ORCID Profile
0000-0003-2496-9724
Current Organisation
Vanderbilt University Medical Center
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Publisher: Proceedings of the National Academy of Sciences
Date: 04-03-2013
Abstract: Rapid antigenic variation of HA, the major virion surface protein of influenza A virus, remains the principal challenge to the development of broader and more effective vaccines. Some regions of HA, such as the stem region proximal to the viral membrane, are nevertheless highly conserved across strains and among most subtypes. A fundamental question in vaccine design is the extent to which HA stem regions on the surface of the virus are accessible to broadly neutralizing antibodies. Here we report 3D structures derived from cryoelectron tomography of HA on intact 2009 H1N1 pandemic virions in the presence and absence of the antibody C179, which neutralizes viruses expressing a broad range of HA subtypes, including H1, H2, H5, H6, and H9. By fitting previously derived crystallographic structures of trimeric HA into the density maps, we deduced the locations of the molecular surfaces of HA involved in interaction with C179. Using computational methods to distinguish in idual unliganded HA trimers from those that have bound C179 antibody, we demonstrate that ∼75% of HA trimers on the surface of the virus have C179 bound to the stem domain. Thus, despite their close packing on the viral membrane, the majority of HA trimers on intact virions are available to bind anti-stem antibodies that target conserved HA epitopes, establishing the feasibility of universal influenza vaccines that elicit such antibodies.
Publisher: American Society for Microbiology
Date: 15-02-2016
DOI: 10.1128/JVI.02418-15
Abstract: In August 2014, an outbreak of enterovirus D68 (EV-D68) occurred in North America, causing severe respiratory disease in children. Due to a lack of complete genome sequence data, there is only a limited understanding of the molecular evolution and epidemiology of EV-D68 during this outbreak, and it is uncertain whether the differing clinical manifestations of EV-D68 infection are associated with specific viral lineages. We developed a high-throughput complete genome sequencing pipeline for EV-D68 that produced a total of 59 complete genomes from respiratory s les with a 95% success rate, including 57 genomes from Kansas City, MO, collected during the 2014 outbreak. With these data in hand, we performed phylogenetic analyses of complete genome and VP1 capsid protein sequences. Notably, we observed considerable genetic ersity among EV-D68 isolates in Kansas City, manifest as phylogenetically distinct lineages, indicative of multiple introductions of this virus into the city. In addition, we identified an intersubclade recombination event within EV-D68, the first recombinant in this virus reported to date. Finally, we found no significant association between EV-D68 genetic variation, either lineages or in idual mutations, and a variety of demographic and clinical variables, suggesting that host factors likely play a major role in determining disease severity. Overall, our study revealed the complex pattern of viral evolution within a single geographic locality during a single outbreak, which has implications for the design of effective intervention and prevention strategies. IMPORTANCE Until recently, EV-D68 was considered to be an uncommon human pathogen, associated with mild respiratory illness. However, in 2014 EV-D68 was responsible for more than 1,000 disease cases in North America, including severe respiratory illness in children and acute flaccid myelitis, raising concerns about its potential impact on public health. Despite the emergence of EV-D68, a lack of full-length genome sequences means that little is known about the molecular evolution of this virus within a single geographic locality during a single outbreak. Here, we doubled the number of publicly available complete genome sequences of EV-D68 by performing high-throughput next-generation sequencing, characterized the evolutionary history of this outbreak in detail, identified a recombination event, and investigated whether there was any correlation between the demographic and clinical characteristics of the patients and the viral variant that infected them. Overall, these results will help inform the design of intervention strategies for EV-D68.
