Transmission, infectivity, and neutralization of a spike L452R SARS-CoV-2 variant.

We identified an emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant by viral whole-genome sequencing of 2,172 nasal/nasopharyngeal swab samples from 44 counties in California, a state in the western United States. Named B.1.427/B.1.429 to denote its two lineages, the variant emerged in May 2020 and increased from 0% to >50% of sequenced cases from September 2020 to January 2021, showing 18.6%-24% increased transmissibility relative to wild-type circulating strains. The variant carries three mutations in the spike protein, including an L452R substitution. We found 2-fold increased B.1.427/B.1.429 viral shedding in vivo and increased L452R pseudovirus infection of cell cultures and lung organoids, albeit decreased relative to pseudoviruses carrying the N501Y mutation common to variants B.1.1.7, B.1.351, and P.1. Antibody neutralization assays revealed 4.0- to 6.7-fold and 2.0-fold decreases in neutralizing titers from convalescent patients and vaccine recipients, respectively. The increased prevalence of a more transmissible variant in California exhibiting decreased antibody neutralization warrants further investigation.

Quantum Sensing for Real-Time Monitoring of Drug Efficacy in Synovial Fluid from Arthritis Patients.

Diamond-based T1 relaxometry is a new technique that allows nanoscale magnetic resonance measurements. Here we present its first application in patient samples. More specifically, we demonstrate that relaxometry can determine the free radical load in samples from arthritis patients. We found that we can clearly differentiate between osteoarthritis and rheumatoid arthritis patients in both the synovial fluid itself and cells derived from it. Furthermore, we tested how synovial fluid and its cells respond to piroxicam, a common nonsteroidal anti-inflammatory drug (NSAID). It is known that this drug leads to a reduction in reactive oxygen species production in fibroblast-like synoviocytes (FLS). Here, we investigated the formation of free radicals specifically. While FLS from osteoarthritis patients showed a drastic decrease in the free radical load, cells from rheumatoid arthritis retained a similar radical load after treatment. This offers a possible explanation for why piroxicam is more beneficial for patients with osteoarthritis than those with rheumatoid arthritis.

Quantum Sensing of Free Radicals in Primary Human Dendritic Cells.

Free radicals are crucial indicators for stress and appear in all kinds of pathogenic conditions, including cancer, cardiovascular diseases, and infection. However, they are difficult to detect due to their reactivity and low abundance. We use relaxometry for the detection of radicals with subcellular resolution. This method is based on a fluorescent defect in a diamond, which changes its optical properties on the basis of the magnetic surroundings. This technique allows nanoscale MRI with unprecedented sensitivity and spatial resolution. Recently, this technique was used inside living cells from a cell line. Cell lines differ in terms of endocytic capability and radical production from primary cells derived from patients. Here we provide the first measurements of phagocytic radical production by the NADPH oxidase (NOX2) in primary dendritic cells from healthy donors. The radical production of these cells differs greatly between donors. We investigated the cell response to stimulation or inhibition.

Endovascular therapeutic hypothermia adjunctive to percutaneous coronary intervention in acute myocardial infarction: realistic simulation as a game changer.

BACKGROUND: Endovascular therapeutic hypothermia (ETH) reduces the damage by ischemia/reperfusion cell syndrome in cardiac arrest and has been studied as an adjuvant therapy to percutaneous coronary intervention (PCI) in ST-elevation myocardial infarction (STEMI). New available advanced technology allows cooling much faster, but there is paucity of resources for training to avoid delays in door-to-balloon time (DTB) due to ETH and subsequently coronary reperfusion, which would derail the procedure. The aim of the study was to describe the process for the development of a simulation, training & educational protocol for the multidisciplinary team to perform optimized ETH as an adjunctive therapy for STEMI. METHODS AND RESULTS: We developed an optimized simulation protocol using modern mannequins in different realistic scenarios for the treatment of patients undergoing ETH adjunctive to PCI for STEMIs starting from the emergency room, through the CathLab, and to the intensive care unit (ICU) using the Proteus® Endovascular System (Zoll Circulation Inc™, San Jose, CA, USA). The primary endpoint was door-to-balloon (DTB) time. We successfully trained 361 multidisciplinary professionals in realistic simulation using modern mannequins and sham situations in divisions of the hospital where real patients would be treated. The focus of simulation and training was logistical optimization and educational debriefing with strategies to reduce waste of time in patient's transportation from different departments, and avoiding excessive rewarming during transfer. Afterwards, the EHT protocol was successfully validated in a trial randomizing 50 patients for 18 minutes cooling before coronary recanalization at the target temperature of 32 ± 1.0 ∘C or PCI-only. A total of 35 patients underwent ETH (85.7% [30/35] in 90 ± 15 minutes), without delays in the mean door-to-balloon time for primary PCI when compared to 15 control group patients (92.1 minutes versus 87 minutes, respectively; p = 0.509). CONCLUSIONS: Realistic simulation, intensive training and educational debriefing for the multidisciplinary team propitiated feasible endovascular therapeutic hypothermia as an adjuvant therapy to primary PCI in STEMI. CLINICALTRIALS: gov: NCT02664194.

