The impact of cytomegalovirus infections and acute rejection episodes on the development of vascular changes in 6-month protocol biopsy specimens of cadaveric kidney allograft recipients

Postnatal cytomegalovirus infection and pulmonary vascular disease in extremely premature infants: A case series

BACKGROUND

Pulmonary vascular disease (PVD) is a major determinant of both morbidity and mortality in extremely low birth weight infants. It is biologically plausible that postnatal cytomegalovirus (pCMV) infection may lead to PVD in premature infants secondary to pneumonitis or via derangement of pulmonary vascular development directly through endothelial dysfunction. Uncertainty remains, however, regarding thresholds for intervention in premature infants with cardiorespiratory instability and presumed CMV infection likely secondary to the limited understanding of the natural history of the disease.

METHODS/RESULTS

We describe four cases of premature infants with clinical and echocardiography features of PVD, in the setting of postnatally acquired CMV. All patients had atypical PVD trajectories, refractory to vasodilator treatment, which improved after initiation of CMV treatment.

CONCLUSION

We highlight the need to consider postnatally acquired CMV infection in patients with PVD non-responsive to standard pulmonary vasodilator therapies or disease severity which is out of proportion of the usual clinical trajectory. Treatment of extremely premature infants with CMV-associated PVD may have positive impact on cardiorespiratory health, although duration of therapy remains uncertain.

Efficacy and Safety of Antiviral Agents in Preventing Allograft Rejection Following CMV Prophylaxis in High-Risk Kidney Transplantation: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials

Many antiviral agents have been studied in clinical trials for allograft rejection prevention following cytomegalovirus (CMV) prophylaxis in high-risk kidney transplant patients. However, data on the most effective and safest treatment are lacking. We conducted a systematic review and network meta-analysis to rank CMV prophylaxis agents for allograft rejection prevention following CMV prophylaxis in high-risk kidney transplant patients according to their efficacy and safety. We conducted searches on the MEDLINE, Embase, SCOPUS, and CENTRAL databases, as well as the reference lists of selected studies up to December 2021, for published and peer-reviewed randomized controlled trials assessing the efficacy of CMV prophylaxis agents in high-risk kidney transplant patients. Thirteen studies were independently selected by three reviewers and included post-kidney transplant patients indicated for CMV prophylaxis who had been randomized to receive prophylactic antiviral agents or standard of care. The reviewers independently extracted data from the included studies, and direct and network meta-analyses were applied to assess the study outcomes. The probability of efficacy and safety was evaluated, and the drugs were assigned a numerical ranking. We evaluated the risk of bias using the Cochrane Risk of Bias 2.0 tool. The primary outcome was an incidence of biopsy-proven acute rejection, whereas the secondary outcome was a composite of major adverse drug reactions. Each outcome referred to the definition provided in the original studies. Valganciclovir, valacyclovir, and ganciclovir were identified to significantly decrease the incidence of biopsy-proven acute rejection with pooled risk differences (RDs) of −20.53% (95% confidence interval [CI] = −36.09% to −4.98%), −19.3% (95% CI = −32.7% to −5.93%), and −10.4% (95% CI = −19.7% to −0.12%), respectively. The overall major adverse drug reaction was 5.7% without a significant difference when compared with placebo. Valganciclovir had the best combined efficacy and safety among the examined antiviral agents and was the most effective and safest antiviral agent overall for allograft rejection prevention following CMV prophylaxis. Valacyclovir was the optimal alternative antiviral agent for patients who were unable to tolerate intravenous ganciclovir or access oral valganciclovir as financial problem. However, compliance and dose-related toxicities should be closely monitored.

Immunosenescence: an unexplored role in glomerulonephritis

Immunosenescence is a natural ageing phenomenon with alterations in innate and especially adaptive immunity and contributes to reduced antimicrobial defence and chronic low‐grade inflammation. This is mostly reflected by an increase in organ‐directed and/or circulating reactive and cytolytic terminally differentiated T cells that have lost their expression of the costimulatory receptor CD28. Apart from being induced by a genetic predisposition, ageing or viral infections (particularly cytomegalovirus infection), immunosenescence is accelerated in many inflammatory diseases and uraemia. This translates into an enhancement of vascular inflammation and cardiovascular disease varying from endothelial dysfunction to plaque rupture. Emerging data point to a mechanistic role of CD28^null T cells in glomerulonephritis, where they initiate and propagate local inflammation in concordance with dendritic cells and macrophages. They are suitably equipped to escape immunological dampening by the absence of homing to lymph nodes, anti‐apoptotic properties and resistance to suppression by regulatory T cells. Early accumulation of senescent CD28^null T cells precedes glomerular or vascular injury, and targeting these cells could open avenues for early treatment interventions that aim at abrogating a detrimental vicious cycle.

Clinical consequences of primary CMV infection after renal transplantation: a case-control study

The impact of primary cytomegalovirus infection (pCMV) on renal allograft function and histology is controversial. We evaluated the influence on incidence of acute rejection, allograft loss, allograft function and interstitial fibrosis/tubular atrophy (IF/TA). Retrospective case-control study, recipients transplanted between 2000 and 2014. Risk of acute rejection and allograft loss for those who experienced pCMV infection compared with those who did not, within an exposure period of two months after transplantation. Besides, its influence on allograft function and histology at one to three years after transplantation. Of 113 recipients experienced pCMV infection, 306 remained CMV seronegative. pCMV infection in the exposure period could not be proven as increasing the risk for acute rejection [HR = 2.18 (95% CI 0.80-5.97) P = 0.13] or allograft loss [HR = 1.11 (95%CI 0.33-3.72) P = 0.87]. Combination of pCMV infection and acute rejection posed higher hazard for allograft loss than acute rejection alone [HR = 3.69 (95% CI 1.21-11.29) P = 0.02]. eGFR(MDRD) values did not significantly differ at years one [46 vs. 50], two [46 vs. 51] and three [46 vs. 52]. No association between pCMV infection and IF/TA could be demonstrated [OR = 2.15 (95%CI 0.73-6.29) P = 0.16]. pCMV infection was not proven to increase the risk for acute rejection or allograft loss. However, it increased the risk for rejection-associated allograft loss. In remaining functioning allografts, it was not significantly associated with decline in function nor with presence of IF/TA.

