Comparison of the Cytomegalovirus (CMV) Enzyme-Linked Immunosorbent Spot and CMV QuantiFERON Cell-Mediated Immune Assays in CMV-Seropositive and -Seronegative Pregnant and Nonpregnant Women

Human cytomegalovirus (CMV) infection is a major cause of congenital infection leading to birth defects and sensorineural anomalies, including deafness. Recently, cell-mediated immunity (CMI) in pregnant women has been shown to correlate with congenital CMV transmission. In this study, two interferon gamma release assays (IGRA), the CMV enzyme-linked immunosorbent spot (ELISPOT) and CMV QuantiFERON assays, detecting CMV-specific CMI were compared. These assays were performed for 80 CMV-infected (57 primarily and 23 nonprimarily) pregnant women and 115 controls, including 89 healthy CMV-seropositive pregnant women without active CMV infection, 15 CMV-seronegative pregnant women, and 11 seropositive or seronegative nonpregnant women. Statistical tests, including frequency distribution analysis, nonparametric Kruskal-Wallis equality-of-populations rank test, Wilcoxon rank sum test for equality on unmatched data, and lowess smoothing local regression, were employed to determine statistical differences between groups and correlation between the assays. The CMV ELISPOT and CMV QuantiFERON assay data were not normally distributed and did not display equal variance. The CMV ELISPOT but not CMV QuantiFERON assay displayed significant higher values for primarily CMV-infected women than for the healthy seropositive pregnant and nonpregnant groups (P = 0.0057 and 0.0379, respectively) and those with nonprimary infections (P = 0.0104). The lowess local regression model comparing the assays on an individual basis showed a value bandwidth of 0.8. Both assays were highly accurate in discriminating CMV-seronegative pregnant women. The CMV ELISPOT assay was more effective than CMV-QuantiFERON in differentiating primary from the nonprimary infections. A substantial degree of variability exists between CMV ELISPOT and CMV QuantiFERON assay results for CMV-seropositive pregnant women.     

Ex vivo monitoring of human cytomegalovirus‐specific CD8+ T‐Cell responses using the QuantiFERON®‐CMV assay in allogeneic hematopoietic stem cell transplant recipients attending an Irish hospital

Reconstitution of human cytomegalovirus (HCMV) T‐cell immunity is crucial in hematopoietic stem cell transplant (HSCT) recipients. The QuantiFERON®‐CMV assay for cellular HCMV‐specific immunity was evaluated in allogeneic HSCT recipients (n = 43) and patients with hematological malignancies (n = 29) attending a tertiary‐care Irish hospital. An intracellular cytokine (ICC) assay correlated with the QuantiFERON®‐CMV assay. Although there was agreement between HCMV seropositivity and QuantiFERON®‐CMV assay, six HCMV seropositive immunosuppressed patients with hematological malignancy had negative QuantiFERON®‐CMV results. The 43 HSCT recipients were classified as high risk (D^?/R⁺) (n = 18), intermediate risk (D⁺/R⁺ and D⁺/R^?) (n = 17), and low risk (D^?/R^?) (n = 8). During episodes of HCMV DNAemia no evidence of HCMV‐specific immunity was found using the QuantiFERON®‐CMV assay. Furthermore, the recovery of HCMV‐specific CD8⁺ T‐cell responses in high‐risk seropositive recipients of matched unrelated donors was severely delayed, a mean of 200 (SD = 117) days compared to 58 (SD = 23) days for sibling donors (P ≤ 0.028). In addition, three patients with late HCMV infection (infection >100 days post‐transplant) had delayed reconstitution of HCMV‐specific CD8⁺ T cells. Interestingly, two recipients (R⁺/D^?) developed rapid immune reconstitution by days 15 and 36 post‐HSCT, suggesting HCMV‐specific T‐cell lymphopoiesis of recipient origin. Levels of CD8⁺ T‐cell immunity in HCMV seropositive HSCT recipients were lowest following HSCT. A high number (33%) of indeterminate results was observed immediately after transplantation. Patients with indeterminate QuantiFERON®‐CMV results had low levels of HCMV‐specific CD8⁺ T cells. J. Med. Virol. 82:433–440, 2010. © 2010 Wiley‐Liss, Inc.     

