An additional copy of the β-amyloid precursor protein (APP) gene causes early-onset Alzheimer's disease (AD) in trisomy 21 (DS). Endosome dysfunction develops very early in DS and AD and has been ...implicated in the mechanism of neurodegeneration. Here, we show that morphological and functional endocytic abnormalities in fibroblasts from individuals with DS are reversed by lowering the expression of APP or β-APP-cleaving enzyme 1 (BACE-1) using short hairpin RNA constructs. By contrast, endosomal pathology can be induced in normal disomic (2N) fibroblasts by overexpressing APP or the C-terminal APP fragment generated by BACE-1 (βCTF), all of which elevate the levels of βCTFs. Expression of a mutant form of APP that cannot undergo β-cleavage had no effect on endosomes. Pharmacological inhibition of APP γ-secretase, which markedly reduced Aβ production but raised βCTF levels, also induced AD-like endosome dysfunction in 2N fibroblasts and worsened this pathology in DS fibroblasts. These findings strongly implicate APP and the βCTF of APP, and exclude Aβ and the αCTF, as the cause of endocytic pathway dysfunction in DS and AD, underscoring the potential multifaceted value of BACE-1 inhibition in AD therapeutics.
Despite the success of potent anti-retroviral drugs in controlling human immunodeficiency virus type 1 (HIV-1) infection, little progress has been made in generating an effective HIV-1 vaccine. ...Although passive transfer of anti-HIV-1 broadly neutralizing antibodies can protect mice or macaques against a single high-dose challenge with HIV or simian/human (SIV/HIV) chimaeric viruses (SHIVs) respectively, the long-term efficacy of a passive antibody transfer approach for HIV-1 has not been examined. Here we show, on the basis of the relatively long-term protection conferred by hepatitis A immune globulin, the efficacy of a single injection (20 mg kg(-1)) of four anti-HIV-1-neutralizing monoclonal antibodies (VRC01, VRC01-LS, 3BNC117, and 10-1074 (refs 9 - 12)) in blocking repeated weekly low-dose virus challenges of the clade B SHIVAD8. Compared with control animals, which required two to six challenges (median = 3) for infection, a single broadly neutralizing antibody infusion prevented virus acquisition for up to 23 weekly challenges. This effect depended on antibody potency and half-life. The highest levels of plasma-neutralizing activity and, correspondingly, the longest protection were found in monkeys administered the more potent antibodies 3BNC117 and 10-1074 (median = 13 and 12.5 weeks, respectively). VRC01, which showed lower plasma-neutralizing activity, protected for a shorter time (median = 8 weeks). The introduction of a mutation that extends antibody half-life into the crystallizable fragment (Fc) domain of VRC01 increased median protection from 8 to 14.5 weeks. If administered to populations at high risk of HIV-1 transmission, such an immunoprophylaxis regimen could have a major impact on virus transmission.
An mRNA Vaccine against SARS-CoV-2 - Preliminary Report Jackson, Lisa A; Anderson, Evan J; Rouphael, Nadine G ...
New England journal of medicine/The New England journal of medicine,
11/2020, Volume:
383, Issue:
20
Journal Article
Peer reviewed
Open access
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in late 2019 and spread globally, prompting an international effort to accelerate development of a vaccine. The candidate ...vaccine mRNA-1273 encodes the stabilized prefusion SARS-CoV-2 spike protein.
We conducted a phase 1, dose-escalation, open-label trial including 45 healthy adults, 18 to 55 years of age, who received two vaccinations, 28 days apart, with mRNA-1273 in a dose of 25 μg, 100 μg, or 250 μg. There were 15 participants in each dose group.
After the first vaccination, antibody responses were higher with higher dose (day 29 enzyme-linked immunosorbent assay anti-S-2P antibody geometric mean titer GMT, 40,227 in the 25-μg group, 109,209 in the 100-μg group, and 213,526 in the 250-μg group). After the second vaccination, the titers increased (day 57 GMT, 299,751, 782,719, and 1,192,154, respectively). After the second vaccination, serum-neutralizing activity was detected by two methods in all participants evaluated, with values generally similar to those in the upper half of the distribution of a panel of control convalescent serum specimens. Solicited adverse events that occurred in more than half the participants included fatigue, chills, headache, myalgia, and pain at the injection site. Systemic adverse events were more common after the second vaccination, particularly with the highest dose, and three participants (21%) in the 250-μg dose group reported one or more severe adverse events.
The mRNA-1273 vaccine induced anti-SARS-CoV-2 immune responses in all participants, and no trial-limiting safety concerns were identified. These findings support further development of this vaccine. (Funded by the National Institute of Allergy and Infectious Diseases and others; mRNA-1273 ClinicalTrials.gov number, NCT04283461).
Testing of vaccine candidates to prevent infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in an older population is important, since increased incidences of illness and ...death from coronavirus disease 2019 (Covid-19) have been associated with an older age.
We conducted a phase 1, dose-escalation, open-label trial of a messenger RNA vaccine, mRNA-1273, which encodes the stabilized prefusion SARS-CoV-2 spike protein (S-2P) in healthy adults. The trial was expanded to include 40 older adults, who were stratified according to age (56 to 70 years or ≥71 years). All the participants were assigned sequentially to receive two doses of either 25 μg or 100 μg of vaccine administered 28 days apart.
