Regions of hepatitis C virus E2 required for membrane association.

Hepatitis C virus (HCV) uses a hybrid entry mechanism. Current structural data suggest that upon exposure to low pH and Cluster of Differentiation 81 (CD81), the amino terminus of envelope glycoprotein E2 becomes ordered and releases an internal loop with two invariant aromatic residues into the host membrane. Here, we present the structure of an amino-terminally truncated E2 with the membrane binding loop in a bent conformation and the aromatic side chains sequestered. Comparison with three previously reported E2 structures with the same Fab indicates that this internal loop is flexible, and that local context influences the exposure of hydrophobic residues. Biochemical assays show that the amino-terminally truncated E2 lacks the baseline membrane-binding capacity of the E2 ectodomain. Thus, the amino terminal region is a critical determinant for both CD81 and membrane interaction. These results provide new insights into the HCV entry mechanism.

Leishmaniasis: the act of transmission.

The contribution of vector transmission to pathogen establishment is largely underrated. For Leishmania, transmission by sand flies is critical to early survival involving an irreproducible myriad of parasite, vector, and host molecules acting in concert to promote infection at the bite site. Here, we review recent breakthroughs that provide consequential insights into how vector transmission of Leishmania unfolds. We focus on recent work pertaining to the effect of gut microbiota, sand fly immunity, and changes in metacyclogenesis upon multiple blood meals, on Leishmania development and transmission. We also explore how sand fly saliva, egested parasite molecules and vector gut microbiota, and bleeding have been implicated in modulating the early innate host response to Leishmania, affecting the phenotype of neutrophils and monocytes arriving at the bite site.

Visualizing the Dynamics of T Cell-Dendritic Cell Interactions in Intact Lymph Nodes by Multiphoton Confocal Microscopy.

Multiphoton microscopy has provided us the ability to visualize cell behavior and biology in intact organs due to its superiority in reaching deep into tissues. Because skin draining lymph nodes are readily accessible via minimal surgery, it is possible to characterize the intricate interactions taking place in peripheral lymph nodes intravitally. Here we describe our protocol to visualize antigen-specific T cell-dendritic cell interactions in the popliteal lymph node of immunocompetent mice. With this method, behaviors of up to four cell types, such as T cells with different antigen specificities, T cells differentiated into different effector and regulatory lineages and dendritic cells originating from mice that bear mutations in functional genes can be imaged simultaneously.

Ixodid Tick Dissection and Tick Ex Vivo Organ Cultures for Tick-Borne Virus Research.

Tick-borne viruses cause thousands of cases of disease worldwide every year. Specific countermeasures to many tick-borne viruses are not commercially available. Very little is known regarding tick-virus interactions and increasing this knowledge can lead to potential targets for countermeasure development. Virus infection of ex vivo organ cultures from ticks can provide an approach to identify susceptible cell types of tissue to infection. Additionally, these organ cultures can be used for functional genomic studies to pinpoint tick-specific genes involved in the virus lifecycle. Provided here are step-by-step procedures to set up basic tick organ cultures in combination with virus infection and/or functional genomic studies. These procedures can be adapted for future use to characterize other tick-borne pathogen infections as well as tick-specific biological processes. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Loading 96-well plates with gelfoam substrate Basic Protocol 2: Step-by-step aseptic dissection of unfed female/male Ixodes scapularis ticks for multiple organs Basic Protocol 3: Step-by-step aseptic dissection of fed female Ixodes scapularis ticks to remove salivary glands Basic Protocol 4: Metabolic viability analyses of tick organ cultures Basic Protocol 5: Virus infection of tick organ cultures Basic Protocol 6: Functional RNA interference analyses using tick organ cultures.

Synthesis and crystal structure of a mixed alkaline-earth powellite, Ca0.84Sr0.16MoO4.

A mixed alkaline-earth powellite, Ca0.84Sr0.16MoO4 (calcium strontium molybdate), was synthesized by a flux method and its crystal structure was solved using single-crystal X-ray diffraction (SC-XRD) data. The compound crystallized in the I41/a space group as with a typical CaMoO4 powellite, but with larger unit-cell parameters and unit-cell volume as a result of the partial incorporation of larger Sr cations into the Ca sites within the crystal. The unit cell and volume were well fitted with the trendline calculated from literature values, and the powder X-ray diffraction (P-XRD) pattern of the ground crystal is in good agreement with the calculated pattern from the solved structure.