Impact of pretransplant CMV-specific T-cell immune response in the control of CMV infection after solid organ transplantation: a prospective cohort study

IntroductionAlthough solid organ transplant (SOT) recipients with pretransplant serology for cytomegalovirus (CMV-R+) are considered at intermediate risk for CMV infection post transplantation, CMV infection remains a major cause of morbidity in this population. We prospectively characterized whether having pretransplant CMV-specific cellular immunity is independently associated with controlling infection after transplantation in R + SOT recipients.MethodsA prospective cohort of consecutive R + SOT recipients that received pre-emptive treatment for CMV infection was monitored after transplantation and variables were recorded during the follow-up. The cytomegalovirus-specific T-cell immune response was characterized by intracellular cytokine staining and viral loads determined using real-time PCR.ResultsOne hundred and thirty-five R + SOT recipients were included (67 kidney, 64 liver, four liver–kidney). Only one-third of the patients (42; 31.85%) had CMV-specific T-cell immunity (CD8⁺CD69⁺INF-γ⁺ T cells >0.25%) before transplantation. Patients with negative pretransplant immunity had more CMV infection (49, 52.7% vs. 15, 35.7%; p 0.07) and received more antiviral therapy than those with immunity (32, 34.4% vs. 6, 14.3%, p 0.016). Having CMV specific immunity was an independent factor for protection from developing viraemia ≥2000 IU/mL (OR 0.276, 95% CI 0.105–0.725, p < 0.01) and lower administration of treatment (OR 0.398, 95% CI 0.175–0.905, p 0.028). Only patients with no pretransplant CMV-specific T-cell response were diagnosed with CMV-disease (8, 8.6% vs. 0, 0%, p 0.05).Discussion.Our results show that having a pretransplant CMV specific T-cell response may be associated with a lower rate of CMV viraemia and less antiviral treatment after transplantation; however, more prospective studies are needed to confirm these findings.     

Determination,validation and standardization of a CMV DNA cut-off value in plasma for preemptive treatment of CMV infection in solid organ transplant recipients at lower risk for CMV infection

BackgroundValganciclovir preemptive therapy guided by the viral load is the current strategy recommended for preventing CMV disease in CMV-seropositive Solid Organ Transplant Recipients (SOTR) at lower risk for developing CMV infection. However, universal viral load cut-off has not been established for initiating therapy.ObjectivesOur goal was to define and validate a standardized cut-off determined in plasma by real-time PCR assay for initiating preemptive therapy in this population.Study designA prospective cohort study of consecutive cases of CMV-seropositive SOTR was carried out. The cut-off value was determined in a derivation cohort and was validated in the validation cohort. Viral loads were determined using the Quant CMV LightCycler 2.0 real-time PCR System (Roche Applied Science) and results were standardized using the WHO International Standard for human CMV.ResultsA viral load of 3983 IU/ml (2600 copies/ml) was established as the optimal cut-off for initiating preemptive therapy in a cohort of 141 patients with 982 tests and validated in a cohort of 252 recipients with a total of 2022 test. This cut-off had a 99.6% NPV indicating that the great majority of patients at lower risk will not develop CMV disease without specific antiviral therapy. The high sensitivity and specificity (89.9% and 88.9%, respectively) and the relatively small numbers of patients with CMV disease confirm that real-time PCR was optimal.ConclusionsWe have established a cut-off viral load for starting preemptive therapy for CMV-seropositive SOT recipients. Our results emphasized the importance of a mandatory follow-up protocol for CMV-seropositive patients receiving preemptive treatment.     