Two Sides of a Coin: a Zika Virus Mutation Selected in Pregnant Rhesus Macaques Promotes Fetal Infection in Mice but at a Cost of Reduced Fitness in Nonpregnant Macaques and Diminished Transmissibility by Vectors.

Although fetal death is now understood to be a severe outcome of congenital Zika syndrome, the role of viral genetics is still unclear. We sequenced Zika virus (ZIKV) from a rhesus macaque fetus that died after inoculation and identified a single intrahost substitution, M1404I, in the ZIKV polyprotein, located in nonstructural protein 2B (NS2B). Targeted sequencing flanking position 1404 in 9 additional macaque mothers and their fetuses identified M1404I at a subconsensus frequency in the majority (5 of 9, 56%) of animals and some of their fetuses. Despite its repeated presence in pregnant macaques, M1404I has occurred rarely in humans since 2015. Since the primary ZIKV transmission cycle is human-mosquito-human, mutations in one host must be retained in the alternate host to be perpetuated. We hypothesized that ZIKV I1404 increases viral fitness in nonpregnant macaques and pregnant mice but is less efficiently transmitted by vectors, explaining its low frequency in humans during outbreaks. By examining competitive fitness relative to that of ZIKV M1404, we observed that ZIKV I1404 produced lower viremias in nonpregnant macaques and was a weaker competitor in tissues. In pregnant wild-type mice, ZIKV I1404 increased the magnitude and rate of placental infection and conferred fetal infection, in contrast to ZIKV M1404, which was not detected in fetuses. Although infection and dissemination rates were not different, Aedes aegypti mosquitoes transmitted ZIKV I1404 more poorly than ZIKV M1404. Our data highlight the complexity of arbovirus mutation-fitness dynamics and suggest that intrahost ZIKV mutations capable of augmenting fitness in pregnant vertebrates may not necessarily spread efficiently via mosquitoes during epidemics.IMPORTANCE Although Zika virus infection of pregnant women can result in congenital Zika syndrome, the factors that cause the syndrome in some but not all infected mothers are still unclear. We identified a mutation that was present in some ZIKV genomes in experimentally inoculated pregnant rhesus macaques and their fetuses. Although we did not find an association between the presence of the mutation and fetal death, we performed additional studies with ZIKV with the mutation in nonpregnant macaques, pregnant mice, and mosquitoes. We observed that the mutation increased the ability of the virus to infect mouse fetuses but decreased its capacity to produce high levels of virus in the blood of nonpregnant macaques and to be transmitted by mosquitoes. This study shows that mutations in mosquito-borne viruses like ZIKV that increase fitness in pregnant vertebrates may not spread in outbreaks when they compromise transmission via mosquitoes and fitness in nonpregnant hosts.

Metagenomic Next-Generation Sequencing of the 2014 Ebola Virus Disease Outbreak in the Democratic Republic of the Congo.

