Last data update: Oct 28, 2024. (Total: 48004 publications since 2009)
Records 1-28 (of 28 Records) |
Query Trace: Chakrabarti AK[original query] |
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Adverse outcomes in patients hospitalized with pneumonia at age 60 or more: A prospective multi-centric hospital-based study in India
Kanungo S , Bhattacharjee U , Prabhakaran AO , Kumar R , Rajkumar P , Bhardwaj SD , Chakrabarti AK , Kumar CPG , Potdar V , Manna B , Amarchand R , Choudekar A , Gopal G , Sarda K , Lafond KE , Azziz-Baumgartner E , Saha S , Dar L , Krishnan A . PLoS One 2024 19 (5) e0297452 BACKGROUND: Limited data exists regarding risk factors for adverse outcomes in older adults hospitalized with Community-Acquired Pneumonia (CAP) in low- and middle-income countries such as India. This multisite study aimed to assess outcomes and associated risk factors among adults aged ≥60 years hospitalized with pneumonia. METHODS: Between December 2018 and March 2020, we enrolled ≥60-year-old adults admitted within 48 hours for CAP treatment across 16 public and private facilities in four sites. Clinical data and nasal/oropharyngeal specimens were collected by trained nurses and tested for influenza, respiratory syncytial virus (RSV), and other respiratory viruses (ORV) using the qPCR. Participants were evaluated regularly until discharge, as well as on the 7th and 30th days post-discharge. Outcomes included ICU admission and in-hospital or 30-day post-discharge mortality. A hierarchical framework for multivariable logistic regression and Cox proportional hazard models identified risk factors (e.g., demographics, clinical features, etiologic agents) associated with critical care or death. FINDINGS: Of 1,090 CAP patients, the median age was 69 years; 38.4% were female. Influenza viruses were detected in 12.3%, RSV in 2.2%, and ORV in 6.3% of participants. Critical care was required for 39.4%, with 9.9% in-hospital mortality and 5% 30-day post-discharge mortality. Only 41% of influenza CAP patients received antiviral treatment. Admission factors independently associated with ICU admission included respiratory rate >30/min, blood urea nitrogen>19mg/dl, altered sensorium, anemia, oxygen saturation <90%, prior cardiovascular diseases, chronic respiratory diseases, and private hospital admission. Diabetes, anemia, low oxygen saturation at admission, ICU admission, and mechanical ventilation were associated with 30-day mortality. CONCLUSION: High ICU admission and 30-day mortality rates were observed among older adults with pneumonia, with a significant proportion linked to influenza and RSV infections. Comprehensive guidelines for CAP prevention and management in older adults are needed, especially with the co-circulation of SARS-CoV-2. |
Cost of acute respiratory illness episode and its determinants among community-dwelling older adults: a four-site cohort study from India
Krishnan A , Shekhawat K , Ortega-Sanchez IR , Kanungo S , Rajkumar P , Bhardwaj SD , Kumar R , Prabhakaran AO , Gopal G , Chakrabarti AK , Purushothaman GKC , Potdar V , Manna B , Gharpure R , Amarchand R , Choudekar A , Lafond KE , Dar L , Bhattacharjee U , Azziz-Baumgartner E , Saha S . BMJ Public Health 2023 1 (1) e000103 INTRODUCTION: Advocacy for the provision of public health resources, including vaccine for the prevention of acute respiratory illnesses (ARIs) among older adults in India, needs evidence on costs and benefits. Using a cohort of community-dwelling adults aged 60 years and older in India, we estimated the cost of ARI episode and its determinants. METHODS: We enrolled 6016 participants in Ballabgarh, Chennai, Kolkata and Pune from July 2018 to March 2020. They were followed up weekly to identify ARI and classified them as acute upper respiratory illness (AURI) or pneumonia based on clinical features based on British Thoracic Society guidelines. All pneumonia and 20% of AURI cases were asked about the cost incurred on medical consultation, investigation, medications, transportation, food and lodging. The cost of services at public facilities was supplemented by WHO-Choosing Interventions that are Cost-Effective(CHOICE) estimates for 2019. Indirect costs incurred by the affected participant and their caregivers were estimated using human capital approach. We used generalised linear model with log link and gamma family to identify the average marginal effect of key determinants of the total cost of ARI. RESULTS: We included 2648 AURI and 1081 pneumonia episodes. Only 47% (range 36%-60%) of the participants with pneumonia sought care. The mean cost of AURI episode was US$13.9, while that of pneumonia episode was US$25.6, with indirect costs comprising three-fourths of the total. The cost was higher among older men by US$3.4 (95% CI: 1.4 to 5.3), those with comorbidities by US$4.3 (95% CI: 2.8 to 5.7) and those who sought care by US$17.2 (95% CI: 15.1 to 19.2) but not by influenza status. The mean per capita annual cost of respiratory illness was US$29.5. CONCLUSION: Given the high community disease and cost burden of ARI, intensifying public health interventions to prevent and mitigate ARI among this fast-growing older adult population in India is warranted. |
SARS-CoV-2 infection risk among vaccinated and unvaccinated household members during the Alpha variant surge - Denver, Colorado, and San Diego, California, January-April 2021.