Comparison of Quantitative Cytomegalovirus Real-time PCR in Whole Blood and pp65 Antigenemia Assay: Clinical Utility of CMV Real-time PCR in Hematopoietic Stem Cell Transplant Recipients

Successful preemptive therapy for cytomegalovirus (CMV) infection in transplant patients depends on the availability of sensitive, specific, and timely diagnostic tests for CMV infection. Although the pp65 antigenemia assay has been widely used for this purpose, real-time quantification of CMV DNA has recently been recognized as an alternative diagnostic approach. However, the guidelines for antiviral therapy based on real-time quantitative polymerase chain reaction (RQ-PCR) have yet to be established. From November 2004 to March 2005, a total of 555 whole blood samples from 131 hematopoietic stem cell transplant (HSCT) recipients were prospectively collected. RQ-PCR was conducted using an Artus® CMV LC PCR kit (QIAGEN). Both qualitative and quantitative correlations were drawn between the two methods. Exposure to the antiviral agent influenced the results of the two assays. Additionally, the discrepancy was observed at low levels of antigenemia and CMV DNA load. Via ROC curve analysis, the tentative cutoff value for preemptive therapy was determined to be approximately 2×10⁴ copies/mL (sensitivity, 80.0%; specificity, 50.0%) in the high risk patients, and approximately 3×10⁴ copies/mL (sensitivity, 90.0%; specificity, 70.0%) in the patients at low risk for CMV disease. Further study to validate the optimal cutoff value for the initiation of preemptive therapy is currently underway.     

CMV antigenemia following bone marrow transplantation: risk factors and outcomes.

Cytomegalovirus (CMV) infection remains a major problem in blood and bone marrow transplant (BMT) recipients. Recent efforts have been directed at prevention, early diagnosis, and treatment of CMV disease following BMT. Assay for CMV early antigen pp65 on circulating leukocytes has been shown to be sensitive, and specific in detecting early CMV infection. We examined the frequency, risk factors, and outcomes of a positive CMV antigen assay in 118 consecutive BMT patients. Forty-three (36%) of the 118 patients developed CMV antigenemia a median of 26 days post-BMT (range, -6 to 209 days). The incidence of antigenemia in autologous, related donor, and unrelated donor BMT recipients was 15%, 50%, and 48%, respectively (P < .01) and was lower in CMV-seronegative patients (19% versus 51% in seropositive patients; P < .01). Patients with grade II to IV acute graft-versus-host disease (GVHD) had 2.2 times the risk of antigenemia of patients with no or only limited GVHD (P = .03). Age at transplantation, underlying disease, CMV prophylaxis regimen, and GVHD prophylaxis regimen did not affect the risk of CMV antigenemia. Ten of the 43 antigenemic patients, all CMV-seropositive allogeneic BMT (alloBMT) recipients, developed CMV organ disease a median of 101 days (range, 28-283 daya) post-BMT. These data suggest that CMV-seropositive alloBMT patients are at highest risk for CMV antigenemia and for organ disease as well. CMV disease may occur before antigenemia is detectable in leukopenic patients and may also develop late post-BMT, even in patients still receiving antiviral prophylaxis. In high-risk groups, intensive surveillance continuing for more than 6 months after BMT may be indicated.     

How immunosuppressive therapy affects T cells from kidney transplanted patients of different age: the role of latent cytomegalovirus infection

The average age of patients receiving renal transplantation is increasing as programmes have been established which support the donation of organs from elderly donors to older recipients. Little is known about the effect of immunosuppressive therapy on the immune system of older patients. In this study, T cell function and the composition of the T cell repertoire were analysed in immunosuppressed renal transplant recipients of different age and cytomegalovirus (CMV) status in comparison to age-and CMV-matched controls. Independent of age and CMV status, the production of interleukin (IL)-2 and interferon (IFN)-γ by T cells was decreased in the patient groups and autologous serum from patients was capable of inhibiting the proliferation of CD3⁺ T cells. CXCR5 expression on T cells was increased in patients versus controls reflecting reduced endogenous IL-2 signalling under immunosuppressive therapy. In CMV-seronegative patients kidney transplantation and immunosuppressive therapy did not induce changes in the CD8⁺ T cell pool, but there was a moderate increase in CD4⁺CD28⁻ effector T cells when compared to age-matched controls. In contrast, latent CMV infection triggered a shift from early to late differentiated CD4⁺ and CD8⁺ T cells in patients and controls. This shift was most pronounced in elderly transplant patients under immunosuppressive therapy. In conclusion, our results demonstrate that immunosuppressive therapy following kidney transplantation is effective in patients older than 65 years. Latent CMV infection, however, accelerates age-related changes in the T cell repertoire in elderly people under immunosuppressive therapy. These patients should therefore be monitored with special care.     