A high burden of cytomegalovirus marks poor vascular health in transplant recipients more clearly than in the general population

Objectives

Meta‐analyses have now confirmed that persistent infections with cytomegalovirus (CMV) can accelerate the onset of diseases of ageing, notably cardiovascular pathologies. We address the circumstances in which the association may be strong enough to warrant intervention to reduce the viral burden.

Results

We compare markers of the burden of CMV with established indices of vascular pathology in healthy adults (n = 82) and in renal transplant recipients (RTR; n = 81). Levels of all inflammatory and vascular biomarkers and CMV antibodies were higher in RTR, and flow‐mediated dilation (FMD) values were lower indicating inferior endothelial function. In multivariable regression models without adjustment for estimated glomerular filtration rate (eGFR), CMV antibody levels, age and gender were independently associated with FMD in RTR, whilst only CRP associated with FMD in healthy adults. After adjustment for eGFR, associations between CMV antibody and FMD in RTR were reduced.

Methods

Carotid intima‐media thickness, FMD, eGFR and plasma levels of CMV antibodies (reactive with a lysate, CMV IE‐1 or CMV gB), ICAM‐1, VCAM‐1, P‐selectin, sIFNαR2, sTNFR1, sCD14 and CRP were determined.

Conclusion

Levels of CMV antibody predict declining endothelial health in RTR and not in healthy adults, presumably by reflecting a high burden of CMV. The levels of CMV antibodies were a poor reflection of plasma biomarkers thought to reflect ‘inflammaging’ or vascular damage.

A high level of urinary retinol-binding protein is associated with cytomegalovirus infection in kidney transplantation

The indirect effects of cytomegalovirus (CMV) viremia can be related to chronic changes in renal allograft structure, but its real impact in early and late graft function remains speculative. A total of 159 patients undergoing renal transplantation using a preemptive therapeutic strategy to prevent CMV disease were included in the present study. The patients were prospectively followed, with serial measurements of urinary retinol-binding protein (uRBP), a marker of proximal tubule injury. uRBP levels and their dynamic performance were compared according to CMV viremia and the 5-year estimated glomerular filtration rate (eGFR), as measured with the modification of diet in renal disease (MDRD) equation. CMV viremia was detected in 79.9% of the patients, with high uRBP levels being detected in 76.0% of these patients (compared with 40.7% in CMV-, P=0.005). High uRBP was associated with male recipients (P=0.02), the number of mismatches (P=0.02) and CMV infection (P=0.001). Five-year eGFR was worse in patients with high uRBP levels (50.3 ± 25.8 compared with 59.8 ± 26.4 ml/min, P=0.04). In a multivariate model, eGFR <60 ml/min was associated with donor age (P<0.001), the number of mismatches (P=0.04), thymoglobulin dose (P=0.02), the presence of and time with delayed graft function (DGF) (P=0.005 and P=0.04), 1-month tacrolimus levels (P=0.03), and uRBP levels after CMV treatment (P=0.01). Patients with CMV viremia in whom uRBP levels were normalized up to 3 months after treatment showed significantly better 5-year eGFR than those in whom uRBP remained high: 61.0 ± 24.2 compared with 42.3 ± 23.9 ml/min, P<0.001. CMV viremia was associated with high uRBP levels, which represent a profile of proximal tubule injury, and the dynamic performance of uRBP after treatment was associated with long-term kidney graft function.

New therapies for human cytomegalovirus infections

The recent approval of letermovir marks a new era of therapy for human cytomegalovirus (HCMV) infections, particularly for the prevention of HCMV disease in hematopoietic stem cell transplant recipients. For almost 30 years ganciclovir has been the therapy of choice for these infections and by today's standards this drug exhibits only modest antiviral activity that is often insufficient to completely suppress viral replication, and drives the selection of drug-resistant variants that continue to replicate and contribute to disease. While ganciclovir remains the therapy of choice, additional drugs that inhibit novel molecular targets, such as letermovir, will be required as highly effective combination therapies are developed not only for the treatment of immunocompromised hosts, but also for congenitally infected infants. Sustained efforts, largely in the biotech industry and academia, have identified additional highly active lead compounds that have progressed into clinical studies with varying levels of success and at least two have the potential to be approved in the near future. Some of the new drugs in the pipeline inhibit new molecular targets, remain effective against isolates that have developed resistance to existing therapies, and promise to augment existing therapeutic regimens. Here, we will describe some of the unique features of HCMV biology and discuss their effect on therapeutic needs. Existing drugs will also be discussed and some of the more promising candidates will be reviewed with an emphasis on those progressing through clinical studies. The in vitro and in vivo antiviral activity, spectrum of antiviral activity, and mechanism of action of new compounds will be reviewed to provide an update on potential new therapies for HCMV infections that have progressed significantly in recent years.