Publisher: Centers for Disease Control and Prevention (CDC)
Date: 04-2017
Publisher: American Society for Microbiology
Date: 02-07-2012
Abstract: In 2009, a novel H1N1 influenza A virus (2009 pH1N1) emerged and caused a pandemic. A human monoclonal antibody (hMAb EM4C04), highly specific for the 2009 pH1N1 virus hemagglutinin (HA), was isolated from a severely ill 2009 pH1N1 virus-infected patient. We postulated that under immune pressure with EM4C04, the 2009 pH1N1 virus would undergo antigenic drift and mutate at sites that would identify the antibody binding site. To do so, we infected MDCK cells in the presence of EM4C04 and generated 11 escape mutants, displaying 7 distinct amino acid substitutions in the HA. Six substitutions greatly reduced MAb binding (K123N, D131E, K133T, G134S, K157N, and G158E). Residues 131, 133, and 134 are contiguous with residues 157 and 158 in the globular domain structure and contribute to a novel pH1N1 antibody epitope. One mutation near the receptor binding site, S186P, increased the binding affinity of the HA to the receptor. 186P and 131E are present in the highly virulent 1918 virus HA and were recently identified as virulence determinants in a mouse-passaged pH1N1 virus. We found that pH1N1 escape variants expressing these substitutions enhanced replication and lethality in mice compared to wild-type 2009 pH1N1 virus. The increased virulence of these viruses was associated with an increased affinity for α2,3 sialic acid receptors. Our study demonstrates that antibody pressure by an hMAb targeting a novel epitope in the Sa region of 2009 pH1N1 HA is able to inadvertently drive the development of a more virulent virus with altered receptor binding properties. This broadens our understanding of antigenic drift. IMPORTANCE Influenza viruses accumulate amino acid substitutions to evade the antibody response in a process known as antigenic drift, making it necessary to vaccinate against influenza annually. Mapping human monoclonal antibody (hMAb) epitopes is a necessary step towards understanding antigenic drift in humans. We defined the specificity of an hMAb that specifically targeted the 2009 pH1N1 virus and describe a novel epitope. In addition, we identified a previously unappreciated potential for antibody escape to enhance the pathogenicity of a virus. The escape mutation that we identified with in vitro immune pressure was independently reported by other investigators using in vivo selection in nonimmune mice. Although in vitro generation of escape mutants is unlikely to recapitulate antigenic drift in its entirety, the data demonstrate that pressure by a human monoclonal antibody targeting a novel epitope in the hemagglutinin of the 2009 pandemic H1N1 virus can inadvertently drive the development of escape mutants, of which a subset have increased virulence and altered receptor binding properties.
Publisher: Frontiers Media SA
Date: 24-01-2022
DOI: 10.3389/FCIMB.2021.781968
Abstract: The upper respiratory tract (URT) is the portal of entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and SARS-CoV-2 likely interacts with the URT microbiome. However, understanding of the associations between the URT microbiome and the severity of coronavirus disease 2019 (COVID-19) is still limited. Our primary objective was to identify URT microbiome signature/s that consistently changed over a spectrum of COVID-19 severity. Using data from 103 adult participants from two cities in the United States, we compared the bacterial load and the URT microbiome between five groups: 20 asymptomatic SARS-CoV-2-negative participants, 27 participants with mild COVID-19, 28 participants with moderate COVID-19, 15 hospitalized patients with severe COVID-19, and 13 hospitalized patients in the ICU with very severe COVID-19. URT bacterial load, bacterial richness, and within-group microbiome composition dissimilarity consistently increased as COVID-19 severity increased, while the relative abundance of an licon sequence variant (ASV), Corynebacterium _unclassified.ASV0002, consistently decreased as COVID-19 severity increased. We observed that the URT microbiome composition significantly changed as COVID-19 severity increased. The URT microbiome could potentially predict which patients may be more likely to progress to severe disease or be modified to decrease severity. However, further research in additional longitudinal cohorts is needed to better understand how the microbiome affects COVID-19 severity.
