Arboviruses are maintained in nature in chronically infected arthropods. In humans and animals, they can cause a wide range of diseases, from mild, febrile forms, to very serious diseases such as encephalitis or hemorrhagic fever. Viral growth in cell cultures is traditionally monitored by classical virological techniques such as 50 % tissue culture infective dose (TCID50) and plaque forming units, but both techniques require highly trained staff and access to biosafety level 3 laboratory. In addition to the exceptional complexity, the methods are also time-consuming. Recently, several laboratories decided to use modern molecular approaches to determine viral titters, but the comparison or standardization between molecular techniques and classical virological techniques is still not-existent. We compared results obtained with TCID50 and digital polymerase chain reaction (dPCR) for determination of arboviral concentration in cell culture. We have included 4 different arboviruses: tick-borne encephalitis virus (TBEV), West Nile virus (WNV), Usutu virus (USUV) and yellow fever virus (YFV). In conclusion, we have found that in some cases dPCR could be substituted for TCID50, since the coefficient of comparison was maintained through passages, whereby molecular methods were successfully applied, and the ratios between the values of TCID50/ml and the number of RNA copies/ml were calculated. In our case, we successfully implemented the molecular method and the coefficient for TBEV, WNV (lineage 2), YFV and USUV. Definitely, molecular methods can not completely replace classical techniques, they can only be helpful in routine diagnostics, as they are faster, more repeatable and less dangerous for technical staff.
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