Impaired SARS-CoV-2 specific T-cell response in patients with severe COVID-19.

Cellular immune responses are of pivotal importance to understand SARS-CoV-2 pathogenicity. Using an enzyme-linked immunosorbent spot (ELISpot) interferon-γ release assay with wild-type spike, membrane and nucleocapsid peptide pools, we longitudinally characterized functional SARS-CoV-2 specific T-cell responses in a cohort of patients with mild, moderate and severe COVID-19. All patients were included before emergence of the Omicron (B.1.1.529) variant. Our most important finding was an impaired development of early IFN-γ-secreting virus-specific T-cells in severe patients compared to patients with moderate disease, indicating that absence of virus-specific cellular responses in the acute phase may act as a prognostic factor for severe disease. Remarkably, in addition to reactivity against the spike protein, a substantial proportion of the SARS-CoV-2 specific T-cell response was directed against the conserved membrane protein. This may be relevant for diagnostics and vaccine design, especially considering new variants with heavily mutated spike proteins. Our data further strengthen the hypothesis that dysregulated adaptive immunity plays a central role in COVID-19 immunopathogenesis.

Differential abundance of IgG antibodies against the spike protein of SARS-CoV-2 and seasonal coronaviruses in patients with fatal COVID-19.

Infection with the novel pandemic SARS-CoV-2 virus has been shown to elicit a cross-reactive immune response that could lead to a back-boost of memory recall to previously encountered seasonal (endemic) coronaviruses (eCoVs). Whether this response is associated with a fatal clinical outcome in patients with severe COVID-19 remains unclear. In a cohort of hospitalized patients, we have previously shown that heterologous immune responses to eCoVs can be detected in severe COVID-19. Here, we report that COVID-19 patients with fatal disease have decreased SARS-CoV-2 neutralizing antibody titers at hospital admission, which correlated with lower SARS-CoV-2 spike-specific IgG and was paralleled by a relative abundance of IgG against spike protein of eCoVs of the genus Betacoronavirus. Additional research is needed to assess if eCoV-specific back-boosted IgG is a bystander phenomenon in severe COVID-19, or a factor that influences the development of an efficient anti-viral immune response.

[A 30-year-old man with a puddle of pleural effusion]. / A 30-year-old man with a puddle of pleural effusion.

BACKGROUND: The pleural effusion found in urinothorax is traditionally classified as transudate. In some cases, however, the Light-criteria can show an exudate. CASE DESCRIPTION: We describe the case of a 30-year-old man who attended the emergency department with shortness of breath and severe, diffuse, chest pain; this occurred two days after he had undergone a left-sided percutaneous nephrolithotomy by a urologist. A chest X-ray showed pleural effusion in the left basal region. Based on the Light-criteria, this effusion was an exudate. We made the diagnosis of urinothorax following percutaneous nephrolithotomy. CONCLUSION: When urinothorax is suspected, biochemical analysis can reveal either a transudate or an exudate. The pleural fluid/serum creatinine ratio can be a valuable addition to the Light-criteria in this setting. The Light-criteria should always be interpreted in a clinical context.

Clinical relevance of Corynebacterium pseudodiphtheriticum in lower respiratory tract specimens.

BACKGROUND: Corynebacterium pseudodiphtheriticum may be present as commensal flora of the respiratory tract and therefore it may be difficult to assess clinical relevance when it is cultured from lower respiratory tract specimens. Our objective was to determine the clinical relevance of C. pseudodiphtheriticum as a lower respiratory tract pathogen and to define patients at risk of developing lower respiratory tract infections caused by C. pseudodiphtheriticum. METHODS: We retrospectively identified all lower respiratory tract cultures positive for C. pseudodiphtheriticum over a 10-year period and assessed clinical relevance by predefined criteria. RESULTS: Clinical relevance was likely or possible in 86% of patients. Pre-existent comorbidity was present in 86% of patients, mostly underlying cardiac or pulmonary disease. All isolates were susceptible to amoxicillin. CONCLUSION: C. pseudodiphtheriticum should be considered a clinically relevant pathogen when cultured from the lower respiratory tract in symptomatic patients.

Diagnosis of Coxiella burnetii infection: comparison of a whole blood interferon-gamma production assay and a Coxiella ELISPOT.

Diagnosis of ongoing or past infection with Coxiella burnetii, the causative agent of Q fever, relies heavily on serology: the measurement of C. burnetii-specific antibodies, reflecting the host's humoral immune response. However, cell-mediated immune responses play an important, probably even more relevant, role in infections caused by the intracellular C. burnetii bacterium. Recent studies have investigated interferon-gamma (IFN-γ) based assays, including a whole-blood IFN-γ production assay and a Coxiella enzyme-linked immunospot (Coxiella ELISPOT), as potential diagnostic tools for Q fever diagnosis. Both are in-house developed assays using stimulating antigens of different origin. The main objective of this study was to compare the test performance of the IFN-γ production assay and the Coxiella ELISPOT for detecting a cellular immune response to C. burnetii in Q fever patients, and to assess the correlation between both assays. To that end, both tests were performed in a well-defined patient group of chronic Q fever patients (n = 16) and a group of healthy seronegative individuals (n = 17). Among patients, both the Coxiella ELISPOT and the IFN-γ production assay detected positive response in 14/16. Among controls, none were positive in the Coxiella ELISPOT, whereas the IFN-γ production assay detected positive results in 1/17 and 3/17, when using Henzerling and Nine Mile as stimulating antigens, respectively. These results suggest the Coxiella ELISPOT has a somewhat higher specificity than the IFN-γ production assay when Nine Mile is used as antigen stimulus. The assays showed moderate correlation: the Spearman correlation coefficient r ranged between 0.37-0.60, depending on the antigens used. Further investigation of the diagnostic potential for C. burnetii infection of both assays is warranted.

