Quantity of SARS-CoV-2 RNA copies exhaled per minute during natural breathing over the course of COVID-19 infection (preprint)

SARS-CoV-2 is spread through exhaled breath of infected individuals. A fundamental question in understanding transmission of SARS-CoV-2 is how much virus an individual is exhaling into the environment while they breathe, over the course of their infection. Research on viral load dynamics during COVID-19 infection has focused on internal swab specimens, which provide a measure of viral loads inside the respiratory tract, but not on breath. Therefore, the dynamics of viral shedding on exhaled breath over the course of infection are poorly understood. Here, we collected exhaled breath specimens from COVID-19 patients and used RTq-PCR to show that numbers of exhaled SARS-CoV-2 RNA copies during COVID-19 infection do not decrease significantly until day 8 from symptom-onset. COVID-19-positive participants exhaled an average of 80 SARS-CoV-2 viral RNA copies per minute during the first 8 days of infection, with significant variability both between and within individuals, including spikes over 800 copies a minute in some patients. After day 8, there was a steep drop to levels nearing the limit of detection, persisting for up to 20 days. We further found that levels of exhaled viral RNA increased with self-rated symptom-severity, though individual variation was high. Levels of exhaled viral RNA did not differ across age, sex, time of day, vaccination status or viral variant. Our data provide a fine-grained, direct measure of the number of SARS-CoV-2 viral copies exhaled per minute during natural breathing, including 312 breath specimens collected multiple times daily over the course of infection, in order to fill an important gap in our understanding of the time course of exhaled viral loads in COVID-19.

Severity of Illness Caused by Severe Acute Respiratory Syndrome Coronavirus 2 Variants of Concern in Children: A Single-Center Retrospective Cohort Study (preprint)

BackgroundRecent surges in coronavirus 2019 disease (COVID-19) is attributed to the emergence of more transmissible severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs). However, the relative severity of SARS-CoV-2 VOCs in children is unknown. MethodsThis retrospective single-center cohort study was performed at the Ann & Robert H. Lurie Childrens Hospital of Chicago, academic free-standing childrens hospital. We included all children [≤] 18 years-old diagnosed with COVID-19 between October 15th, 2020 and August 31st, 2021 and whose SARS-CoV-2 isolate was sequenced using the Illumina platform. For each patient sample, we identified the SARS-CoV-2 lineage, which was assigned to one of the following groups: Non-VOC, alpha VOC, beta VOC, gamma VOC, or delta VOC. We measured frequency of 5 markers of COVID-19 severity: hospitalization; COVID-19 pharmacologic treatment; respiratory support; intensive care unit admission; and severe disease as classified by the COVID-19 World Health Organization (WHO) Clinical Progression Scale (severe disease; score [≥] 6). A series of logistic regression models were fitted to estimate odds of each severity marker with each VOC (in comparison to non-VOCs), adjusting for COVID-19 community incidence and demographic and clinical co-variates. ResultsDuring the study period, 2,025 patients tested positive for SARS-CoV-2; 1,422 (70.2%) had sufficient viral load to permit sequencing. Among the 499 (35.1%) patients whose isolate was sequenced, median (inter-quartile range) age was 7 (1,12) years; 256 (51.3%) isolates were a VOC: 96 (37.5%) alpha, 38 (14.8%) gamma, and 119 (46.5%) delta. After adjusting for age, Black race, Hispanic ethnicity, high-risk medical conditions, and COVID-19 community incidence, neither alpha nor delta was associated with severe COVID-19. Gamma was independently associated with hospitalization (OR 5.9, 95% CI 1.6-21.5, p=0.007), respiratory support (OR 8.3, 95% CI 1.5-56.3, p=0.02), and severe disease as classified by the WHO Clinical Progression Scale (OR 7.7, 95% CI 1.0-78.1, p=0.05). ConclusionsCompared to non-VOC COVID-19 infections, the gamma VOC, but not the alpha or delta VOCs, was associated with increased severity. These data suggest that recent increased in pediatric COVID-19 hospitalizations are related to increased delta COVID-19 incidence rather than increased delta virulence in children.

