The SARS-CoV-2 virus enters host cells via an interaction between its Spike protein and the host cell receptor angiotensin converting enzyme 2 (ACE2). By screening a yeast surface-displayed library of synthetic nanobody sequences, we developed nanobodies that disrupt the interaction between Spike and ACE2. Cryogenic electron microscopy (cryo-EM) revealed that one nanobody, Nb6, binds Spike in a fully inactive conformation with its receptor binding domains (RBDs) locked into their inaccessible down-state, incapable of binding ACE2. Affinity maturation and structure-guided design of multivalency yielded a trivalent nanobody, mNb6-tri, with femtomolar affinity for Spike and picomolar neutralization of SARS-CoV-2 infection. mNb6-tri retains function after aerosolization, lyophilization, and heat treatment, which enables aerosol-mediated delivery of this potent neutralizer directly to the airway epithelia.

Zika virus (ZIKV) is a significant global health threat, as infection has been linked to serious neurological complications, including microcephaly. Using a human stem cell-derived neural progenitor model system, we find that a critical cellular quality control process called the nonsense-mediated mRNA decay (NMD) pathway is disrupted during ZIKV infection. Importantly, disruption of the NMD pathway is a known cause of microcephaly and other neurological disorders. We further identify an interaction between the capsid protein of ZIKV and up-frameshift protein 1 (UPF1), the master regulator of NMD, and show that ZIKV capsid targets UPF1 for degradation. Together, these results offer a new mechanism for how ZIKV infection can cause neuropathology in the developing brain.

In tri-trophic systems, herbivores may benefit from their host plants in fighting parasitic infections. Plants can provide parasite resistance in two contrasting ways: either directly, by interfering with the parasite, or indirectly, by increasing herbivore immunity or health. In monarch butterflies, the larval diet of milkweed strongly influences the fitness of a common protozoan parasite. Toxic secondary plant chemicals known as cardenolides correlate strongly with parasite resistance of the host, with greater cardenolide concentrations in the larval diet leading to lower parasite growth. However, milkweed cardenolides may covary with other indices of plant quality including nutrients, and a direct experimental link between cardenolides and parasite performance has not been established. To determine if the anti-parasitic activity of milkweeds is indeed due to secondary chemicals, as opposed to nutrition, we supplemented the diet of infected and uninfected monarch larvae with milkweed latex, which contains cardenolides but no nutrients. Across three experiments, increased dietary cardenolide concentrations reduced parasite growth in infected monarchs, which consequently had longer lifespans. However, uninfected monarchs showed no differences in lifespan across treatments, confirming that cardenolide-containing latex does not increase general health. Our results suggest that cardenolides are a driving force behind plant-derived resistance in this system.

Without an effective prophylactic solution, infections from SARS-CoV-2 continue to rise worldwide with devastating health and economic costs. SARS-CoV-2 gains entry into host cells via an interaction between its Spike protein and the host cell receptor angiotensin converting enzyme 2 (ACE2). Disruption of this interaction confers potent neutralization of viral entry, providing an avenue for vaccine design and for therapeutic antibodies. Here, we develop single-domain antibodies (nanobodies) that potently disrupt the interaction between the SARS-CoV-2 Spike and ACE2. By screening a yeast surface-displayed library of synthetic nanobody sequences, we identified a panel of nanobodies that bind to multiple epitopes on Spike and block ACE2 interaction via two distinct mechanisms. Cryogenic electron microscopy (cryo-EM) revealed that one exceptionally stable nanobody, Nb6, binds Spike in a fully inactive conformation with its receptor binding domains (RBDs) locked into their inaccessible down-state, incapable of binding ACE2. Affinity maturation and structure-guided design of multivalency yielded a trivalent nanobody, mNb6-tri, with femtomolar affinity for SARS-CoV-2 Spike and picomolar neutralization of SARS-CoV-2 infection. mNb6-tri retains stability and function after aerosolization, lyophilization, and heat treatment. These properties may enable aerosol-mediated delivery of this potent neutralizer directly to the airway epithelia, promising to yield a widely deployable, patient-friendly prophylactic and/or early infection therapeutic agent to stem the worst pandemic in a century.

