Cytomegalovirus nucleic acids in allografted hearts

Antiviral anticoagulation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel envelope virus that causes coronavirus disease 2019 (COVID-19). Hallmarks of COVID-19 are a puzzling form of thrombophilia that has elevated D-dimer but only modest effects on other parameters of coagulopathy. This is combined with severe inflammation, often leading to acute respiratory distress and possible lethality. Coagulopathy and inflammation are interconnected by the transmembrane receptor, tissue factor (TF), which initiates blood clotting as a cofactor for factor VIIa (FVIIa)-mediated factor Xa (FXa) generation. TF also functions from within the nascent TF/FVIIa/FXa complex to trigger profound changes via protease-activated receptors (PARs) in many cell types, including SARS-CoV-2-trophic cells. Therefore, aberrant expression of TF may be the underlying basis of COVID-19 symptoms. Evidence suggests a correlation between infection with many virus types and development of clotting-related symptoms, ranging from heart disease to bleeding, depending on the virus. Since numerous cell types express TF and can act as sites for virus replication, a model envelope virus, herpes simplex virus type 1 (HSV1), has been used to investigate the uptake of TF into the envelope. Indeed, HSV1 and other viruses harbor surface TF antigen, which retains clotting and PAR signaling function. Strikingly, envelope TF is essential for HSV1 infection in mice, and the FXa-directed oral anticoagulant apixaban had remarkable antiviral efficacy. SARS-CoV-2 replicates in TF-bearing epithelial and endothelial cells and may stimulate and integrate host cell TF, like HSV1 and other known coagulopathic viruses. Combined with this possibility, the features of COVID-19 suggest that it is a TFopathy, and the TF/FVIIa/FXa complex is a feasible therapeutic target.

Long-term results of CMV hyperimmune globulin prophylaxis in 377 heart transplant recipients

BACKGROUND

Cytomegalovirus (CMV) has emerged as the most important pathogen to affect the post-operative course after heart transplantation. We performed a retrospective analysis to evaluate the efficiency of CMV hyperimmune globulin (CMVIG) prophylaxis in preventing CMV disease in aggressively immunosuppressed patients after heart transplantation.

METHODS

We studied 377 heart transplant recipients who received quadruple-immunosuppressive therapy and CMVIG as sole CMV prophylaxis. The study population was categorized into 4 groups according to donor and recipient CMV serology at the time of transplantation (D+/R+, D+/R-, D-/R+, D-/R-) and was monitored for CMV immediate early antigen in peripheral blood cells, in urine sediments, and in throat washings; for the presence of serum CMV immunoglobulin M and CMV immunoglobulin G; and for clinical evidence of CMV-related symptoms. In addition, we compared the incidence of cardiac allograft vasculopathy and infection among the groups.

RESULTS

During the first 5 years after transplantation, CMV disease developed in 79 patients (20.96%). Comparison among the groups showed significantly increased risk for CMV disease in allograft recipients of organs from seropositive donors (D+, 27.31%; D-, 11.33%; p = 0.0003). We observed 6 CMV-associated deaths, all in CMV-antibody-negative recipients. Additionally CMV-positive recipients had a greater incidence of cardiac allograft vasculopathy (p = 0.048), and a greater overall infection rate (p = 0.0034).

CONCLUSIONS

Cytomegalovirus hyperimmune globulin administration prevents CMV disease and infection in aggressively immunosuppressed heart transplant recipients. Because fatal CMV disease in CMV-negative recipients of organs from seropositive donors could not be prevented with CMVIG alone, we recommend the additional use of prophylactic ganciclovir in this CMV-mismatched population.

Infections and solid organ transplant rejection: a cause-and-effect relationship?

Although evidence is far from being conclusive, several studies have suggested that infections could trigger rejection in different transplant settings. In this review we examine the evidence linking cytomegalovirus (CMV), adenovirus, enterovirus, parvovirus, and herpes simplex virus infections to the vasculopathy leading to cardiac allograft rejection, the association between CMV and chronic kidney, lung, and liver graft rejection, and the association of human herpesvirus 6 reactivation with CMV-related disease in kidney and liver transplant recipients. We also review the numerous antiviral prophylactic or pre-emptive treatments in use to control CMV infection, and suggest that they do not limit immune reactions leading to graft rejection or lower the risk of developing post-transplantation atherosclerosis in allograft recipients. Finally, we emphasise the need for prospective, international studies to clarify the role of infections in transplant rejection, to look at virus-to-virus interactions, and to establish specific therapeutic strategies. Such strategies must not rely exclusively on expensive antiviral agents but also on vaccination or other, innovative approaches, such as the use of agents able to inhibit the activity of natural killer cells, which might have an important role in acute allograft rejection.