Polymorphism in programmed cell death 1 gene is strongly associated with lung and kidney allograft survival in recipients from CMV-positive donors

BACKGROUND

Cytomegalovirus (CMV) has a role in chronic rejection and graft loss in kidney transplant (KTx) and lung transplant (LTx) recipients. In addition, donor CMV seropositivity is an independent risk factor for renal graft loss. The anti-CMV response might modulate this risk. Expression of programmed cell death 1 (PD-1), a receptor involved in viral-specific T-cell exhaustion, is influenced by a single nucleotide polymorphism called PD-1.3 (wild-type allele G, variant allele A).

METHODS

We performed a retrospective study to assess the impact of PD-1.3 on graft outcome in donor CMV seropositive (D+) and donor CMV seronegative (D-) KTx and LTx. We also performed a case-control study to evaluate the anti-CMVpp65 response according to genotype.

RESULTS

PD-1.3 was determined in 1,119 KTx and 181 LTx. In 481 D+ KTx, A allele carriers (24%) experienced significantly less graft failure compared with GG carriers (p = 0.001). Multivariate analysis showed that this association was independent of donor and recipient age, acute rejection episodes, and number of human leukocyte antigen mismatches (hazard ratio, 0.381; 95% confidence interval, 0.209-0.696; p = 0.002). Analysis in 85 D+ LTx showed similar results: A allele carriers had better survival (hazard ratio, 0.302; 95% confidence interval, 0.128-0.716; p = 0.006) and greater 6-month forced expiratory volume (71% ± 17% vs 54% ± 16%, p = 0.001). In D- recipients, PD-1.3 did not affect KTx or LTx outcome. Finally, AA recipients had a stronger anti-CMVpp65 T-cell response than matched GG recipients (p = 0.003).

CONCLUSIONS

The A variant allele in PD-1.3 single nucleotide polymorphism improved graft survival in kidney and lung transplant recipients receiving grafts from CMV-positive donors.

Cytomegalovirus infection in immunosuppressed patients after kidney transplantation

The first kidney transplantation was performed in 1951 and ever since then living donor transplantation became a more and more important solution for patients with end-stage renal disease (ESRD).

Renal transplantation is a life-saving procedure. Morbidity and mortality on waiting-lists are strongly correlated with the time of dialysis and end-stage renal disease is one of the most important causes of death; this is the reason why transplantation has to be performed as soon as possible in order to reduce the time of dialysis.

Once the transplantation is performed, a number of complications may occur in post-transplant evolution, the most important of which is rejection.

The rejection may appear through several mechanisms, but one of the most frequent causes of rejection is cytomegalovirus (CMV) infection. It is very important to have a precocious and fast diagnosis of CMV infection in order to maintain the functionality and survival of the graft. PP65 CMV antigenemia has proven its effectiveness in detecting and monitoring the CMV infection in transplanted patients.

In the laboratory of the Clinical Institute of Urology and Renal Transplantation (ICUTR) of Cluj Napoca the CMV infection is evidenced by two methods: PP65antigenemia and IgM antibody identification by chemiluminiscence.

The Cell Biology of Cytomegalovirus: Implications for Transplantation

Interpretation of clinical data regarding the impact of cytomegalovirus (CMV) infection on allograft function is complicated by the diversity of viral strains and substantial variability of cellular receptors and viral gene expression in different tissues. Variation also exists in nonspecific (monocytes and dendritic cells) and specific (NK cells, antibodies) responses that augment T cell antiviral activities. Innate immune signaling pathways and expanded pools of memory NK cells and γδ T cells also serve to amplify host responses to infection. The clinical impact of specific memory T cell anti-CMV responses that cross-react with graft antigens and alloantigens is uncertain but appears to contribute to graft injury and to the abrogation of allograft tolerance. These responses are modified by diverse immunosuppressive regimens and by underlying host immune deficits. The impact of CMV infection on the transplant recipient reflects cellular changes and corresponding host responses, the convergence of which has been termed the "indirect effects" of CMV infection. Future studies will clarify interactions between CMV infection and allograft injury and will guide interventions that may enhance clinical outcomes in transplantation.

Cytomegalovirus infection in renal transplantation: clinical aspects, management and the perspectives

Cytomegalovirus infection is one of most frequent infectious complications after renal transplantation, and can be classified as primo-infection, when the transmission occurs through the graft, or reactivation, when the recipient is cytomegalovirus seropositive. After transplantation, cytomegalovirus can appear as an infection, when the patient presents with evidence of viral replication without symptoms or disease, which has two clinical spectra: typical viral syndrome or invasive disease, which is a less common form. Their effects can be classified as direct, while the disease is developed, or indirect, with an increase of acute rejection and chronic allograft dysfunction risks. Diagnosis must be made based on viremia by one of the standardized methods: antigenemia or PCR, which is more sensitive. The risk factors related to infection after transplantation are the serologic matching (positive donor and negative recipient) and anti-lymphocyte antibody drugs. One of the strategies to reduce risk of disease should be chosen for patients at high risk: preemptive treatment or universal prophylaxis. Recent clinical research has described ganciclovir resistance as an emergent problem in management of cytomegalovirus infection. Two types of mutation that cause resistance were described: UL97 (most frequent) and UL54. Today, sophisticated methods of immunologic monitoring to detect specific T-cell clones against cytomegalovirus are used in clinical practice to improve the management of high-risk patients after renal transplantation.

