Current Research
- Virus-Host Interactions
Abstract: 
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. https://pubmed.ncbi.nlm.nih.gov/32898168/
: RNA viruses that replicate in the cytoplasm often disrupt nucleocytoplasmic transport to preferentially translate their own transcripts and prevent host antiviral responses. The Sarbecovirus accessory protein ORF6 has previously been shown to be the major inhibitor of interferon production in both SARS-CoV and SARS-CoV-2. SARS-CoV-2 ORF6 was recently shown to co-purify with the host mRNA export factors Rae1 and Nup98. Here, we demonstrate SARS-CoV-2 ORF6 strongly represses protein expression of co-transfected reporter constructs and imprisons host mRNA in the nucleus, which is associated with its ability to co-purify with Rae1 and Nup98. These protein-protein interactions map to the C-terminus of ORF6 and can be abolished by a single amino acid mutation in Met58. Overexpression of Rae1 restores reporter expression in the presence of SARS-CoV-2 ORF6. We further identify an ORF6 mutant containing a 9-amino acid deletion, ORF6 Δ22-30, in multiple SARS-CoV-2 clinical isolates that can still downregulate the expression of a co-transfected reporter and interact with Rae1 and Nup98. SARS-CoV ORF6 also interacts with Rae1 and Nup98. However, SARS-CoV-2 ORF6 more strongly co-purifies with Rae1 and Nup98 and results in significantly reduced expression of reporter proteins compared to SARS-CoV ORF6, a potential mechanism for the delayed symptom onset and pre-symptomatic transmission uniquely associated with the SARS-CoV-2 pandemic.
Abstract:
The activity of phosphatidylinositol 4-kinase class III beta (PI4KIIIB) has been shown to be recruited for the replication of multiple picornaviruses; however, it is unclear whether a physical association between PI4KIIIB and the viral replication machinery exists and, if it does, whether association is necessary. In this study, we characterized associations between the picornavirus nonstructural protein 3A and host factors using a mass spectrometry-based proteomic approach. We demonstrated that the 3A protein from multiple picornaviruses associates with PI4KIIIB and the Golgi adaptor protein ACBD3. Through genetic and chemical inhibition, we further defined the molecular determinants in Aichi virus 3A that are required for its physical association with ACBD3 and PI4KIIIB. https://www.ncbi.nlm.nih.gov/pubmed/22258260
Abstract:
Despite wide sequence divergence, multiple picornaviruses use the Golgi adaptor acyl coenzyme A (acyl-CoA) binding domain protein 3 (ACBD3/GCP60) to recruit phosphatidylinositol 4-kinase class III beta (PI4KIIIβ/PI4KB), a factor required for viral replication. The molecular basis of this convergent interaction and the cellular function of ACBD3 are not fully understood. Using affinity purification-mass spectrometry, we identified the putative Rab33 GTPase-activating proteins TBC1D22A and TBC1D22B as ACBD3-interacting factors. Fine-scale mapping of binding determinants within ACBD3 revealed that the interaction domains for TBC1D22A/B and PI4KB are identical. Affinity purification confirmed that PI4KB and TBC1D22A/B interactions with ACBD3 are mutually exclusive, suggesting a possible regulatory mechanism for recruitment of PI4KB. The C-terminal Golgi dynamics (GOLD) domain of ACBD3 has been previously shown to bind the 3A replication protein from Aichi virus. We find that the 3A proteins from several additional picornaviruses, including hepatitis A virus, human parechovirus 1, and human klassevirus, demonstrate an interaction with ACBD3 by mammalian two-hybrid assay; however, we also find that the enterovirus and kobuvirus 3A interactions with ACBD3 are functionally distinct with respect to TBC1D22A/B and PI4KB recruitment. These data reinforce the notion that ACBD3 organizes numerous cellular functionalities and that RNA virus replication proteins likely modulate these interactions by more than one mechanism.
