease, and 2 (11%) had CMV hepatitis. Female patients (P=0.01) and younger age at transplant (P=0.03) were associated with an increased risk, whereas diabetes mellitus (P<0.001) was significantly associated with a lower risk of delayed-onset primary CMV disease. Allograft loss or mortality occurred in 8 (12%) patients during the median follow-up period of 3.31 (range: 0.8-5.9) years. No significant association was observed between CMV disease and patient and allograft survival. In conclusion, CMV disease remains a common complication in CMV D+/R- liver transplant patients during the contemporary era of antiviral prophylaxis. Female patients and younger patients are at increased risk of delayed-onset primary CMV disease.     

Clinical Utility of Cytomegalovirus (CMV) Serology Testing in High-risk CMV D+/R− Transplant Recipients

Late-onset cytomegalovirus (CMV) disease is a significant problem in D+/R- solid organ transplant (SOT) patients who receive antiviral prophylaxis. We assessed the clinical utility of CMV IgG and IgM serology testing for predicting late-onset CMV disease. We evaluated 352 D+/R- transplant recipients who participated in a trial comparing 100 days of ganciclovir versus valganciclovir prophylaxis. CMV serology was assessed on day 28, 56, 100, and 6 and 12 months post-transplant. IgG seroconversion occurred in 26.9% of patients by day 100, and in 63.4% and 75.3% by 6 and 12 months, respectively. IgM seroconversion occurred in 8.3%, 41.8% and 54.9% by day 100, month 6 and month 12, respectively. Seroconversion by day 100 (end of prophylaxis) was not predictive of subsequent CMV disease (CMV disease 13.3% if seropositive vs. 17.8% if seronegative; p = NS). However, at 6 months post-transplant, IgG serostatus was predictive of subsequent CMV disease between month 6 and 12 (CMV disease 1.3% if seropositive vs. 10.0% if seronegative; p = 0.002). In D+/R- patients, CMV serology testing is for the most part not clinically useful for predicting subsequent disease. However, seroconversion by 6 months may be useful for identifying patients at risk of late-onset CMV disease.     

CMV-specific CD8 T-cell dynamics in the blood and the lung allograft reflect viral reactivation following lung transplantation.

Despite the potentially high burden of cytomegalovirus (CMV)-related disease following lung transplantation, the role of the cytotoxic T-lymphocyte (CTL) response to CMV in this patient group is ill-defined. We assessed the CMV-specific T-cell response in the blood and lung allograft of immunosuppressed lung transplant recipients receiving antiviral prophylaxis and following their withdrawal. While the proportion of CMV-specific CTL varied between patients, in the absence of CMV reactivation the level of CMV-specific CD8+ T cells in the blood remained stable over time. In the majority of patients CMV-specific cells could be detected in the lung allograft, often in the absence of viral DNA. Additionally, following primary CMV lung infection, CMV-specific CD8+ T cells were detected no earlier than 100 days post-transplantation but still prior to the detection of viral DNA in the lung allograft. Together these findings suggest that very low levels of CMV replication are sufficient to both prime and recruit CMV-specific CD8+ T cells to the MHC-mismatched lung allograft. The direct detection of CMV-specific T cells with an effector phenotype in the lung allograft suggests a protective antiviral function. This study provides a framework upon which the association between CMV and chronic allograft rejection can be further studied.     

CCL8 and the Immune Control of Cytomegalovirus in Organ Transplant Recipients

Monitoring of cytomegalovirus cell‐mediated immunity is a promising tool for the refinement of preventative and therapeutic strategies posttransplantation. Typically, the interferon‐γ response to T cell stimulation is measured. We evaluated a broad range of cytokine and chemokines to better characterize the ex vivo host‐response to CMV peptide stimulation. In a cohort of CMV viremic organ transplant recipients, chemokine expression—specifically CCL8 (AUC 0.849 95% CI 0.721–0.978; p = 0.003) and CXCL10 (AUC 0.841, 95% CI 0.707–0.974; p = 0.004)—was associated with control of viral replication. In a second cohort of transplant recipients at high‐risk for CMV, the presence of a polymorphism in the CCL8 promoter conferred an increased risk of viral replication after discontinuation of antiviral prophylaxis (logrank hazard ratio 3.6; 95% CI 2.077–51.88). Using cell‐sorting experiments, we determined that the primary cell type producing CCL8 in response to CMV peptide stimulation was the monocyte fraction. Finally, in vitro experiments using standard immunosuppressive agents demonstrated a dose‐dependent reduction in CCL8 production. Chemokines appear to be important elements of the cell‐mediated response to CMV infection posttransplant, as here suggested for CCL8, and translation of this knowledge may allow for the tailoring and improvement of preventative strategies.