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To evaluate lymphopenia as a marker for coronavirus disease severity, we conducted a meta-analysis of 10 studies. Severe illness was associated with lower lymphocyte and higher leukocyte counts. Using these markers for early identification of patients with severe disease may help healthcare providers prioritize the need to obtain therapy.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel β-coronavirus, is the main pathogenic agent of the rapidly spreading pneumonia called coronavirus disease 2019 (COVID-19). SARS-CoV-2 infects much more people, especially the elder population, around the world than other coronavirus, such as SARS-CoV and MERS-CoV, which is challenging current global public health system. Beyond the pathogenesis of SARS-CoV-2, microbial coinfection plays an important role in the occurrence and development of SARS-CoV-2 infection by raising the difficulties of diagnosis, treatment, prognosis of COVID-19, and even increasing the disease symptom and mortality. We summarize the coinfection of virus, bacteria and fungi with SARS-CoV-2, their effects on COVID-19, the reasons of coinfection, and the diagnosis to emphasize the importance of microbial coinfection in COVID-19.Key points• Microbial coinfection is a nonnegligible factor in COVID-19.• Microbial coinfection exacerbates the processes of the occurrence, development and prognosis of COVID-19, and the difficulties of clinical diagnosis and treatment.• Different virus, bacteria, and fungi contributed to the coinfection with SARS-CoV-2.

Understanding the T cell response to SARS-CoV-2 is critical to vaccine development, epidemiological surveillance and disease control strategies. This systematic review critically evaluates and synthesises the relevant peer-reviewed and pre-print literature published from 01/01/2020-26/06/2020. For this systematic review, keyword-structured literature searches were carried out in MEDLINE, Embase and COVID-19 Primer. Papers were independently screened by two researchers, with arbitration of disagreements by a third researcher. Data were independently extracted into a pre-designed Excel template and studies critically appraised using a modified version of the MetaQAT tool, with resolution of disagreements by consensus. Findings were narratively synthesised. 61 articles were included. 55 (90%) studies used observational designs, 50 (82%) involved hospitalised patients with higher acuity illness, and the majority had important limitations. Symptomatic adult COVID-19 cases consistently show peripheral T cell lymphopenia, which positively correlates with increased disease severity, duration of RNA positivity, and non-survival; while asymptomatic and paediatric cases display preserved counts. People with severe or critical disease generally develop more robust, virus-specific T cell responses. T cell memory and effector function has been demonstrated against multiple viral epitopes, and, cross-reactive T cell responses have been demonstrated in unexposed and uninfected adults, but the significance for protection and susceptibility, respectively, remains unclear. A complex pattern of T cell response to SARS-CoV-2 infection has been demonstrated, but inferences regarding population level immunity are hampered by significant methodological limitations and heterogeneity between studies, as well as a striking lack of research in asymptomatic or pauci-symptomatic individuals. In contrast to antibody responses, population-level surveillance of the T cell response is unlikely to be feasible in the near term. Focused evaluation in specific sub-groups, including vaccine recipients, should be prioritised.

Background Newborn screening (NBS) by quantification of T-cell receptor excision circles (TREC) identifies a considerable number of infants with T-cell lymphopenia (TCL) other than severe combined immunodeficiency (SCID). While some of these children have well-defined inborn errors of immunity (IEI), many lack a clear genetic diagnosis, complicating their management and causing prognostic uncertainty. Objective To characterize the natural history of non-SCID TCL detected through NBS in Swiss infants between 2019 and 2023. Methods Clinical, genetic and laboratory data from all non-SCID TCL cases were extracted from the national NBS registry and analyzed. Results Out of 435 985 screened infants, 42 patients were identified with non-SCID, non-congenital athymia TCL, without an obvious secondary cause. A clear genetic diagnosis of IEI was established in 20 (48%) patients. Infants with confirmed IEI had significantly lower total T-cell, CD4 + T-cell and recent thymic emigrant (RTE) counts on initial lymphocyte phenotyping. In contrast, those with an unclear genetic diagnosis despite full investigations demonstrated faster normalization of total T-cell counts (hazard ratio 5.2, 95% CI 1.9 to 14.5, p  = 0.001). All infants with initial CD4 + T-cell < 0.3 × 10 9 /L showed minimal recovery of T-cell counts and remained on long-term prophylactic measures. All infants with an unclear genetic diagnosis despite investigations were able to discontinue prophylaxis at median age 6 months without experiencing opportunistic or severe infections. Conclusion Infants with non-SCID TCL identified by NBS represent a heterogenous group, ranging from severe, persistent TCL to mild, transient lymphopenia. Management should be tailored based on individual immunological and genetic profiles. Highlights Initial T-cell counts and genetic diagnosis are key prognostic factors in newborn screening-identified non-SCID T-cell lymphopenia. Patients with milder lymphopenia and no genetic diagnosis are more likely to experience T-cell recovery.

