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Human infections with Japanese encephalitis virus (JEV) are a leading cause of viral encephalitis, with ≈70,000 symptomatic cases (≈40% with long-term neurological sequelae) and ≈20,000 deaths reported annually, primarily in Asia and the Western Pacific. An outbreak of JEV genotype 4 was also recently reported in Australia, with an isolate (JEVNSW/22) obtained from a stillborn piglet. Herein we characterize the neuropathology of JEVNSW/22, JEVFU(genotype 2) and JEVNakayama(genotype 3) in adult C57BL/6J wild-type mice, mice deficient in interferon regulatory factor 7 (IRF7-/-), and mice deficient in the type I interferon receptor (IFNAR-/-). In C57BL/6J and IRF7-/-mice with lethal outcomes, viral antigen was detected by immunohistochemistry ininter aliathe cortex, thalamus and hippocampus. In these mice, histological lesions included neuronal degeneration, neuronal vacuolation, perivascular cuffing, leukocyte infiltrates, hemorrhage, and microgliosis, with apoptosis and astrocyte activation detected by immunohistochemistry. Microgliosis and hemorrhage persisted in some surviving mice ≈3-4 weeks post infection. JEV was universally lethal in IFNAR-/-mice by day 3 with histological signs of brain hemorrhage, but produced no other detectable brain infection or lesions, with NS1 readily detected in blood vessels, but not neurons, by immunohistochemistry. All JEV isolates showed robust productive cytopathic infection of human cortical brain organoids (hBOs), as well as a human neural progenitor cell line (RENcell VM). We thus describe a new IRF7-/-mouse model for JEV, which shows increased penetrance of lethal neuroinvasiveness and recapitulates many aspects human disease. Although less virulent in IRF7-/-mice, JEVNSW/22retained the capacity to cause lethal encephalitis and to replicate and destroy human neuronal cells.

The reduced pathogenicity of the omicron BA.1 sub-lineage compared to earlier variants is well described, although whether such attenuation is retained for later variants like BA.5 remains controversial. We show that a BA.5 isolate was significantly more pathogenic in K18-hACE2 mice than a BA.1 isolate, with BA.5 infections showing increased neuroinvasiveness, resulting in brain infection and mortality, similar to that seen for original ancestral isolates. BA.5 also infected human cortical brain organoids to a greater extent than the BA.1 and original ancestral isolates. In the brains of mice neurons were the main target of infection, and in human organoids neuronal progenitor cells and immature neurons were infected. Evidence for brain infection and brain damage in certain COVID-19 patients is becoming compelling, with the results herein illustrating the increasing intrinsic neuropathogenic potential of evolving omicron variants.

Mayaro virus (MAYV) is a mosquito-transmitted alphavirus that causes often debilitating rheumatic disease in tropical Central and South America. There are currently no licensed vaccines or antiviral drugs available for MAYV disease. Here, we generated Mayaro virus-like particles (VLPs) using the scalable baculovirus-insect cell expression system. High-level secretion of MAYV VLPs in the culture fluid of Sf9 insect cells was achieved, and particles with a diameter of 64 to 70 nm were obtained after purification. We characterize a C57BL/6J adult wild-type mouse model of MAYV infection and disease and used this model to compare the immunogenicity of VLPs from insect cells with that of VLPs produced in mammalian cells. Mice received two intramuscular immunizations with 1 μg of nonadjuvanted MAYV VLPs. Potent neutralizing antibody responses were generated against the vaccine strain, BeH407, with comparable activity seen against a contemporary 2018 isolate from Brazil (BR-18), whereas neutralizing activity against chikungunya virus was marginal. Sequencing of BR-18 illustrated that this virus segregates with genotype D isolates, whereas MAYV BeH407 belongs to genotype L. The mammalian cell-derived VLPs induced higher mean neutralizing antibody titers than those produced in insect cells. Both VLP vaccines completely protected adult wild-type mice against viremia, myositis, tendonitis, and joint inflammation after MAYV challenge. IMPORTANCE Mayaro virus (MAYV) is associated with acute rheumatic disease that can be debilitating and can evolve into months of chronic arthralgia. MAYV is believed to have the potential to emerge as a tropical public health threat, especially if it develops the ability to be efficiently transmitted by urban mosquito vectors, such as Aedes aegypti and/or Aedes albopictus. Here, we describe a scalable virus-like particle vaccine against MAYV that induced neutralizing antibodies against a historical and a contemporary isolate of MAYV and protected mice against infection and disease, providing a potential new intervention for MAYV epidemic preparedness.

