Severe SARS-CoV-2 infection1 has been associated with highly inflammatory immune activation since the earliest days of the COVID-19 pandemic2–5. More recently, these responses have been associated with the emergence of self-reactive antibodies with pathologic potential6–10, although their origins and resolution have remained unclear11. Previously, we and others have identified extrafollicular B cell activation, a pathway associated with the formation of new autoreactive antibodies in chronic autoimmunity12,13, as a dominant feature of severe and critical COVID-19 (refs. 14–18). Here, using single-cell B cell repertoire analysis of patients with mild and severe disease, we identify the expansion of a naive-derived, low-mutation IgG1 population of antibody-secreting cells (ASCs) reflecting features of low selective pressure. These features correlate with progressive, broad, clinically relevant autoreactivity, particularly directed against nuclear antigens and carbamylated proteins, emerging 10–15 days after the onset of symptoms. Detailed analysis of the low-selection compartment shows a high frequency of clonotypes specific for both SARS-CoV-2 and autoantigens, including pathogenic autoantibodies against the glomerular basement membrane. We further identify the contraction of this pathway on recovery, re-establishment of tolerance standards and concomitant loss of acute-derived ASCs irrespective of antigen specificity. However, serological autoreactivity persists in a subset of patients with postacute sequelae, raising important questions as to the contribution of emerging autoreactivity to continuing symptomology on recovery. In summary, this study demonstrates the origins, breadth and resolution of autoreactivity in severe COVID-19, with implications for early intervention and the treatment of patients with post-COVID sequelae.

Rhabdomyolysis is characterised by muscle breakdown with release of damaging proteins that can have devastating consequences. Acute influenza infection is being increasingly recognised as an underlying aetiology. We report an unusual case of severe rhabdomyolysis with acute renal failure due to influenza A infection that improved with high-dose oseltamivir and intravenous fluids. In our case, we also noticed a temporal relation between fever spikes and subsequent increase in serum creatine kinase. The precise mechanism between the rise in temperature and creatine kinase is unclear but it could be due to direct viral invasion of myocytes or due to release of new viral progeny following replication in the myocyte.

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Recent studies have demonstrated the significant breadth of emerging autoreactivity in severe SARS-CoV-2 infection. Importantly, we have identified a relaxation of peripheral tolerance within early antibody secreting cells that emerge in patients with COVID-19 as important drivers of those responses. While often viral-specific, these extrafollicular-derived cells also display cross reactivity to autoantigens present in the inflammatory lung environment, and despite resolution of most autoreactivity within 6 months, they persisted in some patients. These results raise questions regarding autoreactive antibodies that arise during acute SARS-CoV-2 infection and their persistence in patients with symptoms in Post-Acute Sequelae of SARS-CoV-2 infection (PASC). Through clinical autoreactive antibody screening of 95 patients with PASC and no history of autoimmune disease, we identify significant autoreactive profiles in patients with ongoing symptoms post-recovery, with 80% of patients returning positive tests for at least one autoantigen, and 40% showing breaks in tolerance to 2 or more. Anti-nuclear antigen positivity was most common, displaying positivity in 63% of patients, however, positive tests were broad and included reactivities against carbamylated protein responses, RNA polymerase III, and phospholipids. We also identify patients with reactivity against dsDNA in the PASC cohort -- a reactivity not observed in acute infection even in the critically ill. These results demonstrate evidence of serum autoantibodies in patients who present to PASC clinics with persistent symptoms up 14 months following SARS-CoV-2 infection, and further confirm the growing linkage between COVID-19 and observed clinical autoreactivity -- even into the recovery phase of disease.

We report a case of a hospitalised patient who developed probable serotonin toxicity shortly after the initiation of linezolid in whom the selective serotonin reuptake inhibitor (SSRI) escitalopram had been recently discontinued. On day 2 of linezolid administration, the patient reported severe anxiety and was observed to have full body jerking and twitching motions without mental status change. Notably, the patient was concomitantly receiving the antidepressant, trazodone and the benzodiazepine, clonazepam possibly affecting the severity and manifestations of serotonin toxicity. Linezolid was discontinued after 5 days and the patient’s symptoms resolved. Serotonin toxicity can present with an array of symptoms and be life threatening if left unrecognised. This report highlights the clinical lessons that discontinuation of an SSRI upon initiation of linezolid does not eliminate the risk of serotonin toxicity and that other concomitant medications may worsen or improve some of the symptoms lending delay and uncertainty to the diagnosis.

Asthma is a chronic respiratory disease characterized by chronic airway inflammation and airflow obstruction. Up to ten percent of asthmatics have severe asthma, and many remain uncontrolled despite optimal medical management. With our increased understanding of the heterogeneity of asthma and its complex pathophysiology, several biomarkers have been developed and in the recent past, several biologic therapies for severe asthma have been developed and are now in widespread use. Although these biological agents have shown great benefit in treating severe asthma, not all patients respond equally well, and some do not derive any benefit. As much of the current literature of these medications have not assessed biomarkers or have used different cutoffs, it is often challenging to decide the best medication for an individual patient. Here, we review common asthma subtypes, current available biologic therapies for asthma, the clinical application of currently available type 2 biomarkers, as well as summarizing the evidence on how patient characteristics and biomarkers can help with choosing the optimal biologic for a patient that has the highest likelihood of success.

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