What we have learned from animal models of HCMV

Although human cytomegalovirus (HCMV) primary infection is generally asymptomatic, in immune-compromised patients HCMV increases morbidity and mortality. As a member of the betaherpesvirus family, in vivo studies of HCMV are limited due to its species specificity. CMVs from other species are often used as surrogates to express HCMV genes/proteins or used as models for inferring HCMV protein function in humans. Using innovative experiments, these animal models have answered important questions about CMV's life cycle, dissemination, pathogenesis, immune evasion, and host immune response. This chapter provides CMV biologists with an overview of the insights gained using these animal models. Subsequent chapters will provide details of the specifics of the experimental methods developed for each of the animal models discussed here.

[Lights and shadows of cytomegalovirus infection in solid organ transplantation]

Cytomegalovirus (CMV) develops in 30-80% of patients undergoing solid organ transplantation (SOT). The incidence and presence of symptomatic disease varies depending on the type of transplant, the presence of associated risk factors, the intensity of immunosuppression, and the prevention strategies used. The impact of CMV on SOT is due not only to the effects of CMV disease per se, but also to its multiple indirect effects resulting from its immunomodulatory role and immunoactivation caused by viral latency. The two prophylactic strategies used (universal prophylaxis and preemptive therapy) are equally useful. Both strategies have advantages and disadvantages, and uncertainties remain on the populations that should receive prophylaxis and for how long. Viral monitoring to detect CMV infection is important for diagnosis, prognosis and evaluation of treatment response. The new real-time polymerase chain reaction techniques have provided numerous advantages but standardization remains an issue and common reference values are required. Specific anti-CMV drugs are available but issues such as the role of valganciclovir versus ganciclovir, the development of resistances and optimal treatment length are still being debated. Complementary therapy with mTOR inhibitors and vaccine strategies against CMV are alternatives for which conclusive data are lacking.

Viral infection in renal transplant recipients

Viruses are among the most common causes of opportunistic infection after transplantation. The risk for viral infection is a function of the specific virus encountered, the intensity of immune suppression used to prevent graft rejection, and other host factors governing susceptibility. Although cytomegalovirus is the most common opportunistic pathogen seen in transplant recipients, numerous other viruses have also affected outcomes. In some cases, preventive measures such as pretransplant screening, prophylactic antiviral therapy, or posttransplant viral monitoring may limit the impact of these infections. Recent advances in laboratory monitoring and antiviral therapy have improved outcomes. Studies of viral latency, reactivation, and the cellular effects of viral infection will provide clues for future strategies in prevention and treatment of viral infections. This paper will summarize the major viral infections seen following transplant and discuss strategies for prevention and management of these potential pathogens.

Ganciclovir transiently attenuates murine cytomegalovirus-associated renal allograft inflammation

BACKGROUND

Prophylactic ganciclovir (GCV) is used in high-risk renal transplant patients to prevent acute cytomegalovirus (CMV) disease, but its impact on inflammation within the allograft itself remains undefined.

METHODS

To study the effect of GCV prophylaxis on allograft inflammation, murine CMV (MCMV)-infected allografts were analyzed in a murine donor positive/recipient negative allogeneic renal transplantation model by flow cytometry and immunofluorescent staining.

RESULTS

By flow cytometry, CD45+ leukocyte infiltrates were more abundant in MCMV-infected allografts at 14 days posttransplant compared with uninfected grafts (P<0.01) and decreased in the presence of GCV (P<0.05). CD11c+ dendritic cells, Gr-1+ myeloid cells, CD204+ macrophages, and CD49b+ natural killer cells were reduced in GCV-treated allografts compared with MCMV-infected grafts without GCV treatment (P<0.05). However, GCV failed to reduce these cell types to levels found in MCMV-uninfected allografts. By day 7 after cessation of GCV prophylaxis, dendritic cells, macrophages, and natural killer cells increased in number and became statistically indistinguishable from numbers of cells found in MCMV-infected allografts without GCV. GCV treatment did not affect the numbers of CD4+, CD8+, or CD19+/B220+ lymphocytes infiltrating the allografts. Infiltrates were confirmed histologically by immunofluorescent staining for CD3+ and CD11b+ cells.

CONCLUSIONS

In this model, MCMV-infected allografts developed significantly greater innate and adaptive leukocytic infiltrates compared with uninfected grafts. GCV attenuated the MCMV-associated innate leukocyte infiltrates in infected allografts but not the lymphocytic infiltrates. The attenuated innate response was limited to the period of GCV prophylaxis.

Revisiting the effects of CMV on long-term transplant outcome

PURPOSE OF THE REVIEW

Indirect effects of cytomegalovirus (CMV) in transplantation are of three types: increase in systemic immunosuppression, increased risk of malignancy (especially Epstein-Barr virus-related B-cell lymphoproliferative disease), and the possible contribution to allograft injury. Despite modern and potent antiviral drugs, the real impact of CMV in transplantation, especially kidney transplantation, remains a challenge because many confounding factors arise when analyzing this question.This review will fuel the discussion and review some of the recent data.

RECENT FINDINGS

A recent study on cardiac allograft in mice has shown that CMV in latently infected recipients could break graft acceptance. Although the exact nature of response was not addressed, this study suggested that CMV reactivation inside the graft played an important part in graft losses. Other recent results suggest that the quality of immune response against CMV influences graft outcome in both cardiac and kidney transplant patients. Other evidence suggests the link between CMV infection, immune senescence and vascular disease in the whole population. Studies have opened the perspective for new strategies to prevent indirect effects of CMV.

SUMMARY

Although a causal relationship between CMV reactivation and graft injury is supported by a large body of experimental and clinical data, definitive proof in clinical transplantation is still lacking to exclude an associative relationship. Large randomized clinical trials analyzing long-term graft survival and comparing prophylaxis with preemptive, especially D/R, is probably an efficient way to establish a causal relationship. Research on new antiviral strategies applicable over the long term is important.