- clinical virology and microbiology
Abstract: The development of vaccines against SARS-CoV-2 would be greatly facilitated by the identification of immunological correlates of protection in humans. However, to date, studies on protective immunity have only been performed in animal models and correlates of protection have not been established in humans. Here, we describe an outbreak of SARS-CoV-2 on a fishing vessel associated with a high attack rate. Predeparture serological and viral RT-PCR testing along with repeat testing after return to shore was available for 120 of the 122 persons on board over a median follow-up of 32.5 days (range 18.8 to 50.5 days). A total of 104 individuals had an RT-PCR positive viral test with Ct <35 or seroconverted during the follow-up period, yielding an attack rate on board of 85.2% (104/122 individuals). Metagenomic sequencing of 39 viral genomes suggested the outbreak originated largely from a single viral clade. Only three crewmembers tested seropositive prior to the boat’s departure in initial serological screening and also had neutralizing and spike-reactive antibodies in follow-up assays. None of these crewmembers with neutralizing antibody titers showed evidence of bona fide viral infection or experienced any symptoms during the viral outbreak. Therefore, the presence of neutralizing antibodies from prior infection was significantly associated with protection against re-infection (Fisher’s exact test, p=0.002). https://pubmed.ncbi.nlm.nih.gov/32826322/
Abstract: Coronavirus disease 2019 (COVID-19), the novel respiratory illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is associated with severe morbidity and mortality. The rollout of diagnostic testing in the United States was slow, leading to numerous cases that were not tested for SARS-CoV-2 in February and March 2020 and necessitating the use of serological testing to determine past infections. Here, we evaluated the Abbott SARS-CoV-2 IgG test for detection of anti-SARS-CoV-2 IgG antibodies by testing 3 distinct patient populations. We tested 1,020 serum specimens collected prior to SARS-CoV-2 circulation in the United States and found one false positive, indicating a specificity of 99.90%. We tested 125 patients who tested reverse transcription-PCR (RT-PCR) positive for SARS-CoV-2 for whom 689 excess serum specimens were available and found that sensitivity reached 100% at day 17 after symptom onset and day 13 after PCR positivity. Alternative index value thresholds for positivity resulted in 100% sensitivity and 100% specificity in this cohort. We tested specimens from 4,856 individuals from Boise, ID, collected over 1 week in April 2020 as part of the Crush the Curve initiative and detected 87 positives for a positivity rate of 1.79%. These data demonstrate excellent analytical performance of the Abbott SARS-CoV-2 IgG test as well as the limited circulation of the virus in the western United States. We expect that the availability of high-quality serological testing will be a key tool in the fight against SARS-CoV-2. https://pubmed.ncbi.nlm.nih.gov/32381641/
Abstract: Antiviral resistance frequently complicates the treatment of herpes simplex virus (HSV) infections in immunocompromised patients. Here we present the case of an adolescent boy with dedicator of cytokinesis 8 (DOCK8) deficiency, who experienced recurrent infections with resistant HSV-1. We used both phenotypic and genotypic methodologies to characterize the resistance profile of HSV-1 in the patient and conclude that genotypic testing outperformed phenotypic testing. We also present the first analysis of intrahost HSV-1 evolution in an immunocompromised patient. While HSV-1 can remain static in an immunocompetent individual for decades, the virus from this patient rapidly acquired genetic changes throughout its genome. Finally, we document a likely case of transmitted resistance in HSV-1 between the patient and his brother, who also has DOCK8 deficiency. This event demonstrates that resistant HSV-1 is transmissible among immunocompromised persons. https://pubmed.ncbi.nlm.nih.gov/31970398/
- viral genomics, transmission, and discovery
Abstract: Human cytomegalovirus (CMV) infections comprise a leading cause of newborn impairments worldwide and are pervasive concerns among the immunocompromised. Quantification of CMV viral loads is increasingly used to guide definitions of CMV disease but standardization of CMV quantitation remains problematic, mostly due to differences in qPCR amplicon sizes between clinical laboratories. Here, we used plasma cfDNA sequencing data from 2,208 samples sent for non-invasive prenatal aneuploidy screening to detect CMV and precisely measure the length of CMV fragments in human plasma. CMV reads were identified in 120 (5.4%) samples. Median cfDNA fragment size derived from CMV was significantly shorter than cfDNA derived from human chromosomes (103 vs 172 bp, p < 0.0001), corresponding to the 3rd percentile of human cfDNA. Sequencing of cfDNA from seven plasma samples from transplant patients positive for CMV confirmed the extraordinarily short nature of CMV cfDNA fragment size with a median length of 149 bp. We further show that these high-resolution measurements of CMV DNA fragment size accurately predict measured discrepancies in serum viral load measurements by different qPCR assays. These results highlight the exceptionally fragmented nature of CMV cfDNA and illustrate the promise of plasma cfDNA sequencing for quantitating viral loads through detection of fragments that would be unrecoverable by qPCR. https://pubmed.ncbi.nlm.nih.gov/32111931/
Background: The ubiquitous human pathogens, herpes simplex virus (HSV)-1 and HSV-2, are distinct viral species that diverged approximately 6 million years ago. At least 4 small, ancient HSV-1 × HSV-2 interspecies recombination events have affected the HSV-2 genome, with recombinants and nonrecombinants at each locus circulating today. However, it is unknown whether interspecies recombination can affect other loci and whether new recombinants continue to be generated.
