Explore the vast range of titles available.

This winter, the circulating strain of seasonal influenza A virus (H1N1) is resistant to the neuraminidase inhibitor oseltamivir. Dr. Anne Moscona writes that the surprise element of the circulating resistant virus is its apparently spontaneous emergence since 2007. Seemingly from one influenza season to the next, we have lost the use of our leading antiviral influenza drug because of resistance. This winter, the circulating strain of seasonal influenza A virus (H1N1) is resistant to the neuraminidase inhibitor oseltamivir. Moreover, rather than emerging under selective pressure of drug use, as many antibiotic-resistant bacteria do and as has been the concern for influenza, this resistant strain seems to be a natural, spontaneously arising variant. Nevertheless, science has given us the tools with which to anticipate these events — and should allow us to develop new clinical solutions that build on . . .

Chen et al. generate lung bud organoids from human pluripotent stem cells that recapitulate early lung development, such as branching airway formation and early alveolar structures, which could potentially be used to model lung disease. Recapitulation of lung development from human pluripotent stem cells (hPSCs) in three dimensions (3D) would allow deeper insight into human development, as well as the development of innovative strategies for disease modelling, drug discovery and regenerative medicine 1 . We report here the generation from hPSCs of lung bud organoids (LBOs) that contain mesoderm and pulmonary endoderm and develop into branching airway and early alveolar structures after xenotransplantation and in Matrigel 3D culture. Expression analysis and structural features indicated that the branching structures reached the second trimester of human gestation. Infection in vitro with respiratory syncytial virus, which causes small airway obstruction and bronchiolitis in infants 2 , led to swelling, detachment and shedding of infected cells into the organoid lumens, similar to what has been observed in human lungs 3 . Introduction of mutation in HPS1, which causes an early-onset form of intractable pulmonary fibrosis 4 , 5 , led to accumulation of extracellular matrix and mesenchymal cells, suggesting the potential use of this model to recapitulate fibrotic lung disease in vitro . LBOs therefore recapitulate lung development and may provide a useful tool to model lung disease.

Despite limited genomic diversity, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has shown a wide range of clinical manifestations in different patient populations. The mechanisms behind these host differences are still unclear. Here, we examined host response gene expression across infection status, viral load, age, and sex among shotgun RNA sequencing profiles of nasopharyngeal (NP) swabs from 430 individuals with PCR-confirmed SARS-CoV-2 and 54 negative controls. SARS-CoV-2 induced a strong antiviral response with up-regulation of antiviral factors such as OAS1-3 and IFIT1-3 and T helper type 1 (Th1) chemokines CXCL9/10/11, as well as a reduction in transcription of ribosomal proteins. SARS-CoV-2 culture in human airway epithelial (HAE) cultures replicated the in vivo antiviral host response 7 days post infection, with no induction of interferon-stimulated genes after 3 days. Patient-matched longitudinal specimens (mean elapsed time = 6.3 days) demonstrated reduction in interferon-induced transcription, recovery of transcription of ribosomal proteins, and initiation of wound healing and humoral immune responses. Expression of interferon-responsive genes, including ACE2, increased as a function of viral load, while transcripts for B cell-specific proteins and neutrophil chemokines were elevated in patients with lower viral load. Older individuals had reduced expression of the Th1 chemokines CXCL9/10/11 and their cognate receptor CXCR3, as well as CD8A and granzyme B, suggesting deficiencies in trafficking and/or function of cytotoxic T cells and natural killer (NK) cells. Relative to females, males had reduced B cell-specific and NK cell-specific transcripts and an increase in inhibitors of nuclear factor kappa-B (NF-κB) signaling, possibly inappropriately throttling antiviral responses. Collectively, our data demonstrate that host responses to SARS-CoV-2 are dependent on viral load and infection time course, with observed differences due to age and sex that may contribute to disease severity.

Antiviral peptides for Nipah virus can be administered prophylactically by the respiratory route, targeted to the respiratory tract, and provide protection to hamsters and nonhuman primates from lethal infection. Abstract Background The emerging zoonotic paramyxovirus Nipah virus (NiV) causes severe respiratory and neurological disease in humans, with high fatality rates. Nipah virus can be transmitted via person-to-person contact, posing a high risk for epidemic outbreaks. However, a broadly applicable approach for human NiV outbreaks in field settings is lacking. Methods We engineered new antiviral lipopeptides and analyzed in vitro fusion inhibition to identify an optimal candidate for prophylaxis of NiV infection in the lower respiratory tract, and we assessed antiviral efficiency in 2 different animal models. Results We show that lethal NiV infection can be prevented with lipopeptides delivered via the respiratory route in both hamsters and nonhuman primates. By targeting retention of peptides for NiV prophylaxis in the respiratory tract, we avoid its systemic delivery in individuals who need only prevention, and thus we increase the safety of treatment and enhance utility of the intervention. Conclusions The experiments provide a proof of concept for the use of antifusion lipopeptides for prophylaxis of lethal NiV. These results advance the goal of rational development of potent lipopeptide inhibitors with desirable pharmacokinetic and biodistribution properties and a safe effective delivery method to target NiV and other pathogenic viruses.

