Four methods for the assay of human interferon in Vero cells were compared based on the inhibition of viral cytopathic effect (CPE) in tubes, the inhibition of CPE in microplates, the reduction of plaques, and the inhibition of quantitative hemadsorption. For inhibition of CPE, Sindbis virus, vesicular stomatitis virus, poliovirus type 2, and vaccinia virus were used for challenge. In the plaque reduction method, Sindbis virus, vesicular stomatitis virus, and poliovirus were employed, and Newcastle disease virus was used in the quantitative hemadsorption assay. Sindbis virus was most susceptible to interferon in those tests measuring inhibition of CPE, but vesicular stomatitis virus was as sensitive in the plaque reduction method. Highest titers of interferon were recorded in microplates, especially with Sindbis virus as the challenge agent, followed by the quantitative inhibition assay. The CPE inhibition method was the simplest, and the quantitative hemadsorption assay was the most rapid to perform. Reproducibilities, as shown by the coefficient of variation, were 15, 39, and 59% for plaque reduction, CPE inhibition in tubes, and CPE inhibition in microplates, respectively.

Ganciclovir (GCV) is the first therapeutic choice for prevention and treatment of active cytomegalovirus (CMV) infection in solid organ transplant recipients in Bahia state, Brazil. Prolonged and repeated GCV therapy may result in drug-resistant virus, associated with progressive and disseminated disease. We present a case report of a young male kidney recipient, who was CMV-seronegative with a CMV-seropositive donor (D(+)/R(-)), and who developed clinical GCV resistance, confirmed by mutation in viral UL97 phosphotransferase responsible for GCV activation. Under prophylactic therapy with intravenous GCV for 6 weeks post-transplantation, he developed severe anaemia and hepatic enzyme increases, probably due to drug side effects. At this moment, the drug was discontinued and he started to be monitored by pp65 antigen test. At week 10 post-transplantation, he presented fever, myalgia, thrombocytopenia and neutropaenia, with a positive CMV antigen test. During treatment with intravenous GCV, antigenaemia assay demonstrated a higher number of positive cells, requiring GCV at higher doses. Pre-emptive therapy lasted for 31 days and he started the maintenance therapy with oral GCV. However, antigenaemia assay demonstrated an extremely high number of positive cells, and he was rehospitalized and prescribed intravenous GCV. Severe leukopaenia led to GCV interruption, but immunosuppressive dose reduction helped to control the active CMV infection. GCV-resistant CMV infection resulted in increased morbidity, rehospitalization episodes and increased costs; therefore, implementation of resistance diagnostic tests in the transplantation routine is of great importance. We documented the first case of GCV-resistant CMV infection due to the L595S mutation in UL97 phosphotransferase gene in a kidney recipient from Bahia state, Brazil.

Several group C arboviruses are able to induce interferon in chick embryo fibroblasts, primary human amnion and mouse L ceils.