Methods: Using 255 newly sequenced and 230 existing HSV genome sequences, we comprehensively assessed interspecies recombination in HSV.
Results: Our findings show that the sizes and locations of interspecies recombination events in HSV-2 are significantly more variable than previously appreciated and that they can impact species-specific T-cell recognition of HSV.
Conclusions: We describe 2 large (>5 kb) recombination events, one of which arose in its current host, demonstrating that interspecies recombination continues to occur today. These results raise concerns about the use of live-attenuated HSV-2 vaccines in high HSV-1 prevalence areas. https://pubmed.ncbi.nlm.nih.gov/31016321/
- bacterial genomics
Abstract: 
Developing a vaccine against Treponema pallidum subspecies pallidum, the causative agent of syphilis, remains a public health priority. Syphilis vaccine design efforts have been complicated by lack of an in vitro T. pallidum culture system, prolific antigenic variation in outer membrane protein TprK, and lack of functional annotation for nearly half of the genes. Understanding the genetic basis of T. pallidum reinfection can provide insights into variation among strains that escape cross-protective immunity. Here, we present comparative genomic sequencing and deep, full-length tprK profiling of two T. pallidum isolates from blood from the same patient that were collected six years apart. Notably, this patient was diagnosed with syphilis four times, with two of these episodes meeting the definition of neurosyphilis, during this interval. Outside of the highly variable tprK gene, we identified 14 coding changes in 13 genes. Nine of these genes putatively localized to the periplasmic or outer membrane spaces, consistent with a potential role in serological immunoevasion. Using a newly developed full-length tprK deep sequencing protocol, we profiled the diversity of this gene that far outpaces the rest of the genome. Intriguingly, we found that the reinfecting isolate demonstrated less diversity across each tprK variable region compared to the isolate from the first infection. Notably, the two isolates did not share any full-length TprK sequences. Our results are consistent with an immunodominant-evasion model in which the diversity of TprK explains the ability of T. pallidum to successfully reinfect individuals, even when they have been infected with the organism multiple times. https://pubmed.ncbi.nlm.nih.gov/32251462/
Abstract:
Immune evasion and disease progression of Treponema pallidum subspecies pallidum are associated with sequence diversity in the hypervariable, putative outer membrane protein TprK. Previous attempts to study variation within TprK have sequenced at depths insufficient to fully appreciate the hypervariable nature of the protein, failed to establish linkage between the protein’s 7 variable regions, or were conducted on strains passed through rabbits. As a consequence, a complete profiling of tprK during infection in the human host is still lacking. Furthermore, prior studies examining how T. pallidum uses its repertoire of genomic donor sites to generate diversity within the V regions of the tprK also yielded a partial understanding of this process, due to the limited number of tprK alleles examined. In this study, we used short- and long-read deep sequencing to directly characterize full-length tprK alleles from T. pallidum collected from early lesions of patients attending two STD clinics in Italy. Our data, combined with recent data available on Chinese T. pallidum strains, show the near complete absence of overlap in TprK sequences among the 41 strains profiled to date. Moreover, our data allowed us to redefine the boundaries of tprK V regions, identify 55 donor sites, and estimate the total number of TprK variants that T. pallidum can potentially generate. Altogether, our results support how T. pallidum TprK antigenic variation system is an unsurmountable obstacle for the human immune system to naturally achieve infection eradication, and reiterate the importance of this mechanism for pathogen persistence in the host. https://www.biorxiv.org/content/10.1101/2020.01.23.917484v1.full
Background: Campylobacter spp. are among the most common causes of enteric bacterial infections worldwide. Men who have sex with men (MSM) are at increased risk for sexually transmitted enteric infections, including globally-distributed strains of multidrug-resistant Shigella spp.
Methods: Retrospective study of MSM-associated Campylobacter in Seattle and Montréal with phenotypic antimicrobial resistance profiles and whole genome sequencing.
Results: We report the isolation of two clonal lineages of multidrug-resistant Campylobacter coli from MSM in Seattle, Washington and Montréal, Québec. Whole genome sequencing revealed nearly identical strains obtained from the two regions over a four-year period. Comparison with the NCBI Pathogen Detection database revealed extensive Campylobacter spp. clusters carrying multiple drug resistance genes that segregated with these isolates. Examination of the genetic basis of antimicrobial resistance revealed multiple macrolide resistance determinants including a novel ribosomal RNA methyltransferase situated in a CRISPR array locus in a Campylobacter coli isolate.
