Zika virus (ZIKV) is an emerging mosquito-borne (Aedes genus) arbovirus of the Flaviviridae family. Although ZIKV has been predominately associated with a mild or asymptomatic dengue-like disease, its appearance in the Americas has been accompanied by a multi-fold increase in reported incidence of fetal microcephaly and brain malformations. The source and mode of vertical transmission from mother to fetus is presumptively transplacental, although a causal link explaining the interval delay between maternal symptoms and observed fetal malformations following infection has been missing. In this study, we show that primary human placental trophoblasts from non-exposed donors (n = 20) can be infected by primary passage ZIKV-FLR isolate, and uniquely allowed for ZIKV viral RNA replication when compared to dengue virus (DENV). Consistent with their being permissive for ZIKV infection, primary trophoblasts expressed multiple putative ZIKV cell entry receptors, and cellular function and differentiation were preserved. These findings suggest that ZIKV-FLR strain can replicate in human placental trophoblasts without host cell destruction, thereby serving as a likely permissive reservoir and portal of fetal transmission with risk of latent microcephaly and malformations.

Mosquito saliva is a very complex concoction of >100 proteins, many of which have unknown functions. The effects of mosquito saliva proteins injected into our skin during blood feeding have been studied mainly in mouse models of injection or biting, with many of these systems producing results that may not be relevant to human disease. Here, we describe the numerous effects that mosquito bites have on human immune cells in mice engrafted with human hematopoietic stem cells. We used flow cytometry and multiplex cytokine bead array assays, with detailed statistical analyses, to detect small but significant variations in immune cell functions after 4 mosquitoes fed on humanized mice footpads. After preliminary analyses, at different early times after biting, we focused on assessing innate immune and subsequent cellular responses at 6 hours, 24 hours and 7 days after mosquito bites. We detected both Th1 and Th2 human immune responses, and delayed effects on cytokine levels in the blood, and immune cell compositions in the skin and bone marrow, up to 7 days post-bites. These are the first measurements of this kind, with human immune responses in whole animals, bitten by living mosquitoes, versus previous studies using incomplete mouse models and salivary gland extracts or needle injected saliva. The results have major implications for the study of hematophagous insect saliva, its effects on the human immune system, with or without pathogen transmission, and the possibility of determining which of these proteins to target for vaccination, in attempts to block transmission of numerous tropical diseases.

Faecal specimens collected from two outbreaks of acute gastroenteritis that occurred in southern Mumbai, India in March and October, 2006 were tested for seven different enteric viruses. Among the 218 specimens tested, 95 (43.6%) were positive, 73 (76.8%) for a single virus and 22 (23.2%) for multiple viruses. Single viral infections in both, March and October showed predominance of enterovirus (EV, 33.3% and 40%) and rotavirus A (RVA, 33.3% and 25%). The other viruses detected in these months were norovirus (NoV, 12.1% and 10%), rotavirus B (RVB, 12.1% and 10%), enteric adenovirus (AdV, 6.1% and 7.5%), Aichivirus (AiV, 3% and 7.5%) and human astrovirus (HAstV, 3% and 0%). Mixed viral infections were largely represented by two viruses (84.6% and 88.9%), a small proportion showed presence of three (7.7% and 11%) and four (7.7% and 0%) viruses in the two outbreaks. Genotyping of the viruses revealed predominance of RVA G2P[4], RVB G2 (Indian Bangladeshi lineage), NoV GII.4, AdV-40, HAstV-8 and AiV B types. VP1/2A junction region based genotyping showed presence of 11 different serotypes of EVs. Although no virus was detected in the tested water samples, examination of both water and sewage pipelines in gastroenteritis affected localities indicated leakages and possibility of contamination of drinking water with sewage water. Coexistence of multiple enteric viruses during the two outbreaks of gastroenteritis emphasizes the need to expand such investigations to other parts of India.

One of the most important clinical signs of dengue virus infection is the reduction of white blood cells and platelets in human peripheral blood (leukopenia and thrombocytopenia, respectively), which may significantly impair the clearance of dengue virus by the immune system. The cause of thrombocytopenia and leukopenia during dengue infection is still unknown, but may be related to severe suppression of bone marrow populations including hematopoietic stem cells and megakaryocytes, the progenitors of white blood cells and platelets respectively. Here, we explored the possibility that bone marrow suppression, including ablation of megakaryocyte populations, is caused by dengue virus infection of megakaryocytes. We used three different models to measure dengue virus infection and replication: in vitro, in a human megakaryocyte cell line with viral receptors, ex vivo, in primary human megakaryocytes, and in vivo, in humanized mice. All three systems support dengue virus infection and replication, including virus strains from serotypes 1, 2, and 3, and clinical signs, in vivo; all assays showed viral RNA and/or infectious viruses 7–14 days post-infection. Although we saw no significant decrease in cell viability in vitro, there was significant depletion of mature megakaryocytes in vivo. We conclude that megakaryocytes can produce dengue viruses in the bone marrow niche, and a reduction of cell numbers may affect bone marrow homeostasis.

