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Antibodies are a principal determinant of immunity for most RNA viruses and have promise to reduce infection or disease during major epidemics. The novel coronavirus SARS-CoV-2 has caused a global pandemic with millions of infections and hundreds of thousands of deaths to date.sup.1,2. In response, we used a rapid antibody discovery platform to isolate hundreds of human monoclonal antibodies (mAbs) against the SARS-CoV-2 spike (S) protein. We stratify these mAbs into five major classes on the basis of their reactivity to subdomains of S protein as well as their cross-reactivity to SARS-CoV. Many of these mAbs inhibit infection of authentic SARS-CoV-2 virus, with most neutralizing mAbs recognizing the receptor-binding domain (RBD) of S. This work defines sites of vulnerability on SARS-CoV-2 S and demonstrates the speed and robustness of advanced antibody discovery platforms. A platform for rapid antibody discovery enabled the isolation of hundreds of human monoclonal antibodies against SARS-CoV-2 and the prioritization of potent antibody candidates for clinical trials in patients with COVID-19., Author(s): Seth J. Zost [sup.1] , Pavlo Gilchuk [sup.1] , Rita E. Chen [sup.2] [sup.3] , James Brett Case [sup.3] , Joseph X. Reidy [sup.1] , Andrew Trivette [sup.1] , [...]

Although broadly protective, stem-targeted Abs against the Influenza A virus hemagglutinin (HA) have been well studied, very limited information is available on Abs that broadly recognize the head domain. We determined the crystal structure of the HA protein of the avian H7N9 influenza virus in complex with a pan-H7, non-neutralizing, protective human Ab. The structure revealed a B cell epitope in the HA head domain trimer interface (TI). This discovery of a second major protective TI epitope supports a model in which uncleaved HA trimers exist on the surface of infected cells in a highly dynamic state that exposes hidden HA head domain features., Introduction Avian influenza A virus (IAV) H7N9 strains have caused several outbreaks in humans, with high morbidity and mortality. The potential for H7N9 viruses to acquire the capacity for human-to-human [...]

A prophylactic hepatitis C virus (HCV) vaccine that elicits neutralizing antibodies could be key to HCV eradication. However, the genetic and antigenic properties of HCV envelope (E1E2) proteins capable of inducing anti-HCV broadly neutralizing antibodies (bNAbs) in humans have not been defined. Here, we investigated the development of bNAbs in longitudinal plasma of HCV-infected persons with persistent infection or spontaneous clearance of multiple reinfections. By measuring plasma antibody neutralization of a heterologous virus panel, we found that the breadth and potency of the antibody response increased upon exposure to multiple genetically distinct infections and with longer duration of viremia. Greater genetic divergence between infecting strains was not associated with enhanced neutralizing breadth. Rather, repeated exposure to antigenically related, antibody-sensitive E1E2s was associated with potent bNAb induction. These data reveal that a prime-boost vaccine strategy with genetically distinct, antibody-sensitive viruses is a promising approach to inducing potent bNAbs in humans., Introduction An estimated 71 million people are infected with hepatitis C virus (HCV) worldwide (1). Given the largely asymptomatic nature of this disease, only a fraction of the HCV-infected population [...]

The protective human antibody response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) focuses on the spike (S) protein, which decorates the virion surface and mediates cell binding and entry. Most SARS-CoV-2 protective antibodies target the receptor-binding domain or a single dominant epitope ('supersite') on the N-terminal domain (NTD). Using the single B cell technology called linking B cell receptor to antigen specificity through sequencing (LIBRASeq), we isolated a large panel of NTD-reactive and SARS-CoV-2-neutralizing antibodies from an individual who had recovered from COVID-19. We found that neutralizing antibodies against the NTD supersite were commonly encoded by the IGHV1-24 gene, forming a genetic cluster representing a public B cell clonotype. However, we also discovered a rare human antibody, COV23434, that recognizes a site of vulnerability on the SARS-CoV-2 S protein in the trimer interface (TI) and possesses a distinct class of functional activity. COV2-3434 disrupted the integrity of S protein trimers, inhibited the cell-to-cell spread of the virus in culture, and conferred protection in human angiotensin-converting enzyme 2-transgenic (ACE2-transgenic) mice against the SARS-CoV-2 challenge. This study provides insight into antibody targeting of the S protein TI region, suggesting this region may be a site of virus vulnerability., Introduction During the COVID-19 pandemic, more than 150 vaccine candidates were developed, but only a few have been licensed. Most licensed vaccines encode the full-length spike (S) protein, including 2 [...]