We applied metagenomic next-generation sequencing (mNGS) to detect Zaire Ebola virus (EBOV) and other potential pathogens from whole-blood samples from 70 patients with suspected Ebola hemorrhagic fever during a 2014 outbreak in Boende, Democratic Republic of the Congo (DRC) and correlated these findings with clinical symptoms. Twenty of 31 patients (64.5%) tested in Kinshasa, DRC, were EBOV positive by quantitative reverse transcriptase PCR (qRT-PCR). Despite partial degradation of sample RNA during shipping and handling, mNGS followed by EBOV-specific capture probe enrichment in a U.S. genomics laboratory identified EBOV reads in 22 of 70 samples (31.4%) versus in 21 of 70 (30.0%) EBOV-positive samples by repeat qRT-PCR (overall concordance = 87.1%). Reads from Plasmodium falciparum (malaria) were detected in 21 patients, of which at least 9 (42.9%) were coinfected with EBOV. Other positive viral detections included hepatitis B virus (n = 2), human pegivirus 1 (n = 2), Epstein-Barr virus (n = 9), and Orungo virus (n = 1), a virus in the Reoviridae family. The patient with Orungo virus infection presented with an acute febrile illness and died rapidly from massive hemorrhage and dehydration. Although the patient's blood sample was negative by EBOV qRT-PCR testing, identification of viral reads by mNGS confirmed the presence of EBOV coinfection. In total, 9 new EBOV genomes (3 complete genomes, and an additional 6 ≥50% complete) were assembled. Relaxed molecular clock phylogenetic analysis demonstrated a molecular evolutionary rate for the Boende strain 4 to 10× slower than that of other Ebola lineages. These results demonstrate the utility of mNGS in broad-based pathogen detection and outbreak surveillance.

[Subcutaneous injection of metallic mercury. The importance of early removal]. / Inyección subcutánea de mercurio elemental. Importancia de la remoción precoz.

Accidental or intentional subcutaneous or intramuscular injection of metallic mercury is an uncommon form of intoxication. We present the case of a 22 year-old man, who had psychotic disorders and autoaggressive behavior, with a preceding history of self-injection of mercury into the soft tissues of the neck, thorax and abdomen. Clinical examination, radiographs, and computed tomography showed the affected area. Mercury was measured in blood and urine. The mercury was surgically resected from the affected areas. Early detection and removal of mercury from the body by physical removal or chelation is required to prevent short- and long-term toxicity.

Characterization of human astrovirus cell entry.

Human astroviruses (HAstV) are a frequent cause of gastroenteritis in young children and immunocompromised patients. To understand the early steps of HAstV infection in the highly permissive Caco-2 cell line, the binding and entry processes of the virus were characterized. The half-time of virus binding to the cell surface was about 10 min, while virus decapsidation took around 130 min. Drugs affecting clathrin-mediated endocytosis, endosome acidification, and actin filament polymerization, as well as those that reduce the presence of cholesterol in the cell membrane, decreased the infectivity of the virus. The infection was also reduced by silencing the expression of the clathrin heavy chain (CHC) by RNA interference or by overexpression of dominant-negative mutants of dynamin 2 and Eps15. Furthermore, the entry of HAstV apparently depends on the maturation of endosomes, since the infection was reduced by silencing the expression of Rab7, a small GTPase involved in the early- to late-endosome maturation. Altogether, our results suggest that HAstV enters Caco-2 cells using a clathrin-dependent pathway and reaches late endosomes to enter cells. Here, we have characterized the mechanism used by human astroviruses, important agents of gastroenteritis in children, to gain entry into their host cells. Using a combination of biochemical and genetic tools, we found that these viruses enter Caco-2 cells using a clathrin-dependent endocytic pathway, where they most likely need to travel to late endosomes to reach the cytoplasm and begin their replication cycle.

Cross-inhibition of chikungunya virus fusion and infection by alphavirus E1 domain III proteins.

Alphaviruses are small enveloped RNA viruses that include important emerging human pathogens, such as chikungunya virus (CHIKV). These viruses infect cells via a low-pH-triggered membrane fusion reaction, making this step a potential target for antiviral therapies. The E1 fusion protein inserts into the target membrane, trimerizes, and refolds to a hairpin-like conformation in which the combination of E1 domain III (DIII) and the stem region (DIII-stem) pack against a core trimer composed of E1 domains I and II (DI/II). Addition of exogenous DIII proteins from Semliki Forest virus (SFV) has been shown to inhibit E1 hairpin formation and SFV fusion and infection. Here we produced and characterized DIII and DI/II proteins from CHIKV and SFV. Unlike SFV DIII, both core trimer binding and fusion inhibition by CHIKV DIII required the stem region. CHIKV DIII-stem and SFV DIII-stem showed efficient cross-inhibition of SFV, Sindbis virus, and CHIKV infections. We developed a fluorescence anisotropy-based assay for the binding of SFV DIII-stem to the core trimer and used it to demonstrate the relatively high affinity of this interaction (Kd [dissociation constant], ∼85 nM) and the importance of the stem region. Together, our results support the conserved nature of the key contacts of DIII-stem in the alphavirus E1 homotrimer and describe a sensitive and quantitative in vitro assay for this step in fusion protein refolding.

Fluorescent nanodiamond labels: Size and concentration matters for sperm cell viability.

