Dengue-3 Virus Entry into Vero Cells: Role of Clathrin-Mediated Endocytosis in the Outcome of Infection.

The endocytic uptake and intracellular trafficking for penetration of DENV-3 strain H-87 into Vero cells was analyzed by using several biochemical inhibitors and dominant negative mutants of cellular proteins. The results presented show that the infective entry of DENV-3 into Vero cells occurs through a non-classical endocytosis pathway dependent on low pH and dynamin, but non-mediated by clathrin. After uptake, DENV-3 transits through early endosomes to reach Rab 7-regulated late endosomes, and according with the half-time for ammonium chloride resistance viral nucleocapsid is released into the cytosol approximately at 12 min post-infection. Furthermore, the influence of the clathrin pathway in DENV-3 infective entry in other mammalian cell lines of human origin, such as A549, HepG2 and U937 cells, was evaluated demonstrating that variable entry pathways are employed depending on the host cell. Results show for the first time the simultaneous coexistence of infective and non -infective routes for DENV entry into the host cell, depending on the usage of clathrin-mediated endocytosis.

Inhibition of the PI3K/Akt pathway by Ly294002 does not prevent establishment of persistent Junín virus infection in Vero cells.

In previous work, we demonstrated that the arenavirus Junín virus (JUNV) is able to activate Akt by means of the phosphatidylinositol-3-kinase (PI3K) survival pathway during virus entry. This work extends our study, emphasizing the relevance of this pathway in the establishment and maintenance of persistent infection in vitro. During the course of infection, JUNV-infected Vero cells showed a typical cytopathic effect that may be ascribed to apoptotic cell death. Treatment of infected cultures with Ly294002, an inhibitor of the PI3K/Akt pathway, produced an apoptotic response similar to that observed for uninfected cells treated with the drug. This result suggests that virus-induced activation of the PI3K/Akt pathway does not deliver a strong enough anti-apoptotic signal to explain the low proportion of apoptotic cells observed during infection. Also, inhibition of the PI3K/Akt pathway during the acute stage of infection did not prevent the establishment of persistence. Furthermore, treatment of persistently JUNV-infected cells with Ly294002 did not alter viral protein expression. These findings indicate that despite the positive modulation of the PI3/Akt pathway during Junín virus entry, this would not play a critical role in the establishment and maintenance of JUNV persistence in Vero cells.

Anti-adenovirus activity of epiandrosterone and dehydroepiandrosterone derivatives.

BACKGROUND: Dehydroepiandrosterone (DHEA) exhibits a wide range of biological functions including antiviral activity. In this work, we present in vitro anti-adenovirus (AdV) activity of seven DHEA and twelve epiandrosterone (EA) analogues. METHODS: The cytotoxic effect of the compounds was determined by the MTT assay and the antiviral activity by a virus yield inhibition assay. The mode of antiviral activity was examined using time-of-addition experiments, adsorption and internalization assays and Western blot analysis. RESULTS: EA, DHEA, and two synthetic derivatives inhibit virus replication with selectivity indices ranging between 42 and 83. Virus adsorption and internalization are not the target of the inhibitory action; meanwhile, AdV protein synthesis was diminished in the presence of DHEA. CONCLUSIONS: DHEA and some synthetic derivatives present antiviral activity similar to cidofovir, which was used as reference drug. These steroidal compounds adversely affect virus protein synthesis and viral mature particle formation.

Functional entry of dengue virus into Aedes albopictus mosquito cells is dependent on clathrin-mediated endocytosis.

Entry of dengue virus 2 (DENV-2) into Aedes albopictus mosquito C6/36 cells was analysed using biochemical and molecular inhibitors, together with confocal and electron microscopy observations. Treatment with monodansylcadaverine, chlorpromazine, sucrose and ammonium chloride inhibited DENV-2 virus yield and protein expression, whereas nystatin, a blocker of caveolae-mediated endocytosis, did not have any effect. Using confocal microscopy, co-localization of DENV-2 E glycoprotein and the marker protein transferrin was observed at the periphery of the cytoplasm. To support the requirement of clathrin function for DENV-2 entry, overexpression of a dominant-negative mutant of Eps15 in C6/36 cells was shown to impair virus entry. The disruption of actin microfilaments by cytochalasin D also significantly affected DENV-2 replication. In contrast, microtubule disruption by colchicine treatment did not impair DENV-2 infectivity, suggesting that DENV-2 does not require transport from early to late endosomes for successful infection of mosquito cells. Furthermore, using transmission electron microscopy, DENV-2 particles of approximately 44-52 nm were found attached within electron-dense invaginations of the plasma membrane and in coated vesicles that resembled those of clathrin-coated pits and vesicles, respectively. Together, these results demonstrate for the first time that DENV-2 enters insect cells by receptor-mediated, clathrin-dependent endocytosis, requiring traffic through an acidic pH compartment for subsequent uncoating and completion of a productive infection.

Compuestos lisosomotrópicos inhibidores de la multiplicación del virus Junín / Lysosomotropic compounds inhibiting the multiplication of Junin virus

La multiplicación del virus Junín en células Vero fue inhibida por la acción de drogas lisosomotrópicas de carácter básico como cloruro de amonio, clorhidrato de procaína y clorofeniramina. El efecto inhibitorio del cloruro de amonio (15mM) es máximo cuando la droga es agregada junto con el inóculo viral o inmediatamente después de la infección, pero aun agregado 8 horas después de la infección produce una inhibición significativa del 97,8%. Estos resultados indicarían que la droga actúa fundamentalmente sobre una etapa temprana del ciclo de multiplicación viral. Por lo tanto, el mecanismo de entrada del virus Junín a la célula transcurriría a través de una endocitosis mediada por receptor