Lung and airway epithelial cells generated in vitro from human pluripotent stem cells (hPSCs) have applications in regenerative medicine, modeling of lung disease, drug screening and studies of human lung development. Here, we describe a strategy for directed differentiation of hPSCs into mature lung and airway epithelial cells obtained through maturation of NKX2.1 + hPSC-derived lung progenitors in a 3D matrix of collagen I in the absence of glycogen synthase kinase 3 inhibition. This protocol is an extension of our previously published protocol on the directed differentiation of lung and airway epithelium from hPSCs that modifies the technique and offers additional applications. This protocol is conducted in defined media conditions, has a duration of 50–80 d, does not require reporter lines and results in cultures containing mature alveolar type II and I cells as well as airway basal, ciliated, club and neuroendocrine cells. We also present a flow cytometry strategy to assess maturation in the cultures. Several of these populations, including mature NGFR + basal cells, can be prospectively isolated by cell sorting and expanded for further investigation. This protocol describes how to direct differentiation of human pluripotent stem cells in a 3D matrix of collagen I to cultures containing mature alveolar type II and I cells plus airway basal, ciliated, club and neuroendocrine cells.

Paramyxoviruses including measles, Nipah, and parainfluenza viruses are public health threats with pandemic potential. Human parainfluenza virus type 3 (HPIV3) is a leading cause of illness in pediatric, older, and immunocompromised populations. There are no approved vaccines or therapeutics for HPIV3. Neutralizing monoclonal antibodies (mAbs) that target viral fusion are a potential strategy for mitigating paramyxovirus infection, however their utility may be curtailed by viral evolution that leads to resistance. Paramyxoviruses enter cells by fusing with the cell membrane in a process mediated by a complex consisting of a receptor binding protein (HN) and a fusion protein (F). Existing atomic resolution structures fail to reveal physiologically relevant interactions during viral entry. We present cryo-ET structures of pre-fusion HN-F complexes in situ on surfaces of virions that evolved resistance to an anti-HPIV3 F neutralizing mAb. Single mutations in F abolish mAb binding and neutralization. In these complexes, the HN protein that normally restrains F triggering has shifted to uncap the F apex. These complexes are more readily triggered to fuse. These structures shed light on the adaptability of the pre-fusion HN-F complex and mechanisms of paramyxoviral resistance to mAbs, and help define potential barriers to resistance for the design of mAbs. Monoclonal antibodies hold promise for combating serious respiratory virus infections but viruses may evolve to evade them. Here, using structural analysis, the authors show how human parainfluenza virus adapts to escape a powerful antibody by modulating its cell entry mechanism.

Infection by human parainfluenza viruses (HPIVs) causes widespread lower respiratory diseases, including croup, bronchiolitis, and pneumonia, and there are no vaccines or effective treatments for these viruses. HPIV3 is a member of the Respirovirus species of the Paramyxoviridae family. These viruses are pleomorphic, enveloped viruses with genomes composed of single-stranded negative-sense RNA. During viral entry, the first step of infection, the viral fusion complex, comprised of the receptor-binding glycoprotein hemagglutinin-neuraminidase (HN) and the fusion glycoprotein (F), mediates fusion upon receptor binding. The HPIV3 transmembrane protein HN, like the receptor-binding proteins of other related viruses that enter host cells using membrane fusion, binds to a receptor molecule on the host cell plasma membrane, which triggers the F glycoprotein to undergo major conformational rearrangements, promoting viral entry. Subsequent fusion of the viral and host membranes allows delivery of the viral genetic material into the host cell. The intermediate states in viral entry are transient and thermodynamically unstable, making it impossible to understand these transitions using standard methods, yet understanding these transition states is important for expanding our knowledge of the viral entry process. In this study, we use cryo-electron tomography (cryo-ET) to dissect the stepwise process by which the receptor-binding protein triggers F-mediated fusion, when forming a complex with receptor-bearing membranes. Using an on-grid antibody capture method that facilitates examination of fresh, biologically active strains of virus directly from supernatant fluids and a series of biological tools that permit the capture of intermediate states in the fusion process, we visualize the series of events that occur when a pristine, authentic viral particle interacts with target receptors and proceeds from the viral entry steps of receptor engagement to membrane fusion.

