Viral prophylaxis in organ transplant patients

Skin infections in organ transplant recipients

In contrast to the well-described high risk of skin cancer in organ transplant recipients, skin infections in these patients are not as well explored. Skin infections caused by viruses, bacteria or fungi represent a growing diagnostic and therapeutic challenge in the dermatological aftercare of organ transplant recipients. Differing immunosuppressive drugs and their variable dosage in chronologic sequence after transplantation probably influence the type and appearance of skin infections. The typical chronology of skin infections are wound infections, pyoderma or the reactivation of herpes viruses in the first month post-transplant; the main problems in months 2-5 are opportunistic infections and reactivation of varicella-zoster virus. After 6 months as immunosuppression is reduced, the spectrum of causative organisms approaches that of the general population; mycoses and human papilloma virus (HPV) infections dominate. A causal connection exists between infection with oncogenic viruses such as HPV, Epstein-Barr virus and human herpesvirus 8 and specific skin cancers (squamous cell carcinoma, Kaposi sarcoma and post-transplant lymphoproliferative disorders). Dermatological care of organ transplant recipients using appropriate diagnostic methods adapted to the modified clinical pattern may lead to early adequate treatment.

Herpes simplex and varicella zoster viruses: forgotten but not gone

Herpesvirus infections are common complications of organ transplantation. The most frequent herpesvirus infections are caused by cytomegalovirus (CMV), herpes simplex (HSV) and varicella zoster (VZV). Despite expansion of the therapeutic armamentarium, HSV and VZV continue to cause morbidity and occasional mortality in transplant recipients. Here we review the incidence and risk factors for HSV and VZV disease, their clinical presentation, effects of newer immunosuppressive regimens and prophylaxis for HSV and VZV in solid organ transplant recipients.

Regenerative endodontics: a review of current status and a call for action

Millions of teeth are saved each year by root canal therapy. Although current treatment modalities offer high levels of success for many conditions, an ideal form of therapy might consist of regenerative approaches in which diseased or necrotic pulp tissues are removed and replaced with healthy pulp tissue to revitalize teeth. Researchers are working toward this objective. Regenerative endodontics is the creation and delivery of tissues to replace diseased, missing, and traumatized pulp. This review provides an overview of regenerative endodontics and its goals, and describes possible techniques that will allow regenerative endodontics to become a reality. These potential approaches include root-canal revascularization, postnatal (adult) stem cell therapy, pulp implant, scaffold implant, three-dimensional cell printing, injectable scaffolds, and gene therapy. These regenerative endodontic techniques will possibly involve some combination of disinfection or debridement of infected root canal systems with apical enlargement to permit revascularization and use of adult stem cells, scaffolds, and growth factors. Although the challenges of introducing endodontic tissue engineering therapies are substantial, the potential benefits to patients and the profession are equally ground breaking. Patient demand is staggering both in scope and cost, because tissue engineering therapy offers the possibility of restoring natural function instead of surgical placement of an artificial prosthesis. By providing an overview of the methodological issues required to develop potential regenerative endodontic therapies, we hope to present a call for action to develop these therapies for clinical use.

Vaccine-induced immunity in children after orthotopic liver transplantation: a 12-yr review of the Swiss national reference center

Infections represent a significant threat in solid-organ recipients. However, a certain number of infections can be prevented by immunizing patients before their transplantation. The aim of this study is to determine the level of immunity of children undergoing liver transplantation and to assess their capacity to maintain protective levels after surgery. Charts of 44 children transplanted with deceased donation livers between 1990 and 2002 at the Children's Hospital of Geneva were reviewed. Vaccine antibody responses were established pre- and post-transplantation. Only 43% of patients were up to date for diphtheria, tetanus, acellular pertussis, and polio vaccines at the pretransplantation visit, while 44% of children older than 12 months had received their required measles-mumps-rubella vaccines. Six of 44 children had received at least one dose of hepatitis B vaccine, while only two patients had received at least one dose of hepatitis A vaccine. After immunization, and one yr after transplantation, only 14 of 44 patients had detectable anti-HBs antibodies and seven of 18 had anti-HAV antibodies. Varicella antibodies were undetectable in 15 of 19 patients immunized prior to transplantation. This study highlights the need to enforce vaccination before transplantation, follow-up on vaccine- induced immunity, and adapt vaccination schedules after liver transplantation in children, especially for non-live vaccines, which are universally recommended in this population.

