Opportunistic Viral Pathogens in Transplant Recipients

By Dr. Sukhendra Choudhury, Senior Scientist, Virology

The immune system acts as a natural defense that protects against infections and diseases. When receiving an organ transplant, the body tries to eliminate the transplanted organ through rejection. The immune system involved in the process of rejection protects your body from harmful viruses and bacteria. Following transplantation, the patient is prescribed antirejection (immunosuppressive) medicines to assure that the organ stays healthy and functional. As a result, viruses that remain latent in the human body are often reactivated in transplant recipients and cause major illnesses.  

Reactivated BK human polyomavirus (BKpyv) infection causes interstitial nephritis in ~10% of renal allograft recipients and graft loss in 1–2% of patients. BKpyv is associated with hemorrhagic cystitis and ureteric stenosis in hematopoietic stem cell transplant (HSCT) recipients.    

Human Cytomegalovirus (HCMV) is the most frequent opportunistic viral pathogen after solid organ (e.g. kidney, liver, heart) and HSCT transplantation. This can arise from HCMV acquired from the donor organ or from latent HCMV reactivation within the recipients, causing acute, systemic febrile illness sometimes referred to as “CMV Syndrome.??? This illness can be prevented by pre-transplant screening of donors and recipients for HCMV infection and prophylactic or therapeutic use of any antiviral drugs (e.g. Ganciclovir, Foscarnet, Cidofovir).

Epstein-Barr Virus (EBV) infection causes post transplant lymphoproliferative disease (PTLD) in transplant recipients, with rates of incidence varying between 1% to 5% (kidney, liver, heart, lung, bone marrow) transplants, and 20% in small intestine transplant recipients. The risk of EBV-PTLD is increased in persons who have a primary EBV infection, graft viruses host disease or HCMV infection and who receive second transplant – or anti T-cell antibodies and the use of certain immunosuppressive drugs. 

Post-transplantation Kaposi’s Sarcoma (KS) is caused by KSHV/Human Herpesvirus (HHV-8). KS has been associated with the transplantation of kidney bone marrow, heart and lungs. There is 1% to 3% risk of KS with kidney transplantation, and may be as high as 5% in geographical areas of higher prevalence of KSHV/HHV-8 infection. Transplant recipients who are seropositive  at the time of transplantation at more at risk of developing KS. Monitoring transplant recipients for HHV-8 infection by molecular or Serologic assays might predict the development of KS and give guidance for preventive antiviral therapy.

Human Herpesvirus 6 (HHV-6) reactivation is common in bone marrow or solid organ transplant recipients. It may lead to bone marrow suppression, kidney rejection, and thrombocytopenia in liver transplant recipients. 

According to a recent study, organ transplant recipients have a high risk of developing 32 different types of cancer. As recently as 2010, there were over 28,000 organ transplants in the United States alone. A few months ago, an innovative research program at Northwestern University received $12 million in funding to investigate if stem cells could provide a key in helping patients find alternatives to using immunosuppressive medications following transplant procedures. Using engineered stem cells from kidney donors, the goal is to reprogram the recipient’s immune system to recognize the transplanted organ as its own. Five of the eight participants in the study, all of whom had undergone kidney transplants, were able to stop taking immunosuppressive medicines within one year of their procedures.