A vaccine for hepatitis C virus (HCV) is urgently needed. Development of broadly neutralizing plasma antibodies during acute infection is associated with HCV clearance, but the viral epitopes of these plasma antibodies are unknown. Identifying these epitopes could define the specificity and function of neutralizing antibodies (NAbs) that should be induced by a vaccine. Here, we present the development and application of a high-throughput method that deconvolutes polyclonal anti-HCV NAbs in plasma, delineating the epitope specificities of anti-HCV NAbs in acute-infection plasma of 44 humans with subsequent clearance or persistence of HCV. Remarkably, we identified multiple broadly neutralizing antibody combinations that were associated with greater plasma neutralizing breadth and with HCV clearance. These studies have the potential to inform new strategies for vaccine development by identifying broadly neutralizing antibody combinations in plasma associated with the natural clearance of HCV, while also providing a high-throughput assay that could identify these responses after vaccination trials., Introduction A vaccine to prevent hepatitis C virus (HCV) infection is urgently needed. Although recently developed direct-acting antivirals are highly effective for HCV treatment, most individuals are unaware of their [...]

Broadly reactive antibodies targeting the influenza A virus hemagglutinin (HA) head domain are thought to be rare and to require extensive somatic mutations or unusual structural features to achieve breadth against divergent HA subtypes. Here we describe common genetic and structural features of protective human antibodies from several individuals recognizing the trimer interface (TI) of the influenza A HA head, a recently identified site of vulnerability. We examined the sequence of Tl-reactive antibodies, determined crystal structures for TI antibody-antigen complexes, and analyzed the contact residues of the antibodies on HA to discover common genetic and structural features of TI antibodies. Our data reveal that many TI antibodies are encoded by a light chain variable gene segment incorporating a shared somatic mutation. In addition, these antibodies have a shared acidic residue in the heavy chain despite originating from diverse heavy chain variable gene segments. These studies show that the TI region of influenza A HA is a major antigenic site with conserved structural features that are recognized by a common human B cell public clonotype. The canonical nature of this antibody-antigen interaction suggests that the TI epitope might serve as an important target for structure-based vaccine design., Introduction Influenza A virus (IAV) is one of the most common causes of severe lower respiratory illness in humans and exhibits a wide antigenic diversity in circulating field strains. Seasonal [...]

Author(s): Gopal Sapparapu [1, 2]; Estefania Fernandez [3]; Nurgun Kose [2]; Bin Cao [4]; Julie M. Fox [5]; Robin G. Bombardi [2]; Haiyan Zhao [3]; Christopher A. Nelson [3]; Aubrey [...]

Several HIV envelope-targeting (Env-targeting) antibodies with broad and potent neutralizing activity have been Identified and shown to have unusual features. Of these, the PG9 antibody has a long heavy chain complementarity determining region 3 (HCDR3) and possesses unique structural elements that interact with protein and glycan features of the HIV Env glycoprotein. Here, we used the Rosetta software suite to design variants of the PG9 antibody HCDR3 loop with the goal of identifying variants with increased potency and breadth of neutralization for diverse HIV strains. One variant, designated [PG9_N100.sub.F]Y, possessed increased potency and was able to neutralize a diverse set of PG9- resistant HIV strains, including those lacking the Env N160 glycan, which is critical for PG9 binding. An atomic resolution structure of the [PG9_N100.sub.F]Y fragment antigen binding (Fab) confirmed that the mutated residue retains the paratope surface when compared with WT PG9. Differential scanning calorimetry experiments revealed that the mutation caused a modest increase in thermodynamic stability of the Fab, a feature predicted by the computational model. Our findings suggest that thermodynamic stabilization of the long HCDR3 in its active conformation is responsible for the increased potency of [PG9_N100.sub.F]Y, and strategies aimed at stabilizing this region in other HIV antibodies could become an important approach to in silico optimization of antibodies., Introduction Recent studies have described the isolation of a number of human mAbs directed to the HIV envelope (Env) that exhibit broad and potent neutralizing activity, many of which exhibit [...]