McCormick DW , Konkle SL , Magleby R , Chakrabarti AK , Cherney B , Lindell K , Namageyo-Funa A , Visser S , Soto RA , Donnelly MAP , Stringer G , Austin B , Beatty ME , Stous S , Albanese BA , Chu VT , Chuey M , Dietrich EA , Drobeniuc J , Folster JM , Killerby ME , Lehman JA , McDonald EC , Ruffin J , Schwartz NG , Sheldon SW , Sleweon S , Thornburg NJ , Hughes LJ , Petway M , Tong S , Whaley MJ , Kirking HL , Tate JE , Hsu CH , Matanock A . Vaccine 2022 40 (33) 4845-4855 BACKGROUND: COVID-19 vaccination reduces SARS-CoV-2 infection and transmission. However, evidence is emerging on the degree of protection across variants and in high-transmission settings. To better understand the protection afforded by vaccination specifically in a high-transmission setting, we examined household transmission of SARS-CoV-2 during a period of high community incidence with predominant SARS-CoV-2 B.1.1.7 (Alpha) variant, among vaccinated and unvaccinated contacts. METHODS: We conducted a household transmission investigation in San Diego County, California, and Denver, Colorado, during January-April 2021. Households were enrolled if they had at least one person with documented SARS-CoV-2 infection. We collected nasopharyngeal swabs, blood, demographic information, and vaccination history from all consenting household members. We compared infection risks (IRs), RT-PCR cycle threshold values, SARS-CoV-2 culture results, and antibody statuses among vaccinated and unvaccinated household contacts. RESULTS: We enrolled 493 individuals from 138 households. The SARS-CoV-2 variant was identified from 121/138 households (88%). The most common variants were Alpha (75/121, 62%) and Epsilon (19/121, 16%). There were no households with discordant lineages among household members. One fully vaccinated secondary case was symptomatic (13%); the other 5 were asymptomatic (87%). Among unvaccinated secondary cases, 105/108 (97%) were symptomatic. Among 127 households with a single primary case, the IR for household contacts was 45% (146/322; 95% Confidence Interval [CI] 40-51%). The observed IR was higher in unvaccinated (130/257, 49%, 95% CI 45-57%) than fully vaccinated contacts (6/26, 23%, 95% CI 11-42%). A lower proportion of households with a fully vaccinated primary case had secondary cases (1/5, 20%) than households with an unvaccinated primary case (66/108, 62%). CONCLUSIONS: Although SARS-CoV-2 infections in vaccinated household contacts were reported in this high transmission setting, full vaccination protected against SARS-CoV-2 infection. These findings further support the protective effect of COVID-19 vaccination and highlight the need for ongoing vaccination among eligible persons. |
Cohort profile: Indian Network of Population-Based Surveillance Platforms for Influenza and Other Respiratory Viruses among the Elderly (INSPIRE).
Krishnan A , Dar L , Amarchand R , Prabhakaran AO , Kumar R , Rajkumar P , Kanungo S , Bhardwaj SD , Choudekar A , Potdar V , Chakrabarti AK , Kumar CG , Parameswaran GG , Dhakad S , Manna B , Choudhary A , Lafond KE , Azziz-Baumgartner E , Saha S . BMJ Open 2021 11 (10) e052473 PURPOSE: We describe here a multicentric community-dwelling cohort of older adults (>60 years of age) established to estimate incidence, study risk factors, healthcare utilisation and economic burden associated with influenza and respiratory syncytial virus (RSV) in India. PARTICIPANTS: The four sites of this cohort are in northern (Ballabgarh), southern (Chennai), eastern (Kolkata) and western (Pune) parts of India. We enrolled 5336 participants across 4220 households and began surveillance in July 2018 for viral respiratory infections with additional participants enrolled annually. Trained field workers collected data about individual-level and household-level risk factors at enrolment and quarterly assessed frailty and grip strength. Trained nurses surveilled weekly to identify acute respiratory infections (ARI) and clinically assessed individuals to diagnose acute lower respiratory infection (ALRI) as per protocol. Nasal and oropharyngeal swabs are collected from all ALRI cases and one-fifth of the other ARI cases for laboratory testing. Cost data of the episode are collected using the WHO approach for estimating the economic burden of seasonal influenza. Handheld tablets with Open Data Kit platform were used for data collection. FINDINGS TO DATE: The attrition of 352 participants due to migration and deaths was offset by enrolling 680 new entrants in the second year. All four sites reported negligible influenza vaccination uptake (0.1%-0.4%), low health insurance coverage (0.4%-22%) and high tobacco use (19%-52%). Ballabgarh had the highest proportion (54.4%) of households in the richest wealth quintile, but reported high solid fuel use (92%). Frailty levels were highest in Kolkata (11.3%) and lowest in Pune (6.8%). The Chennai cohort had highest self-reported morbidity (90.1%). FUTURE PLANS: The findings of this cohort will be used to inform prioritisation of strategies for influenza and RSV control for older adults in India. We also plan to conduct epidemiological studies of SARS-CoV-2 using this platform. |
Antibody-mediated virus neutralization is not a universal mechanism of Marburg, Ebola or Sosuga virus clearance in Egyptian rousette bats
Schuh AJ , Amman BR , Sealy TK , Kainulainen MH , Chakrabarti AK , Guerrero LW , Nichol ST , Albarino CG , Towner JS . J Infect Dis 2018 219 (11) 1716-1721 Although bats are increasingly being recognized as natural reservoir hosts of emerging zoonotic viruses, little is known about how they control and clear virus infection in the absence of clinical disease. Here, we test >50 convalescent sera from Egyptian rousette bats (ERBs) experimentally primed or prime-boosted with Marburg virus, Ebola virus or Sosuga virus for the presence of virus-specific neutralizing antibodies using infectious reporter viruses. After serum neutralization testing, we conclude that antibody-mediated virus neutralization does not contribute significantly to the control and clearance of Marburg virus, Ebola virus or Sosuga virus infection in ERBs. |
Complete Genome Sequences of Monongahela Hantavirus from Pennsylvania, USA.