[Cytomegalovirus effects in solid organ transplantation and the role of antiviral prophylaxis]

Cytomegalovirus (CMV) belongs to β-Herpesviridae family. Morbidity related to this infectious agent remains a serious concern in the context of immunosuppression. Occurence of CMV infection within the first 3 months post-renal transplantation without any antiviral prophylaxis is about 70% of patients. Direct and indirect effects of CMV infection in the setting of organ transplantation are described in this review. A 3 to 6 months course of prophylaxis with valganciclovir is advised concerning high-risk transplant recipients (D+/R-) but recommendation regarding intermediate-risk transplant recipients (CMV-seropositive patients) is still unclear. Recent studies highlight a benefit of long time prophylaxis (until 6 months) in terms of CMV disease occurence among D+/R- patients. News assays that measures IFNγ responses to a variety of CMV epitopes (Quantiferon(®) and Elispot IFNγ) are developped to predict CMV disease onset after discontinuation of antiviral prophylaxis. These assays could contribute to adapt prophylaxis to each recipient.

Cytomegalovirus infection leads to microvascular dysfunction and exacerbates hypercholesterolemia-induced responses

Cytomegalovirus (CMV) persistently infects more than 60% of the worldwide population. In immunocompetent hosts, it has been implicated in several diseases, including cardiovascular disease, possibly through the induction of inflammatory pathways. Cardiovascular risk factors promote an inflammatory phenotype in the microvasculature long before clinical disease is evident. This study determined whether CMV also impairs microvascular homeostasis and synergizes with hypercholesterolemia to exaggerate these responses. Intravital microscopy was used to assess endothelium-dependent and -independent arteriolar vasodilation and venular leukocyte and platelet adhesion in mice after injection with either mock inoculum or murine CMV (mCMV). Mice were fed a normal (ND) or high-cholesterol (HC) diet beginning at 5 weeks postinfection (p.i.), or a HC diet for the final 4 weeks of infection. mCMV-ND mice exhibited impaired endothelium-dependent vasodilation versus mock-ND at 9 and 12 weeks and endothelium-independent arteriolar dysfunction by 24 weeks. Transient mild leukocyte adhesion occurred in mCMV-ND venules at 7 and 21 weeks p.i. HC alone caused temporary arteriolar dysfunction and venular leukocyte and platelet recruitment, which were exaggerated and prolonged by mCMV infection. The time of introduction of HC after mCMV infection determined whether mCMV+HC led to worse venular inflammation than either factor alone. These findings reveal a proinflammatory influence of persistent mCMV on the microvasculature, and suggest that mCMV infection enhances microvasculature susceptibility to both inflammatory and thrombogenic responses caused by hypercholesterolemia.

Cytomegalovirus-specific T-cell responses and viral replication in kidney transplant recipients

Background

Cytomegalovirus (CMV) seronegative recipients (R-) of kidney transplants (KT) from seropositive donors (D+) are at higher risk for CMV replication and ganciclovir(GCV)-resistance than CMV R(+). We hypothesized that low CMV-specific T-cell responses are associated with increased risk of CMV replication in R(+)-patients with D(+) or D(-) donors.

Methods

We prospectively evaluated 73 consecutive KT-patients [48 R(+), 25 D(+)R(-)] undergoing routine testing for CMV replication as part of a preemptive strategy. We compared CMV-specific interferon-γ (IFN-γ) responses of CD4+CD3+ lymphocytes in peripheral blood mononuclear cells (PBMC) using three different antigen preparation (CMV-lysate, pp72- and pp65-overlapping peptide pools) using intracellular cytokine staining and flow cytometry.

Results

Median CD4+ and CD8+T-cell responses to CMV-lysate, pp72- and pp65-overlapping peptide pools were lower in D(+)R(-) than in R(+)patients or in non-immunosuppressed donors. Comparing subpopulations we found that CMV-lysate favored CD4+- over CD8+-responses, whereas the reverse was observed for pp72, while pp65-CD4+- and -CD8+-responses were similar. Concurrent CMV replication in R(+)-patients was associated with significantly lower T-cell responses (pp65 median CD4+ 0.00% vs. 0.03%, p = 0.001; CD8+ 0.01% vs. 0.03%; p = 0.033). Receiver operated curve analysis associated CMV-pp65 CD4+ responses of > 0.03% in R(+)-patients with absence of concurrent (p = 0.003) and future CMV replication in the following 8 weeks (p = 0.036). GCV-resistant CMV replication occurred in 3 R(+)-patients (6.3%) with pp65- CD4+ frequencies < 0.03% (p = 0.041).

Conclusion

The data suggest that pp65-specific CD4+ T-cells might be useful to identify R(+)-patients at increased risk of CMV replication. Provided further corroborating evidence, CMV-pp65 CD4+ responses above 0.03% in PBMCs of KT patients under stable immunosuppression are associated with lower risk of concurrent and future CMV replication during the following 8 weeks.

