| 1. |
- Alsved, Malin, et al.
(författare)
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Droplet, aerosol and SARS-CoV-2 emissions during singing and talking
- 2021
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Konferensbidrag (refereegranskat)abstract
- IntroductionAs the pandemic continues to spread, more knowledge is needed about the viral transmission routes. Several super spreading events during the Covid-19 pandemic have been linked to singing in choirs and talking loud. However, in the beginning of the pandemic there was only one study about emitted aerosols and droplets from singing, published in 1968, and only a handful on emissions from talking. Therefore, we conducted a study to measure the aerosol and droplet emissions from talking and singing. We also evaluated the emissions from singing when wearing a face mask.We have further developed our setup so that we collect the aerosol particles from Covid-19 infected patients that are talking and singing, and analyze our samples for SARS-CoV-2, the virus causing Covid-19.MethodTwelve healthy singers (7 professionals, 5 amateurs) were included in the first study part on quantifying the amount of emitted aerosols and droplets. The singers were singing or talking a short consonant rich text repeatedly at a constant pitch with their face in the opening of a funnel. The aerosol particle size and concentration was measured from the other end of the funnel using an aerodynamic particle sizer (APS, 3321, TSI Inc). In addition, the amount of un-evaporated droplets were captured with a high-speed camera and quantified using image analysis.During February and March 2021 we will collect aerosol particles from patients with confirmed Covid-19 that are singing and talking into a funnel. We will use a growth tube condensation collector, a BioSpot (Aerosol Devices), operating at 8 L min-1, and a NIOSH BC-251 cyclone sampler operating at 3.5 L min-1 (TISCH Environmental). The BioSpot collects the whole range of exhaled aerosol particles with high (95%) efficiency into liquid, and the NIOSH cyclone sampler collects particles into three size fractions: <1 µm (filter), 1-4 µm (liquid), >4 µm (liquid). The APS is again used to measure size and concentration of the emitted aerosol particles, so that emissions from infected test subjects can be compared with those of the healthy test subjects. Air samples will be analyzed for detection of SARS-CoV-2 genes, and if possible, SARS-CoV-2 infectivity in cell cultures.ResultsAerosol particle emissions from healthy test subjects were significantly higher during normal singing (median 690, range [320–2870] particles/s) than during normal talking (270 [120–1380] particles/s) (Wilcoxon’s signed rank test, p=0.002). Loud singing produced even more aerosol particles (980 [390–2870] particles/s) than normal singing (p=0.002). The amount of non-evaporated droplets detected by the high-speed camera setup showed similar results: more droplets during loud singing or talking. For both aerosol particle concentrations and droplet numbers, the levels were reduced by on average 70-80% when wearing a surgical face mask.ConclusionsSinging and talking give rise to high aerosol and droplet emissions from the respiratory tract. This is likely an important transmission route for Covid-19. In our upcoming part of the study we hope to determine how much SARS-CoV-2 that is emitted during these social activities.
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| 2. |
- Alsved, Malin, et al.
(författare)
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Infectivity of exhaled SARS-CoV-2 aerosols is sufficient to transmit covid-19 within minutes
- 2023
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Ingår i: Scientific Reports. - 2045-2322. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Exhaled SARS-CoV-2-containing aerosols contributed significantly to the rapid and vast spread of covid-19. However, quantitative experimental data on the infectivity of such aerosols is missing. Here, we quantified emission rates of infectious viruses in exhaled aerosol from individuals within their first days after symptom onset from covid-19. Six aerosol samples from three individuals were culturable, of which five were successfully quantified using TCID50. The source strength of the three individuals was highest during singing, when they exhaled 4, 36, or 127 TCID50/s, respectively. Calculations with an indoor air transmission model showed that if an infected individual with this emission rate entered a room, a susceptible person would inhale an infectious dose within 6 to 37 min in a room with normal ventilation. Thus, our data show that exhaled aerosols from a single person can transmit covid-19 to others within minutes at normal indoor conditions.
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| 3. |
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| 4. |
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| 5. |
- Alsved, Malin, et al.