Albarino CG , Guerrero LW , Chakrabarti AK , Rollin PE , Nichol ST . Microbiol Resour Announc 2018 7 (11) Monongahela hantavirus was first identified in deer mice and was later found responsible for hantavirus pulmonary syndrome cases in Pennsylvania and West Virginia in the United States. Here, we report the complete sequences of Monongahela virus S, M, and L genomic segments obtained from a fatal clinical case reported in 1997. Copyright © 2018 Microbiology Resource Announcements. All rights reserved. |
The S Genome Segment Is Sufficient to Maintain Pathogenicity in Intra-Clade Lassa Virus Reassortants in a Guinea Pig Model.
Welch SR , Scholte FEM , Albarino CG , Kainulainen MH , Coleman-McCray JD , Guerrero LW , Chakrabarti AK , Klena JD , Nichol ST , Spengler JR , Spiropoulou CF . Front Cell Infect Microbiol 2018 8 240 Genome reassortment in Lassa virus (LASV) has been reported in nature, but phenotypic consequences of this phenomenon are not well described. Here we characterize, both in vitro and in vivo, reassortment between 2 LASV strains: the prototypic 1976 Josiah strain and a more recently isolated 2015 Liberian strain. In vitro analysis showed that although cis- and trans-acting elements of viral RNA synthesis were compatible between strains, reassortants demonstrated different levels of viral replication. These differences were also apparent in vivo, as reassortants varied in pathogenicity in the guinea pig model of LASV infection. The reassortant variant containing the Josiah S segment retained the virulence of the parental Josiah strain, but the reassortant variant containing the S segment of the Liberian isolate was highly attenuated compared to both parental strains. Contrary to observations in reassortants between LASV and other arenavirus species, which suggest that L segment-encoded factors are responsible for virulence, these studies highlight a role for S segment-encoded virulence factors in disease, and also suggest that inefficient interactions between proteins of heterologous strains may limit the prevalence of reassortant LASV variants in nature. |
Transcriptional analysis of viral mRNAs reveals common transcription patterns in cells infected by five different filoviruses.
Albarino CG , Wiggleton Guerrero L , Chakrabarti AK , Nichol ST . PLoS One 2018 13 (8) e0201827 Filoviruses are notorious viral pathogens responsible for high-consequence diseases in humans and non-human primates. Transcription of filovirus mRNA shares several common features with transcription in other non-segmented negative-strand viruses, including differential expression of genes located across the viral genome. Transcriptional patterns of Ebola virus (EBOV) and Marburg virus (MARV) have been previously described using traditional, laborious methods, such as northern blots and in vivo labeling of viral mRNAs. More recently, however, the availability of the next generation sequencing (NGS) technology has offered a more straightforward approach to assess transcriptional patterns. In this report, we analyzed the transcription patterns of four ebolaviruses-EBOV, Sudan (SUDV), Bundibugyo (BDBV), and Reston (RESTV) viruses-in two different cell lines using standard NGS library preparation and sequencing protocols. In agreement with previous reports mainly focused on EBOV and MARV, the remaining filoviruses used in this study also showed a consistent transcription pattern, with only minor variations between the different viruses. We have also analyzed the proportions of the three mRNAs transcribed from the GP gene, which are characteristic of the genus Ebolavirus and encode the glycoprotein (GP), the soluble GP (sGP), and the small soluble GP (ssGP). In addition, we used NGS methodology to analyze the transcription pattern of two previously described recombinant MARV. This analysis allowed us to correct our construction design, and to make an improved version of the original MARV expressing reporter genes. |
Development of a reverse genetics system for Sosuga virus allows rapid screening of antiviral compounds.
Welch SR , Chakrabarti AK , Wiggleton Guerrero L , Jenks HM , Lo MK , Nichol ST , Spiropoulou CF , Albarino CG . PLoS Negl Trop Dis 2018 12 (3) e0006326 Sosuga virus (SOSV) is a recently discovered zoonotic paramyxovirus isolated from a single human case in 2012; it has been ecologically and epidemiologically associated with transmission by the Egyptian rousette bat (Rousettus aegyptiacus). Bats have long been recognized as sources of novel zoonotic pathogens, including highly lethal paramyxoviruses like Nipah virus (NiV) and Hendra virus (HeV). The ability of SOSV to cause severe human disease supports the need for studies on SOSV pathogenesis to better understand the potential impact of this virus and to identify effective treatments. Here we describe a reverse genetics system for SOSV comprising a minigenome-based assay and a replication-competent infectious recombinant reporter SOSV that expresses the fluorescent protein ZsGreen1 in infected cells. First, we used the minigenome assay to rapidly screen for compounds inhibiting SOSV replication at biosafety level 2 (BSL-2). The antiviral activity of candidate compounds was then tested against authentic viral replication using the reporter SOSV at BSL-3. We identified several compounds with anti-SOSV activity, several of which also inhibit NiV and HeV. Alongside its utility in screening for potential SOSV therapeutics, the reverse genetics system described here is a powerful tool for analyzing mechanisms of SOSV pathogenesis, which will facilitate our understanding of how to combat the potential public health threats posed by emerging bat-borne paramyxoviruses. |
Insights into Reston virus spillovers and adaption from virus whole genome sequences.