Nanodiamonds are increasingly popular in biomedical applications, including optical labelling, drug delivery and nanoscale sensing. Potential new applications are in studying infertility or labelling sperm cells. However, for these applications, it is necessary that nanodiamonds are inert and do not alter sperm properties. In this article, we assessed the biocompatibility of nanodiamonds in detail. We investigated different sizes and concentrations of nanodiamonds and sperm preparation methods. We evaluated if the metabolic activity, membrane integrity, morphology and formation of reactive oxygen species were altered. These parameters were tested for sperm cells in their uncapacitated and capacitated states. Unfortunately, FNDs are not universally biocompatible. Generally, cells in the capacitated state are more prone to stress. Additionally, larger particles and lower concentrations are tolerated better than smaller and higher concentrated particles.

The domain I-domain III linker plays an important role in the fusogenic conformational change of the alphavirus membrane fusion protein.

The alphavirus Semliki Forest virus (SFV) infects cells through a low-pH-dependent membrane fusion reaction mediated by the virus fusion protein E1. Acidic pH initiates a series of E1 conformational changes that culminate in membrane fusion and include dissociation of the E1/E2 heterodimer, insertion of the E1 fusion loop into the target membrane, and refolding of E1 to a stable trimeric hairpin conformation. A highly conserved histidine (H3) on the E1 protein was previously shown to promote low-pH-dependent E1 refolding. An SFV mutant with an alanine substitution at this position (H3A) has a lower pH threshold and reduced efficiency of virus fusion and E1 trimer formation than wild-type SFV. Here we addressed the mechanism by which H3 promotes E1 refolding and membrane fusion. We identified E1 mutations that rescue the H3A defect. These revertants implicated a network of interactions that connect the domain I-domain III (DI-DIII) linker region with the E1 core trimer, including H3. In support of the importance of these interactions, mutation of residues in the network resulted in more acidic pH thresholds and reduced efficiencies of membrane fusion. In vitro studies of truncated E1 proteins demonstrated that the DI-DIII linker was required for production of a stable E1 core trimer on target membranes. Together, our results suggest a critical and previously unidentified role for the DI-DIII linker region during the low-pH-dependent refolding of E1 that drives membrane fusion.

Nanoscale MRI for Selective Labeling and Localized Free Radical Measurements in the Acrosomes of Single Sperm Cells.

Free radicals play a major role in sperm development, including maturation and fertilization, but they are also linked to infertility. Since they are short-lived and reactive, they are challenging to detect with state of the art methodologies. Thus, many details surrounding their role remain unknown. One unknown factor is the source of radicals that plays a role in the sperm maturation process. Two alternative sources have been postulated: First, the NADPH-oxidase system embedded in the plasma membrane (NOX5) and second, the NADH-dependent oxidoreductase of mitochondria. Due to a lack of localized measurements, the relative contribution of each source for capacitation remains unknown. To answer this question, we use a technique called diamond magnetometry, which allows nanoscale MRI to perform localized free radical detection. With this tool, we were able to quantify radical formation in the acrosome of sperm heads. This allowed us to quantify radical formation locally in real time during capacitation. We further investigated how different inhibitors or triggers alter the radical generation. We were able to identify NOX5 as the prominent source of radical generation in capacitation while the NADH-dependent oxidoreductase of mitochondria seems to play a smaller role.

Applying NV center-based quantum sensing to study intracellular free radical response upon viral infections.

Although viruses are known to modify the free radical concentration in infected cells, the exact location and concentrations of such changes remain unknown. Although this information is important to understand the virus pathogenesis and design better anti-viral drugs or vaccines, obtaining it with the conventional free radical/ROS detection techniques is impossible. Here, we elucidate the utility of diamond magnetometry for studying the free radical response of baby hamster kidney-21 cells upon Semliki Forest virus infection. Specifically, we optically probe the alterations in free radical concentration near infectious viruses via measuring the spin-lattice relaxation (T1) of NV defect ensembles embedded in intracellular nanodiamonds. We performed measurements both at random locations as well as close to the virus entry by conjugating viruses to nanodiamond sensors. We observed alterations of T1, which represent the intracellular free radical concentration during the viral replication process. Moreover, relaxometry is also used to monitor real-time free radical variation during the early infectious process.

In vitro reconstitution reveals key intermediate states of trimer formation by the dengue virus membrane fusion protein.