(författare)
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SARS-CoV-2 in aerosol particles exhaled from COVID-19 infected patients during breathing, talking and singing
- 2021
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Konferensbidrag (refereegranskat)abstract
- In the beginning of the COVID-19 pandemic, several super spreader events occurred during singing in choirs, which lead to an increased attention to airborne transmission of SARS-CoV-2, the virus causing COVID-19. Since then, aerosol generation from singing has been studied in more detail, however, only from healthy subjects. In this study, we collected aerosol particles in the exhaled breath of 40 COVID-19 infected patients during breathing, talking and singing, respectively, and analysed the samples for detection of SARS-CoV-2.MethodPatients that were contacted by the COVID-19 testing service due to a positive test result were asked to volunteer for the study. A team of researchers drove a small truck hosting a mobile laboratory to the home address of the patient to perform exhaled breath aerosol collection using a condensational particle collector (BioSpot, Aerosol Devices) and a two-stage cyclone sampler (NIOSH bc-251, Tisch Environmental). Samples were collected for 10 min each when the patient was breathing, talking and singing, respectively.All samples were stored at -80°C until RNA extraction and analysis by reverse transcription quantitative polymerase chain reaction (RT-qPCR) targeting the N-gene.ResultsA first screening of air samples collected with the BioSpot showed that SARS-CoV-2 could be detected in the exhaled aerosols from three of nine patients during singing or talking. Two of these samples contained 103 and 104 viral RNA copies, corresponding to a viral emission rate of approximately 4 and 25 viruses per second, respectively. Samples from the remaining 31 patients are to be analysed during the spring. We hope to contribute to quantifying and understanding the Covid-19 transmission via the airborne route.This study was approved by the Swedish Ethics Review Authority (2020-07103). This work was supported by AFA Insurances and the Swedish Research Council FORMAS.
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| 6. |
- Alsved, Malin, et al.
(författare)
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SARS-CoV-2 in aerosol particles exhaled from COVID-19 infected patients during breathing, talking and singing
- 2021
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Konferensbidrag (refereegranskat)abstract
- In the beginning of the COVID-19 pandemic, several super spreader events occurred during choir singing, which lead to an increased attention to airborne transmission of SARS-CoV-2. Since then, aerosol generation from singing has been studied in detail, however, mainly from healthy subjects. In this study, we collected aerosol particles in the exhaled breath of 38 COVID-19 infected patients during breathing, talking and singing, respectively, and analyzed the samples for detection of SARS-CoV-2.MethodPatients that were contacted by the COVID-19 testing service due to a positive test result early in the phase of their infection (median 2, range: 0-6 days from symptom onset) were asked to volunteer for the study. A team of researchers drove a small truck hosting a mobile laboratory to the home address of the patient to perform exhaled breath aerosol collection using a condensational particle collector (BioSpot, Aerosol Devices) and a two-stage cyclone sampler (NIOSH bc-251, Tisch Environmental). Samples were collected for 10 min each when the patients were breathing, talking and singing, respectively. In addition, patient samples from nasopharynx and saliva were collected, and patients filled out a questionnaire about symptoms. All samples were stored at -80 °C until RNA extraction and analysis by reverse transcription quantitative polymerase chain reaction (RT-qPCR) targeting the N-gene.ResultsA first preliminary screening of air samples collected with the BioSpot showed that SARS-CoV-2 could be detected in the exhaled aerosols from 14 of 38 (37%) patients during respiratory activities. 50% of patients in the early phase of the infection, day 0-1 from symptom onset, emitted detectable levels of airborne SARS-CoV-2 RNA, 35% of patients on day 2-3, and 0% of patients on day 4-6. The highest viral RNA concentrations in aerosol samples were found in those collected during singing. Further analysis is ongoing and we hope that our results will contribute to quantifying and understanding the Covid-19 transmission via the airborne route.This study was approved by the Swedish Ethics Review Authority (2020-07103). This work was supported by AFA Insurances and the Swedish Research Council FORMAS.
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| 7. |
- Alsved, Malin, et al.
(författare)
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SARS-CoV-2 in exhaled aerosol particles from covid-19 cases and its association to household transmission
- 2022
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Ingår i: Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. - : Oxford University Press (OUP). - 1537-6591. ; 75:1, s. 50-56
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Covid-19 transmission via exhaled aerosol particles has been considered an important route for the spread of infection, especially during super-spreading events involving loud talking or singing. However, no study has previously linked measurements of viral aerosol emissions to transmission rates.METHODS: During Feb-Mar 2021, covid-19 cases that were close to symptom onset were visited with a mobile laboratory for collection of exhaled aerosol particles during breathing, talking and singing, respectively, and of nasopharyngeal and saliva samples. Aerosol samples were collected using a BioSpot-VIVAS and a NIOSH bc-251 two-stage cyclone, and all samples were analyzed by RT-qPCR for SARS-CoV-2 RNA detection. We compared transmission rates between households with aerosol-positive and aerosol-negative index cases.RESULTS: SARS-CoV-2 RNA was detected in at least one aerosol sample from 19 of 38 (50%) included cases. The odds ratio of finding positive aerosol samples decreased with each day from symptom onset (OR 0.55, 95CI 0.30-1.0, p=0.049). The highest number of positive aerosol samples were from singing, 16 (42%), followed by talking, 11 (30%), and the least from breathing, 3 (8%). Index cases were identified for 13 households with 31 exposed contacts. Higher transmission rates were observed in households with aerosol-positive index cases, 10/16 infected (63%), compared to households with aerosol-negative index cases, 4/15 infected (27%) (Chi-square test, p=0.045).CONCLUSIONS: Covid-19 cases were more likely to exhale SARS-CoV-2-containing aerosol particles close to symptom onset and during singing or talking as compared to breathing. This study supports that individuals with SARS-CoV-2 in exhaled aerosols are more likely to transmit covid-19.
