Objective(s) Primary human trophoblasts were previously shown to be resistant to viral infection, and able to confer this resistance to non-trophoblast cells. Can trophoblasts protect non-trophoblastic cells from infection by viruses or other intracellular pathogens that are implicated in perinatal infection? Study Design Isolated primary term human trophoblasts were cultured for 72 h. Diverse non-placental human cell lines (U2OS, HFF, TZM-bl, MeWo, and Caco-2) were pre-exposed to either trophoblast conditioned, non-conditioned medium, or miR-517-3p for 24 h. Cells were infected with several viral and non-viral pathogens known to be associated with perinatal infections. Cellular infection was defined and quantified by plaque assays, luciferase assays, microscopy, and/or colonization assays. Differences in infection were assessed by Student's t-test or ANOVA with Bonferroni's correction. Results Infection by rubella and other togaviruses, HIV-1, and varicella zoster, was attenuated in cells pre-exposed to trophoblast conditioned medium (p <0.05), and a partial effect by the Ch.19 microRNA miR-517-3p on specific pathogens. The conditioned medium had no effect on infection by Toxoplasma gondii or Listeria monocytogenes. Conclusion Our findings indicate that medium conditioned by primary human trophoblasts attenuate viral infection in non-trophoblastic cells. Our data point to a trophoblast-specific antiviral effect that may be exploited therapeutically.

BackgroundIt is generally thought that viruses require the cytoskeleton during their replication cycle. However, recent experiments in our laboratory with rubella virus, a member of the family Togaviridae (genus rubivirus), revealed that replication proceeded in the presence of drugs that inhibit microtubules. This study was done to expand on this observation.FindingsThe replication of three diverse viruses, Sindbis virus (SINV; family Togaviridae family), vesicular stomatitis virus (VSV; family Rhabdoviridae), and Herpes simplex virus (family Herpesviridae), was quantified by the titer (plaque forming units/ml; pfu/ml) produced in cells treated with one of three anti-microtubule drugs (colchicine, noscapine, or paclitaxel) or the anti-actin filament drug, cytochalasin D. None of these drugs affected the replication these viruses. Specific steps in the SINV infection cycle were examined during drug treatment to determine if alterations in specific steps in the virus replication cycle in the absence of a functional cytoskeletal system could be detected, i.e. redistribution of viral proteins and replication complexes or increases/decreases in their abundance. These investigations revealed that the observable impacts were a colchicine-mediated fragmentation of the Golgi apparatus and concomitant intracellular redistribution of the virion structural proteins, along with a reduction in viral genome and sub-genome RNA levels, but not double-stranded RNA or protein levels.ConclusionsThe failure of poisons affecting the cytoskeleton to inhibit the replication of a diverse set of viruses strongly suggests that viruses do not require a functional cytoskeletal system for replication, either because they do not utilize it or are able to utilize alternate pathways when it is not available.