Longitudinal analysis of SARS-CoV-2 vaccine breakthrough infections reveal limited infectious virus shedding and restricted tissue distribution (preprint)

The global effort to vaccinate people against SARS-CoV-2 in the midst of an ongoing pandemic has raised questions about the nature of vaccine breakthrough infections and the potential for vaccinated individuals to transmit the virus. These questions have become even more urgent as new variants of concern with enhanced transmissibility, such as Delta, continue to emerge. To shed light on how vaccine breakthrough infections compare with infections in immunologically naive individuals, we examined viral dynamics and infectious virus shedding through daily longitudinal sampling in a small cohort of adults infected with SARS-CoV-2 at varying stages of vaccination. The durations of both infectious virus shedding and symptoms were significantly reduced in vaccinated individuals compared with unvaccinated individuals. We also observed that breakthrough infections are associated with strong tissue compartmentalization and are only detectable in saliva in some cases. These data indicate that vaccination shortens the duration of time of high transmission potential, minimizes symptom duration, and may restrict tissue dissemination.

Assessment and Modeling of COVID-19 Outcomes in a Longitudinal Cohort of Hospitalized Adults (preprint)

Background: While several demographic and clinical correlates of Coronavirus Disease 2019 (COVID-19) outcome have been identified, they remain imprecise tools for clinical management of disease. Furthermore, there are limited data on how these factors are associated with virological and immunological parameters over time. Methods and Findings: Nasopharyngeal swabs and blood samples were longitudinally collected from a cohort of 58 hospitalized adults with COVID-19 in Chicago, Illinois between March 27 and June 9, 2020. Samples were assessed for SARS-CoV-2 viral load, viral genotype, viral diversity, and antibody titer. Demographic and clinical information, including patient blood tests and several composite measures of disease severity, were extracted from electronic health records. All parameters were assessed for association with three patient outcome groups: discharge without intensive care unit (ICU) admission (n = 23), discharge with ICU admission (n = 29), and COVID-19 related death (n = 6). Higher age, male sex, and higher body mass index (BMI) were significantly associated with ICU admission. At hospital admission, higher 4C Mortality scores and lactate dehydrogenase (LDH) levels were likewise associated with ICU admission. Longitudinal trends in Deterioration Index (DI) score, Modified Early Warning Score (MEWS), and serum neutrophil count were also associated with ICU admission, though only the retrospectively calculated median DI score was predictive of death. While viral load and genotype were not significantly associated with outcome in this study, viral load did correlate positively with C-reactive protein levels and negatively with D-dimer, lymphocyte count, and antibody titer. Intra-host viral genetic diversity resulted in changes in viral genotype in some participants over time, though intra-host evolution was not associated with outcome. A stepwise-generated multivariable model including BMI, lymphocyte count at admission, and neutrophil count at admission was sufficient to predict outcome with a 0.82 accuracy rate in this cohort. Conclusions: These studies suggest that COVID-19 disease severity and poor outcomes among hospitalized patients are likely driven by dysfunctional host responses to infection and underlying co-morbid conditions rather than SARS-CoV-2 viral loads. Several parameters, including 4C mortality score, LDH levels, and DI score, were ultimately predictive of participant outcome and warrant further exploration in larger cohort studies for use in clinical management and risk assessment. Finally, the prevalence of intra-host diversity and viral evolution in hospitalized patients suggests a mechanism for population-level change, further emphasizing the need for effective antivirals to suppress viral replication and to avoid the emergence of new variants.

High prevalence of SARS-CoV-2 B.1.1.7 (UK variant) and the novel B.1.525 lineage in Oyo State, Nigeria (preprint)

The spread of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), has resulted in a global pandemic that has claimed the lives of millions of people. Genomic surveillance of the virus has proven to be a critical tool for tracking the emergence and spread of variants with increased transmission or immune evasion potential. Despite the global distribution of infection, differences in viral genomic surveillance capabilities between countries and regions have resulted in gaps in our understanding of the viral population dynamics underlying the pandemic. Nigeria, despite having the largest population of any country in Africa, has had relatively little SARS-CoV-2 sequence data made publicly available. In this study, we report the whole-genome sequences of 74 SARS-CoV-2 isolates collected from individuals in Oyo State, Nigeria over the first two weeks of January 2021. Forty-six of the isolates belong to the B.1.1.7 ''UK variant'' lineage. Comparison to available regional and global sequences suggest that the B.1.1.7 isolates in Nigeria are primarily monophyletic, possibly representing a singular successful introduction into the country. The majority of the remaining isolates (17 of 74) belong to the B.1.525 lineage, which contains multiple spike protein mutations, including the E484K mutation associated with potential immune escape. Indeed, Nigeria has the highest reported frequency of this lineage despite its relative rarity worldwide. Phylogenetic analysis of the B.1.525 isolates in this study relative to other local and global isolates suggested a recent origin and rapid expansion of this lineage in Nigeria, with the country serving as a potential source for this lineage in other outbreaks. These results demonstrate the importance of genomic surveillance for identifying SARS-CoV-2 variants of concern in Nigeria and in other undersampled regions across the globe.