Factors influencing the occurrence of active cytomegalovirus (CMV) infections after organ transplantation.

In this study, several factors influencing the occurrence of active CMV infection after organ transplantation (Tx) are analysed. For this purpose, 105 heart, kidney and lung transplant recipients who were CMV-positive or had a CMV-positive donor, were closely monitored for active CMV infection by antigenaemia, cultures, CMV serology and lymphocyte proliferation (LP) to CMV. Univariate and multivariate regression analysis were performed. As pretransplant risk factors the HLA-type and numbers of HLA mismatches between recipients and their donors, and the CMV serology of the recipient and donor were analysed. A new finding was that recipients of donors positive for HLA-B7 were especially at risk for developing active CMV infection (P = 0.03) and CMV disease (P = 0.03). This was not due to increased rejection treatment in these patients. Post-transplant risk factors for development of active CMV infection were absence of detectable cellular immunity to CMV (lymphocyte proliferation) after Tx (P < 0.01) and rejection treatment with OKT3 or ATG (P = 0.05). High levels of IgG anti-CMV did not prevent occurrence of active CMV infection or CMV disease in the CMV+ recipients.     

Cytomegalovirus infection induces the accumulation of short-lived, multifunctional CD4+CD45RA+CD27+ T cells: the potential involvement of interleukin-7 in this process

The relative roles that ageing and lifelong cytomegalovirus (CMV) infection have in shaping naive and memory CD4⁺ T-cell repertoires in healthy older people is unclear. Using multiple linear regression analysis we found that age itself is a stronger predictor than CMV seropositivity for the decrease in CD45RA⁺ CD27⁺ CD4⁺ T cells over time. In contrast, the increase in CD45RA⁻ CD27⁻ and CD45RA⁺ CD27⁻ CD4⁺ T cells is almost exclusively the result of CMV seropositivity, with age alone having no significant effect. Furthermore, the majority of the CD45RA⁻ CD27⁻ and CD45RA⁺ CD27⁻ CD4⁺ T cells in CMV-seropositive donors are specific for this virus. CD45RA⁺ CD27⁻ CD4⁺ T cells have significantly reduced CD28, interleukin-7 receptor α (IL-7Rα) and Bcl-2 expression, Akt (ser473) phosphorylation and reduced ability to survive after T-cell receptor activation compared with the other T-cell subsets in the same donors. Despite this, the CD45RA⁺ CD27⁻ subset is as multifunctional as the CD45RA⁻ CD27⁺ and CD45RA⁻ CD27⁻ CD4⁺ T-cell subsets, indicating that they are not an exhausted population. In addition, CD45RA⁺ CD27⁻ CD4⁺ T cells have cytotoxic potential as they express high levels of granzyme B and perforin. CD4⁺ memory T cells re-expressing CD45RA can be generated from the CD45RA⁻ CD27⁺ population by the addition of IL-7 and during this process these cells down-regulated expression of IL-7R and Bcl-2 and so resemble their counterparts in vivo. Finally we showed that the proportion of CD45RA⁺ CD27⁻ CD4⁺ T cells of multiple specificities was significantly higher in the bone marrow than the blood of the same individuals, suggesting that this may be a site where these cells are generated.     

CMV drives the expansion of highly functional memory T cells expressing NK‐cell receptors in renal transplant recipients