Albarino CG , Wiggleton Guerrero L , Jenks HM , Chakrabarti AK , Ksiazek TG , Rollin PE , Nichol ST . PLoS One 2017 12 (5) e0178224 Reston virus (family Filoviridae) is unique among the viruses of the Ebolavirus genus in that it is considered non-pathogenic in humans, in contrast to the other members which are highly virulent. The virus has however, been associated with several outbreaks of highly lethal hemorrhagic fever in non-human primates (NHPs), specifically cynomolgus monkeys (Macaca fascicularis) originating in the Philippines. In addition, Reston virus has been isolated from domestic pigs in the Philippines. To better understand virus spillover events and potential adaption to new hosts, the whole genome sequences of representative Reston virus isolates were obtained using a next generation sequencing (NGS) approach and comparative genomic analysis and virus fitness analyses were performed. Nine virus genome sequences were completed for novel and previously described isolates obtained from a variety of hosts including a human case, non-human primates and pigs. Results of phylogenetic analysis of the sequence differences are consistent with multiple independent introductions of RESTV from a still unknown natural reservoir into non-human primates and swine farming operations. No consistent virus genetic markers were found specific for viruses associated with primate or pig infections, but similar to what had been seen with some Ebola viruses detected in the large Western Africa outbreak in 2014-2016, a truncated version of VP30 was identified in a subgroup of Reston viruses obtained from an outbreak in pigs 2008-2009. Finally, the genetic comparison of two closely related viruses, one isolated from a human case and one from an NHP, showed amino acid differences in the viral polymerase and detectable differences were found in competitive growth assays on human and NHP cell lines. |
25-hydroxycholesterol inhibition of Lassa virus infection through aberrant GP1 glycosylation
Shrivastava-Ranjan P , Bergeron E , Chakrabarti AK , Albarino CG , Flint M , Nichol ST , Spiropoulou CF . mBio 2016 7 (6) Lassa virus (LASV) infection is a major public health concern due to high fatality rates and limited effective treatment. The interferon-stimulated gene cholesterol 25-hydroxylase (CH25H) encodes an enzyme that catalyzes the production of 25-hydroxycholesterol (25HC). 25HC is involved in regulating cholesterol biosynthesis and has recently been identified as a potent antiviral targeting enveloped virus entry. Here, we show a previously unrecognized role of CH25H in inhibiting LASV glycoprotein glycosylation and the production of infectious virus. Overexpression of CH25H or treatment with 25HC decreased LASV G1 glycoprotein N-glycan maturation and reduced the production of infectious LASV. Depletion of endogenous CH25H using small interfering RNA (siRNA) enhanced the levels of fully glycosylated G1 and increased infectious LASV production. Finally, LASV particles produced from 25HC-treated cells were found to be less infectious, to incorporate aberrantly glycosylated GP1 species, and to be defective in binding alpha-dystroglycan, an attachment and entry receptor. Our findings identify a novel role for CH25H in controlling LASV propagation and indicate that manipulation of the expression of CH25H or the administration of 25HC may be a useful anti-LASV therapy. IMPORTANCE: Lassa fever is an acute viral hemorrhagic fever in humans caused by Lassa virus (LASV). No vaccine for LASV is currently available. Treatment is limited to the administration of ribavirin, which is only effective when given early in the course of illness. Cholesterol 25-hydroxylase (CH25H) is a recently identified interferon-stimulated gene (ISG); it encodes an enzyme that catalyzes the production of 25-hydroxycholesterol (25HC), which inhibits several viruses. Here, we identify a novel antiviral mechanism of 25HC that is dependent on inhibiting the glycosylation of Lassa virus (LASV) glycoprotein and reducing the infectivity of LASV as a means of suppressing viral replication. Since N-linked glycosylation is a critical feature of other enveloped-virus glycoproteins, 25HC may be a broad inhibitor of virus infectivity. |
Novel activities by ebolavirus and marburgvirus interferon antagonists revealed using a standardized in vitro reporter system.
Guito JC , Albarino CG , Chakrabarti AK , Towner JS . Virology 2016 501 147-165 Filoviruses are highly lethal in humans and nonhuman primates, likely due to potent antagonism of host interferon (IFN) responses early in infection. Filoviral protein VP35 is implicated as the major IFN induction antagonist, while Ebola virus (EBOV) VP24 or Marburg virus (MARV) VP40 are known to block downstream IFN signaling. Despite progress elucidating EBOV and MARV antagonist function, those for most other filoviruses, including Reston (RESTV), Sudan (SUDV), Tai Forest (TAFV), Bundibugyo (BDBV) and Ravn (RAVV) viruses, remain largely neglected. Thus, using standardized vectors and reporter assays, we characterized activities by each IFN antagonist from all known ebolavirus and marburgvirus species side-by-side. We uncover noncanonical suppression of IFN induction by ebolavirus VP24, differing potencies by MARV and RAVV proteins, and intriguingly, weaker antagonism by VP24 of RESTV. These underlying molecular explanations for differential virulence in humans could guide future investigations of more-neglected filoviruses as well as treatment and vaccine studies. |
Lassa and Ebola virus inhibitors identified using minigenome and recombinant virus reporter systems.