Tolerance and chronic rejection

The most common cause of chronic allograft loss is an incompletely understood clinicopathological entity called chronic rejection (CR). Recent reports suggest an improvement in long-term renal allograft survival, although it is not clear from these data whether a true reduction of biopsy-proven CR has occurred. Although newer immunosuppressive medications have greatly reduced the incidence of acute rejection (AR) in the early post-transplantation period, the ideal therapy for both AR and CR would be to achieve a state of tolerance. By definition, such a state should allow for indefinite allograft survival, with no histopathological evidence of CR, despite immunocompetence in the host (i.e. without the need for chronic immunosuppression). Although several experimental studies are able to achieve tolerance, with clear improvement in allograft survival, detailed studies on graft function and morphology are often not included. This review will discuss possible ways that tolerance induction could lead to a CR-free state. General mechanisms of CR and transplantation tolerance induction are discussed as well as the difficulties in translating small animals studies into large animals and humans.

The WAF1-mediated p53 growth-suppressor pathway is intact in the coronary arteries of heart transplant recipients

It has been suggested that the interaction of cytomegalovirus (CMV) with the p53 tumor suppressor gene product plays a role in the development of coronary artery restenosis after angioplasty. CMV nucleic acids have been observed in the coronary arteries of allografted hearts, suggesting a possible role for the interaction of CMV with p53 in the development of accelerated graft arteriosclerosis in transplant recipients. Formalin-fixed, paraffin-embedded sections of coronary arteries from 19 transplanted hearts were immunostained for the p53 gene product using Target Unmasking Fluid (TUF)-mediated immunohistochemistry and the anti-p53 antibodies CM1 and DO7. Fresh-frozen sections of coronary arteries were also available from six of the 19 hearts, and these fresh-frozen sections were immunostained for the p53 gene product with the DO7 antibody and for WAF1 using the anti-WAF1 antibody EA10. Focal and weak staining for p53 was observed in smooth muscle and endothelial cells in two of 19 vessels, whereas the remaining 17 did not stain. CMV nucleic acids were previously shown in six of 13 of these hearts by in situ hybridization. The fresh-frozen sections of coronary arteries also did not stain for p53, but the smooth muscle cells in these vessels did stain intensely for WAF1. These results suggest three possibilities: (1) CMV-p53 interactions are not important in the development of accelerated graft arteriosclerosis; or (2) there is an interaction, but it is transient and not detectable at the time points examined in this study; or (3) there is an interaction, but binding of CMV to p53 leads to accelerated degradation of p53, as occurs with HPV-E6. The expression of WAF1 further suggests that the WAF1-mediated antiproliferative signal is intact in these vessels.

Correlation between the intensity of cytomegalovirus infection and the amount of perivasculitis in aortic allografts

We previously demonstrated that cytomegalovirus (CMV) infection enhanced perivascular inflammation in rat aortic allografts. In this study, we investigated the relationship between the CMV infection load and the magnitude of perivasculitis (chronic rejection) in aortic transplants. Rats received orthotopic abdominal aortic grafts, different degrees of total body irradiation (TBI) for immunosuppression and CMV inoculation. The spleens of the rats receiving 5 Gy of TBI contained more infectious virus and viral antigens than those of rats receiving 3 Gy of TBI or no TBI. Although the number of inflammatory cells infiltrating the perivascular area was decreased after TBI, CMV infection resulted in increased perivasculitis in rats that received 5 Gy of TBI as compared to non-infected animals. This virus-induced effect was characterized predominantly by an increased T-cell infiltration, including CD4 and CD8 T-cells. It is concluded that an enhanced systemic CMV infection during severe immunosuppressive therapy can accelerate the development of chronic rejection, which seems to be mediated mainly by T-cells.

Association of cytomegalovirus infection with post-transplantation cardiac rejection as studied using the polymerase chain reaction