Newborn screening efforts focusing on the quantification of T cell receptor excision circles (TRECs), as a biomarker for abnormal thymic production of T cells, have allowed for the identification and definitive treatment of severe combined immunodeficiency (SCID) in asymptomatic neonates. With the adoption of TREC quantification in Guthrie cards across the USA and abroad, typical, and atypical SCID constitutes only ~ 10% of cases identified with abnormal TRECs associated with T cell lymphopenia. Several other non-SCID-related conditions may be identified by newborn screening in a term infant. Thus, it is important for physicians to recognize that other factors, such as prematurity, are often associated with low TRECs initially, but often improve with age. This paper focuses on a challenge that immunologists face: the diagnostic evaluation and management of cases in which abnormal TRECs are associated with variants of T cell lymphopenia in the absence of a genetically defined form of typical or atypical SCID. Various syndromes associated with T cell impairment, secondary forms of T cell lymphopenia, and idiopathic T cell lymphopenia are identified using this screening approach. Yet there is no consensus or guidelines to assist in the evaluation and management of these newborns, despite representing 90% of the patients identified, resulting in significant work for the clinical teams until a diagnosis is made. Using a case-based approach, we review pearls relevant to the evaluation of these newborns, as well as the management dilemmas for the families and team related to the resolution of genetic ambiguities.

Sepsis and other acute injuries such as severe trauma, extensive burns, or major surgeries, are usually followed by a period of marked immunosuppression. In particular, while lymphocytes play a pivotal role in immune response, their functions and numbers are profoundly altered after severe injuries. Apoptosis plays a central role in this process by affecting immune response at various levels. Indeed, apoptosis-induced lymphopenia duration and depth have been associated with higher risk of infection and mortality in various clinical settings. Therapies modulating apoptosis represent an interesting approach to restore immune competence after acute injury, although their use in clinical practice still presents several limitations. After briefly describing the apoptosis process in physiology and during severe injuries, we will explore the immunological consequences of injury-induced lymphocyte apoptosis, and describe associations with clinically relevant outcomes in patients. Therapeutic perspectives targeting apoptosis will also be discussed.

Data on pathologic changes of the 2019 novel coronavirus disease (COVID-19) are scarce. To gain knowledge about the pathology that may contribute to disease progression and fatality, we performed postmortem needle core biopsies of lung, liver, and heart in four patients who died of COVID-19 pneumonia. The patients’ ages ranged from 59 to 81, including three males and one female. Each patient had at least one underlying disease, including immunocompromised status (chronic lymphocytic leukemia and renal transplantation) or other conditions (cirrhosis, hypertension, and diabetes). Time from disease onset to death ranged from 15 to 52 days. All patients had elevated white blood cell counts, with significant rise toward the end, and all had lymphocytopenia except for the patient with leukemia. Histologically, the main findings are in the lungs, including injury to the alveolar epithelial cells, hyaline membrane formation, and hyperplasia of type II pneumocytes, all components of diffuse alveolar damage. Consolidation by fibroblastic proliferation with extracellular matrix and fibrin forming clusters in airspaces is evident. In one patient, the consolidation consists of abundant intra-alveolar neutrophilic infiltration, consistent with superimposed bacterial bronchopneumonia. The liver exhibits mild lobular infiltration by small lymphocytes, and centrilobular sinusoidal dilation. Patchy necrosis is also seen. The heart shows only focal mild fibrosis and mild myocardial hypertrophy, changes likely related to the underlying conditions. In conclusion, the postmortem examinations show advanced diffuse alveolar damage, as well as superimposed bacterial pneumonia in some patients. Changes in the liver and heart are likely secondary or related to the underlying diseases.