The flavivirus dengue virus (DV) infects cells through a low-pH-triggered membrane fusion reaction mediated by the viral envelope protein E. E is an elongated transmembrane protein with three domains and is organized as a homodimer on the mature virus particle. During fusion, the E protein homodimer dissociates, inserts the hydrophobic fusion loop into target membranes, and refolds into a trimeric hairpin in which domain III (DIII) packs against the central trimer. It is clear that E refolding drives membrane fusion, but the steps in hairpin formation and their pH requirements are unclear. Here, we have used truncated forms of the DV E protein to reconstitute trimerization in vitro. Protein constructs containing domains I and II (DI/II) were monomeric and interacted with membranes to form core trimers. DI/II-membrane interaction and trimerization occurred efficiently at both neutral and low pH. The DI/II core trimer was relatively unstable and could be stabilized by binding exogenous DIII or by the formation of mixed trimers containing DI/II plus E protein with all three domains. The mixed trimer had unoccupied DIII interaction sites that could specifically bind exogenous DIII at either low or neutral pH. Truncated DV E proteins thus reconstitute hairpin formation and define properties of key domain interactions during DV fusion.

Different rotavirus strains enter MA104 cells through different endocytic pathways: the role of clathrin-mediated endocytosis.

Rotaviruses, the single most important agents of acute severe gastroenteritis in children, are nonenveloped viruses formed by a three-layered capsid that encloses a genome formed by 11 segments of double-stranded RNA. The mechanism of entry of these viruses into the host cell is not well understood. The best-studied strain, RRV, which is sensitive to neuraminidase (NA) treatment of the cells, uses integrins alpha2 beta1 and alphav beta3 and the heat shock protein hsc70 as receptors and enters MA104 cells through a non-clathrin-, non-caveolin-mediated pathway that depends on a functional dynamin and on the presence of cholesterol on the cell surface. In this work, using a combination of pharmacological, biochemical, and genetic approaches, we compared the entry characteristics of four rotavirus strains known to have different receptor requirements. We chose four rotavirus strains that represent all phenotypic combinations of NA resistance or sensitivity and integrin dependence or independence. We found that even though all the strains share their requirements for hsc70, dynamin, and cholesterol, three of them differ from the simian strain RRV in the endocytic pathway used. The human strain Wa, porcine strain TFR-41, and bovine strain UK seem to enter the cell through clathrin-mediated endocytosis, since treatments that inhibit this pathway block their infectivity; consistent with this entry route, these strains were sensitive to changes in the endosomal pH. The inhibition of other endocytic mechanisms, such as macropinocytosis or caveola-mediated uptake, had no effect on the internalization of the rotavirus strains tested here.

Male subfertility and oxidative stress.

To date 15% of couples are suffering from infertility with 45-50% of males being responsible. With an increase in paternal age as well as various environmental and lifestyle factors worsening these figures are expected to increase. As the so-called free radical theory of infertility suggests, free radicals or reactive oxygen species (ROS) play an essential role in this process. However, ROS also fulfill important functions for instance in sperm maturation. The aim of this review article is to discuss the role reactive oxygen species play in male fertility and how these are influenced by lifestyle, age or disease. We will further discuss how these ROS are measured and how they can be avoided during in-vitro fertilization.

Cooling as an Adjunctive Therapy to Percutaneous Intervention in Acute Myocardial Infarction: COOL-MI InCor Trial.