A frequently repeated premise is that viruses evolve to become less pathogenic. This appears also to be true for SARS-CoV-2, although the increased level of immunity in human populations makes it difficult to distinguish between reduced intrinsic pathogenicity and increasing protective immunity. The reduced pathogenicity of the omicron BA.1 sub-lineage compared to earlier variants is well described and appears to be due to reduced utilization of TMPRRS2. That this reduced pathogenicity remains true for omicron BA.5 was recently reported. In sharp contrast, we show that a BA.5 isolate was significantly more pathogenic in K18-hACE2 mice than a BA.1 isolate, with BA.5 infection showing increased neurovirulence, encephalitis and mortality, similar to that seen for an original ancestral isolate. BA.5 also infected human cortical brain organoids to a greater extent than a BA.1 and original ancestral isolate. Neurons were the target of infection, with increasing evidence of neuron infection in COVID-19 patients. These results argue that while omicron virus may be associated with reduced respiratory symptoms, BA.5 shows increased neurovirulence compared to earlier omicron sub-variants.

Warmer climatic conditions have been associated with fewer COVID-19 cases. Herein we infected K18-hACE2 mice housed at the standard animal house temperature of ∼22 °C, or at ∼31 °C, which is considered to be thermoneutral for mice. On day 2 post infection, RNA-Seq analyses showed no significant differential gene expression lung in lungs of mice housed at the two temperatures, with almost identical viral loads and type I interferon responses. There was also no significant difference in viral loads in lungs on day 5, but RNA-Seq and histology analyses showed clearly elevated inflammatory signatures and infiltrates. Thermoneutrality thus promoted lung inflammation. On day 2 post infection mice housed at 31 °C showed reduced viral loads in nasal turbinates, consistent with increased mucociliary clearance at the warmer ambient temperature. These mice also had reduced virus levels in the brain, and an ensuing amelioration of weight loss and a delay in mortality. Warmer air temperatures may thus reduce infection of the upper respiratory track and the olfactory epithelium, resulting in reduced brain infection. Potential relevance for anosmia and neurological sequelae in COVID-19 patients is discussed.

While the properties of hybrid fiber-reinforced concrete (HyFRC) have been well-reported in the literature, the behavior of reinforced HyFRC (i.e., HyFRC with embedded steel rebar) is less understood. This paper investigates the mechanics and failure characteristics of reinforced HyFRC under direct tension. Samples with a low longitudinal steel reinforcement ratio were studied to evaluate the feasibility of reducing rebar congestion in structural applications through the use of fiber-reinforced concrete. Although reinforced HyFRC forms multiple cracking sites when loaded, rebar strain and HyFRC crack opening are generally concentrated at a single location under post-yield displacements. The onset of rebar plastic deformation and the exhaustion of fibers’ bridging load capacity are coincident events at a dominant crack. For a cracked reinforced HyFRC section to strengthen, the magnitude of load resistance increase from strain hardening rebar must exceed the magnitude of load resistance decrease from fiber pull-out processes. Comparisons are made with studies reported in the literature to demonstrate how longitudinal reinforcement ratio and fiber type influence cracking behavior and ultimate strain capacity. The research presented herein has far-reaching impacts on the structural design of all types of reinforced fiber-reinforced concrete materials detailed for a ductile response under large displacements.

While fiber-reinforced concrete has been proposed for corrosion damage control of reinforced concrete, long-term behavior of these composites remains largely uninvestigated. In this study, reinforced concrete and reinforced hybrid fiber-reinforced concrete (HyFRC) were subjected to a chloride environment for 2.2 years. Samples were mechanically loaded prior to chloride exposure to induce varied matrix cracking characteristics. When precracked, the time to corrosion initiation is correlated to flexural stiffness degradation. After corrosion initiation, fiber reinforcement restricts corrosion-induced cracking, causes more extensive diffusion of corrosion products into the cementitious matrix, and lowers overall mass loss of steel reinforcing bars. The mechanical responses of corroded samples are also reported.

© 2018 Elsevier Ltd In this paper, we investigate the influence of cementitious matrix cracking on the electrochemical polarization and impedance behaviors of corroding reinforced concrete and crack-resistant reinforced hybrid fiber-reinforced concrete (HyFRC). Samples were exposed to a chloride environment for 2.5 years while in either a continuous tensile stress state or in a nonloaded condition, and were periodically monitored for Tafel polarization responses. Electrochemical impedance spectroscopy (EIS) was additionally performed at the conclusion of the test program. Greater severity of corrosion-induced matrix splitting cracks along the length of embedded steel reinforcing bars and subsequent formation of anodic surfaces were found to affect several electrochemical parameters, including increase of the corrosion current and decrease of the ohmic resistance of concrete. Cathodic and anodic Tafel coefficients and Stern-Geary coefficients for passive and active samples are also reported, highlighted by a Stern-Geary coefficient of B = 28.1 mV for active corrosion.

