Acute rejection and cardiac allograft vascular disease is reduced by suppression of subclinical cytomegalovirus infection

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.

Cytomegalovirus hyperimmunoglobulin: mechanisms in allo-immune response in vitro

BACKGROUND

Cytomegalovirus hyperimmunoglobulin (CMVIg) containing drugs are routinely administered in cardiac transplantation for prophylaxis against CMV disease. Yet little is known about their influence on transplant relevant immune functions. The aim of this study was to evaluate the effect of CMVIg on cellular immunity in in vitro experiments and to define their role in tolerance inducing mechanisms.

MATERIALS AND METHODS/RESULTS

CMVIg reduces proliferation in mixed lymphocyte reactions and anti-CD3 blastogenesis assays and is related to decreased production of immune modulating cytokines interleukin (IL)-2, interferonr (IFNgamma), IL-10. This antiproliferative effect is associated with a cell-cycle arrest in the G0/G1 phase and induction of apoptosis in CD8+ and natural killer cells. Co-incubation with CMVIg causes down-regulation of cell bound immunoglobulin and FcgammaRIII surface expression on natural killer cells and leads to attenuation of antibody dependent cellular cytotoxicity effector functions.

CONCLUSIONS

We conclude that CMVIg induces immunological features on leukocytes in vitro that are known to be related to tolerance induction. Our observations extend the current concept of CMVIg as passive CMV prophylaxis to a therapeutic drug compound capable of reducing allogeneic immune response.

TH1/TH2 cytokine release pattern during in vivo cytomegalovirus disease in solid organ transplantation

BACKGROUND

Cytomegalovirus (CMV) disease is associated with an increased net immunosuppressive state in solid organ transplant recipients, leading to more bacterial and fungal infections. The release of pro- and anti-inflammatory cytokines could be one of the responsible factors.

METHODS

We prospectively included all patients undergoing solid organ transplantation between April and November 2004. During follow-up, plasma samples were collected in the immediate postsurgical period, at the first and second months, at the time of maximum antigenemia during CMV disease, and at 6 months posttransplantation. We determine the levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-10. Log-transformed data were compared by a nonparametric Wilcoxon test for related variables.

RESULTS

During the study period, we monitored 146 recipients of solid organ transplantation: 77 kidneys, 8 kidney-pancreas, 46 liver, 11 heart, 2 liver-kidney, and 2 heart-kidney. No differences were observed between the TNF-alpha and IL-10 levels in the immediate postsurgical period or during CMV disease. TNF-alpha and IL-10 levels during CMV disease were higher than levels during the first month (mean TNF-alpha first month = 12.71 pg/mL vs CMV disease = 22.71 pg/mL, P = .028; mean IL-10 first month = 3.47 pg/mL vs CMV disease = 19.2 pg/mL, P = .018). Th1/Th2 ratio (measured as TNF-alpha/IL-10) was 1.75 in the immediate postsurgical period, 7.5 during the first month, 1.86 at the time of CMV disease, and 4.61 at the sixth month. The difference in Th1/Th2 ratio during CMV disease and in the first month was statistically significant (P = .043).

CONCLUSION

During CMV disease, we observed an increase in TNF-alpha and IL-10 release, which was similar to that during the postsurgical period. An imbalance toward an anti-inflammatory pattern was noted in these two periods. This could reflect a cooperative factor increasing the net state of immunosuppression during CMV disease.

Prophylaxis and treatment of cytomegalovirus disease in recipients of solid organ transplants: current approach and future challenges

PURPOSE OF REVIEW

Cytomegalovirus infection is a major cause of morbidity and mortality in solid-organ transplant recipients, in terms of cytomegalovirus disease itself and the associated outcomes of organ rejection and death. This review focuses on recent literature concerning prevention and treatment of cytomegalovirus disease in this population.

RECENT FINDINGS

Two major strategies for the prevention of cytomegalovirus infection in solid-organ transplant recipients - preemptive and prophylactic treatment - are reviewed. Both strategies result in a lower incidence of cytomegalovirus disease when compared to a 'wait and treat' approach, and are generally considered cost-effective. Neither prophylaxis nor preemption has yet been shown to be superior. Newer trials are also reviewed, which are beginning to evaluate protocols of preemption or prophylaxis representative of current practice, as well as to explore alternative dosing strategies, the benefits of cytomegalovirus immune globulin, and the potential benefit of a longer course of prophylaxis. Concerns for the selection of ganciclovir-resistant strains of cytomegalovirus are also addressed.

SUMMARY

The consensus is that there is benefit for the treatment of solid-organ transplant patients with an antiviral agent before clinical evidence of cytomegalovirus disease. So far, there has been no demonstration of the superiority of prophylactic or preemptive regimens, nor has the exact nature and dosing of the oral antiviral agent of choice been established.

Late-onset cytomegalovirus disease in patients with solid organ transplant

PURPOSE OF REVIEW

To review existing data regarding late cytomegalovirus disease occurring after antiviral prophylaxis.

