Antiviral Activity of Kappaphycus alvarezii Seaweed against ZIKV

Introduction: Zika virus (ZIKV) is a flavivirus transmitted through the bites of infected Aedes mosquitoes. These viruses can also be transmitted through sexual contact, vertical transmission, and possibly transfusion. Most cases are asymptomatic, but symptoms can include rash, conjunctivitis, fever, and arthralgia, which are characteristic of other arboviruses. Zika infection can lead to complications such as microcephaly, miscarriage, brain abnormalities, and Guillain-Barré syndrome (GBS). Objective: The aim is to determine the inhibitory potential of the algae Kappaphycus alvarezii (K. alvarezii) on ZIKV replication. Methodology: Cytotoxicity experiments were performed using Vero cells to determine the CC50, and ZIKV replication inhibition assays (ATCC^® VR-1839™) were conducted to determine the EC50. The mechanism of action was also studied to assess any synergistic effect with Ribavirin. Results: K. alvarezii demonstrated low toxicity with a CC50 of 423 μg/mL and a potent effect on ZIKV replication with an EC50 of 0.65 μg/mL and a Selectivity Index (SI) of 651, indicating the extract's safety. Virucidal effect assays were carried out to evaluate the possible mechanism of action, and the compound addition time was studied, showing the potential to delay the treatment of infected cells by up to 6 hours. A potential synergistic effect was observed when K. alvarezii extract was combined with suboptimal concentrations of Ribavirin, resulting in 99% inhibition of viral replication. Conclusion: Our data demonstrate the significant potential of K. alvarezii extract and highlight the need for further studies to investigate its mechanism of action. We propose this extract as a potential anti-Zika compound.