Cellular immunotherapy for viral infections in solid organ transplant recipients:

Immunity to Polyomavirus BK Infection: Immune Monitoring to Regulate the Balance between Risk of BKV Nephropathy and Induction of Alloimmunity

Polyomavirus BK-associated nephropathy (PyVAN) is the main infectious cause of allograft damage after kidney transplantation. A number of studies revealed an association between the presence of BKV-specific cellular immunity and BK viral clearance, with patients failing to recover specific T cells progressing to PyVAN. Evolution to allograft dysfunction can be prevented by restoration of BKV-specific immunity through a stepwise reduction of maintenance immunosuppressive drugs. Prospective monitoring of BK viral load and specific immunity, together with B-cell alloimmune surveillance, may allow a targeted modification/reduction of immunosuppression, with the aim of obtaining viral clearance while preventing graft injury due to deposition of de novo donor-specific HLA antibodies and late/chronic antibody-mediated allograft injury. Innovative, immune-based therapies may further contribute to BKV infection prevention and control.

Monitoring and managing viral infections in pediatric renal transplant recipients

Viral infections remain a significant cause of morbidity and mortality following renal transplantation. The pediatric cohort is at high risk of developing virus-related complications due to immunological naiveté and the increased alloreactivity risk that requires maintaining a heavily immunosuppressive environment. Although cytomegalovirus is the most common opportunistic pathogen seen in transplant recipients, numerous other viruses may affect clinical outcome. Recent technological advances and novel antiviral therapy have allowed implementation of viral and immunological monitoring protocols and adoption of prophylactic or preemptive treatment approaches in high-risk groups. These strategies have led to improved viral infection management in the immunocompromised host, with significant impact on outcome. We review the major viral infections seen following kidney transplantation and discuss strategies for preventing and managing these pathogens.

Cell-based therapies: careful safety assessment for minimization of risk

Cell therapy can be numbered among the novel biologic therapeutics that will increase our ability to cure human disease in the years to come. While the general feeling is that in vivo use of ex-vivo expanded cellular products is relatively safe, the attempt at augmenting potency have increased the risk for adverse events. Future efforts are warranted to better characterize cellular products, and collect and analyze clinical trial outcomes through national databases, to identify risks connected to their in vivo use.

Cellular immune responses to BK virus

PURPOSE OF REVIEW

Defects in cellular immunity to persistent viral infections are associated with an increased frequency and severity of viral diseases after transplantation. Polyomavirus BK (BKV) infection has emerged as an important cause of virus-related nephropathy after kidney allograft. Cell-mediated immunity seems to have a central role in preserving BKV latency. However, characterization of BKV-specific immunity has only recently begun.

RECENT FINDINGS

Immune responses to BKV are not fully understood, but pioneer work points to cell-mediated immunity as a critical factor for the control of viral replication and recovery from BKV disease.

SUMMARY

Advances in immunological techniques will provide further insight into the specificity and patterns of cellular response to BKV, which should assist translation into improved patient management and development of immunotherapeutic approaches.

Specific autologous cytotoxic T lymphocytes for chronic varicella in a liver transplanted child

Infections by herpesviruses may have severe complications in liver transplant patients. Although prophylactic varicella zoster virus vaccination is strongly recommended and widely applied, severe infection may still occur. We report the case of systemic chronic varicella, which developed in a liver allograft recipient, unresponsive to antiviral drug treatment, successfully treated by varicella zooster-specific CTL. Graft failure ensued, likely, because of massive cytolysis of infected hepatocytes. The patient, who was re-transplanted in the absence of signs of varicella zooster reactivation, is now well and disease free 3 yr after second liver transplant.

Treatment of EBV-related post-renal transplant lymphoproliferative disease with a tailored regimen including EBV-specific T cells

The treatment of EBV-associated post-transplant lymphoproliferative disease (PTLD) poses a considerable challenge. Efforts have been made to define regimens based on combination of the available therapeutic agents, chosen and tailored on a patient-by-patient basis, with the aim of augmenting event-free patient and graft survival. Recently, autologous EBV-specific cytotoxic T-lymphocytes (CTL) have proved effective in enhancing EBV-specific immune responses and reducing viral load in organ transplant recipients with active infection. We investigated the use of a tailored combined approach including autologous EBV-specific CTL for the treatment of EBV-related PTLD developing after pediatric kidney transplantation. Five patients with disseminated monoclonal (n = 3) or localized polyclonal (n = 2) PTLD unresponsive to reduction of immunosuppression were enrolled. The patients with disseminated PTLD received 4-5 courses of reduced-dosage polychemotherapy, accompanied by rituximab on the first day of each course, while localized disease was removed surgically. At treatment completion, autologous EBV-specific CTL were infused. All patients showed a complete response to treatment, without therapy-related toxicity or rejection, and persist in remission with good renal function at a median follow-up of 31 months. These preliminary results suggest that a combined chemoimmunotherapy regimen including virus-specific T-cells is well tolerated and potentially effective as first-line treatment of EBV-related PTLD.