The 2009 H1N1 swine flu is the first influenza pandemic in decades. The crystal structure of the hemagglutinin from the A/California/04/2009 H1N1 virus shows that its antigenic structure, particularly within the Sa antigenic site, is extreme[y similar to those of human H1N1 viruses circulating early in the 20th century. The cocrystal structure of the 1918 hemagglutinin with 2D1, an antibody from a survivor of the 1918 Spanish flu that neutralizes both 1918 and 2009 H1N1 viruses, reveals an epitope that is conserved in both pandemic viruses. Thus, antigenic similarity between the 2009 and 1918-like viruses provides an explanation for the age-related immunity to the current influenza pandemic. 10.1126/science.1186430

Respiratory syncytial virus (RSV) infects polarized epithelia, which have tightly regulated trafficking because of the separation and maintenance of the apical and basolateral membranes. Previously we established a link between the apical recycling endosome (ARE) and the assembly of RSV. The current studies tested the role of a major ARE-associated protein, Rab11 family interacting protein 2 (FIP2) in the virus life cycle. A dominant-negative form of FIP2 lacking its N-terminal C2 domain reduced the supernatant-associated RSV titer 1,000-fold and also caused the cell-associated virus titer to increase. These data suggested that the FIP2 C2 mutant caused a failure at the final budding step in the virus life cycle. Additionally, truncation of the Rab-binding domain from FIP2 caused its accumulation into mature filamentous virions. RSV budding was independent of the ESCRT machinery, the only well-defined budding mechanism for enveloped RNA viruses. Therefore, RSV uses a virus budding mechanism that is controlled by FIP2. Pneumovirinae | Rab11 protein | virus replication | virus shedding

A double-blind, randomized controlled trial was conducted to compare the vaccination success rate and the reaction profile of various Aventis Pasteur smallpox vaccine (APSV). ASPV was found as an effective vaccine even at diluted doses allowing for expansion of the current stockpile while, reactogenicity was found not reduced with dilution of the vaccine and as with other smallpox vaccine may impair daily activities.

Human metapneumovirus may cause up to 15% of all upper respiratory tract infections and 12% of all lower respiratory tract infections in young children, according to a study of 321 children. It can cause pneumonia, croup, an asthma exacerbation, and a lung inflammation called bronchiolitis. Human metapneumovirus was first identified in 2001.

Respiratory syncytial virus (RSV) is the major viral cause of serious lower respiratory tract illness in infants and young children worldwide. RSV infection is limited to the superficial layers of the respiratory epithelium in immunocompetent individuals. Consistent with this in vivo observation, we and others have found that RSV buds preferentially from the apical surface of infected polarized epithelial cells. In contrast, directional budding is not observed in nonpolarized human epithelial cells. These findings suggest that RSV uses specific cellular trafficking pathways to accomplish viral replication. The host cell proteins that regulate directional budding of RSV are undefined. Apical sorting of cellular proteins in polarized epithelial cells involves the apical recycling endosome (ARE). To investigate whether ARE-mediated protein sorting plays a role during RSV replication, we expressed a fragment of the myosin Vb tail that functions as a dominant negative inhibitor of ARE-mediated protein sorting in polarized Madin-Darby canine kidney cells. When these cells were infected with RSV, a >9,000-fold reduction in viral yield was observed. A similar effect on virus replication was observed when a carboxyl-terminal fragment of another ARE-associated protein, the Rab11 family interacting protein 1, was expressed in Madin-Darby canine kidney cells. These data suggest that RSV requires proper ARE-mediated protein sorting for efficient egress from the apical surface of polarized epithelial cells.

The fusion glycoproteins of human respiratory syncytial virus (RSV) and human parainfluenza virus type-3 (PIV-3) mediate virus entry and syncytium formation. Interaction between the fusion protein of RSV and RhoA, a small GTPase, facilitates virus-induced syncytium formation. We show here a RhoA-derived peptide inhibits RSV and syncytium formation induced by RSV and PIV-3, both in vitro by inhibition of cell-to-cell fusion and in vivo by reduction of peak titer by 2 log[sub.10] in RSV-infected mice. These findings indicate that the interaction between these two paramyxovirus fusion proteins and RhoA is an important target for new antiviral strategies., Author(s): Manoj K. Pastey [1]; Tara L. Gower [2]; Paul W. Spearman [2, 3]; James E. Crowe, Jr. [2, 3]; Barney S. Graham (corresponding author) [1, 2] Human respiratory syncytial [...]

Therapeutic efficacy is evident for recombinant human respiratory syncytical virus (RSV) monoclonal antibody Fab upon direct introduction into the lungs of mice infected with RSV. Treatment of RSV disease and diseases induced by other viruses, where replication in vivo is restricted to the lumenal lining of the respiratory tract, can benefit from human monoclonal Fabs grown in Escherichia coli.

A combinatorial antibody library wasscreened for Fab fragments for the cross-reactive F glycoprotein of respiratorysyncytial virus (RSV). The antibody library yielded 30 clones of which 28 showed clear reactivity with the F glycoprotein. One of these neutralized a wide range of virus isolates at high efficiency. These human Fab fragments willbe useful for the care and treatment of RSV infections of the lower respiratorytract.