Patterns and persistence of SARS-CoV-2 IgG antibodies in a US metropolitan site (preprint)

BackgroundEstimates of seroprevalence to SARS-CoV-2 vary widely. We ascertained IgG levels across a single US metropolitan site, Chicago, over the 2020 summer, a period when restrictions on activities had been lifted. MethodsWe utilized a self-sampled dried blood spot assay to quantitatively monitor antibodies to the receptor binding domain (RBD) of the spike glycoprotein of SARS-CoV-2 in 1545 participants, with return of blood spot cards either by mail or in-person drop-off. ResultsSeroprevalence was 19.8%, with no significant difference between method of contact, or between essential and non-essential workers. Only a small number (1.2%) of participants reported having had a diagnosis of COVID-19 based on virus detection, consistent with a 16-fold greater exposure to SARS-CoV-2 measured by serology than detected by viral testing. Only a modest correlation was observed between having antibodies to SARS-CoV-2 nucleocapsid compared to RBD, with many only having detectable anti-RBD antibodies. From a subset of those who participated in repeat testing, three-quarters of seropositive individuals retained detectable antibodies for at least 120 days. One seropositive individual experienced a strong boost in IgG levels following a symptomatic illness, suggestive of potential re-exposure. ConclusionsThese data underscore the importance of a self-collected, quantitative assay with adequate sensitivity to detect antibodies at the lower levels among non-hospitalized persons with community-acquired exposure to COVID-19.

Sequential ER stress and inflammatory responses are induced by SARS-CoV-2 ORF3 through ERphagy (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have resulted in a number of severe cases of COVID-19 and deaths worldwide. However, knowledge of SARS-CoV-2 infection, diseases and therapy remains limited, underlining the urgency of fundamental studies and drug development. Studies have shown that induction of autophagy and hijacking of autophagic machinery are essential for infection and replication of SARS-CoV-2; however, the mechanism of this manipulation and function of autophagy during SARS-CoV-2 infection remain unclear. In the present study, we identified ORF3 as an inducer of autophagy and revealed that ORF3 localizes to the ER and induces FAM134B-related ERphagy through the HMGB1-Beclin1 pathway. As a consequence, ORF3 induces ER stress and inflammatory responses through ERphagy and sensitizes cells to ER stress-induced cell death, suggesting that SARS-CoV-2 ORF3 hijacks ERphagy and then harms ER homeostasis to induce inflammatory responses through excessive ER stress. These findings reveal a sequential induction of ERphagy, ER stress and acute inflammatory responses during SARS-CoV-2 infection and provide therapeutic potential for ERphagy and ER stress-related drugs for COVID-19 treatment and prevention. ImportanceSARS-CoV-2 infection and replication require autophagosome-like double-membrane vacuoles. Inhibition of autophagy suppresses viral replication, indicating the essential role of autophagy in SARS-CoV-2 infection. However, how SARS-CoV-2 hijacks autophagy and the function of autophagy in the disease progression remain unknown. Here, we reveal that SARS-CoV-2 ORF3 induces ERphagy and consequently induces ER stress to trigger acute inflammatory responses and enhance sensitivity to ER stress-induced apoptosis. Our studies uncover ERphagy-induced inflammatory responses during SARS-CoV-2 infection and provide a promising therapeutic approach for treating SARS-CoV-2 infection and inflammatory responses in COVID-19 by manipulating autophagy and ER stress.

Single-cell Transcriptome of Bronchoalveolar Lavage Fluid Reveals Dynamic Change of Macrophages During SARS-CoV-2 Infection in Ferrets (preprint)

Although the profile of immune cells changes during the natural course of SARS-CoV-2 inflection in human patients, few studies have used a longitudinal approach to reveal their dynamic features. Here, we performed single-cell RNA sequencing of bronchoalveolar lavage fluid cells longitudinally obtained from SARS-CoV-2-infected ferrets. Landscape analysis of the lung immune microenvironment showed dynamic changes in cell proportions and characteristics in uninfected control, at 2 days post-infection (dpi) (early stage of SARS-CoV-2 infection with peak viral titer), and 5 dpi (resolution phase). NK cells and CD8+ T cells exhibited activated subclusters with interferon-stimulated features, which were peaked at 2 dpi. Intriguingly, macrophages were classified into 10 distinct subpopulations, and their relative proportions changed over the time. We observed prominent transcriptome changes among monocyte-derived infiltrating macrophages and differentiated M1/M2 macrophages, especially at 2 dpi. Moreover, trajectory analysis revealed gene expression changes from monocyte-derived infiltrating macrophages toward M1 or M2 macrophages and identified the distinct macrophage subpopulation that had rapidly undergone SARS-CoV-2-mediated activation of inflammatory responses. Finally, we found that different spectrums of M1 or M2 macrophages showed distinct patterns of gene modules downregulated by immune-modulatory drugs. Overall, these results elucidate fundamental aspects of the immune response dynamics provoked by SARS-CoV-2 infection.