Our results indicate that ZIKV favors infection of stromal cells more so than epithelial cells in organoids, possibly indicating a preference for stem cells in general. Overall, these results suggest that ZIKV replication occurs in the human prostate and can account for ZIKV secretion in semen, thus leading to sexual transmission.

BackgroundZika virus (Flavivirus genus) is the first mosquito-borne virus known to cause high rates of microcephaly and abortion in humans. Typically, Zika virus causes a self-limiting, systemic illness; however, the current outbreak of Zika virus in the Americas has been associated with increased rates of fetal malformations and Guillain-Barré syndrome. Very few Zika virus isolates have been described in the literature, and live viruses are needed to perform studies of pathogenesis and to develop vaccines and treatments.Methodology/Clinical findingsWe isolated Zika virus, strain FLR, directly from the serum of an individual infected in Barranquilla, Colombia (December, 2015). Here, we describe the patient’s clinical course and characterize strain FLR by its growth characteristics in mosquito and mammalian cells and its partial resistance to UV-inactivation. The full genome sequence of FLR was also analyzed (including the 3’ un-translated region), to determine its probable geographic origin, and to pinpoint structural differences from other Zika virus strains.Conclusions/SignificanceWe anticipate that the study of this low passage, clinical isolate of Zika virus, which is available for worldwide distribution, will help uncover the mechanisms of viral replication and host immune responses contributing to the varied and sometimes severe clinical presentations seen during the current epidemic in the Americas.

Dengue virus (DENV) infection disrupts host innate immune signaling at various checkpoints. Cellular levels and stability of intermediate signaling molecules are a crucial hijacking point for a successful viral pathogenesis. Stability and turnover of all the cellular proteins including intermediate signaling molecules are principally regulated by proteasomal degradation pathway. In this study, we show that how DENV infection and particularly DENV-NS1 can modulate the host extracellular vesicle (EV) cargo to manipulate the deubiquitination machinery of the human microglial cell (CHME3). We have performed EV harvesting, size analysis by nanoparticle tracking analysis, identification of cargo microRNA via quantitative PCR, microRNA target validation by overexpression, and knockdown via mimics and anti-miRs, immunoblotting, dual luciferase reporter assay, in vivo ubiquitination assay, chase assay, and promoter activity assay to reach the conclusion. In this study, we show that DENV-infected monocytes and DENV-NS1-transfected cells release high amounts of EVs loaded with miR-148a. These EVs get internalized by human microglial cells, and miR-148a suppresses the ubiquitin-specific peptidase 33 (USP33) protein expression levels via binding to its 39 untranslated region. Reduced USP33 in turn decreases the stability of cellular ATF3 protein via deubiquitylation. ATF3 acts as a suppressor of major proinflammatory gene expression pathways of TNF-a, NF-kB, and IFN-b. Our mechanistic model explains how DENV uses the EV pathway to transfer miR-148a for modulating USP33 and downstream ATF3 levels in human microglial cells and contributes in neuroinflammation within the CNS.

Dengue virus (DENV) infection can cause either self-limited dengue fever or hemorrhagic complications. Low platelet count is one of the manifestations of dengue fever. Megakaryocytes are the sole producers of platelets. However, the role of both host and viral factors in megakaryocyte development, maturation, and platelet production is largely unknown in DENV infection. PI3K/AKT/mTOR pathway plays a significant role in cell survival, maturation, and megakaryocyte development. We were interested to check whether pathogenic insult can impact this pathway. We observed decreased expression of most of the major key molecules associated with the PI3K/AKT/mTOR pathway in DENV infected MEG-01 cells. In this study, the involvement of PI3K/AKT/mTOR pathway in megakaryocyte development and maturation was confirmed with the use of specific inhibitors in infected MEG-01 cells. Our results showed that direct pharmacologic inhibition of this pathway greatly impacted megakaryopoiesis associated molecule CD61 and some essential transcription factors (GATA-1, GATA-2, and NF-E2). Additionally, we observed apoptosis in megakaryocytes due to DENV infection. Our results may suggest that DENV impairs PI3K/AKT/mTOR axis and molecules involved in the development and maturation of megakaryocytes. It is imperative to investigate the role of these molecules in the context of megakaryopoiesis during DENV infection to better understand the pathways and mechanisms, which in turn might provide insights into the development of antiviral strategies.