Welch SR , Guerrero LW , Chakrabarti AK , McMullan LK , Flint M , Bluemling GR , Painter GR , Nichol ST , Spiropoulou CF , Albarino CG . Antiviral Res 2016 136 9-18 Lassa virus (LASV) and Ebola virus (EBOV) infections are important global health issues resulting in significant morbidity and mortality. While several promising drug and vaccine trials for EBOV are ongoing, options for LASV infection are currently limited to ribavirin treatment. A major factor impeding the development of antiviral compounds to treat these infections is the need to manipulate the virus under BSL-4 containment, limiting research to a few institutes worldwide. Here we describe the development of a novel LASV minigenome assay based on the ambisense LASV S segment genome, with authentic terminal untranslated regions flanking a ZsGreen (ZsG) fluorescent reporter protein and a Gaussia princeps luciferase (gLuc) reporter gene. This assay, along with a similar previously established EBOV minigenome, was optimized for high-throughput screening (HTS) of potential antiviral compounds under BSL-2 containment. In addition, we rescued a recombinant LASV expressing ZsG, which, in conjunction with a recombinant EBOV reporter virus, was used to confirm any potential antiviral hits in vitro. Combining an initial screen to identify potential antiviral compounds at BSL-2 containment before progressing to HTS with infectious virus will reduce the amount of expensive and technically challenging BSL-4 containment research. Using these assays, we identified 6-azauridine as having anti-LASV activity, and demonstrated its anti-EBOV activity in human cells. We further identified 2'-deoxy-2'-fluorocytidine as having potent anti-LASV activity, with an EC50 value 10 times lower than that of ribavirin. |
Ebola Virus Disease Diagnostics, Sierra Leone: Analysis of Real-time Reverse Transcription-Polymerase Chain Reaction Values for Clinical Blood and Oral Swab Specimens.
Erickson BR , Sealy TK , Flietstra T , Morgan L , Kargbo B , Matt-Lebby VE , Gibbons A , Chakrabarti AK , Graziano J , Presser L , Flint M , Bird BH , Brown S , Klena JD , Blau DM , Brault AC , Belser JA , Salzer JS , Schuh AJ , Lo M , Zivcec M , Priestley RA , Pyle M , Goodman C , Bearden S , Amman BR , Basile A , Bergeron E , Bowen MD , Dodd KA , Freeman MM , McMullan LK , Paddock CD , Russell BJ , Sanchez AJ , Towner JS , Wang D , Zemtsova GE , Stoddard RA , Turnsek M , Guerrero LW , Emery SL , Stovall J , Kainulainen MH , Perniciaro JL , Mijatovic-Rustempasic S , Shakirova G , Winter J , Sexton C , Liu F , Slater K , Anderson R , Andersen L , Chiang CF , Tzeng WP , Crowe SJ , Maenner MJ , Spiropoulou CF , Nichol ST , Stroher U . J Infect Dis 2016 214 S258-S262 During the Ebola virus outbreak of 2013-2016, the Viral Special Pathogens Branch field laboratory in Sierra Leone tested approximately 26 000 specimens between August 2014 and October 2015. Analysis of the B2M endogenous control Ct values showed its utility in monitoring specimen quality, comparing results with different specimen types, and interpretation of results. For live patients, blood is the most sensitive specimen type and oral swabs have little diagnostic utility. However, swabs are highly sensitive for diagnostic testing of corpses. |
Virus fitness differences observed between two naturally occurring isolates of Ebola virus Makona variant using a reverse genetics approach.
Albarino CG , Guerrero LW , Chakrabarti AK , Kainulainen MH , Whitmer SL , Welch SR , Nichol ST . Virology 2016 496 237-243 During the large outbreak of Ebola virus disease that occurred in Western Africa from late 2013 to early 2016, several hundred Ebola virus (EBOV) genomes have been sequenced and the virus genetic drift analyzed. In a previous report, we described an efficient reverse genetics system designed to generate recombinant EBOV based on a Makona variant isolate obtained in 2014. Using this system, we characterized the replication and fitness of 2 isolates of the Makona variant. These virus isolates are nearly identical at the genetic level, but have single amino acid differences in the VP30 and L proteins. The potential effects of these differences were tested using minigenomes and recombinant viruses. The results obtained with this approach are consistent with the role of VP30 and L as components of the EBOV RNA replication machinery. Moreover, the 2 isolates exhibited clear fitness differences in competitive growth assays. |
Humanized mouse model of Ebola virus disease mimics immune responses in human disease
Bird BH , Spengler JR , Chakrabarti AK , Khristova ML , Sealy TK , Coleman-McCray JD , Martin BE , Dodd KA , Goldsmith CS , Sanders J , Zaki SR , Nichol ST , Spiropoulou CF . J Infect Dis 2015 213 (5) 703-11 Animal models recapitulating human Ebola virus disease (EVD) are critical for insights into virus pathogenesis. Ebola virus (EBOV) isolates derived directly from human specimens do not cause disease in immunocompetent adult rodents without adaptation. Here we describe EVD in humanized BLT mice (hu-BLT) engrafted with human immune cells. Hu-BLT mice developed EVD following wild-type EBOV infection. Infection with high-dose EBOV resulted in rapid lethal EVD with high viral loads, alterations in key human antiviral immune cytokines and chemokines, and severe histopathology similar to that shown in the limited human post-mortem data available. A dose- and donor- dependent clinical course was observed in hu-BLT infected with lower doses of either Mayinga (1976) or Makona (2014) isolates derived from human EBOV cases. Engraftment of the human cellular immune system appeared to be essential for the observed virulence, as non-engrafted mice did not support productive EBOV replication or develop lethal disease. Hu-BLT mice offer a unique model for investigating the human immune response in EVD; and offer an alternative animal model for EVD pathogenesis studies and therapeutic screening. |