RECENT FINDINGS

There is a continued debate as to the respective merits of the preemptive and the prophylactic approach to prevent cytomegalovirus disease after transplantation. Arguably, by allowing some infection, the preemptive approach helps build immunity in contrast to prophylaxis, explaining the occurrence of late cytomegalovirus disease in the latter approach. No study comparing directly both approaches is large enough to definitely determine whether the preemptive approach leads to a faster development of immune response protective from late disease nor whether late disease is clinically different after prophylaxis compared to early cytomegalovirus diseases. While risk factors for late cytomegalovirus disease all point to a delay in mounting immune responses, there are no identified markers that would help predict the risk for late disease at the time of prophylaxis discontinuation. Various approaches to prevent late cytomegalovirus disease have been developed: prolonged prophylaxis, microbiological surveillance and preemptive treatment after prophylaxis discontinuation. Considering the identifying risk factors for late disease, it would also make sense to envision vaccinating cytomegalovirus-seronegative recipients.

SUMMARY

The best approach to prevent or manage late cytomegalovirus disease associated with cytomegalovirus prophylaxis remains to be defined.

Cytomegalovirus-associated allograft rejection in heart transplant patients

PURPOSE OF REVIEW

Modern antiviral strategies are effective in controlling the clinical syndromes associated with acute cytomegalovirus infection in heart transplant recipients. Despite this effectiveness, subclinical cytomegalovirus infection is a common finding in these patients and its impact on long-term graft outcome is currently underestimated.

RECENT FINDINGS

Recent studies provide evidence implicating subclinical cytomegalovirus infection in the pathogenesis of allograft rejection and cardiac allograft vasculopathy. In this process, cytomegalovirus interacts with local inflammatory pathways, and systemic immune-regulation mechanisms, which may lead to graft damage, even in the absence of cytomegalovirus replication within the graft. Consequently, in addition to pharmacologic strategies that inhibit viral replication, immune-based therapies that abrogate host immune response may provide an effective tool to prevent the indirect impact of cytomegalovirus on graft function.

SUMMARY

Current evidence suggests that subclinical cytomegalovirus infection plays an important role in the pathogenesis of long-term graft dysfunction in heart transplant recipients and in other solid organ transplant recipients. Pending the availability of definitive data from randomized trials, we propose that the use of pharmacologic and immune-based approaches, directed at complete suppression of cytomegalovirus infection, represents the best strategy for prevention of cytomegalovirus-induced rejection, cardiac allograft vasculopathy and chronic allograft damage.

Frequent occult infection with Cytomegalovirus in cardiac transplant recipients despite antiviral prophylaxis

Despite antiviral prophylaxis, a high percentage (over 90%) of heart transplant patients experience active cytomegalovirus (CMV) infection, diagnosed by detection of viral DNA in peripheral blood polymorphonuclear leukocytes within the first few months posttransplantation. Viral DNA was detected in mononuclear cells prior to detection in granulocytes from CMV-seropositive recipients (R+) receiving a heart from a CMV-seropositive donor (D+). Based on assessment of systemic infection in leukocyte populations, both R+ subgroups (R+/D- and R+/D+) experienced a greater infection burden than the R-/D+ subgroup, which was aggressively treated because of a higher risk of acute CMV disease. Despite widespread systemic infection in all at-risk patient subgroups, CMV DNA was rarely (< 3% of patients) detected in transplanted heart biopsy specimens. The R+ patients more frequently exceeded the 75th percentile of the CMV DNA copy number distribution in leukocytes (110 copies/10(5) polymorphonuclear leukocytes) than the R-/D+ subgroup. Therefore, active systemic CMV infection involving leukocytes is common in heart transplant recipients receiving prophylaxis to reduce acute disease. Infection of the transplanted organ is rare, suggesting that chronic vascular disease attributed to CMV may be driven by the consequences of systemic infection.

Interplay Between Systemic Inflammation and Markers of Insulin Resistance in Cardiovascular Prognosis After Heart Transplantation

BACKGROUND

Metabolic and immuno-inflammatory risk factors contribute to cardiac allograft vasculopathy (CAV) pathogenesis. Although systemic inflammation, as detected by C-reactive protein (CRP), predicts CAV development, the relationship between CRP and markers of metabolic abnormalities remains unexplored.

METHODS

CRP and the entire metabolic panel were evaluated in 98 consecutive heart transplant recipients at the time of annual coronary angiography, 5.8 years after transplant (range, 1-12 years). A ratio of triglycerides (TG) to high-density lipoproteins (HDL) of 3.0 or more was considered a marker of insulin resistance. CAV prevalence was defined by angiography, and subsequent prognosis was evaluated as incidence of major cardiac adverse events.

RESULTS

CRP was higher in the 34 patients with angiographic CAV than in those without CAV (1.10 +/- 0.20 vs 0.50 +/- 0.05 mg/dl, p < 0.001). Patients with insulin resistance had higher CRP concentrations (p = 0.023) and higher CAV prevalence (p = 0.005). High CRP and a TG/HDL of 3.0 or more were independently associated with an increased likelihood of CAV (odds ratio, > or = 3.9; p = 0.02) and predicted an increased risk of major cardiac adverse events. The combination of high CRP and a TG/HDL of 3.0 or more identified a subgroup of patients having a 4-fold increased risk for CAV and a 3-fold increased risk for major cardiac adverse events compared with patients with low CRP and normal values for metabolic indicators.

CONCLUSIONS

Both CRP and insulin resistance, as estimated by TG/HDL, appear to be strong, synergic risk factors for CAV and for major cardiac adverse events. These findings support the hypothesis that in heart transplant recipients, systemic inflammation may be an important mediator of graft vascular injury associated with metabolic syndrome.