Replicating bacterium-vectored vaccine expressing SARS-CoV-2 Membrane and Nucleocapsid proteins protects against severe COVID-19 disease in hamsters (preprint)

An inexpensive readily manufactured COVID-19 vaccine that protects against severe disease is needed to combat the pandemic. We have employed the LVS {Delta}capB vector platform, previously used successfully to generate potent vaccines against the Select Agents of tularemia, anthrax, plague, and melioidosis, to generate a COVID-19 vaccine. The LVS {Delta}capB vector, a replicating intracellular bacterium, is a highly attenuated derivative of a tularemia vaccine (LVS) previously administered to millions of people. We generated vaccines expressing SARS-CoV-2 structural proteins and evaluated them for efficacy in the golden Syrian hamster, which develops severe COVID-19 disease. Hamsters immunized intradermally or intranasally with a vaccine co-expressing the Membrane (M) and Nucleocapsid (N) proteins, then challenged 5-weeks later with a high dose of SARS-CoV-2, were protected against severe weight loss and lung pathology and had reduced viral loads in the oropharynx and lungs. Protection by the vaccine, which induces murine N-specific interferon-gamma secreting T cells, was highly correlated with pre-challenge serum anti-N TH1-biased IgG. This potent vaccine against severe COVID-19 should be safe and easily manufactured, stored, and distributed, and given the high homology between MN proteins of SARS-CoV and SARS-CoV-2, has potential as a universal vaccine against the SARS subset of pandemic causing {beta}-coronaviruses.

Functional Landscape of SARS-CoV-2 Cellular Restriction (preprint)

A deficient interferon response to SARS-CoV-2 infection has been implicated as a determinant of severe COVID-19. To identify the molecular effectors that govern interferon control of SARS-CoV-2 infection, we conducted a large-scale gain-of-function analysis that evaluated the impact of human interferon stimulated genes (ISGs) on viral replication. A limited subset of ISGs were found to control viral infection, including endosomal factors that inhibited viral entry, nucleic acid binding proteins that suppressed viral RNA synthesis, and a highly enriched cluster of ER and Golgi-resident ISGs that inhibited viral translation and egress. These included the type II integral membrane protein BST2/tetherin, which was found to impede viral release, and is targeted for immune evasion by SARS-CoV-2 Orf7a protein. Overall, these data define the molecular basis of early innate immune control of viral infection, which will facilitate the understanding of host determinants that impact disease severity and offer potential therapeutic strategies for COVID-19.

A Unique Clade of SARS-CoV-2 Viruses is Associated with Lower Viral Loads in Patient Upper Airways (preprint)

BackgroundThe rapid spread of SARS-CoV-2, the causative agent of Coronavirus disease 2019 (COVID- 19), has been accompanied by the emergence of distinct viral clades, though their clinical significance remains unclear. Here, we aimed to investigate the phylogenetic characteristics of SARS-CoV-2 infections in Chicago, Illinois and assess their relationship to clinical parameters. MethodsWe performed whole-genome sequencing of SARS-CoV-2 isolates collected from COVID-19 patients in a Chicago healthcare system in mid-March, 2020. Using these and other publicly available sequences, we performed phylogenetic, phylogeographic, and phylodynamic analyses. Patient data was assessed for correlations between demographic or clinical characteristics and virologic features. FindingsThe 88 SARS-CoV-2 genome sequences in our study separated into three distinct phylogenetic clades. Clade 1 was most closely related to viral sequences from New York, and showed evidence of rapid expansion across the US, while Clade 3 was most closely related to those in Washington state. Clade 2 was localized primarily to the Chicago area with limited evidence of expansion elsewhere. At the time of diagnosis, patients infected with Clade 1 viruses had significantly higher average viral loads in their upper airways relative to patients infected with Clade 2 viruses, independent of time to symptom onset and disease severity. InterpretationThese results show that multiple variants of SARS-CoV-2 are circulating in the Chicago area that differ in their relative viral loads in patient upper airways. These data suggest that differences in virus genotype impact viral load and may in turn influence viral transmission and spread. FundingDixon Family Translational Research Award, Northwestern University Clinical and Translational Sciences Institute (NUCATS), National Institute of Allergy and Infectious Diseases (NIAID)