The relationship between cytomegalovirus (CMV) infection and cardiac allograft rejection is controversial, some authors reporting a significant association, others not, on the basis of the results of conventional virological diagnosis by culture or serology. This problem was reinvestigated in 88 patients using a semi-quantitative nest polymerase chain reaction (PCR) procedure for detecting CMV DNA in endomyocardial biopsy specimens. Significantly more positive biopsies were obtained from patients with moderate (grade 2; P = 0.02) or severe (grade 3a-4; P = 0.03) rejection than with no or mild (grade 0-1b) rejection, whereas there was no significant association between rejection and CMV as diagnosed by virus isolation from urine, throat or blood, or by the detection of CMV-IgM. PCR-positive biopsies originated most frequently from CMV-antibody positive recipients (R+) of hearts from seropositive donors (D+), in association with moderate or severe rejection rather than with mild or no rejection The detection of CMV in the heart thus seemed to be related more to R+D+ serological status than to severity of rejection, that is, to circumstances that favoured co-infection with strains of CMV from both donor and recipient. Studies on sequential biopsy specimens from selected patients also provided evidence that CMV infection and rejection were not always related events. The PCR was able to differentiate latent from active CMV infection; moreover, some seronegative individuals gave repeatedly positive biopsies, thereby supporting the work of others that some patients undergo CMV infection without mounting a detectable antibody response.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytomegalovirus infection accelerates cardiac allograft vasculopathy: correlation between angiographic and endomyocardial biopsy findings in heart transplant patients

In order to determine the impact of cytomegalovirus (CMV) infection on cardiac allograft vasculopathy (CAV), we quantitated angiograms and endomyocardial biopsy (EMB) specimens obtained from 53 heart transplant recipients. CMV infection was particularly associated with the development of discrete stenosis in major branch vessels (P < 0.03). Also, the number of diffusely affected vessel segments was significantly higher in CMV patients than in CMV-free recipients after the 2nd postoperative year (P < 0.05). The EMB histology correlated well with angiography. Significantly higher levels of arteriolar endothelial cell proliferation and intimal thickness were recorded in biopsies of CMV patients than in those of CMV-free recipients during the 1st postoperative year (P < 0.02 and P < 0.005, respectively). The CMV-associated vascular changes in EMB histology clearly preceded angiographically detectable CAV findings. Taken together, CMV infection accelerated heart allograft arteriosclerosis. The histological changes appeared prior to changes detected by coronary angiography. The CMV effect was particularly pronounced during the first 2 post-transplant years but leveled off thereafter. Thus, CMV-accelerated allograft arteriosclerosis may be linked in particular with early graft loss of CMV-infected heart transplant recipients.

Graft vascular disease in the great vessels and vasa vasorum

To determine whether the great vessels were subject to transplantation-associated arteriosclerosis (graft vascular disease) we studied sections of aorta and pulmonary arteries from 19 cardiac explant cases. Sections of the same vessels from five autopsied hearts from patients who had received liver and/or kidney transplants with immunotherapy as well as from eight recipient hearts served as controls. In addition, eight donor hearts (three aortae and eight pulmonary arteries) that were not used for heart transplantation were examined. Intimal proliferation was noted in the aorta but affected the pulmonary arteries only slightly, whereas the vasa vasorum of both vessels were involved and were occluded or stenosed by thickened intima containing recanalized capillaries. On morphometric study the ratio of intima to media in the aorta was significantly higher in the heart transplant group than in the control group (0.14 +/- 0.14 [n = 19] v 0.02 +/- 0.02 [n = 16]; P < .01). This intimal thickening was not correlated with the use of cyclosporine or with other clinicopathologic factors. The cytomegalovirus infection rate was higher in the heart transplant group (85%) than in the control group (40%).

Cytomegalovirus infection enhances smooth muscle cell proliferation and intimal thickening of rat aortic allografts

Inbred DA (AG-B4, RT1a) and WF (AG-B2, RT1v) rats were used as donors and recipients of aortic allografts. The recipient rats were inoculated i.p. either on day 1 (early infection) or on day 60 (late infection) with 10(5) plaque-forming units of rat cytomegalovirus (RCMV). The control rats were left noninfected. The presence of viral infection was demonstrated by plaque assays from biopsies of the salivary glands, liver, and spleen at sacrifice. The rats received 300 microCi[3H]thymidine by i.v. injection 3 h before sacrifice, and the grafts were removed at various time points for histology, immunohistochemistry, and autoradiography. RCMV infection significantly enhanced the generation of allograft arteriosclerosis. Infection at the time of transplantation had two important effects. First, the infection was associated with an early, prominent inflammatory episode and proliferation of inflammatory cells in the allograft adventitia. Second, the viral infection doubled the proliferation rate of smooth muscle cells and the arteriosclerotic alterations in the intima. In late infection the impact of RCMV infection on the allograft histology was nearly nonexistent. RCMV infection showed no effect in syngeneic grafts. These results suggest that early infection is more important to the generation of accelerated allograft arteriosclerosis than late infection, and that an acute alloimmune response must be associated with virus infection, to induce accelerated allograft arteriosclerosis. RCMV-infected aortic allografts, as described here, provide the first experimental model to investigate the interaction between the virus and the vascular wall of the transplant.