Cytomegalovirus (CMV) is a common opportunistic infection encountered in renal transplant recipients (RTRs) and may be reactivated without symptoms at any time post‐transplant. We describe how active and latent CMV affect T‐cell subsets in RTRs who are stable on maintenance therapy. T‐cell responses to CMV were assessed in RTRs (n = 54) >2 years post‐transplant, and healthy controls (n = 38). Seven RTRs had CMV DNA detectable in plasma. CMV antibody and DNA aligned with increased proportions of CD8⁺ T cells and reduced CD4/CD8 ratios. This paralleled an expansion of effector memory T‐cell (T_EM), terminally differentiated T‐cell (T_EMRA) and CD57⁺ T_EMRA cell populations. Expression of NK‐cell receptors, LIR‐1 and KLRG1 on CD4⁺ and CD8⁺ CD57⁺ T_EM and T_EMRA cells correlated with elevated interferon‐γ and cytotoxic responses to anti‐CD3 and increased cytotoxic responses to CMV phosphoprotein (pp) 65 in RTRs who carried CMV DNA. CD8⁺ T cells from all CMV seropositive RTRs responded efficiently to CMV immediate early (IE) ‐1 peptides. The data show that latent and active CMV infection can alter T‐cell subsets in RTRs many years after transplantation, and up‐regulate T‐cell expression of NK‐cell receptors. This may enhance effector responses of CD4⁺ and CD8⁺ T cells against CMV.     

Simultaneous Monitoring of Cytomegalovirus-Specific Antibody and T-cell levels in Seropositive Heart Transplant Recipients

Purpose

Human cytomegalovirus (CMV) active infection (CMV infection) poses serious risks to CMV-seropositive heart transplant recipients. We evaluated the usefulness of simultaneous assessment of CMV-specific values for parameters of the humoral (antibodies) and cellular (CD4+ and CD8+ T-cells) immune responses in the identification of heart recipients at risk of developing CMV infection after transplantation.

Methods

We prospectively studied 38 CMV-seropositive heart recipients. Anti-CMV antibody titers were assessed using enzyme-linked immunosorbent assays. CD4+ and CD8+ T-cell responses to overlapping peptide pools of the CMV proteins pp65 and immediate early protein-1 (IE1) were evaluated by flow cytometry. Immunological studies were performed before transplantation and at 30?days after transplantation. Patients with CMV infection were compared with heart recipients without CMV infection.

Results

During the 6-month follow-up period, 13 (34.2%) patients developed CMV infection. At baseline, the mean anti-CMV-IgG antibody titer was lower in patients who developed CMV infection. This difference remained at 30?days after transplantation. One month after transplantation, the mean percentage of IE1-specific CD8+ T cells that are IFNg-positive (CD8/IFNg?+?IE1) was lower in CMV-infected patients. The predictive value of these variables at 30?days was increased when they were combined. Cox regression analysis revealed an association between the risk of developing CMV infection and the combination marker (low anti-CMV titer [<16,100] and low CD8/IFNg?+?IE1 percentages [<0.40%], relative hazard, 6.07; p?=?0.019). The combination marker remained significant after adjustment for clinical variables.

Conclusions

This novel approach of a simultaneous assessment of specific anti-CMV antibody titers and CD8/IFNg?+?IE1 percentages might help identify heart transplant recipients with an increased risk of developing CMV infection.     

Early detection of active cytomegalovirus (CMV) infection after heart and kidney transplantation by testing for immediate early antigenemia and influence of cellular immunity on the occurrence of CMV infection.

To determine the incidence of active cytomegalovirus (CMV) infection after organ transplantation and its relationship with the immune system, 55 renal and 14 cardiac transplant recipients were closely monitored for active CMV infection (expression of CMV immediate early antigen in granulocytes--antigenemia--and positive cultures) and immune parameters. All 19 CMV-seronegative recipients with seronegative donors remained seronegative, showing that no CMV transmission occurred by leukocyte-depleted blood products. Primary CMV infection occurred in 4 of 11 (36%) patients with positive donors and was symptomatic in 1 (9%) patient. Active CMV infection was found in 29 of 39 (74%) seropositive patients and was symptomatic in 3 (8%) patients. CMV antigenemia was always the first indication of active CMV infection (antigenemia, on average, at day 45 +/- 15; immunoglobulin G rise at day 71 +/- 36; and positive cultures at day 70 +/- 17). Cellular immunity, as measured by lymphocyte proliferation (LPT), proved to be of importance in the prevention of active CMV infection, as 14 of 15 patients with negative LPT obtained active CMV infections with antigenemia and positive cultures, whereas 1 of 10 patients with positive LPT did so (P less than 0.0001).     

