Use of dry blots for serotyping and genotyping of dengue viruses: A pilot study

Background & objectives: Dengue (DEN) is a result of infection by one or multiple types of four dengue viruses known as Dengue virus (DENV) 1-4. Identifying circulating serotype and genotype is epidemiologically important, however, it is challenging in resource limited areas. Moreover, transporting samples from the collation site to the laboratory in appropriate condition is an exigent task. To overcome this, we evaluated the usefulness of dry blots of serum for DENV diagnosis, serotyping and genotyping. Methods: Serum samples received for diagnosis were divided into parts; one was used for providing the diagnosis. Remaining sample was distributed in three parts (100 mu l each), one part was used for molecular testing and two parts were mixed with RNAlater reagent (R) in equal volumes and was blotted on Whatman filter paper no 3. The blots were dried and stored at 4 degrees C and 28 degrees C and tested for presence of dengue RNA, serotypes and genotypes after 7 days of incubation. Results: The diagnosis and serotyping results of serum sample and dry serum blots were in concordance. Out of 20 positive samples, 13 (65%) gave satisfactory sequencing results. Genotype III of DENV-1, Genotype IV of DENV 2 and Genotype I of DENV-4 were detected. Interpretation & conclusion: The results demonstrate that serum mixed with RNA protective solution and blotted on Whatman filter paper no 3 can be effectively used for diagnosis, serotyping and genotyping of DENVs. This will help in easy transportation, diagnosis and effective data generation in resource limited settings.