Induction of an epithelial integrin alphavbeta6 in human cytomegalovirus-infected endothelial cells leads to activation of transforming growth factor-beta1 and increased collagen production

Human cytomegalovirus (CMV) infection is a major cause of morbidity in immunosuppressed individuals, and congenital CMV infection is a leading cause of birth defects in newborns. Infection with pathogenic viral strains alters cell-cell and cell-matrix interactions, affecting extracellular matrix remodeling and endothelial cell migration. The multifunctional cytokine transforming growth factor (TGF)-beta1 regulates cell proliferation, differentiation, and extracellular matrix remodeling. Secreted as a latent protein complex, TGF-beta1 requires activation before binding to receptors that phosphorylate intracellular effectors. TGF-beta1 is activated by integrin alphavbeta6, which is strongly induced in the epithelium by injury and inflammation but has not previously been found in endothelial cells. Here, we report that CMV infection induces integrin alphavbeta6 expression in endothelial cells, leading to activation of TGF-beta1, signaling through its receptor ALK5, and phosphorylation of its intracellular effector Smad3. Infection of endothelial cells was also found to stimulate collagen synthesis through a mechanism dependent on both TGF-beta1 and integrin alphavbeta6. Immunohistochemical analysis showed integrin alphavbeta6 up-regulation in capillaries proximal to foci of CMV infection in lungs, salivary glands, uterine decidua, and injured chorionic villi of the placenta, demonstrating both its induction in endothelium and up-regulation in epithelium in vivo. Our results suggest that activation of TGF-beta1 by integrin alphavbeta6 contributes to pathological changes and may impair endothelial cell functions in tissues that are chronically infected with CMV.

Viral subversion mechanisms in chronic kidney disease pathogenesis

Viruses cannot autonomously replicate but must rely on the host cellular machinery to support their life cycle. Through natural selection, viruses have evolved strategies to co-opt the host organism to be a better site for their propagation. Some of these strategies are directed at the cellular machinery and involve complicated and ingenious solutions to optimize infection, replication, viral gene expression, and new virion assembly and shedding. Other strategies are directed at the host's innate and adaptive immune systems that permit the virus to evade clearance mechanisms. The more common pathogenic viral infections in nephrology-cytomegalovirus, HIV-1, hepatitis C virus, polyomavirus BK, and parvovirus B19-all have acquired subversion strategies that benefit the virus but because they interfere with normal cellular and immune processes also have become pathogenic to the host. In addition, the highly prevalent viruses cytomegalovirus, BK, and B19 cause severe disease only in the setting of immunosuppression, revealing the very delicate balance that some viruses have achieved with their host's immune system. Thus, selective pressure for survival drives both the evolution of more sophisticated viruses and the host immune system as it evolves to combat the environment of adapting and emerging infectious agents. Understanding the molecular mechanisms of these viral subversion strategies may reveal new targets for the development of highly specific antiviral therapies and also aid vaccine development.

Cytomegalovirus accelerates chronic allograft nephropathy in a rat renal transplant model with associated provocative chemokine profiles

BACKGROUND

Studies have shown that rat cytomegalovirus (RCMV) infection accelerates transplant vascular sclerosis (TVS) in rat heart and small bowel allotransplants. In these models, RCMV-accelerated TVS results from increased graft infiltration of inflammatory cells through up-regulation of chemokine expression. The aim of this study was to determine if RCMV infection accelerates renal transplant chronic allograft nephropathy (CAN), and the role of chemokines in this process.

METHODS

F344 kidneys were transplanted into Lewis recipients with and without RCMV infection. To monitor CAN, serum creatinine (Cr) levels were measured starting at 4 weeks posttransplantation. At 7 and 21 days, and at terminal rejection, grafts were examined for histologic changes, inflammatory cell infiltrates, viral load, and chemokine expression profiles.

RESULTS

By week 8, serum Cr showed significant elevation (P < .01) in the RCMV-infected group vs uninfected group, and remained significantly elevated through the end of the study. RCMV+ renal allografts had significant inflammatory cell infiltration and increased CAN at postoperative day (POD) 28. The CC chemokines RANTES, MCP-1, and MIP-1alpha, and the CXC chemokine IP-10 were up-regulated in RCMV-infected vs uninfected allografts. IP-10 was significantly up-regulated early in the process, whereas RANTES and MCP-1 were induced at a later time.

CONCLUSIONS

RCMV infection accelerates CAN, with associated graft inflammatory infiltrates, which is paralleled by an increase in expression of CC and CXC chemokines. Our findings suggest that the early induction of IP-10 in the infected allografts promotes alterations in T-cell and monocyte migration to the graft, which initiates accelerated inflammatory and fibrotic changes associated with CAN.

Persistent cytomegalovirus infection in kidney allografts is associated with inferior graft function and survival

The long-term effects of cytomegalovirus (CMV) infections on kidney allografts are unknown. We examined the impact of persistent intragraft CMV infection on long-term kidney allograft function and survival. CMV was diagnosed in 82/172 renal transplant recipients by antigenemia test and viral cultures. Biopsies from 48 of 82 patients taken after CMV infection and from 15 patients with no previous CMV infection detected were available for the immunohistochemical demonstration of CMV antigens and DNA hybridization in situ. Five-year follow-up data from these 63 patients were analysed. In 17 patients, CMV antigens and/or DNA persisted in the biopsy >2 months after the last positive finding in blood or urine. Patients with persistent intragraft CMV had reduced graft survival (P = 0.041) and Cox regression analysis showed persistent CMV as a risk factor for reduced graft survival (RR: 3.5). Recipients with persistent intragraft CMV had reduced creatinine clearance 1 and 2 years after transplantation (P = 0.007) and in multivariate logistic regression analyses including several potential pre- and posttransplant risk factors, persistent CMV was an independent risk factor for lower clearance at 1 and 2 years (OR: 4.4 and 4.9). Our novel findings show that persistent intragraft CMV infection was associated with reduced kidney allograft function and survival.

