Mucosal Immunity

A small spray in to the nose could protect people from COVID-19 and hamstring the pandemic, but the science still faces major challenges.

One ‘superspreader’ with Omicron shed three times as much viral RNA as those with Alpha or Delta.  People infected with the highly transmissible Alpha, Delta and Omicron variants of SARS-CoV-2 spew out higher amounts of virus than do those infected with other variants, according to a study1. Furthermore, individuals who contract COVID-19 after vaccination, and even after a booster dose, still shed virus into the air. The work was posted on the medRxiv preprint server on 29 July. It has not yet been peer reviewed. “This research showed that all three of those variants that have won the infection race … come out of the body more efficiently when people talk or shout than the earliest strains of the coronavirus,” says John Volckens, a public-health engineer at Colorado State University in Fort Collins. Study co-author Kristen Coleman, who researches emerging infectious diseases at the University of Maryland in College Park, says this means that people should be “pushing governments to invest in improving indoor air quality by improving ventilation and filtration systems”.

Breathe out

For the study, Coleman and her colleagues recruited 93 people between mid-2020 and early 2022 who were infected with SARS-CoV-2. Participants’ infections were caused by strains including the Alpha variant, which emerged in late 2020, and the later Delta and Omicron variants. All participants with the latter two strains had been fully vaccinated before catching the virus. The infected people faced into a cone-shaped apparatus and sang and shouted — with inevitable coughs and sneezes in between — for 30 minutes, while an attached machine collected the particles they exhaled. The device, called a Gesundheit-II, separated out the fine ‘aerosol’ droplets measuring 5 micrometres or less in diameter, which can linger in the air and leak through cloth and surgical masks.  The team found that participants infected with the Alpha, Delta and Omicron variants emitted significantly more viral RNA when exhaling than did people infected with other variants. These include ancestral variants, such as the one first detected in Wuhan, China, and those not associated with increased transmissibility — such as Gamma, which arose in late 2020. For participants with Delta and Omicron, their fine aerosol contained on average five times the amount of virus that was detected in their larger, coarse aerosol. The team also seeded cells in the laboratory with aerosol samples and found that four samples, each from a participant with either Delta or Omicron, infected the cells. Shed virus is not always infectious, says study co-author Jianyu Lai, an epidemiologist at the University of Maryland, and the samples’ ability to infect laboratory cells means that viral RNA in exhaled aerosols can spread the disease. Malin Alsved, an aerosol technology scientist at Lund University in Sweden, says: “I’m bit concerned that they mix all the respiratory [aerosols] — they have breathing, talking, speaking, screaming, coughing, even sneezing in the sample.” Coleman responds that the team combined respiratory samples to mimic a real-life scenario such as being in a restaurant.

Published in Nature (August 17, 2022):

https://doi.org/10.1038/d41586-022-02202-z

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Article Text Article menu PDF Editorial Mucosal associated invariant T cells in ARDS: MAIT cells set fire to macrophages via cytokines Dong Hyun Kim1, Bonah Kim1, http://orcid.org/0000-0002-5347-9591Won-Woo Lee1,2,3 Laboratory of Autoimmunity and Inflammation (LAI), Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea Cancer Research Institute, Ischemic/Hypoxic Disease Institute, and Institute of Infectious Diseases, Seoul National University College of Medicine, Seoul, Republic of Korea Correspondence to Dr Won-Woo Lee, Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; wonwoolee{at}snu.ac.kr http://dx.doi.org/10.1136/thoraxjnl-2022-218696 Statistics from Altmetric.com Request Permissions If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways. Mucosal-associated invariant T (MAIT) cells are evolutionarily conserved innate-like T cells that play an important role in the maintenance of homeostasis of mucosal and non-mucosal barriers.1 They are highly abundant in the liver and blood and are also present in mucosal tissues. MAIT cells express a semi-invariant T cell receptor (TCR) recognising precursor derivatives of the riboflavin (vitamin B2) biosynthetic pathway, presented by the evolutionarily conserved, monomorphic major histocompatibility complex (MHC) class I-related protein-1 (MR1).1 Since these derivatives are strictly found in riboflavin-synthesising bacteria and yeasts, MAIT cells mediate a broad and potent antimicrobial reactivity.1 Activated MAIT cells rapidly secret proinflammatory cytokines, such as interleukin-17 (IL-17), interferon-γ (IFN-γ), and tumor necrosis factor (TNF) and exert cytolytic activity against cells presenting bacterial ligands on MR1.2 Additionally, MAIT cells can be activated in a TCR/MR1-independent manner by several cytokines, including IL-12, IL-15, IL-18 and type I interferons.2 3 In this issue of Thorax, Kim and colleagues4 broaden our understanding of the pathological role of MAIT cells in acute respiratory distress syndrome (ARDS). ARDS is an acute respiratory illness featured by bilateral chest radiographical opacities with severe hypoxemia due to non-cardiogenic pulmonary oedema.5 ,6 ARDS occurs most often in the setting of pneumonia, non-pulmonary sepsis, aspiration of gastric contents or severe trauma. The authors demonstrate that the frequency … View Full Text FootnotesContributors Conceptualisation: DHK, BK and W-WL. Writing—original draft: DHK and BK, writing—manuscript: W-WL. Funding acquisition: W-WL. Supervision: W-WL. All authors have read and approved the final manuscript.Funding This work was supported by the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT, grant number 2021M3A9I2080493.Competing interests None declared.Provenance and peer review Commissioned; externally peer reviewed. Linked Articles Critical careAltered distribution, activation and increased IL-17 production of mucosal-associated invariant T cells in patients with acute respiratory distress syndrome Tae-Ok Kim Ki-Jeong Park Young-Nan Cho Hye-Mi Jin Young-Goun Jo Hyo Shin Kim Jae Kyun Ju Hong-Joon Shin Bo-Gun Kho Seung-Jung Kee Yong-Wook Park Thorax 2022; 77 865-872 Published Online First: 27 Jan 2022. doi: 10.1136/thoraxjnl-2021-217724 Read the full text or download the PDF: Subscribe Log in

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