This article considers neuraminidase inhibitors, which are active against influenza virus and are crucial to planning for an influenza pandemic from a new influenza virus of any origin, including avian influenza. Neuraminidase inhibitors are active against influenza virus and are crucial to planning for an influenza pandemic from a new influenza virus of any origin, including avian influenza. The impact of influenza infection is felt globally each year when the disease develops in approximately 20 percent of the world's population. In the United States, influenza infections occur in epidemics each winter, generally between late December and early March. Recent events, including human cases of avian influenza, have heightened awareness of the threat of a pandemic and have spurred efforts to develop plans for its control. Although vaccination is the primary strategy for the prevention of influenza, there are a number of likely scenarios for which vaccination is inadequate and effective antiviral agents would be of the utmost importance. . . .

SARS-CoV-2, the causative agent of COVID-19, continues to spread globally, placing strain on health care systems and resulting in rapidly increasing numbers of cases and mortalities. Despite the growing need for medical intervention, no FDA-approved vaccines are yet available, and treatment has been limited to supportive therapy for the alleviation of symptoms. Entry inhibitors could fill the important role of preventing initial infection and preventing spread. Here, we describe the design, synthesis, and evaluation of a lipopeptide that is derived from the HRC domain of the SARS-CoV-2 S glycoprotein that potently inhibits fusion mediated by SARS-CoV-2 S glycoprotein and blocks infection by live SARS-CoV-2 in both cell monolayers ( in vitro ) and human airway tissues ( ex vivo ). Our results highlight the SARS-CoV-2 HRC-derived lipopeptide as a promising therapeutic candidate for SARS-CoV-2 infections. The emergence of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), the etiological agent of the 2019 coronavirus disease (COVID-19), has erupted into a global pandemic that has led to tens of millions of infections and hundreds of thousands of deaths worldwide. The development of therapeutics to treat infection or as prophylactics to halt viral transmission and spread is urgently needed. SARS-CoV-2 relies on structural rearrangements within a spike (S) glycoprotein to mediate fusion of the viral and host cell membranes. Here, we describe the development of a lipopeptide that is derived from the C-terminal heptad repeat (HRC) domain of SARS-CoV-2 S that potently inhibits infection by SARS-CoV-2. The lipopeptide inhibits cell-cell fusion mediated by SARS-CoV-2 S and blocks infection by live SARS-CoV-2 in Vero E6 cell monolayers more effectively than previously described lipopeptides. The SARS-CoV-2 lipopeptide exhibits broad-spectrum activity by inhibiting cell-cell fusion mediated by SARS-CoV-1 and Middle East respiratory syndrome coronavirus (MERS-CoV) and blocking infection by live MERS-CoV in cell monolayers. We also show that the SARS-CoV-2 HRC-derived lipopeptide potently blocks the spread of SARS-CoV-2 in human airway epithelial (HAE) cultures, an ex vivo model designed to mimic respiratory viral propagation in humans. While viral spread of SARS-CoV-2 infection was widespread in untreated airways, those treated with SARS-CoV-2 HRC lipopeptide showed no detectable evidence of viral spread. These data provide a framework for the development of peptide therapeutics for the treatment of or prophylaxis against SARS-CoV-2 as well as other coronaviruses. IMPORTANCE SARS-CoV-2, the causative agent of COVID-19, continues to spread globally, placing strain on health care systems and resulting in rapidly increasing numbers of cases and mortalities. Despite the growing need for medical intervention, no FDA-approved vaccines are yet available, and treatment has been limited to supportive therapy for the alleviation of symptoms. Entry inhibitors could fill the important role of preventing initial infection and preventing spread. Here, we describe the design, synthesis, and evaluation of a lipopeptide that is derived from the HRC domain of the SARS-CoV-2 S glycoprotein that potently inhibits fusion mediated by SARS-CoV-2 S glycoprotein and blocks infection by live SARS-CoV-2 in both cell monolayers ( in vitro ) and human airway tissues ( ex vivo ). Our results highlight the SARS-CoV-2 HRC-derived lipopeptide as a promising therapeutic candidate for SARS-CoV-2 infections.

Enveloped viruses cause a wide range of diseases in humans. At the first step of infection, these viruses must fuse their envelope with a cell membrane to initiate infection. This fusion is mediated by viral proteins that require a critical activating cleavage event. It was previously thought that for parainfluenza virus 3, an important cause of respiratory disease and a representative of a group of important pathogens, this cleavage event was mediated by furin in the cell secretory pathways prior to formation of the virions. We show that this is only true for laboratory strain viruses, and that clinical viruses that infect humans utilize extracellular proteases that are only made by a small subset of cells. These results highlight the importance of studying authentic clinical viruses that infect human tissues for understanding natural infection.