Increased urinary excretion of transforming growth factor-beta(1) in renal transplant recipients during cytomegalovirus infection

AIMS

Cytomegalovirus (CMV) is a suggested risk factor for chronic allograft nephropathy, and transforming growth factor-beta (TGF-beta) is a key fibrogenic molecule in this process. CMV has been shown to induce the expression of TGF-beta and several cytokines. We analyzed the impact of CMV on urinary excretion of TGF-beta, ICAM-1, TNF-alpha and correlated findings with biopsy histology.

MATERIAL

Urine samples from 46 renal transplant recipients were available for the study. Urine samples were taken when CMV infection was suspected, or for controlling of proteinuria or bacteriuria.

METHOD

CMV was diagnosed by antigenemia and viral cultures. Patients with previous CMV infection were excluded from the analysis. Urine samples were analyzed by ELISA-method to detect the levels of TNF-alpha, ICAM-1 and TGF-beta(1). Banff '97 criteria were used for scoring of protocol biopsies taken 6 months after transplantation.

RESULTS

At the time of the urine collection, 13/46 patients had CMV infection. Eight patients with no CMV infection were used as controls. TGF-beta(1) was significantly increased in the CMV group (samples taken mean 137+/-79 days post-transplantation) compared to controls (samples 139+/-64 days post-transplantation) (51.1+/-28.0 vs. 13.3+/-6.7 ng/mmol crea, p<0.001). No differences in the levels of other molecules were recorded. In the biopsies, interstitial fibrosis was significantly increased in the CMV group compared to controls.

CONCLUSIONS

Urinary excretion of TGF-beta(1) was increased in patients during CMV infection. This was associated with increased fibrosis in the biopsies.

The Impact of Pretransplant Cytomegalovirus Infection on Acute Renal Allograft Rejection

BACKGROUND

The role of cytomegalovirus (CMV) infection in renal allograft rejection remains controversial; moreover, there are few studies on pretransplant infections. This study sought to investigate whether pretransplant CMV infections had negative effects on acute rejection episodes (ARE) and to evaluate the effect of preemptive treatment.

METHODS

This retrospective single-center study of 416 transplant recipients from October 1, 2000 to September 1, 2003 had CMV infections diagnosed by CMV antigenemia tests. The incidences of ARE were compared between CMV-infected and noninfected groups. Risk factors for ARE were analyzed. Based on preemptive treatment, pretransplant CMV-infected recipients were divided into ganciclovir-treated and nontreated groups and the incidence of ARE was compared between the two groups.

RESULTS

One hundred eighty four recipients had CMV infections pretransplant; the infection rate was 44.2%. Fifty five recipients had ARE among the pretransplant CMV-positive group, which was significantly higher than that in the noninfected group (29.9% vs 19.5%, P = .014). But the rejection subgroups and renal function recovery had no significant differences. While the presence of pretransplant infection was an independent predictor of ARE (RR = 1.807), severity showed no significant impact on ARE. Among 184 pretransplant CMV infection recipients, the incidences of ARE were 14.3% and 18.0% in ganciclovir-treated versus nontreated patients, respectively (P = .650).

CONCLUSIONS

Pretransplant CMV-positive recipients were at greater risk of ARE. Pretransplant CMV infection was an independent risk factor for ARE. Preemptive antiviral treatment did not show protective effects against ARE related to CMV infection-mediated immunological injuries.

Factors influencing the onset of diabetes mellitus after kidney transplantation: a single French center experience

Posttransplantation diabetes mellitus (PTDM) is a complication arising mostly during the first 6 months after kidney transplantation. Considering the serious outcomes of chronic hyperglycemia in kidney transplant patients, the recognition of factors that contribute to the onset of PTDM is of particular relevance. A retrospective analysis was performed to document the incidence of and the risk factors for diabetes mellitus occurring in the first year after kidney transplantation among 177 adult patients, without previously known diabetes transplanted between January 1998 and December 2000. PTDM, defined as fasting plasma glucose > or = 126 mg/dL confirmed by repeat testing on a different day, occurred in 48 (27.12%) patients of whom 36 showed transient changes during the first year after transplantation. Univariate analysis identified variables to be associated with the onset of PTDM: older recipient age (P = .05), male gender (P = .03), family history of diabetes (P = .04), advanced donor age (P = .008), absence of induction immunosuppression (P = .04), use of tacrolimus (vs cyclosporine; P = .01), one or more than one (steroid-treated) acute rejection episode(s) (P = .000001), cytomegalovirus infection (P = .02), and use of beta-blockers or diuretics (P = .05). By multivariate analysis, five factors were independently associated with the onset of PTDM: two episodes of rejection (odds ratio = 42.69, P = .000025), one episode of rejection (5.01, P = .007), older recipient age (1.06, P = .017), family history of diabetes (7.24, P = .011), and weight at transplantation (1.03, P = .048). Tacrolimus treatment remained of borderline significance (2.77, P = .05). In addition to traditional risk factors predisposing to the development of type 2 diabetes in the general population, episodes of acute rejection significantly influence the incidence of PTDM.

Valganciclovir: oral prevention and treatment of cytomegalovirus in the immunocompromised host

Herpes virus infections, particularly those caused by cytomegalovirus (CMV), lead to significant and, sometimes severe, clinical problems for the immunocompromised host. As effective agents have become available, several treatment and prevention strategies have evolved over the past decade, first in intra-venous form and more recently, as oral preparations. Valganciclovir, the valine ester of ganciclovir, is an orally administered, potent, antiviral agent active against all herpes viruses. When taken orally, valganciclovir has much-improved bioavailability compared with oral ganciclovir and achieves ganciclovir exposures similar to intravenous ganciclovir. Clinical trials evaluating the safety and efficacy of valganciclovir for the treatment of new AIDS-associated CMV retinitis showed equivalency to intravenous ganciclovir and prevented progression of quiescent disease. In solid organ recipients, once-daily valganciclovir has been proven equivalent to oral ganciclovir for the prevention of CMV infection. The high bioavailability and convenient dosing formulation make valganciclovir an attractive option for these indications.