Endovascular Therapeutic hypothermia (ETH) reduces the damage caused by postischemia reperfusion injury syndrome in cardiopulmonary arrest and has already established its role in patients with sudden death; however, its role in ST-segment elevation myocardial infarction (STEMI) remains controversial. The objectives of this study were to investigate the safety, feasibility, and 30-day efficacy of rapid induction of therapeutic hypothermia as adjunctive therapy to percutaneous coronary intervention (PCI) in patients with anterior and inferior STEMIs. This was a prospective, controlled, randomized, two-arm, prospective, interventional study of patients admitted to the emergency department within 6 hours of angina onset, with anterior or inferior STEMI eligible for PCI. Subjects were randomized to the hypothermia group (primary PCI+ETH) or to the control group (primary PCI) at a 4:1 ratio. The ETH was induced by 1 L cold saline (1-4°C) associated with the Proteus™ System, by cooling for at least 18 minutes before coronary reperfusion with a target temperature of 32°C ± 1°C. Maintenance of ETH was conducted for 1-3 hours, and active reheating was done at a rate of 1°C/h for 4 hours. Primary safety outcomes were the feasibility of ETH in the absence of (1) door-to-balloon (DTB) delay; (2) major adverse cardiac events (MACE) within 30 days after randomization. The primary outcomes of effectiveness were infarct size (IS) and left ventricular ejection fraction (LVEF) at 30 days. An as-treated statistical analysis was performed. Fifty patients were included: 35 (70%) randomized to the hypothermia group and 15 (30%) to the control group. The mean age was 58 ± 12 years; 78% were men; and associated diseases were 60% hypertension, 42% diabetes, and 72% dyslipidemia. The compromised myocardial wall was anterior in 38% and inferior in 62%, and the culprit vessels were left anterior descending artery (LAD) (40%), right coronary artery (38%), and left circumflex (18%). All 35 patients who attempted ETH (100%) had successful cooling, with a mean endovascular coronary reperfusion temperature of 33.1°C ± 0.9°C. The mean ischemic time was 375 ± 89.4 minutes in the hypothermia group and 359.5 ± 99.4 minutes in the control group. The mean DTB was 92.1 ± 20.5 minutes in the hypothermia group and 87 ± 24.4 minutes in the control group. The absolute difference of 5.1 minutes was not statistically significant (p = 0.509). The MACE rates were similar between both groups (21.7% vs. 20% respectively, p = 0.237). In the comparison between the hypothermia and control groups, no statistically significant differences were observed at 30 days between mean IS (13.9% ± 8% vs. 13.8% ± 10.8%, respectively, p = 0.801) and mean final LVEF (43.3% ± 11.2% vs. 48.3 ± 10.9%, respectively; p = 0.194). Hypothermia as an adjunctive therapy to primary PCI in STEMI is feasible and can be implemented without delay in coronary reperfusion. Hypothermia was safe regarding the incidence of MACE at 30 days. However, there was a higher incidence of arrhythmia and in-hospital infection in the hypothermia group, with no increase in mortality. Regarding efficacy, there was no difference in IS or LVEF at 30 days that would suggest additional myocardial protection with ETH. ClinicalTrials.gov: NCT02664194.

Differential cholesterol binding by class II fusion proteins determines membrane fusion properties.

The class II fusion proteins of the alphaviruses and flaviviruses mediate virus infection by driving the fusion of the virus membrane with that of the cell. These fusion proteins are triggered by low pH, and their structures are strikingly similar in both the prefusion dimer and the postfusion homotrimer conformations. Here we have compared cholesterol interactions during membrane fusion by these two groups of viruses. Using cholesterol-depleted insect cells, we showed that fusion and infection by the alphaviruses Semliki Forest virus (SFV) and Sindbis virus were strongly promoted by cholesterol, with similar sterol dependence in laboratory and field isolates and in viruses passaged in tissue culture. The E1 fusion protein from SFV bound cholesterol, as detected by labeling with photocholesterol and by cholesterol extraction studies. In contrast, fusion and infection by numerous strains of the flavivirus dengue virus (DV) and by yellow fever virus 17D were cholesterol independent, and the DV fusion protein did not show significant cholesterol binding. SFV E1 is the first virus fusion protein demonstrated to directly bind cholesterol. Taken together, our results reveal important functional differences conferred by the cholesterol-binding properties of class II fusion proteins.

Differentiation enhances Zika virus infection of neuronal brain cells.

Zika virus (ZIKV) is an emerging, mosquito-borne pathogen associated with a widespread 2015-2016 epidemic in the Western Hemisphere and a proven cause of microcephaly and other fetal brain defects in infants born to infected mothers. ZIKV infections have been also linked to other neurological illnesses in infected adults and children, including Guillain-Barré syndrome (GBS), acute flaccid paralysis (AFP) and meningoencephalitis, but the viral pathophysiology behind those conditions remains poorly understood. Here we investigated ZIKV infectivity in neuroblastoma SH-SY5Y cells, both undifferentiated and following differentiation with retinoic acid. We found that multiple ZIKV strains, representing both the prototype African and contemporary Asian epidemic lineages, were able to replicate in SH-SY5Y cells. Differentiation with resultant expression of mature neuron markers increased infectivity in these cells, and the extent of infectivity correlated with degree of differentiation. New viral particles in infected cells were visualized by electron microscopy and found to be primarily situated inside vesicles; overt damage to the Golgi apparatus was also observed. Enhanced ZIKV infectivity in a neural cell line following differentiation may contribute to viral neuropathogenesis in the developing or mature central nervous system.