Solicited adverse events were predominantly mild or moderate in severity and most frequently included fatigue, chills, headache, myalgia, and pain at the injection site. Such adverse events were dose-dependent and were more common after the second immunization. Binding-antibody responses increased rapidly after the first immunization. By day 57, among the participants who received the 25-μg dose, the anti-S-2P geometric mean titer (GMT) was 323,945 among those between the ages of 56 and 70 years and 1,128,391 among those who were 71 years of age or older; among the participants who received the 100-μg dose, the GMT in the two age subgroups was 1,183,066 and 3,638,522, respectively. After the second immunization, serum neutralizing activity was detected in all the participants by multiple methods. Binding- and neutralizing-antibody responses appeared to be similar to those previously reported among vaccine recipients between the ages of 18 and 55 years and were above the median of a panel of controls who had donated convalescent serum. The vaccine elicited a strong CD4 cytokine response involving type 1 helper T cells.
In this small study involving older adults, adverse events associated with the mRNA-1273 vaccine were mainly mild or moderate. The 100-μg dose induced higher binding- and neutralizing-antibody titers than the 25-μg dose, which supports the use of the 100-μg dose in a phase 3 vaccine trial. (Funded by the National Institute of Allergy and Infectious Diseases and others; mRNA-1273 Study ClinicalTrials.gov number, NCT04283461.).
Antibody VRC01 is a human immunoglobulin that neutralizes about 90% of HIV-1 isolates. To understand how such broadly neutralizing antibodies develop, we used x-ray crystallography and 454 ...pyrosequencing to characterize additional VRC01-like antibodies from HIV-1—infected individuals. Crystal structures revealed a convergent mode of binding for diverse antibodies to the same CD4-binding-site epitope. A functional genomics analysis of expressed heavy and light chains revealed common pathways of antibody-heavy chain maturation, confined to the IGHV1-2*02 lineage, involving dozens of somatic changes, and capable of pairing with different light chains. Broadly neutralizing HIV-1 immunity associated with VRC01-like antibodies thus involves the evolution of antibodies to a highly affinity-matured state required to recognize an invariant viral structure, with lineages defined from thousands of sequences providing a genetic roadmap of their development.
To protect against human immunodeficiency virus (HIV-1) infection, broadly neutralizing antibodies (bnAbs) must be active at the portals of viral entry in the gastrointestinal or cervicovaginal ...tracts. The localization and persistence of antibodies at these sites is influenced by the neonatal Fc receptor (FcRn), whose role in protecting against infection in vivo has not been defined. Here, we show that a bnAb with enhanced FcRn binding has increased gut mucosal tissue localization, which improves protection against lentiviral infection in non-human primates. A bnAb directed to the CD4-binding site of the HIV-1 envelope (Env) protein (denoted VRC01) was modified by site-directed mutagenesis to increase its binding affinity for FcRn. This enhanced FcRn-binding mutant bnAb, denoted VRC01-LS, displayed increased transcytosis across human FcRn-expressing cellular monolayers in vitro while retaining FcγRIIIa binding and function, including antibody-dependent cell-mediated cytotoxicity (ADCC) activity, at levels similar to VRC01 (the wild type). VRC01-LS had a threefold longer serum half-life than VRC01 in non-human primates and persisted in the rectal mucosa even when it was no longer detectable in the serum. Notably, VRC01-LS mediated protection superior to that afforded by VRC01 against intrarectal infection with simian-human immunodeficiency virus (SHIV). These findings suggest that modification of FcRn binding provides a mechanism not only to increase serum half-life but also to enhance mucosal localization that confers immune protection. Mutations that enhance FcRn function could therefore increase the potency and durability of passive immunization strategies to prevent HIV-1 infection.
Cross-reactive neutralizing antibodies (NAbs) are found in the sera of many HIV-1-infected individuals, but the virologic basis of their neutralization remains poorly understood. We used knowledge of ...HIV-1 envelope structure to develop antigenically resurfaced glycoproteins specific for the structurally conserved site of initial CD4 receptor binding. These probes were used to identify sera with NAbs to the CD4-binding site (CD4bs) and to isolate individual B cells from such an HIV-1-infected donor. By expressing immunoglobulin genes from individual cells, we identified three monoclonal antibodies, including a pair of somatic variants that neutralized over 90% of circulating HIV-1 isolates. Exceptionally broad HIV-1 neutralization can be achieved with individual antibodies targeted to the functionally conserved CD4bs of glycoprotein 120, an important insight for future HIV-1 vaccine design.
HIV-1 infection depends on effective viral entry mediated by the interaction of its envelope (Env) glycoprotein with specific cell surface receptors. Protective antiviral antibodies generated by ...passive or active immunization must prevent these interactions. Because the HIV-1 Env is highly variable, attention has also focused on blocking the HIV-1 primary cell receptor CD4. We therefore analyzed the in vivo protective efficacy of three potent neutralizing monoclonal antibodies (mAbs) to HIV-1 Env compared to an antibody against the CD4 receptor. Protection was assessed after mucosal challenge of rhesus macaques with simian/HIV (SHIV). Despite its comparable or greater neutralization potency in vitro, the anti-CD4 antibody did not provide effective protection in vivo, whereas the HIV-1-specific mAbs VRC01, 10E8, and PG9, targeting the CD4 binding site, membrane-proximal, and V1V2 glycan Env regions, respectively, conferred complete protection, albeit at different relative potencies. These findings demonstrate the protective efficacy of broadly neutralizing antibodies directed to the HIV-1 Env and suggest that targeting the HIV-1 Env is preferable to the cell surface receptor CD4 for the prevention of HIV-1 transmission.
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