Primary herpes simplex virus type-2 infection as a cause of liver failure after liver transplantation

We report a case of fatal primary herpes simplex virus type-2 (HSV-2) infection following liver transplantation, which manifested with fever and liver failure in the absence of muco-cutaneous disease. The infection was characterized by high levels of HSV DNA in blood and the patient's inability to mount HSV-specific T-cell responses while showing preserved T-cell responses against cytomegalovirus. The donor was HSV-1 immunoglobulin G (IgG) seronegative and HSV-2 IgG seropositive, whereas the recipient was HSV-1 and HSV-2 IgG seronegative, suggesting that the graft may have been the source of the infection. In HSV-seronegative recipients of grafts from HSV-seropositive donors, HSV infection should be included in the differential diagnosis of a febrile illness, regardless of the absence of muco-cutaneous disease. In this setting, real-time polymerase chain reaction applied to blood samples provides a sensitive, rapid, and quantitative diagnostic tool.

Valganciclovir preemptive therapy for the prevention of cytomegalovirus disease in high-risk seropositive solid-organ transplant recipients

BACKGROUND

The role of valganciclovir in the prevention of cytomegalovirus (CMV) disease in high-risk seropositive transplant patients is not known.

METHODS

We prospectively followed 301 seropositive solid organ transplant recipients to assess the efficacy and safety of valganciclovir (VGCV) in the prevention of CMV disease in high-risk patients. Asymptomatic patients with an antigenemia test >or=25 positive cells/2x10(5) polymorphonuclear cells received valganciclovir 900 mg twice a day as preemptive therapy until resolution of antigenemia (minimum 14 days). Additionally, patients treated with antilymphocytic drugs for more than 6 days received prophylaxis with VGCV 900 mg once a day during 90 days. Mean follow-up was 14 months (range 6-20 months).

RESULTS

Thirty-eight patients received VGCV; 24 as preemptive therapy and 14 due to the use of antilymphocytic drugs. No patient developed CMV disease during the follow-up. Viral load (antigenemia) decreased a mean of 78% from baseline after 7 days of VGCV therapy (P=0.024) and 98% at day 14 (P=0.029). Two patients showed a relapse of the antigenemia test >or=25 positive cells and were successfully treated with a repeated course of VGCV. Leukopenia (<2500/mm3) developed in 3/24 (12.5%) recipients in the preemptive therapy group and required to discontinuing the drug in one of them.

CONCLUSIONS

VGCV is safe and highly efficacious in the prevention of CMV disease in high-risk seropositive organ transplant recipients.

Gastrointestinal infections in immunocompromised hosts

PURPOSE OF REVIEW

Gastrointestinal infections in the immunocompromised host continue to have significant morbidity and mortality throughout the world. They all have similar exposures to viruses, bacteria and parasites and respond to these infections in a similar way. This review will summarize the latest reports on the epidemiology, diagnosis and treatment of known and emerging infections over the last 12 months.

RECENT FINDINGS

Highly active antiretroviral therapy has reduced esophageal opportunistic infections in HIV patients compared to patients who are not taking this therapy. Esophageal candidiasis responds to escalating doses of micafungin as effectively as fluconazole. HIV-infected patients with untreated Mycobacterium avium-complex diarrhea are associated with a wasting syndrome that disrupts the somatostatin axis. Polymerase chain reaction testing has improved diagnosis of microsporidial infections. Cytomegalovirus polymerase chain reaction of tissue may improve the diagnosis of cytomegalovirus disease of the gastrointestinal tract in organ-transplant recipients. The treatment of hypogammaglobulinemia in transplant recipients with recurrent cytomegalovirus gastrointestinal disease may resolve their symptoms. Community viruses are an emerging threat to transplant recipients and may affect drug levels. Lastly, anti-tumor necrosis factor alpha therapy in the treatment of inflammatory conditions may cause Listeria monocytogenes to disseminate.