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| 8. |
- Alsved, Malin, et al.
(författare)
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Size distribution of exhaled aerosol particles containing SARS-CoV-2 RNA
- 2023
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Ingår i: Infectious Diseases. - : Informa UK Limited. - 2374-4235 .- 2374-4243. ; 55:2, s. 158-163
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Tidskriftsartikel (refereegranskat)abstract
- Background: SARS-CoV-2 in exhaled aerosols is considered an important contributor to the spread of COVID-19. However, characterizing the size distribution of virus-containing aerosol particles has been challenging as high concentrations of SARS-CoV-2 in exhaled air is mainly present close to symptom onset. We present a case study of a person with COVID-19 who was able to participate in extensive measurements of exhaled aerosols already on the day of symptom onset and then for the following three days. Methods: Aerosol collection was performed using an eight-stage impactor while the subject was breathing, talking and singing, for 30 min each, once every day. In addition, nasopharyngeal samples, saliva samples, room air samples and information on symptom manifestations were collected every day. Samples were analyzed by RT-qPCR for detection of SARS-CoV-2 RNA. Results: SARS-CoV-2 RNA was detected in seven of the eight particle size fractions, from 0.34 to >8.1 µm, with the highest concentrations found in 0.94–2.8 µm particles. The concentration of SARS-CoV-2 RNA was highest on the day of symptom onset, and declined for each day thereafter. Conclusion: Our data showed that 90% of the exhaled SARS-CoV-2 RNA was found in aerosol particles <4.5 µm, indicating the importance of small particles for the transmission of COVID-19 close to symptom onset. These results are important for our understanding of airborne transmission, for developing accurate models and for selecting appropriate mitigation strategies.
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| 9. |
- Boesze-Battaglia, Kathleen, et al.
(författare)
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The Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin Active Subunit CdtB Contains a Cholesterol Recognition Sequence Required for Toxin Binding and Subunit Internalization
- 2015
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Ingår i: Infection and Immunity. - : AMER SOC MICROBIOLOGY. - 0019-9567 .- 1098-5522. ; 83:10, s. 4042-4055
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Tidskriftsartikel (refereegranskat)abstract
- Induction of cell cycle arrest in lymphocytes following exposure to the Aggregatibacter actinomycetemcomitans cytolethal distending toxin (Cdt) is dependent upon the integrity of lipid membrane microdomains. Moreover, we have previously demonstrated that the association of Cdt with target cells involves the CdtC subunit which binds to cholesterol via a cholesterol recognition amino acid consensus sequence (CRAC site). In this study, we demonstrate that the active Cdt subunit, CdtB, also is capable of binding to large unilamellar vesicles (LUVs) containing cholesterol. Furthermore, CdtB binding to cholesterol involves a similar CRAC site as that demonstrated for CdtC. Mutation of the CRAC site reduces binding to model membranes as well as toxin binding and CdtB internalization in both Jurkat cells and human macrophages. A concomitant reduction in Cdt-induced toxicity was also noted, indicated by reduced cell cycle arrest and apoptosis in Jurkat cells and a reduction in the proinflammatory response in macrophages (interleukin 1 beta [IL-1 beta] and tumor necrosis factor alpha [TNF-alpha] release). Collectively, these observations indicate that membrane cholesterol serves as an essential ligand for both CdtC and CdtB and, further, that this binding is necessary for both internalization of CdtB and subsequent molecular events leading to intoxication of cells.
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| 10. |
- Bonvicini, Gillian, et al.
(författare)
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Comparing in vitro affinity measurements of antibodies to TfR1 : Surface plasmon resonance versus on-cell affinity
- 2024
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Ingår i: Analytical Biochemistry. - : Elsevier. - 0003-2697 .- 1096-0309. ; 686
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Tidskriftsartikel (refereegranskat)abstract
- Despite years of utilizing the transferrin receptor 1 (TfR1) to transport large biomolecules into the brain, there is no consensus on how to optimally measure affinity to it. The aim of this study was to compare different methods for measuring the affinities of anti-TfR1 antibodies.Antibodies 15G11, OX26 and 8D3 are known to successfully carry large biologics across the blood-brain barrier in humans, rats, and mice, respectively. The affinity to their respective species of TfR1 was measured with different surface plasmon resonance setups in Biacore and an on-cell assay.When the antibody was captured and TfR1 was the analyte, the dissociation in Biacore was very slow. The dissociation was faster when the antibody was the analyte and TfR1 was the ligand. The Biacore setup with capture of N-terminal FLAG-tag TfR1 yielded the most similar apparent affinities as the cell assay.In conclusion, it is important to evaluate assay parameters including assay orientation, surface capture method, and antibody format when comparing binding kinetics for TfR1 antibodies. Although it seems possible to determine relative affinities of TfR1 antibodies using the methods described here, both the FLAG-tag TfR1 capture setup and cell assays likely yield apparent affinities that are most translatable in vivo.
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