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

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.

Safety and Efficacy of Antiviral Therapy for Prevention of Cytomegalovirus Reactivation in Immunocompetent Critically Ill Patients: A Randomized Clinical Trial

IMPORTANCE

Latent cytomegalovirus (CMV) infection is present in more than half the adult population, and a viral reactivation (ie, when the virus becomes measurable in body fluids such as blood) can occur in up to one-third of these individuals during episodes of critical illness.

OBJECTIVE

To determine whether antiviral therapy is safe and effective for preventing CMV reactivation in a general population of critically ill patients.

DESIGN, SETTING, AND PARTICIPANTS

A single-center, open-label, randomized, controlled clinical trial recruited 124 CMV-seropositive patients undergoing mechanical ventilation for at least 24 hours in the intensive care unit between January 1, 2012, and January 31, 2014. The mean baseline Acute Physiology and Chronic Health Evaluation II score of all patients was 17.6.

INTERVENTIONS

Patients were randomized to receive anti-CMV prophylaxis with valacyclovir hydrochloride (n = 34) or low-dose valganciclovir hydrochloride (n = 46) for up to 28 days to suppress viral reactivation, or to a control group with no intervention (n = 44).

MAIN OUTCOMES AND MEASURES

Time to first CMV reactivation in blood within the 28-day follow-up period following initiation of the study drug.

RESULTS

Among the 124 patients in the study (46 women and 78 men; mean [SD] age, 56.9 [16.9] years), viral reactivation in the blood occurred in 12 patients in the control group, compared with 1 patient in the valganciclovir group and 2 patients in the valacyclovir group (combined treatment groups vs control: hazard ratio, 0.14; 95% CI 0.04-0.50). Although this trial was not powered to assess clinical end points, the valacyclovir arm was halted prematurely because of higher mortality; 14 of 34 patients (41.2%) had died by 28 days, compared with 5 of 37 (13.5%) patients in the control arm at the point of the decision to halt this arm. Other safety end points showed similar outcomes between groups.

CONCLUSIONS AND RELEVANCE

Antiviral prophylaxis with valacyclovir or low-dose valganciclovir suppresses CMV reactivation in patients with critical illness. However, given the higher mortality, a large-scale trial would be needed to determine the clinical efficacy and safety of CMV suppression.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01503918.

Treatment and prevention of cytomegalovirus infection in heart and lung transplantation: an update

INTRODUCTION

Heart and lung transplantation are standard therapeutic strategies to improve survival and quality of life in selected patients with end-stage heart or lung diseases. Cytomegalovirus (CMV) is one the most clinically relevant and frequent post-transplant infectious agents, which may cause direct acute syndromes, and chronic indirect graft-related injury. Despite effective antiviral drugs being available to prevent and treat CMV infection, due to the immunosuppression burden and the specific characteristics of thoracic grafts, CMV infection remains a major clinical problem in heart and lung transplant recipients.

AREAS COVERED

We performed an extensive literature search focused on studies specifically including heart or lung transplantation, when available, or kidney transplant recipients when data on thoracic transplants were not available. We discuss the pros and cons supporting the use of currently available drugs and strategies for CMV prevention and treatment, highlighting current unmet needs.

EXPERT OPINION

While (Val)Ganciclovir remains the cornerstone of anti-CMV therapy, prolonged universal prophylaxis may expose a large number of patients to an excess of drug toxicity. Additional drugs with lower toxicity may be available in the context of anti-CMV prophylaxis, and effective CMV-risk stratification, by means of novel immune monitoring assays, which may help to customize the therapeutic approach.

Cytomegalovirus infection in transplant recipients

Cytomegalovirus infection is a frequent complication after transplantation. This infection occurs due to transmission from the transplanted organ, due to reactivation of latent infection, or after a primary infection in seronegative patients and can be defined as follows: latent infection, active infection, viral syndrome or invasive disease. This condition occurs mainly between 30 and 90 days after transplantation. In hematopoietic stem cell transplantation in particular, infection usually occurs within the first 30 days after transplantation and in the presence of graft-versus-host disease. The major risk factors are when the recipient is cytomegalovirus seronegative and the donor is seropositive as well as when lymphocyte-depleting antibodies are used. There are two methods for the diagnosis of cytomegalovirus infection: the pp65 antigenemia assay and polymerase chain reaction. Serology has no value for the diagnosis of active disease, whereas histology of the affected tissue and bronchoalveolar lavage analysis are useful in the diagnosis of invasive disease. Cytomegalovirus disease can be prevented by prophylaxis (the administration of antiviral drugs to all or to a subgroup of patients who are at higher risk of viral replication) or by preemptive therapy (the early diagnosis of viral replication before development of the disease and prescription of antiviral treatment to prevent the appearance of clinical disease). The drug used is intravenous or oral ganciclovir; oral valganciclovir; or, less frequently, valacyclovir. Prophylaxis should continue for 90 to 180 days. Treatment is always indicated in cytomegalovirus disease, and the gold-standard drug is intravenous ganciclovir. Treatment should be given for 2 to 3 weeks and should be continued for an additional 7 days after the first negative result for viremia.