Utility of oral swab sampling for Ebola virus detection in Guinea pig model
Spengler JR , Chakrabarti AK , Coleman-McCray JD , Martin BE , Nichol ST , Spiropoulou CF , Bird BH . Emerg Infect Dis 2015 21 (10) 1816-9 To determine the utility of oral swabs for diagnosing infection with Ebola virus, we used a guinea pig model and obtained daily antemortem and postmortem swab samples. According to quantitative reverse transcription PCR analysis, the diagnostic value was poor for antemortem swab samples but excellent for postmortem samples. |
Ebola virus diagnostics: the US Centers for Disease Control and Prevention laboratory in Sierra Leone, August 2014 to March 2015
Flint M , Goodman CH , Bearden S , Blau DM , Amman BR , Basile AJ , Belser JA , Bergeron E , Bowen MD , Brault AC , Campbell S , Chakrabarti AK , Dodd KA , Erickson BR , Freeman MM , Gibbons A , Guerrero LW , Klena JD , Lash RR , Lo MK , McMullan LK , Momoh G , Massally JL , Goba A , Paddock CD , Priestley RA , Pyle M , Rayfield M , Russell BJ , Salzer JS , Sanchez AJ , Schuh AJ , Sealy TK , Steinau M , Stoddard RA , Taboy C , Turnsek M , Wang D , Zemtsova GE , Zivcec M , Spiropoulou CF , Stroher U , Towner JS , Nichol ST , Bird BH . J Infect Dis 2015 212 Suppl 2 S350-8 In August 2014, the Viral Special Pathogens Branch of the US Centers for Disease Control and Prevention established a field laboratory in Sierra Leone in response to the ongoing Ebola virus outbreak. Through March 2015, this laboratory tested >12 000 specimens from throughout Sierra Leone. We describe the organization and procedures of the laboratory located in Bo, Sierra Leone. |
RIG-I mediates an antiviral response to Crimean-Congo hemorrhagic fever virus.
Spengler JR , Patel JR , Chakrabarti AK , Zivcec M , Garcia-Sastre A , Spiropoulou CF , Bergeron E . J Virol 2015 89 (20) 10219-29 In the cytoplasm, the retinoic acid-inducible gene I (RIG-I) senses the RNA genomes of several RNA viruses. RIG-I binds to viral RNA, eliciting an antiviral response via the cellular adaptor MAVS. Crimean-Congo hemorrhagic fever virus (CCHFV), a negative sense RNA virus with a 5' -monophosphorylated genome, is a highly pathogenic zoonotic agent with significant public health and clinical implications. We found that, during CCHFV infection, RIG-I mediated a type-I interferon (IFN) response via MAVS. Interfering with RIG-I signaling reduced IFN production and IFN-stimulated gene expression, and increased viral replication. Immunostimulatory RNA was isolated from CCHFV-infected cells and from virion preparations, and RIG-I co-immunoprecipitation of infected cell lysates isolated immunostimulatory CCHFV RNA. This report serves as the first description of a pattern recognition receptor for CCHFV and highlights a critical signaling pathway in the antiviral response to CCHFV. IMPORTANCE: Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus with significant public health and clinical impact. In order for cells to respond to virus infection, they must recognize the virus as foreign and initiate antiviral signaling. To date, the receptors involved in recognition of CCHFV are not known. Herein we investigate and identify retinoic acid-inducible gene I (RIG-I) as a receptor involved in initiating an antiviral response to CCHFV. This receptor was initially not expected to play a role in CCHFV recognition because of characteristics of the viral genome. These findings are important in understanding the antiviral response to CCHFV and support continued investigation into the spectrum of potential viruses recognized by RIG-I. |
Recovery of Recombinant Crimean Congo Hemorrhagic Fever Virus Reveals a Function for Non-structural Glycoproteins Cleavage by Furin.
Bergeron E , Zivcec M , Chakrabarti AK , Nichol ST , Albarino CG , Spiropoulou CF . PLoS Pathog 2015 11 (5) e1004879 Crimean Congo hemorrhagic fever virus (CCHFV) is a negative-strand RNA virus of the family Bunyaviridae (genus: Nairovirus). In humans, CCHFV causes fever, hemorrhage, severe thrombocytopenia, and high fatality. A major impediment in precisely determining the basis of CCHFV's high pathogenicity has been the lack of methodology to produce recombinant CCHFV. We developed a reverse genetics system based on transfecting plasmids into BSR-T7/5 and Huh7 cells. In our system, bacteriophage T7 RNA polymerase produced complementary RNA copies of the viral S, M, and L segments that were encapsidated with the support, in trans, of CCHFV nucleoprotein and L polymerase. The system was optimized to systematically recover high yields of infectious CCHFV. Additionally, we tested the ability of the system to produce specifically designed CCHFV mutants. The M segment encodes a polyprotein that is processed by host proprotein convertases (PCs), including the site-1 protease (S1P) and furin-like PCs. S1P and furin cleavages are necessary for producing the non-structural glycoprotein GP38, while S1P cleavage yields structural Gn. We studied the role of furin cleavage by rescuing a recombinant CCHFV encoding a virus glycoprotein precursor lacking a functional furin cleavage motif (RSKR mutated to ASKA). The ASKA mutation blocked glycoprotein precursor's maturation to GP38, and Gn precursor's maturation to Gn was slightly diminished. Furin cleavage was not essential for replication, as blocking furin cleavage resulted only in transient reduction of CCHFV titers, suggesting that either GP38 and/or decreased Gn maturation accounted for the reduced virion production. Our data demonstrate that nairoviruses can be produced by reverse genetics, and the utility of our system uncovered a function for furin cleavage. This viral rescue system could be further used to study the CCHFV replication cycle and facilitate the development of efficacious vaccines to counter this biological and public health threat. |
Recombinant Marburg viruses containing mutations in the IID region of VP35 prevent inhibition of Host immune responses.