[Recurrent miscarriage turns out to be lung cancer]. / Herhaalde miskraam blijkt longkanker.

BACKGROUND: If a positive pregnancy test is followed by profuse vaginal bleeding, the diagnosis of miscarriage can generally be made. Sometimes, however, elevated hCG levels may be associated with a phantom pregnancy, which may be a paraneoplastic symptom. CASE DESCRIPTION: A 27-year-old woman was referred for a diagnosis after having experienced 3 consecutive miscarriages. The diagnostic workup could not identify an underlying cause. After 3 more biochemical miscarriages, the original diagnosis was called into question and extensive testing for ectopic hCG production was performed. It appeared that the false pregnancies were paraneoplastic symptoms of an hCG-producing non-small cell lung cancer. After a lobectomy, the hCG levels returned to normal and a spontaneous pregnancy and uncomplicated delivery followed. CONCLUSION: Phantom pregnancy as a paraneoplastic symptom is extremely rare, but should be considered in patients presenting with recurrent, non-objectifiable miscarriages. Careful documentation of the menstrual cycle is necessary for early detection of the condition. The fact is that vaginal bleeding after a positive pregnancy test can still be a normal menstruation.

Developing a new clinical tool for diagnosing chronic Q fever: the Coxiella ELISPOT.

Definitively establishing a clinical diagnosis of chronic Q fever remains challenging, as the diagnostic performance of both conventional serological tests and PCR is limited. Given the importance of an early diagnosis of chronic Q fever, there is a need for a reliable diagnostic test. We developed an enzyme-linked immunospot assay to measure Coxiella burnetii (C. burnetii)-specific T-cell responses (Coxiella ELISPOT) to both phase I and phase II antigens and tested convalescent Q fever patients (without chronic disease, n = 9) and patients with an established diagnosis of chronic Q fever (n = 3). The Coxiella ELISPOT adequately identified convalescent Q fever patients from healthy controls by demonstrating C. burnetii-specific T-cell interferon-γ production to both phase I and phase II antigens. Compared to convalescent Q fever patients, chronic Q fever patients showed a distinct Coxiella ELISPOT profile characterized by a much higher spot count for both phase I and phase II (18-fold for phase II, 8-fold higher for phase I) and a consistent shift towards more phase I reactivity. The diagnostic potential of the Coxiella ELISPOT is promising and warrants further investigation.

Diagnostic value of histology compared with cytology in transbronchial aspiration samples obtained by histology needle.

OBJECTIVE: Results from endoscopic needle aspiration [transbronchial needle aspiration (TBNA), esophageal ultrasound-guided fine needle aspiration, real-time endobronchial ultrasound] mainly rely on cytology. We performed a retrospective study to evaluate the possible advantage of obtaining histologic samples during TBNA in the diagnostic assessment of mediastinal lymph node enlargement. MATERIALS AND METHODS: In a retrospective study 2 pathologists evaluated all TBNAs from patients with mediastinal lymph node enlargement in whom representative histologic and cytologic material was obtained, using only a histology needle. Cytology was reviewed before histology in a randomized, blinded fashion. Afterward, the results were related to the diagnosis made in the actual workup of the patient. RESULTS: A total of 50 TBNAs were reviewed. In 86% (43 of 50), both pathologists made the same diagnosis on both specimens, or a difference in cytology and/or histology specimens did not alter the eventual treatment. In 14% (7 of 50) of all TBNAs, histology revealed a diagnosis according to at least 1 pathologist, which altered patient treatment. CONCLUSIONS: Histologic material can reveal additional diagnostic information compared with sole cytologic examination in 14% of representative TBNA samples in patients with mediastinal lymph node enlargement. A discrepancy between cytologic and histologic TBNA results should prompt further investigation.

Learning curve of conventional transbronchial needle aspiration in pulmonologists experienced in bronchoscopy.

BACKGROUND: Despite its proven efficacy, transbronchial needle aspiration (TBNA) remains an underutilized technique for sampling enlarged mediastinal lymph nodes in the staging of lung cancer. Previous investigators have reported on TBNA experience, but without mentioning individual learning curves related to lymph node size in pulmonologists experienced in bronchoscopy. OBJECTIVES: The aim of this study was to evaluate the TBNA learning curve in a group of pulmonologists already experienced in bronchoscopy, and to relate their yields to lymph node size and location. METHODS: Data on TBNA yield and related lymph node size were collected retrospectively for five individual pulmonologists. RESULTS: The diagnostic yield of five pulmonologists who started to perform TBNA was evaluated over the first 32 months. TBNA was performed on 138 lymph nodes in 119 patients. The overall diagnostic yield was 77% (range 67-91%). The average diagnostic yield increased from 77% at the start of the learning curve to 82% after 32 months of experience. It was related to lymph node size, but not to lymph node location. The average lymph node size was 22 mm. CONCLUSIONS: Satisfactory results were obtained immediately after introduction of TBNA in the bronchoscopy workup. There is no significant TBNA learning curve. The diagnostic yield was related to lymph node size but not to lymph node location.