Concrete production requires significant consumption of raw materials and is a major contributor to global greenhouse gas emissions. Because concrete is placed in varied, damage-inducing conditions, its durability performance is crucial for allowing the material to reach its intended service life and avoid premature replacement. In this multidisciplinary research program, a concrete is developed for both reduced environmental impact and enhanced durability compared to conventional solutions. These goals are realized through a novel combination of design parameters: recycled concrete aggregates (RCA) that increase reuse of construction demolition waste; a high-volume fly ash (HVFA) matrix that further incorporates industrial waste products while reducing portland cement content; and internal fiber reinforcement that increases composite crack resistance. The resulting high-performance concrete, designated as green hybrid fiber-reinforced concrete (GHyFRC), contains 39% waste materials by volume and is evaluated by life cycle assessment (LCA), exposure to a corrosive environment for 4.3 years, and structural loading. Corrosion activity of steel rebar embedded within GHyFRC was reduced through the low chloride permeability of a high-volume fly ash matrix and fiber reinforcement that limited crack propagation, maintaining the low designed matrix permeability. GHyFRC can be a more sustainable alternative to concrete under certain conditions by contributing to greater retention of flexural strength after corrosion has begun and lowering global warming potential (GWP) when normalized by flexural strength.

Many reinforced concrete structures susceptible to corrosion damage are subjected to externally applied loads, causing cracking. These cracks increase the permeability of the material, accelerating the ingress of corrosion-inducing deleterious agents. In this paper, the effect of multiple microcracking and macrocrack formation on corrosion initiation was investigated. A hybrid fiber-reinforced concrete (HyFRC), which forms ductile, distributed microcracking prior to dominant crack localization due to multiple tiers of fiber reinforcement, is being studied for its performance against corrosion damage. The effect of matrix cracking on corrosion initiation was studied with beam specimens preloaded in flexure prior to long-term corrosion exposure. Reinforced HyFRC composites were found to have a delayed corrosion initiation response due to reductions in crack widths and suppression of splitting cracks, compared to conventional reinforced concrete. The influence of microcracks on corrosion is studied using X-ray micro-computed tomography (μCT) on reinforced fiber-reinforced cementitious composites and reinforced mortar preloaded in tension.

With the expected replacement of deteriorated reinforced concrete bridges to occur in the next several decades, an opportunity exists to design more economic bridge columns in seismically active regions which are rapidly constructed while having enhanced crack resistance for extended service life. A precast hybrid fiber-reinforced concrete (HyFRC) tube, which contains a column’s steel reinforcement, is proposed for accelerating construction and is to be filled with plain concrete at the construction site. An experimental column was subjected to static, uni-directional, cyclic loading and utilized a base-rocking design for further ductility enhancement. At the conclusion of the test, the column reached a peak drift ratio of 13.1% and showed minor damage, including elimination of cover spalling. The HyFRC tube column design contributed effective resistance against longitudinal reinforcing bar buckling, allowing the column to maintain 93% of its peak load capacity at 9.5% drift. Compared to a monolithic HyFRC column, the precast HyFRC tube column was constructed with less HyFRC volume while having similar seismic performance, making it a more sustainable alternative.

The corrosion of steel reinforcing bars in concrete structures is a primary durability concern in aging infrastructure. Cracks caused by the internal growth of corrosion products increase the permeability of the matrix and degrade the designed capacity of structural elements. In this longterm study, two types of hybrid fiber-reinforced concrete (HyFRC) – a baseline HyFRC and a selfconsolidating HyFRC (SC-HyFRC) – are investigated for serviceability enhancement under a twostage corrosion model (time to corrosion initiation and damage during corrosion propagation). HyFRC, which contains a synergistic blend of microfibers and macrofibers, utilizes a multi-scale approach towards crack control and is extended to durability-related applications. Reinforced HyFRC and reinforced concrete beams were exposed to chloride penetration and monitored for corrosion activity for up to two years. Because concrete structures are subjected to various crack-inducing loads while in service, beam specimens in this study were placed under a cyclic, flexural preloading protocol prior to induced corrosion to account for such service conditions. The time to corrosion initiation was found to increase with reduced maximum flexural crack widths and suppression of surface splitting cracks during preloading, both of which were improved by HyFRC compared to concrete. Crack resistance provided by hybrid fiber reinforcement was evident during the corrosion propagation stage, as additional surface cracking was not detected with reinforced HyFRC and residual flexural testing revealed no significant degradation in flexural performance. In contrast, damage to reinforced concrete beams resulted in nearly complete loss of rebar-matrix bond due to extensive splitting crack formation and widening. The results suggest hybrid fiber reinforcement was effective in resisting tensile stresses from mechanical loading and from the internal growth of corrosion products, ultimately limiting the damage to reinforcing steel and maintaining the service capacity of beam elements.