Correction: Haddad, J.G., et al. Doratoxylon apetalum, an Indigenous Medicinal Plant from Mascarene Islands, Is a Potent Inhibitor of Zika and Dengue Virus Infection in Human Cells Int. J. Mol. Sci. 2019, 20, 2382.

The author wishes to make the following correction to this paper [...].

The Geraniin-Rich Extract from Reunion Island Endemic Medicinal Plant Phyllanthus phillyreifolius Inhibits Zika and Dengue Virus Infection at Non-Toxic Effect Doses in Zebrafish.

The mosquito-borne viruses dengue (DENV) and Zika (ZIKV) viruses are two medically important pathogens in tropical and subtropical regions of the world. There is an urgent need of therapeutics against DENV and ZIKV, and medicinal plants are considered as a promising source of antiviral bioactive metabolites. In the present study, we evaluated the ability of Phyllanthus phillyreifolius, an endemic medicinal plant from Reunion Island, to prevent DENV and ZIKV infection in human cells. At non-cytotoxic concentration in vitro, incubation of infected A549 cells with a P. phillyreifolius extract or its major active phytochemical geraniin resulted in a dramatic reduction of virus progeny production for ZIKV as well as four serotypes of DENV. Virological assays showed that P. phillyreifolius extract-mediated virus inhibition relates to a blockade in internalization of virus particles into the host cell. Infectivity studies on ZIKV showed that both P. phillyreifolius and geraniin cause a loss of infectivity of the viral particles. Using a zebrafish model, we demonstrated that administration of P. phillyreifolius and geraniin has no effect on zebrafish locomotor activity while no morbidity nor mortality was observed up to 5 days post-inoculation. Thus, P. phillyreifolius could act as an important source of plant metabolite geraniin which is a promising antiviral compound in the fight against DENV and ZIKV.

Doratoxylon apetalum, an Indigenous Medicinal Plant from Mascarene Islands, Is a Potent Inhibitor of Zika and Dengue Virus Infection in Human Cells.

Zika virus (ZIKV) and Dengue virus (DENV) are mosquito-borne viruses of the Flavivirus genus that could cause congenital microcephaly and hemorrhage, respectively, in humans, and thus present a risk to global public health. A preventive vaccine against ZIKV remains unavailable, and no specific antiviral drugs against ZIKV and DENV are licensed. Medicinal plants may be a source of natural antiviral drugs which mostly target viral entry. In this study, we evaluate the antiviral activity of Doratoxylum apetalum, an indigenous medicinal plant from the Mascarene Islands, against ZIKV and DENV infection. Our data indicated that D. apetalum exhibited potent antiviral activity against a contemporary epidemic strain of ZIKV and clinical isolates of four DENV serotypes at non-cytotoxic concentrations in human cells. Time-of-drug-addition assays revealed that D. apetalum extract acts on ZIKV entry by preventing the internalisation of virus particles into the host cells. Our data suggest that D. apetalum-mediated ZIKV inhibition relates to virus particle inactivation. We suggest that D. apetalum could be a promising natural source for the development of potential antivirals against medically important flaviviruses.

Extract from Aphloia theiformis, an edible indigenous plant from Reunion Island, impairs Zika virus attachment to the host cell surface.

The mosquito-borne Zika virus (ZIKV) belongs to the flavivirus genus of the Flaviviridae family. Contemporary epidemic strains of ZIKV are associated with congenital malformations in infants, including microcephaly, as well as Guillain-Barré syndrome in adults. A risk of human-to-human transmission of ZIKV is also well documented. A worldwide research effort has been undertaken to identify safe and effective strategies to prevent or treat ZIKV infection. We show here that extract from Aphloia theiformis, an edible endemic plant from Indian Ocean islands, exerts a potent antiviral effect against ZIKV strains of African and Asian lineages, including epidemic strains. The antiviral effect of A. theiformis extract was extended to clinical isolates of dengue virus (DENV) of the four serotypes in human hepatocytes. A. theiformis inhibited virus entry in host cells by acting directly on viral particles, thus impairing their attachment to the cell surface. Electron microscopic observations revealed that organization of ZIKV particles was severely affected by A. theiformis. We propose a model of antiviral action for A. theiformis against flaviviruses that highlights the potential of medicinal plants as promising sources of naturally-derived antiviral compounds to prevent ZIKV and DENV infections.

A new Aura virus isolate in Brazil shows segment duplication in the variable region of the nsP3 gene.

BACKGROUND: A new isolate of Aura virus serendipitously discovered as a cell culture contaminant is reported in this manuscript. Aura virus belongs to the family Togaviridae and is classified in the genus Alphavirus. There are only two reports of Aura virus isolation from mosquitoes in the scientific literature, and the existence of a vertebrate host is still unknown. The discovery of this new isolate was based on transmission electron microscopy and nucleic acid amplification through a non-specific RT-PCR amplification protocol followed by sequencing. RESULTS: Genetic analysis has shown that the new virus shares a high degree of identity with the previously described isolate (GenBank: AF126284.1). A major difference was observed in the nsP3 gene in which a 234-nucleotide duplication has been identified. Furthermore, a pronounced difference was observed in cell cultures compared to the data available for the previously described isolate. Cell permissiveness and phenotypic characteristics in C6/36, Vero and BHK-21 cells were found to differ from previous reports. This may be due to the genetic differences that have been observed. CONCLUSIONS: The genetic and biological characteristics of the new Aura virus isolate are suggestive of viral adaptation to the cell substrate. The development of a cDNA clone will lend a perspective and better understanding of these results as well as open avenues for its use as a biotechnological tool, as seen for other alphaviruses.

Screening of Dengue virus antiviral activity of marine seaweeds by an in situ enzyme-linked immunosorbent assay.

Dengue is a significant public health problem worldwide. Despite the important social and clinical impact, there is no vaccine or specific antiviral therapy for prevention and treatment of dengue virus (DENV) infection. Considering the above, drug discovery research for dengue is of utmost importance; in addition natural marine products provide diverse and novel chemical structures with potent biological activities that must be evaluated. In this study we propose a target-free approach for dengue drug discovery based on a novel, rapid, and economic in situ enzyme-linked immunosorbent assay and the screening of a panel of marine seaweed extracts. The in situ ELISA was standardized and validated for Huh7.5 cell line infected with all four serotypes of DENV, among them clinical isolates and a laboratory strain. Statistical analysis showed an average S/B of 7.2 and Z-factor of 0.62, demonstrating assay consistency and reliability. A panel of fifteen seaweed extracts was then screened at the maximum non-toxic dose previously determined by the MTT and Neutral Red cytotoxic assays. Eight seaweed extracts were able to reduce DENV infection of at least one serotype tested. Four extracts (Phaeophyta: Canistrocarpus cervicornis, Padina gymnospora; Rhodophyta: Palisada perforate; Chlorophyta: Caulerpa racemosa) were chosen for further evaluation, and time of addition studies point that they might act at an early stage of the viral infection cycle, such as binding or internalization.