The effect of cytomegalovirus antigenemia titer on the efficacy of preemptive therapy for the prevention of cytomegalovirus disease after kidney transplantation

There is some controversy regarding the exact cytomegalovirus (CMV) antigenemia titer that should be used as a guideline for preemptive anti-CMV therapy. We performed 634 consecutive kidney transplantations between January 2000 and June 2007. Preemptive therapy employed intravenous gancyclovir treatment when the CMV antigenemia titer was >or=50/4x10(5) leukocytes after kidney transplantation. The 634 recipients were allocated into 2 groups according to the peak CMV antegenemia: group A, CMV antigenemia titer<50/4x10(5) (n=550); and group B, >or=50/40x10(5) (n=84). Among the 634 recipients, 264 were positive for CMV antigenemia, and 61 developed symptomatic CMV infections. The incidence of symptomatic CMV infections in group B was significantly higher than in group A. Two cases in both groups developed tissue-proven CMV disease: group A CMV colitis and CMV nephritis, and group B, 2 cases of CMV colitis. Graft and patient survival rates in groups A and B at 5 years posttransplantation were not different. The authors concluded that a CMV antigenemia titer of >or=50/4x10(5) leukocytes can be considered an appropriate guideline for preemptive anti-CMV therapy.

Passive immunization reduces murine cytomegalovirus-induced brain pathology in newborn mice

Human cytomegalovirus (HCMV) is the most frequent cause of congenital viral infections in humans and frequently leads to long-term central nervous system (CNS) abnormalities that include learning disabilities, microcephaly, and hearing loss. The pathogenesis of the CNS infection has not been fully elucidated and may arise as a result of direct damage of CMV-infected neurons or indirectly secondary to inflammatory response to infection. We used a recently established model of mouse CMV (MCMV) infection in newborn mice to analyze the contribution of humoral immunity to virus clearance from the brain. In brains of MCMV-infected newborn mice treated with immune serum, the titer of infectious virus was reduced below detection limit, whereas in the brains of mice receiving control (nonimmune) serum significant amounts of virus were recovered. Moreover, histopathological and immunohistological analyses revealed significantly less CNS inflammation in mice treated with immune serum. Treatment with MCMV-specific monoclonal antibodies also resulted in the reduction of virus titer in the brain. Recipients of control serum or irrelevant antibodies had more viral foci, marked mononuclear cell infiltrates, and prominent glial nodules in their brains than mice treated with immune serum or MCMV-specific antibodies. In conclusion, our data indicate that virus-specific antibodies have a protective role in the development of CNS pathology in MCMV-infected newborn mice, suggesting that antiviral antibodies may be an important component of protective immunological responses during CMV infection of the developing CNS.

Generation of potent neutralizing human monoclonal antibodies against cytomegalovirus infection from immune B cells

Background

Human monoclonal antibodies (mAbs) generated as a result of the immune response are likely to be the most effective therapeutic antibodies, particularly in the case of infectious diseases against which the immune response is protective.

Human cytomegalovirus (HCMV) is an ubiquitous opportunistic virus that is the most serious pathogenic agent in transplant patients. The available therapeutic armamentarium (e.g. HCMV hyperimmune globulins or antivirals) is associated with severe side effects and the emergence of drug-resistant strains; therefore, neutralizing human mAb may be a decisive alternative in the prevention of primary and re-activated HCMV infections in these patients.

Results

The purpose of this study was to generate neutralizing mAb against HCMV from the immunological repertoire of immune donors. To this aim, we designed an efficient technology relying on two discrete and sequential steps: first, human B-lymphocytes are stimulated with TLR9-agonists and IL-2; second, after both additives are removed, the cells are infected with EBV. Using this strategy we obtained 29 clones secreting IgG neutralizing the HCMV infectivity; four among these were further characterized. All of the mAbs neutralize the infection in different combinations of HCMV strains and target cells, with a potency ~20 fold higher than that of the HCMV hyperimmune globulins, currently used in transplant recipients. Recombinant human monoclonal IgG1 suitable as a prophylactic or therapeutic tool in clinical applications has been generated.

Conclusion

The technology described has proven to be more reproducible, efficient and rapid than previously reported techniques, and can be adopted at low overall costs by any cell biology laboratory for the development of fully human mAbs for immunotherapeutic uses.

Viral infection after renal transplantation: surveillance and management

Viral infections remain a significant cause of morbidity and mortality following renal transplantation. 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 post transplant viral monitoring may limit the impact of these infections. Recent advances in laboratory monitoring and antiviral therapy have improved outcomes. This review will summarize the major viral infections seen following transplant and discuss strategies for prevention and management of these potential pathogens.

Recent Publications on Medications and Pharmacy

Hospital Pharmacy presents this feature to keep pharmacists abreast of new publications in the medical/pharmacy literature. Articles of interest will be abstracted monthly regarding a broad scope of topics.