Albarino CG , Wiggleton Guerrero L , Spengler JR , Uebelhoer LS , Chakrabarti AK , Nichol ST , Towner JS . Virology 2014 476c 85-91 Previous in vitro studies have demonstrated that Ebola and Marburg virus (EBOV and MARV) VP35 antagonize the host cell immune response. Moreover, specific mutations in the IFN inhibitory domain (IID) of EBOV and MARV VP35 that abrogate their interaction with virus-derived dsRNA, lack the ability to inhibit the host immune response. To investigate the role of MARV VP35 in the context of infectious virus, we used our reverse genetics system to generate two recombinant MARVs carrying specific mutations in the IID region of VP35. Our data show that wild-type and mutant viruses grow to similar titers in interferon deficient cells, but exhibit attenuated growth in interferon-competent cells. Furthermore, in contrast to wild-type virus, both MARV mutants were unable to inhibit expression of various antiviral genes. The MARV VP35 mutants exhibit similar phenotypes to those previously described for EBOV, suggesting the existence of a shared immune-modulatory strategy between filoviruses. |
High-throughput, luciferase-based reverse genetics systems for identifying inhibitors of Marburg and Ebola viruses.
Uebelhoer LS , Albarino CG , McMullan LK , Chakrabarti AK , Vincent JP , Nichol ST , Towner JS . Antiviral Res 2014 106 86-94 Marburg virus (MARV) and Ebola virus (EBOV), members of the family Filoviridae, represent a significant challenge to global public health. Currently, no licensed therapies exist to treat filovirus infections, which cause up to 90% mortality in human cases. To facilitate development of antivirals against these viruses, we established two distinct screening platforms based on MARV and EBOV reverse genetics systems that express secreted Gaussia luciferase (gLuc). The first platform is a mini-genome replicon to screen viral replication inhibitors using gLuc quantification in a BSL-2 setting. The second platform is complementary to the first and expresses gLuc as a reporter gene product encoded in recombinant infectious MARV and EBOV, thereby allowing for rapid quantification of viral growth during treatment with antiviral compounds. We characterized these viruses by comparing luciferase activity to virus production, and validated luciferase activity as an authentic real-time measure of viral growth. As proof of concept, we adapt both mini-genome and infectious virus platforms to high-throughput formats, and demonstrate efficacy of several antiviral compounds. We anticipate that both approaches will prove highly useful in the development of anti-filovirus therapies, as well as in basic research on the filovirus life cycle. |
Development of a reverse genetics system to generate recombinant Marburg virus derived from a bat isolate.
Albarino CG , Uebelhoer LS , Vincent JP , Khristova ML , Chakrabarti AK , McElroy A , Nichol ST , Towner JS . Virology 2013 446 230-7 Recent investigations have shown the Egyptian fruit bat (Rousettus aegyptiacus) to be a natural reservoir for marburgviruses. To better understand the life cycle of these viruses in the natural host, a new reverse genetics system was developed for the reliable rescue of a Marburg virus (MARV) originally isolated directly from a R. aegyptiacus bat (371Bat). To develop this system, the exact terminal sequences were first determined by 5' and 3' RACE, followed by the cloning of viral proteins NP, VP35, VP30 and L into expression plasmids. Novel conditions were then developed to efficiently replicate virus mini-genomes followed by the construction of full-length genomic clones from which recombinant wild type and GFP-containing MARVs were rescued. Surprisingly, when these recombinant MARVs were propagated in primary human macrophages, a dramatic difference was found in their ability to grow and to elicit anti-viral cytokine responses. |
Severe hemorrhagic fever in strain 13/n guinea pigs infected with Lujo virus
Bird BH , Dodd KA , Erickson BR , Albarino CG , Chakrabarti AK , McMullan LK , Bergeron E , Stroeher U , Cannon D , Martin B , Coleman-McCray JD , Nichol ST , Spiropoulou CF . PLoS Negl Trop Dis 2012 6 (8) e1801 Lujo virus (LUJV) is a novel member of the Arenaviridae family that was first identified in 2008 after an outbreak of severe hemorrhagic fever (HF). In what was a small but rapidly progressing outbreak, this previously unknown virus was transmitted from the critically ill index patient to 4 attending healthcare workers. Four persons died during this outbreak, for a total case fatality of 80% (4/5). The suspected rodent source of the initial exposure to LUJV remains a mystery. Because of the ease of transmission, high case fatality, and novel nature of LUJV, we sought to establish an animal model of LUJV HF. Initial attempts in mice failed, but infection of inbred strain 13/N guinea pigs resulted in lethal disease. A total of 41 adult strain 13/N guinea pigs were infected with either wild-type LUJV or a full-length recombinant LUJV. Results demonstrated that strain 13/N guinea pigs provide an excellent model of severe and lethal LUJV HF that closely resembles what is known of the human disease. All infected animals experienced consistent weight loss (3-5% per day) and clinical illness characterized by ocular discharge, ruffled fur, hunched posture, and lethargy. Uniform lethality occurred by 11-16 days post-infection. All animals developed disseminated LUJV infection in various organs (liver, spleen, lung, and kidney), and leukopenia, lymphopenia, thrombocytopenia, coagulopathy, and elevated transaminase levels. Serial euthanasia studies revealed a temporal pattern of virus dissemination and increasing severity of disease, primarily targeting the liver, spleen, lungs, and lower gastrointestinal tract. Establishing an animal LUJV model is an important first step towards understanding the high pathogenicity of LUJV and developing vaccines and antiviral therapeutic drugs for this highly transmissible and lethal emerging pathogen. |
Reverse genetics recovery of Lujo virus and role of virus RNA secondary structures in efficient virus growth.
