BackgroundThe rapid rise and spread in dengue cases, together with the unavailability of safe vaccines and effective antiviral drugs, warrant the need to discover and develop novel anti-dengue treatments. In this study the antiviral activity of geraniin, extracted from the rind of Nephelium lappaceum, against dengue virus type-2 (DENV-2) was investigated.MethodsGeraniin was prepared from Nephelium lappaceum rind by reverse phase C-18 column chromatography. Cytotoxicity of geraniin towards Vero cells was evaluated using MTT assay while IC50 value was determined by plaque reduction assay. The mode-of-action of geraniin was characterized using the virucidal, attachment, penetration and the time-of-addition assays’. Docking experiments with geraniin molecule and the DENV envelope (E) protein was also performed. Finally, recombinant E Domain III (rE-DIII) protein was produced to physiologically test the binding of geraniin to DENV-2 E-DIII protein, through ELISA competitive binding assay.ResultsCytotoxicity assay confirmed that geraniin was not toxic to Vero cells, even at the highest concentration tested. The compound exhibited DENV-2 plaque formation inhibition, with an IC50 of 1.75 μM. We further revealed that geraniin reduced viral infectivity and inhibited DENV-2 from attaching to the cells but had little effect on its penetration. Geraniin was observed to be most effective when added at the early stage of DENV-2 infection. Docking experiments showed that geraniin binds to DENV E protein, specifically at the DIII region, while the ELISA competitive binding assay confirmed geraniin’s interaction with rE-DIII with high affinity.ConclusionsGeraniin from the rind of Nephelium lappaceum has antiviral activity against DENV-2. It is postulated that the compound inhibits viral attachment by binding to the E-DIII protein and interferes with the initial cell-virus interaction. Our results demonstrate that geraniin has the potential to be developed into an effective antiviral treatment, particularly for early phase dengue viral infection.

Zika virus (ZIKV) has emerged as a new global health threat. Since its first discovery in Zika forest in Uganda, this virus has been isolated from several mosquito species, including Aedes aegypti and Aedes albopictus. The geographical distribution of these mosquito species across tropical and subtropical regions has led to several outbreaks, including the recent pandemic in Brazil, followed by the Pacific islands and other areas of North and South America. This has gained attention of the scientific community to elucidate the epidemiology and transmission of ZIKV. Despite its strong attention on clinical aspects for healthcare professionals, the relationships between ZIKV and its principal vectors, A. aegypti and A. albopictus, have not gained substantial interest in the scientific research community. As such, this review aims to summarize the current knowledge on ZIKV tropism and some important mechanisms which may be employed by the virus for effective strategies on viral survival in mosquitoes. In addition, this review identifies the areas of research that should be placed attention to, for which to be exploited for novel mosquito control strategies.

Introduction: Chikungunya virus (CHIKV) is a mosquito-borne alphavirus which causes fever, rash and polyarthralgia. CHIKV has expanded its circulating regions to the Indian Ocean islands, Europe, Americas and Southeast Asia. Two CHIKV lineages, the ASIAN and ECSA are circulating in Malaysia. In 2009, a CHIKV strain with a 76 amino acid (aa) duplication in its nsP3 hypervariable domain (HVD), identified as CHIKvASIAN09MUM-Dup+ was isolated from a patient co-infected with DENV-2. Indels and duplication have been found in many other alphaviruses, and suggested to play a role in the survivality of the viruses. Objectives: We aim to compare and relate the replication kinetics and virulency in-vitro of CHIKvASIAN09MUM-Dup+ with the wild-type Asian and ECSA strains. Methods & Results: Genotypic analysis was conducted on three CHIKV strains in Malaysia, the CHIKvASIAN06UM-Dup-, CHIKvECSA08UM-Dup- and CHIKvASIAN09MUM-Dup+. We found that CHIKvASIAN09MUM-Dup+ has significant low replication rates in Vero, C6/36 and Rhabdosarcoma cells as compared to the wild-type strains. The highest titers were reached by CHIKvASIAN09MUM-Dup+ in all cells are 6.5 to 6.75 log10 TCID50/mL, which is 100 fold lower compared to the wild-type strains. Conclusion: The significantly low replication rate of Dup+ strain in all the cells, maybe suggestive to be due to co-infection and co-existence with DENV, where the aa duplication may play a role in overcoming competitive suppression. This preliminary finding agrees with reported events, where alphaviruses use insertion, deletion and duplication of amino acid in nsP3 HVD as strategies to influence replication in host, viral virulency, pathogenesis and survivality for evolution adaptation.

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