In the management of unresectable locally advanced non-small cell lung cancer (LA-NSCLC), the lack of reliable predictive biomarkers for grade ≥ 3 radiation-induced lymphopenia (RIL3+) and prognosis remains a major challenge. This study aims to investigate whether effective dose to immune cells (EDIC) combined with pre-radiotherapy (RT) peripheral blood inflammatory indicators (PBIIs), especially platelet-to-lymphocyte ratio (PLR), could better predict RIL3+ and prognosis in patients with unresectable LA-NSCLC in the immunotherapy era. We enrolled 139 patients with unresectable LA-NSCLC who received chemoradiation and consolidation immunotherapy. Logistic regression was used to identify the predictors of RIL3+. Spearman correlation analyses were used to estimate the correlations between each indicator and absolute lymphocyte count (ALC) nadir. Receiver operating characteristic (ROC) curves were used to determine the predictive performance and optimal cut-off of each indicator. Patients were then divided into low- and high-risk groups based on the above cut-offs. Cox proportional hazards regression was used to determine prognostic factors for progression-free survival (PFS) and overall survival (OS). Survival outcomes were assessed using Kaplan-Meier methods. Logistic regression showed that both EDIC ( = 0.002) and PLR ( < 0.001) were significantly associated with RIL3+. ROC curves showed the highest predictive power of the PLR among the PBIIs. Spearman correlation analysis showed that both EDIC ( < 0.001) and PLR ( < 0.001) were significantly correlated with ALC nadir. Compared to the model using EDIC ( = 0.026) or PLR ( = 0.021) alone, the combination of EDIC and PLR showed superior predictive performance. The optimal cut-offs of EDIC and PLR were 4.44 Gy and 107.70, respectively. The incidence rates of RIL3+ in the low- and high-risk groups were 44.3% and 90.0%, respectively ( < 0.001). Compared to the high-risk group, patients in the low-risk group had a longer median PFS ( = 0.011) and OS ( = 0.013). In the immunotherapy era, the combination of EDIC and pre-RT PLR is a predictive biomarker of RIL3+ and prognosis in patients with unresectable LA-NSCLC. Reducing EDIC and considering pre-RT PLR may potentially avoid RIL3+ and improve prognosis.