Bergeron E , Chakrabarti AK , Bird BH , Dodd KA , McMullan LK , Spiropoulou CF , Nichol ST , Albarino CG . J Virol 2012 86 (19) 10759-65 Arenaviruses are rodent-borne viruses with a bisegmented RNA genome. A genetically unique arenavirus, Lujo virus, was recently discovered as the causal agent of a nosocomial outbreak of acute febrile illness with hemorrhagic manifestations in Zambia and South Africa. The outbreak had a case fatality of 80%. A reverse genetics system to rescue infectious Lujo virus from cDNA was established to investigate the biological properties of this virus. Sequencing the genomic termini showed unique nucleotides at the 3' terminus of the S segment promoter element. While developing this system, we discovered that reconstructing infectious Lujo virus using the previously reported L segment intergenic region (IGR), comprising the arenaviral transcription termination signal, yielded an attenuated Lujo virus. Resequencing revealed that the correct L segment IGR was 36 nucleotide longer, and incorporating it into the reconstructed Lujo virus restored growth rate to that of the authentic clinical virus isolate. These additional nucleotides were predicted to more than double the free energy of the IGR main stem-loop structure. In addition, incorporating the newly determined L-IGR into a replicon reporter system enhanced the expression of a luciferase reporter L segment. Overall, these results imply that an extremely stable secondary structure within the L-IGR is critical for Lujo virus propagation and viral protein production. The technology for producing recombinant Lujo virus now provides a method to precisely investigate the molecular determinants of virulence of this newly identified pathogen. |
The major determinant of attenuation in mice of the Candid1 vaccine for Argentine hemorrhagic fever is located in the G2 glycoprotein transmembrane domain
Albarino CG , Bird BH , Chakrabarti AK , Dodd KA , Flint M , Bergeron E , White DM , Nichol ST . J Virol 2011 85 (19) 10404-8 Candid1, a live-attenuated Junin virus vaccine strain, was developed during the early 1980s to control Argentine hemorrhagic fever, a severe and frequently fatal human disease. Six amino acid substitutions were found to be unique to this vaccine strain, and their role in virulence attenuation in mice was analyzed using a series of recombinant viruses. Our results indicate that Candid1 is attenuated in mice through a single amino acid substitution in the transmembrane domain of the G2 glycoprotein. This work provides insight into the molecular mechanisms of attenuation of the only arenavirus vaccine currently available. |
Efficient rescue of recombinant Lassa virus reveals the influence of S segment noncoding regions on virus replication and virulence.
Albarino CG , Bird BH , Chakrabarti AK , Dodd KA , Erickson BR , Nichol ST . J Virol 2011 85 (8) 4020-4 Lassa virus (LASV), is a significant cause of severe often fatal hemorrhagic fever in humans throughout western Africa with an estimated 100,000 infections each year. No vaccines are commercially available. We report the development of an efficient reverse genetics system to rescue recombinant LASV and to investigate the contributions of the long 5' and 3' non-coding regions (NCR) of the S genomic segment on in vitro growth and in vivo virulence. This work demonstrates that deletions of large portions of these NCRs confer an attenuated phenotype, and are a first step towards further insights on the high virulence of LASV. |
Reverse genetics generation of chimeric infectious Junin/Lassa virus is dependent on interaction of homologous glycoprotein stable signal peptide and G2 cytoplasmic domains.
Albarino CG , Bird BH , Chakrabarti AK , Dodd KA , White DM , Bergeron E , Shrivastava-Ranjan P , Nichol ST . J Virol 2010 85 (1) 112-22 The Arenaviridae are a diverse and globally distributed collection of viruses that are primarily maintained by rodent reservoirs. Junin virus (JUNV) and Lassa virus (LASV) can both cause significant outbreaks of severe and often fatal human disease throughout their respective endemic areas. In an effort to improve upon the existing live attenuated JUNV Candid 1 vaccine, we generated a genetically homogenous stock of this virus from cDNA copies of the virus S and L segments using a reverse genetics system. Further, these cDNAs were used in combination with LASV cDNAs to successfully generate two recombinant Candid1 JUNV/LASV chimeric viruses (via GPC envelope exchange). It was found that while the GPC extra-virion domains were readily exchangeable, homologous stable signal peptide (SSP) and G2 transmembrane and cytoplasmic tail domains were essential for correct GPC maturation and production of infectious chimeric viruses. The switching of the JUNV and LASV G1/G2 ectodomains within the Candid1 vaccine background did not alter the attenuated phenotype of the vaccine strain in a lethal mouse model. These recombinant chimeric viruses shed light on the fundamental requirements of arenavirus GPC maturation and may serve as a strategy for the development of bivalent JUNV and LASV vaccine candidates. |
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