Prophylaxis against herpesvirus infections in transplant recipients

Herpesvirus infections are important after stem cell and organ transplant. During the last decades several antiviral agents have been introduced with efficacy against herpesviruses. These agents are the nucleoside analogues aciclovir, valaciclovir, famciclovir, and ganciclovir; the nucleotide analogue cidofovir; and the pyrophosphate analogue foscarnet. Several studies have been performed with antiviral agents with the aim to reduce morbidity and mortality associated with herpesvirus infections in transplant recipients. Aciclovir and valaciclovir have been examined in randomised, controlled trials in both solid organ and stem cell transplant patients, and were shown to be very effective for the prevention of herpes simplex virus (HSV) and varicella-zoster virus infections. In addition, these drugs were shown to reduce cytomegalovirus (CMV) infection and improve survival in allogenic stem cell transplant patients and to reduce CMV infection, CMV disease (aciclovir and valaciclovir), and acute rejection (valaciclovir) in renal transplant patients. Ganciclovir is very effective for the prevention of CMV infection and disease in both stem cell and solid organ transplant recipients. It can also be used in preemptive strategies in which the aim is to prevent CMV disease in patients who have ongoing CMV infection documented by antigenaemia or detection of CMV DNA. The latter strategy has the advantage of reducing the exposure to the drug and thereby the risk for toxicity. Foscarnet has also been shown to be effective as preemptive therapy for CMV in allogenic stem cell transplant patients and as therapy for aciclovir-resistant HSV infections. Finally cidofovir is an interesting agent with broad spectrum antiherpesvirus efficacy. However, because of the drug's toxicity profile, further studies are needed.