In advanced oestrogen receptor-positive, HER2-negative breast cancer, acquired resistance to aromatase inhibitors frequently stems from ESR1-mutated subclones, which might be sensitive to fulvestrant. The PADA-1 trial aimed to show the efficacy of an early change in therapy on the basis of a rising ESR1 mutation in blood (bESR1mut), while assessing the global safety of combination fulvestrant and palbociclib. We did a randomised, open-label, phase 3 trial in 83 hospitals in France. Women aged at least 18 years with oestrogen receptor-positive, HER2-negative advanced breast cancer and an Eastern Cooperative Oncology Group performance status of 0–2 were recruited and monitored for rising bESR1mut during first-line aromatase inhibitor (2·5 mg letrozole, 1 mg anastrozole, or 25 mg exemestane, orally once per day, taken continuously) and palbociclib (125 mg orally once per day on days 1–21 of a 28-day cycle) therapy. Patients with newly present or increased bESR1mut in circulating tumour DNA and no synchronous disease progression were randomly assigned (1:1) to continue with the same therapy or to switch to fulvestrant (500 mg intramuscularly on day 1 of each 28-day cycle and on day 15 of cycle 1) and palbociclib (dosing unchanged). The randomisation sequence was generated within an interactive web response system using a minimisation method (with an 80% random factor); patients were stratified according to visceral involvement (present or absent) and the time from inclusion to bESR1mut detection (<12 months or ≥12 months). The co-primary endpoints were investigator-assessed progression-free survival from random assignment, analysed in the intention-to-treat population (ie, all randomly assigned patients), and grade 3 or worse haematological adverse events in all patients. The trial is registered with Clinicaltrials.gov (NCT03079011), and is now complete. From March 22, 2017, to Jan 31, 2019, 1017 patients were included, of whom 279 (27%) developed a rising bESR1mut and 172 (17%) were randomly assigned to treatment: 88 to switching to fulvestrant and palbociclib and 84 patients to continuing aromatase inhibitor and palbociclib. At database lock on July 31, 2021, randomly assigned patients had a median follow-up of 35·3 months (IQR 29·2–41·4) from inclusion and 26·0 months (13·8–34·3) from random assignment. Median progression-free survival from random assignment was 11·9 months (95% CI 9·1–13·6) in the fulvestrant and palbociclib group versus 5·7 months (3·9–7·5) in the aromatase inhibitor and palbociclib group (stratified HR 0·61, 0·43–0·86; p=0·0040). The most frequent grade 3 or worse haematological adverse events were neutropenia (715 [70·3%] of 1017 patients), lymphopenia (66 [6·5%]), and thrombocytopenia (20 [2·0%]). The most common grade 3 or worse adverse events in step 2 were neutropenia (35 [41·7%] of 84 patients in the aromatase inhibitor and palbociclib group vs 39 [44·3%] of 88 patients in the fulvestrant and palbociclib group) and lymphopenia (three [3·6%] vs four [4·5%]). 31 (3·1%) patients had grade 3 or worse serious adverse events related to treatment in the overall population. Three (1·7%) of 172 patients randomly assigned had one serious adverse event in step 2: one (1·2%) grade 4 neutropenia and one (1·2%) grade 3 fatigue among 84 patients in the aromatase inhibitor and palbociclib group, and one (1·1%) grade 4 neutropenia among 88 patients in the fulvestrant and palbociclib group. One death by pulmonary embolism in step 1 was declared as being treatment related. PADA-1 is the first prospective randomised trial showing that the early therapeutic targeting of bESR1mut results in significant clinical benefit. Additionally, the original design explored in PADA-1 might help with tackling acquired resistance with new drugs in future trials. Pfizer.

In December 2019, coronavirus disease 2019 (COVID-19), which is caused by the new coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in Wuhan (Hubei province, China) 1 ; it soon spread across the world. In this ongoing pandemic, public health concerns and the urgent need for effective therapeutic measures require a deep understanding of the epidemiology, transmissibility and pathogenesis of COVID-19. Here we analysed clinical, molecular and immunological data from 326 patients with confirmed SARS-CoV-2 infection in Shanghai. The genomic sequences of SARS-CoV-2, assembled from 112 high-quality samples together with sequences in the Global Initiative on Sharing All Influenza Data (GISAID) dataset, showed a stable evolution and suggested that there were two major lineages with differential exposure history during the early phase of the outbreak in Wuhan. Nevertheless, they exhibited similar virulence and clinical outcomes. Lymphocytopenia, especially reduced CD4 + and CD8 + T cell counts upon hospital admission, was predictive of disease progression. High levels of interleukin (IL)-6 and IL-8 during treatment were observed in patients with severe or critical disease and correlated with decreased lymphocyte count. The determinants of disease severity seemed to stem mostly from host factors such as age and lymphocytopenia (and its associated cytokine storm), whereas viral genetic variation did not significantly affect outcomes. Genome sequences from 112 patients with confirmed SARS-CoV-2 infection showed two clades of SARS-CoV-2 virus with similar virulence and clinical outcome, and clinical data from 326 cases suggest that T cell depletion and cytokine bursts are associated with a worse prognosis.