Persistent cytomegalovirus infection is associated with increased expression of TGF- 1, PDGF-AA and ICAM-1 and arterial intimal thickening in kidney allografts

BACKGROUND

Cytomegalovirus (CMV) is a suggested risk factor for the development of chronic allograft nephropathy. Transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF) are important molecules in this process. We analysed the impact of persistent CMV infection in kidney allografts on the expression of growth factors, adhesion molecules and inflammation markers.

METHODS

In a population of 172 renal transplant recipients, CMV was diagnosed in 82 patients by pp65 antigenaemia test and viral cultures. Biopsies taken after CMV infection were available from 48 of the 82 patients for the demonstration of CMV antigens by immunohistochemistry and in situ DNA hybridization. Biopsy material for further analyses was available from 16 CMV patients. Five patients with no previous CMV infection were used as controls. Biopsy histology was scored according to Banff 97 classification.

RESULTS

In 11 out of 16 patients, persistent CMV antigens and/or DNA were demonstrated in the biopsy >2 months after the last positive finding in blood or urine. Increased expression of TGF-beta1 was recorded in tubuli and in arterial endothelium in biopsies with a positive CMV finding compared with controls. Also, the expression of PDGF-AA was increased in tubuli and somewhat in arterial endothelium in CMV-positive biopsies. The expression of intercellular adhesion molecule-1 (ICAM-1) was increased significantly in peritubular capillary endothelium. Vascular intimal thickening was increased in the biopsies with persistent CMV infection.

CONCLUSIONS

Persistent CMV infection in kidney allografts was associated with increased vascular changes and increased expression of TGF-beta1, PDGF-AA and ICAM-1.

Transplanting kidneys from CMV-seropositive donors to CMV-seronegative recipients is not associated with poorer renal allograft function or survival

BACKGROUND

Cytomegalovirus (CMV)-seronegative recipients of renal allografts from CMV-seropositive donors (D+/R-) have a higher rate of acute rejection than other renal transplant recipients. A relationship between CMV infection/disease and chronic allograft nephropathy (CAN) has been proposed from animal studies, although human studies have been inconclusive. The objective of this study was to determine if CMV seromatching has an effect on renal allograft function and allograft survival.

METHODS

A retrospective single centre study was carried out in 333 first cadaveric transplant recipients from January 1, 1991 to December 31, 1997. The primary end-point was creatinine clearance at 3 years post-transplant in groups based on CMV seromatching. The secondary end-point was renal allograft survival.

RESULTS

Mean creatinine clearance 3 years post-transplant was 53.4 ml/min/1.73 m2 of body surface area. There was no significant difference in the mean creatinine clearance for groups formed on the basis of CMV seromatching. Delayed graft function and acute rejection were associated with a lower creatinine clearance at 3 years and reduced overall graft survival [hazard ratios 2.35 (1.56-3.54) (P<0.001) and 1.57 (1.0-2.46) (P = 0.046), respectively]. Considering the end-point of graft loss due to acute rejection (censoring for death with a functioning graft) identified the D+/R- group as having an increased hazard of graft loss due to acute rejection [hazard ratio 3.12 (1.16-8.57) (P = 0.024)].

CONCLUSIONS

The D+/R- group does not appear to have poorer renal allograft function 3 years post-transplant. This group does, however, have an increased risk of early allograft loss due to acute rejection.

Sequential cytomegalovirus antigenemia monitoring in kidney transplant patients treated with antilymphocyte antibodies

BACKGROUND

Antilymphocyte antibodies (ALA) use is related to disseminated cytomegalovirus (CMV) disease after kidney transplantation. Strict surveillance of CMV infection, preemptive antiviral treatment or concomitant ganciclovir and ALA use are proposed as an attempt to prevent related clinical complications. Our objective was to describe the pattern of CMV infection, based on sequential antigenemia detection, after ALA treatment.

PATIENTS AND METHODS

Thirty renal transplant patients were prospectively screened for CMV infection after ALA treatment. CMV antigenemia (pp65 antigen detection) was monitored twice a week in the first month and weekly until 60 days after the beginning of ALA therapy. Any positive value of antigenemia was considered CMV infection.

RESULTS

Twenty-eight (93.3%) patients were CMV positive (IgG) before transplantation. The mean duration of ALA treatment was 12.1+/-2.4 days. Positive antigenemia was detected in 24 (80%) patients, a mean of 52.5+/-15 days after transplant and 44.7+/-14 days after the beginning of ALA treatment. The median antigenemia count was 7 positive cells/300,000 neutrophils (range: 1-227). Antigenemia preceded clinical symptoms by 5.8 days (0-28 days). Eighteen (75%) of 24 positive patients received ganciclovir treatment: 8 patients (26.7%) for viral syndrome, 2 patients (33.3%) for invasive disease, and 8 patients (26.7%) as part of preemptive therapy, asymptomatic with high antigenemia values. Six pp65-positive patients with low counts were followed up until a negative result and remained asymptomatic without any specific treatment.

CONCLUSION

CMV infection was frequent after ALA treatment in this group and generally occurred late after completion of treatment. Antigenemia was a reliable tool to guide preemptive treatment in these patients, and such strategy is an alternative option compared to the prophylactic use of ganciclovir with ALA treatment.