Detection of cytomegalovirus (CMV) in granulocytes by polymerase chain reaction compared with the CMV antigen test.

To compare the sensitivity and suitability of detection of active cytomegalovirus (CMV) infection by using monoclonal antibodies against CMV antigen (antigen test to detect antigenemia) and the polymerase chain reaction (PCR; to detect viral DNA) in granulocytes, 19 heart and 2 lung transplant recipients were closely monitored by these tests for at least 3 months after transplantation. All patients were CMV seropositive or had a seropositive donor. In total, 201 samples were tested; 46 were positive by both tests, 9 samples showed only antigenemia, 54 samples were positive by PCR only, and 102 samples were negative by both tests. PCR was positive earlier after transplantation in eight patients, whereas antigenemia was positive earlier after transplantation in one patient. In another four patients, both tests were positive at the same time. PCR was, on average, positive for a longer period of time. Discordant results showing a positive antigen test and a negative PCR were partly due to sampling error; some were positive by PCR on retesting. Samples which were negative by the antigen test and positive by PCR were taken at the beginning or at the end of an active CMV infection. In two patients, no active CMV infection was detected by the antigen test, cultures of urine and saliva, or serology, although PCR was positive for a long period of time in the two patients.     

Asymptomatic CMV infections in long‐term renal transplant recipients are associated with the loss of FcRγ from LIR‐1+ NK cells

While it is established that cytomegalovirus (CMV) disease affects NK‐cell profiles, the functional consequences of asymptomatic CMV replication are unclear. Here, we characterize NK cells in clinically stable renal transplant recipients (RTRs; n = 48) >2 years after transplantation. RTRs and age‐matched controls (n = 32) were stratified by their CMV serostatus and the presence of measurable CMV DNA. CMV antibody or CMV DNA influenced expression of NKG2C, LIR‐1, NKp30, NKp46, and FcRγ, a signaling adaptor molecule, on CD56^dim NK cells. Phenotypic changes ascribed to CMV were clearer in RTRs than in control subjects and affected NK‐cell function as assessed by TNF‐α and CD107a expression. The most active NK cells were FcRγ^–LIR‐1⁺NKG2C^– and displayed high antibody‐dependent cell cytotoxicity responses in the presence of immobilized CMV glycoprotein B reactive antibody. However, perforin levels in supernatants from RTRs with active CMV replication were low. Overall we demonstrate that CMV can be reactivated in symptom‐free renal transplant recipients, affecting the phenotypic, and functional profiles of NK cells. Continuous exposure to CMV may maintain and expand NK cells that lack FcRγ but express LIR‐1.     

CMV infected or not CMV infected: That is the question

Cytomegalovirus (CMV) infection is widespread in the human population. Normally, in adolescents and adults, prior exposure to CMV can readily be determined by IgG assays. However, in individuals where antibody production is impaired, such as patients with common variable immunodeficiency disease or in the very young where maternal antibodies are present, diagnosis of CMV infection is problematic using such assays. In this issue of the European Journal of Immunology, a study by Sester and colleagues [Eur J Immunol 2013. 43: 1099‐1108] using CD4⁺ T‐cell immunity as a marker of infection clearly differentiates young children with prior exposure to CMV from those who only have passive maternal antibody. This information will quickly find application in the pretransplant screening of young children for CMV infection and help with the stratification of these children to identify those who are truly CMV negative and are therefore at risk for future CMV infection and disease if receiving an organ from a CMV‐positive donor as discussed in this Commentary.     