Conclusions: As previously reported for Shigella, specific multidrug-resistant strains of Campylobacter are circulating by sexual transmission in MSM populations across diverse geographic locations, suggesting a need to incorporate sexual behavior in the investigation of clusters of foodborne pathogens revealed by whole-genome sequence data. https://pubmed.ncbi.nlm.nih.gov/31665255/
- reviews and commentary
Abstract: Diagnostic metagenomics and its associated trail of publications are spreading across the world. Multiple clinical labs in the United States, Europe, and Asia have gone to considerable lengths to optimize and validate a range of protocols for agnostically detecting viral, bacterial, fungal, and eukaryotic parasite nucleic acid across a range of patient specimens to aid in diagnosis for particularly recalcitrant cases. Others see a role for diagnostic metagenomics as a frontline diagnostic to replace other microbiological testing. Areas covered: There are considerable barriers to adoption for diagnostic metagenomics, including analytical sensitivity, interpretation, actionability, turnaround time, antimicrobial susceptibility, clinical utility, laboratory workflow, trial comparators, cost, and reimbursement. Expert commentary: Metagenomics is unlikely to become ‘one test to rule them all’ any time soon, not least because it is not indicative of historical infection like some of the highest volume tests in the clinical virology lab, viral serologies. The high cost and low marginal utility compared to ‘standard of care’ diagnostics have forced metagenomics to be mostly used for last-ditch cases. However, waiting for such patients to declare themselves as being diagnostically challenging in turn likely lessens the diagnostic yield and actionability of the information. Significant reductions in the cost of metagenomic sequencing are required for it to move up in the diagnostic pipeline. This review covers these associated obstacles of metagenomics, arguing for a parsimonious role in last-ditch diagnostics and awaiting the answer of many outstanding questions regarding its adoption. https://pubmed.ncbi.nlm.nih.gov/29898605/
Abstract: It is hard to overemphasize the role that metagenomics has had on our recent understanding of RNA virus diversity. Metagenomics in the 21st century has brought with it an explosion in the number of RNA virus species, genera, and families far exceeding that following the discovery of the microscope in the 18th century for eukaryotic life or culture media in the 19th century for bacteriology or the 20th century for virology. When the definition of success in organism discovery is measured by sequence diversity and evolutionary distance, RNA viruses win. This review explores the history of RNA virus metagenomics, reasons for the successes so far in RNA virus metagenomics, and methodological concerns. In addition, the review briefly covers clinical metagenomics and environmental metagenomics and highlights some of the critical accomplishments that have defined the fast pace of RNA virus discoveries in recent years. Slightly more than a decade in, the field is exhausted from its discoveries but knows that there is yet even more out there to be found. https://pubmed.ncbi.nlm.nih.gov/29055712/
Abstract: The growth of pathogen genomics shows no signs of abating. Whole-genome sequencing of clinical viral and bacterial isolates continues to grow in nearly exponential bounds. Reductions in cost driven by new technology have created a seamless environment for generating, sharing, and analyzing pathogen genomes. The high-resolution view of infectious disease transmission dynamics offered by analyzing whole genomes from pathogens, coupled with the genomicist ethic of widespread data sharing, has created a veritable Internet of pathogens, which inadvertently produces new threats to patient privacy and protected heath information. The health care system, and society more generally, have yet to explore the far-reaching privacy concerns raised by readily accessible pathogen genomic data. The recent use of human genomic databases, the existence of freely available alternative data and metadata sources, and lax regulation of collecting publicly available genomes to identify individuals in a criminal context raise concerning parallels about what is possible with pathogen genomics. The growing ability to ascertain culpability for infectious disease transmission at a nearly individual level could change our perspective on disease outbreaks from one based on public health to one based on individual liability. These technological breakthroughs in the absence of an understanding of potential privacy and liability issues lead to questions about the dominant paradigm of better living through pathogen genomics. https://pubmed.ncbi.nlm.nih.gov/30971462/
Abstract: In early March 2020, the University of Washington Medical Center clinical virology laboratory became one of the first clinical laboratories to offer testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). When we first began test development in mid-January, neither of us believed there would be more than 2 million confirmed SARS-CoV-2 infections nationwide or that we would have performed more than 150,000 real-time PCR (RT-PCR) tests, with many more to come. This article will be a chronological summary of how we rapidly validated tests for SARS-CoV-2, increased our testing capacity, and addressed the many problems that came up along the way. https://pubmed.ncbi.nlm.nih.gov/32703897/