BackgroundA major goal in the search for new anti-malarial compounds is to identify new mechanisms of action or new molecular targets. While cell-based, growth inhibition-based screening have enjoyed tremendous success, an alternative approach is to specifically assay a given pathway or essential cellular process.MethodsHere, this work describes the development of a plate-based, in vitro luciferase assay to probe for inhibitors specific to protein synthesis in Plasmodium falciparum through the use of an in vitro translation system derived from the parasite.ResultsUsing the Medicines for Malaria Venture’s Malaria Box as a pilot, 400 bioactive compounds with minimal human cytotoxicity profiles were screened, identifying eight compounds that displayed greater potency against the P. falciparum translation machinery relative to a mammalian translation system. Dose–response curves were determined in both translation systems to further characterize the top hit compound (MMV008270).ConclusionsThis assay will be useful not only in future anti-malarial screening efforts but also in the investigation of P. falciparum protein synthesis and essential processes in P. falciparum biology.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1231-8) contains supplementary material, which is available to authorized users.

This case series of patients from a Hansen's disease clinic focuses on the frequency of delays in diagnosis and of HD reactions, both known risk factors for nerve damage.

IMPORTANCE Powassan virus is a rare but increasingly recognized cause of severe neurological disease. OBJECTIVE To highlight the diagnostic challenges and neuropathological findings in a fatal case of Powassan encephalitis caused by deer tick virus (lineage II) in a patient with follicular lymphoma receiving rituximab, with nonspecific anti-GAD65 antibodies, who was initially seen with fever and orchiepididymitis. DESIGN, SETTING, AND PARTICIPANTS Comparison of clinical, radiological, histological, and laboratory findings, including immunohistochemistry, real-time polymerase chain reaction, antibody detection, and unbiased sequencing assays, in a single case report (first seen in December 2016) at an academic medical center. EXPOSURE Infection with Powassan virus. MAIN OUTCOMES AND MEASURES Results of individual assays compared retrospectively. RESULTS In a 63-year-old man with fatal Powassan encephalitis, serum and cerebrospinal fluid IgM antibodies were not detected via standard methods, likely because of rituximab exposure. Neuropathological findings were extensive, including diffuse leptomeningeal and parenchymal lymphohistiocytic infiltration, microglial proliferation, marked neuronal loss, and white matter microinfarctions most severely involving the cerebellum, thalamus, and basal ganglia. Diagnosis was made after death by 3 independent methods, including demonstration of Powassan virus antigen in brain biopsy and autopsy tissue, detection of viral RNA in serum and cerebrospinal fluid by targeted real-time polymerase chain reaction, and detection of viral RNA in cerebrospinal fluid by unbiased sequencing. Extensive testing for other etiologies yielded negative results, including mumps virus owing to prodromal orchiepididymitis. Low-titer anti-GAD65 antibodies identified in serum, suggestive of limbic encephalitis, were not detected in cerebrospinal fluid. CONCLUSIONS AND RELEVANCE Owing to the rarity of Powassan encephalitis, a high degree of suspicion is required to make the diagnosis, particularly in an immunocompromised patient, in whom antibody-based assays may be falsely negative. Unbiased sequencing assays have the potential to detect uncommon infectious agents and may prove useful in similar scenarios.

Schistosoma mansoni and other Schistosoma sp. are multicellular parasitic helminths (worms) that infect humans and mammals worldwide. Infection by these parasites, which results in developmental maturation and sexual differentiation of the worms over a period of 5–6 weeks, induces antibodies to glycan antigens expressed in surface and secreted glycoproteins and glycolipids. There is growing interest in defining these unusual parasite-synthesized glycan antigens and using them to understand immune responses, their roles in immunomodulation, and in using glycan antigens as potential vaccine targets. A key problem in this area, however, has been the lack of information about the enzymes involved in elaborating the complex repertoire of glycans represented by the schistosome glycome. Recent availability of the nuclear genome sequences for Schistosoma sp. has created the opportunity to define the glycogenome, which represents the specific genes and cognate enzymes that generate the glycome. Here we describe the current state of information in regard to the schistosome glycogenome and glycome and highlight the important classes of glycans and glycogenes that may be important in their generation.