Prospective long-term study on primary CMV infections in adult liver transplant (D+/R−) patients after valganciclovir prophylaxis

BackgroundCytomegalovirus (CMV) can cause severe infections in transplanted patients. To prevent CMV infection, most liver centers use prophylaxis for CMV-seronegative recipients receiving an organ from a seropositive donor (D+/R−). Valganciclovir is mostly given for 3–6 months after transplantation. However, the patients may develop primary CMV infection after the cessation of prophylaxis and late-onset CMV disease may occur.ObjectivesA prospective long-term follow-up of CMV (D+/R−) adult liver transplant recipients after 3 months valganciclovir prophylaxis was investigated.Study designOf 154 consecutive adult liver recipients transplanted from 2006 to 2009, 20 (13%) were CMV D+/R− and received antiviral prophylaxis up to 3 months after transplantation. After excluding the recipients with incomplete prophylaxis or monitoring, 13 (D+/R−) patients with follow-up of >4 years after the 3-month period of valganciclovir prophylaxis were included in the study.The patients were monitored for CMV by real-time quantitative plasma PCR.ResultsNo break-through CMV infections were recorded during the prophylaxis period. After cessation of valganciclovir prophylaxis 12/13 (90%) patients demonstrated CMV-DNAemia following a post transplantation mean interval of 165 days (range 95–320). Ten patients with high viral loads (peak viral load mean 81,510, range 1900–648950 cps/ml) were successfully treated, 6 with valganciclovir, and 4 with ganciclovir. Two patients with low level CMV-DNAemia (<1000 cps/ml) were asymptomatic and not treated. No intragraft infection was seen, but one patient developed gastrointestinal CMV infection verified from ileum biopsy. During long-term follow-up, 3 patients demonstrated low-level viral replication, but no symptomatic recurrences occurred. One patient died of bacterial sepsis, but no patient or graft was lost due to CMV.ConclusionsPrimary CMV infections after cessation of prophylaxis were common, but were successfully treated with valganciclovir or ganciclovir.     

Prediction of cytomegalovirus (CMV) plasma load from evaluation of CMV whole-blood load in samples from renal transplant recipients

In a prospective cohort of 82 renal transplant recipients, we evaluated the capacity of the cytomegalovirus (CMV) load in whole blood (WB) to predict the plasma CMV load, aiming to identify active CMV infections by using WB samples only and to deduce a WB threshold. Using quantitative real-time PCR, a total of 1,474 WB samples were assayed, of which 279 were positive for CMV, and 140 out of the 276 paired plasma samples tested positive. Thirty (36.6%) patients presented with at least one positive plasma PCR result, and 21 infection episodes (19 patients) required curative treatment (median follow-up time, 12 months). When the plasma CMV load was >500 copies/ml (n = 70), more than 94% (95% confidence interval, 86.0%, 98.4%) of WB samples had >500 copies/ml. Two prediction models were built: log₁₀ plasma viral load (VL) was calculated as −0.3777 + 0.9342 × log₁₀ WB VL and as −0.3777 + 0.8563 × log₁₀ WB VL for patients with and without treatment, respectively. In the validation sample (578 routine samples), 77.2% of the observed and expected plasma viral loads were concordant (95% confidence intervals, 73.5 and 80.5%). According to the model, the plasma viral load was >500 copies/ml when the WB load was >3,170 or >4,000 copies/ml in patients with or without treatment, respectively. WB seems to be an appropriate candidate for routine CMV monitoring of transplant recipients by using a single assay.     

Coordinated expansion of both memory T cells and NK cells in response to CMV infection in humans

NK cells are key players in the fight against persistent viruses. Human cytomegalovirus (HCMV) infection is associated with the presence of a population of CD16⁺ CD56^dim NKG2C⁺ NK cells in both acutely and latently infected individuals. Here, we studied the nature of these terminally differentiated NK cells in different human populations infected with HCMV: healthy donors stratified by age, thymectomized individuals, pregnant women suffering from primary CMV infection, and lung transplant patients. Both CD16⁺ CD56^dim NK‐ and CD8 T‐cell phenotypes as well as functional capacities were determined and stratified according to age and/or CMV event. Similarly to T‐cell responsiveness, we observe an accumulation over time of NKG2C⁺ NK cells, which preferentially expressed CD57. This accumulation is particularly prominent in elderly and amplified further by CMV infection. Latent HCMV infection (without replication) is sufficient for NKG2C⁺ CD57⁺ NK cells to persist in healthy individuals but is not necessarily required in old age. Collectively, the present work supports the emerging concept that CMV shapes both innate and adaptive immunity in humans.