Coronavirus disease 2019 (COVID-19) has emerged as a global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS–CoV-2). So far, viral targets of cellular immunity and factors determining successful mounting of T cell responses are poorly defined. We therefore analyzed cellular responses to membrane, nucleocapsid, and spike proteins in individuals suffering from moderate or severe infection and in individuals who recovered from mild disease. We demonstrate that the CoV-2–specific CD4⁺ T helper cell response is directed against all 3 proteins with comparable magnitude, ex vivo proliferation, and portions of responding patients. However, individuals who died were more likely to have not mounted a cellular response to the proteins. Higher patient age and comorbidity index correlated with increased frequencies of CoV-2–specific CD4⁺ T cells, harboring higher portions of IL-2–secreting, but lower portions of IFN-γ–secreting, cells. Diminished frequencies of membrane protein–reactive IFN-γ⁺ T cells were particularly associated with higher acute physiology and chronic health evaluation II scores in patients admitted to intensive care. CoV-2–specific T cells exhibited elevated PD-1 expression in patients with active disease as compared with those individuals who recovered from previous mild disease. In summary, our data suggest a link between individual patient predisposition with respect to age and comorbidity and impairment of CoV-2–specific Th1-type cellular immunity, thereby supporting a concept of altered T cell function in at-risk patients.

The pathogenesis of severe COVID-19 reflects an inefficient immune reaction to SARS-CoV-2. Here we analyze, at the single cell level, plasmablasts egressed into the blood to study the dynamics of adaptive immune response in COVID-19 patients requiring intensive care. Before seroconversion in response to SARS-CoV-2 spike protein, peripheral plasmablasts display a type 1 interferon-induced gene expression signature; however, following seroconversion, plasmablasts lose this signature, express instead gene signatures induced by IL-21 and TGF-β, and produce mostly IgG1 and IgA1. In the sustained immune reaction from COVID-19 patients, plasmablasts shift to the expression of IgA2, thereby reflecting an instruction by TGF-β. Despite their continued presence in the blood, plasmablasts are not found in the lungs of deceased COVID-19 patients, nor does patient IgA2 binds to the dominant antigens of SARS-CoV-2. Our results thus suggest that, in severe COVID-19, SARS-CoV-2 triggers a chronic immune reaction that is instructed by TGF-β, and is distracted from itself.

COVID-19 intensive care patients occasionally develop neurological symptoms. The absence of SARS-CoV-2 in most cerebrospinal fluid (CSF) samples suggests the involvement of further mechanisms including autoimmunity. We therefore determined whether anti-neuronal or anti-glial autoantibodies are present in eleven consecutive severely ill COVID-19 patients presenting with unexplained neurological symptoms. These included myoclonus, cranial nerve involvement, oculomotor disturbance, delirium, dystonia and epileptic seizures. Most patients showed signs of CSF inflammation and increased levels of neurofilament light chain. All patients had anti-neuronal autoantibodies in serum or CSF when assessing a large panel of autoantibodies against intracellular and surface antigens relevant for central nervous system diseases using cell-based assays and indirect immunofluorescence on murine brain sections. Antigens included proteins well-established in clinical routine, such as Yo or NMDA receptor, but also a variety of specific undetermined epitopes on brain sections. These included vessel endothelium, astrocytic proteins and neuropil of basal ganglia, hippocampus or olfactory bulb. The high frequency of autoantibodies targeting the brain in the absence of other explanations suggests a causal relationship to clinical symptoms, in particular to hyperexcitability (myoclonus, seizures). While several underlying autoantigens still await identification in future studies, presence of autoantibodies may explain some aspects of multi-organ disease in COVID-19 and can guide immunotherapy in selected cases.

Purpose: CytoSorb® (CS) adsorbent is a hemoadsorption filter for extracorporeal blood purification often integrated into continuous kidney replacement therapy (CKRT). It is primarily used in critically ill patients with sepsis and related conditions, including cytokine storms and systemic inflammatory responses. Up to now, there is no evidence nor recommendation for the use of CS filters in sepsis (22). There is limited clinical data on the effect of CS on the plasma concentrations of beta-lactams. We aimed to evaluate the statistical and clinical impact of CS in a post-filter CKRT-CS setting on the plasma concentrations of the antibiotics meropenem and piperacillin in critically ill patients. Methods: Patients admitted to the intensive care unit (ICU) who received a prolonged infusion of piperacillin or meropenem with CS-combined CKRT were included in this retrospective analysis. TDM (therapeutic drug monitoring) plasma blood samples were collected at three different points. The differences in antibiotic concentrations between Pre, Intra, and Post were statistically compared to evaluate the total and isolated contributions of CKRT and CS to antibiotic removal. CS, CKRT and combined clearance (CL) values were calculated. The hypothesis was that the CS filter would have no clinically relevant impact on antibiotic levels. Results: 207 TDM samples were taken from 24 critically ill patients requiring beta-lactam antibiotics. Among these, 129 were meropenem samples, and 78 were piperacillin samples. A decrease in both antibiotic levels was observed between Pre and Intra, and Pre and Post, and the median relative difference between was >15% (meropenem: Pre–Intra 34.8%, Pre–Post 35.8%; piperacillin: Pre–Intra 41.1%, Pre–Post 34.7%), indicating a statistically and clinically significant effect of CKRT on both antibiotic exposures. No significant difference was observed between Intra and Post indicating no clinically relevant drug removal via the CS filter. Changes in CL attributed to CS were minimal, with combined CL differing by ≤8.60% compared to CKRT clearance. Conclusion: The application of CS does not appear to significantly affect plasma concentrations of meropenem and piperacillin in critically ill patients.

Treatment of ventilated pneumonia is often unsuccessful, even when patients are treated according to current guidelines. Therefore, we aimed to investigate the efficacy of the adjunctive inhaled Tobramycin in patients with pneumonia caused by Gram-negative pathogens in addition to the standard systemic treatment. Prospective, multicenter, double-blinded, randomized, placebo-controlled clinical trial. 26 patients in medical and surgical ICUs. Patients with ventilator-associated pneumonia caused by Gram-negative pathogens. Fourteen patients were assigned to the Tobramycin Inhal group and 12 patients to the control group. The microbiological eradication of the Gram-negative pathogens was significantly higher in the intervention group than in the control group (p < 0.001). The probability of eradication was 100% in the intervention group [95% Confidence Interval: 0.78-1.0] and 25% in the control group [95% CI: 0.09-0.53]. The increased eradication frequency was not associated with increased patient survival. Inhaled aerosolized Tobramycin demonstrated clinically meaningful efficacy in patients with Gram-negative ventilator-associated pneumonia. The probability of eradication in the intervention group was 100%. However, the successful eradication was not associated with a reduction in systemic anti-infective therapy, a shorter ICU stay, or even a survival benefit. In the presence of multidrug-resistant Gram-negative pathogens that are sensitive only to colistin and/or aminoglycosides, supplemental inhaled therapy with nebulizers suitable for this purpose should be considered in addition to systemic antibiotic therapy.