SUMMARY

Immunocompromised hosts remain at risk for severe gastrointestinal and even disseminated infections. Management includes an early rapid diagnosis with rapid restoration of the immune system and appropriate anti-infective therapy. With the immunocompromised population rapidly increasing, prevention of these infections remains the greatest challenge.

[Modern immunosuppression following renal transplantation. Standard or tailor made?]

Renal transplantation is by far the best therapeutic option for end-stage kidney disease with respect to quality of life, psychosocial rehabilitation, and even patient survival. Optimal immunosuppressive therapy should provide effective prophylaxis of both acute rejection and chronic allograft dysfunction. Thus immunosuppressive therapy should help to maintain good renal function and could help to prevent premature death of the recipient. With the introduction of new immunosuppressants over the last decade a dramatic reduction of acute rejection rates from approximately 50% to 15-30% could be achieved. However, the search for novel immunosuppressive drugs continues, drugs which not only lead to effective prevention of acute rejection, but also have an impact on chronic allograft dysfunction and prevent further deterioration of this multifactorial process. Based on a short presentation of the "three signal model" of immunoactivation, the most important mechanisms and characteristics of the presently available immunosuppressants are described. Because the immunosuppressive objectives change over time, a phase-dependent adaptation is necessary. At present, most centers in Germany use an immunosuppressive combination therapy, consisting of a calcineurin inhibitor (CNI; cyclosporine or tacrolimus), a glucocorticoid (prednisolone or methylprednisolone), and mycophenolic acid (MPA), which is eventually combined with an antibody (e.g., IL-2R antibody) for induction. In contrast to the clear situation 10 years ago, highly specialized knowledge is required today with respect to mechanism of action, side effects, and potential interactions. This may enable the physician to adopt patient-oriented optimal immunosuppression. In the near future more individualized treatment options will be employed, which are adapted to the characteristics and side effects of the immunosuppressant, as well as to the characteristics of the donor, the recipient, and the transplanted organ such as immunology and ischemia. Another aspect is the reduction or elimination of some immunosuppressants at the earliest possible time. With new diagnostic and genetic markers the relationship between recipient and transplanted organ will be characterized better in the future and therapy will become more individualized. Altogether, these measures as well as optimized supportive therapy will help to further improve the longevity of the transplanted organ.

Viral infection in the renal transplant recipient

Viruses are among the most common causes of opportunistic infection after transplantation and the most important. 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. Viral infection, both symptomatic and asymptomatic, causes the "direct effects" of invasive disease and "indirect effects," including immune suppression predisposing to other opportunistic infections and oncogenesis. Rapid and sensitive microbiologic assays for many of the common viruses after transplantation have replaced, for the most part, serologic testing and in vitro cultures for the diagnosis of infection. Furthermore, quantitative molecular tests allow the individualization of antiviral therapies for prevention and treatment of infection. This advance is most prominent in the management of cytomegalovirus, Epstein-Barr, hepatitis B, and hepatitis C viruses. Diagnostic advances have not been accompanied by the development of specific and nontoxic anti-viral agents or effective antiviral vaccines. Vaccines, where available, should be given to patients as early as possible and well in advance of transplantation to optimize the immune response. 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.

Amplification of autoimmune disease by infection

Reports of infection with certain chronic persistent microbes (herpesviruses or Chlamydiae) in human autoimmune diseases are consistent with the hypothesis that these microbes are reactivated in the setting of immunodeficiency and often target the site of autoimmune inflammation. New experimental animal models demonstrate the principle. A herpesvirus or Chlamydia species can be used to infect mice with induced transient autoimmune diseases. This results in increased disease severity and even relapse. The evidence suggests that the organisms are specifically imported to the inflammatory sites and cause further tissue destruction, especially when the host is immunosuppressed. We review the evidence for the amplification of autoimmune inflammatory disease by microbial infection, which may be a general mechanism applicable to many human diseases. We suggest that patients with autoimmune disorders receiving immunosuppressing drugs should benefit from preventive antiviral therapy.