Publisher: Cold Spring Harbor Laboratory
Date: 04-02-2022
DOI: 10.1101/2022.02.02.22270308
Abstract: Idiopathic subglottic stenosis (iSGS) is a rare fibrotic disease of the proximal airway affecting adult Caucasian women nearly exclusively. Life-threatening ventilatory obstruction occurs secondary to pernicious subglottic mucosal scar. Diverse diseases in ergent organ systems are associated with fibrosis, suggesting common biologic mechanisms. One well characterized pathway is chronic inflammation secondary to pathogen. In the present study, we explored the role of the proximal airway microbiome in iSGS pathogenesis. In human s les, abundant bacteria are detectable in iSGS scar as well as in health subglottic controls or patients that developed subglottic stenosis following endotracheal intubation. Interestingly, the community structure of the iSGS proximal airway microbiome does not appear disrupted. Rather, in iSGS defects in the airway epithelial barrier allow displacement of the native microbiome into the immunoprivileged lamina propria and are associated with adaptive immune activation. Animal models of iSGS confirm both bacteria and an adaptive immune response are necessary for pathologic proximal airway fibrosis. Single cell RNA sequencing of the affected airway in iSGS offers an unbiased characterization of the observed epithelial barrier dysfunction. The airway scar in iSGS patients demonstrates basal cell depletion and epithelial acquisition of a mesenchymal phenotype. The epithelial alterations are associated with the observed microbiome displacement, dysregulated immune activation, and localized fibrosis. These results refine our understanding of iSGS and implicate shared pathogenic mechanisms with distal airway fibrotic diseases.
Publisher: Wiley
Date: 13-04-2022
DOI: 10.1111/IRV.12982
Abstract: The Omicron variant of SARS‐CoV‐2 achieved worldwide dominance in late 2021. Early work suggests that infections caused by the Omicron variant may be less severe than those caused by the Delta variant. We sought to compare clinical outcomes of infections caused by these two strains, confirmed by whole genome sequencing, over a short period of time, from respiratory s les collected from SARS‐CoV‐2 positive patients at a large medical center. We found that infections caused by the Omicron variant caused significantly less morbidity, including admission to the hospital and requirement for oxygen supplementation, and significantly less mortality than those caused by the Delta variant.
Publisher: Cold Spring Harbor Laboratory
Date: 11-04-2020
DOI: 10.1101/2020.04.10.029454
Abstract: Genetic variations across the SARS-CoV-2 genome may influence transmissibility of the virus and the host’s anti-viral immune response, in turn affecting the frequency of variants over-time. In this study, we examined the adjacent amino acid polymorphisms in the nucleocapsid (R203K/G204R) of SARS-CoV-2 that arose on the background of the spike D614G change and describe how strains harboring these changes became dominant circulating strains globally. Deep sequencing data of SARS-CoV-2 from public databases and from clinical s les were analyzed to identify and map genetic variants and sub-genomic RNA transcripts across the genome. Sequence analysis suggests that the three adjacent nucleotide changes that result in the K203/R204 variant have arisen by homologous recombination from the core sequence (CS) of the leader transcription-regulating sequence (TRS) rather than by stepwise mutation. The resulting sequence changes generate a novel sub-genomic RNA transcript for the C-terminal dimerization domain of nucleocapsid. Deep sequencing data from 981 clinical s les confirmed the presence of the novel TRS-CS-dimerization domain RNA in in iduals with the K203/R204 variant. Quantification of sub-genomic RNA indicates that viruses with the K203/R204 variant may also have increased expression of sub-genomic RNA from other open reading frames. The finding that homologous recombination from the TRS may have occurred since the introduction of SARS-CoV-2 in humans resulting in both coding changes and novel sub-genomic RNA transcripts suggests this as a mechanism for ersification and adaptation within its new host.
Publisher: Springer Science and Business Media LLC
Date: 13-02-2017
DOI: 10.1038/NI.3680
Publisher: Springer Science and Business Media LLC
Date: 23-09-2015
DOI: 10.1038/NATURE15379
Publisher: Rockefeller University Press
Date: 07-02-2011
Publisher: Wiley
Date: 30-03-2018
DOI: 10.1111/IRV.12537
Location: United States of America
No related grants have been discovered for Suman Das.