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Study Group

Main Findings

Mast cell activation symptoms are prevalent in Long-COVID [15].

-136 PACS subjects;

-136 health controls;

-80 mast cell activation (MCA) patients.

-Pre-PACS subjects and controls had virtually identical MCA symptom and severity analysis;

-PACS subjects and MCAS patients before treatment had identical MCA symptom and severity analyses.

Mild and Asymptomatic COVID-19 Convalescents Present Long-Term Endotype of Immunosuppression Associated With Neutrophil Subsets Possessing Regulatory Functions [19].

-13 convalescent patients who

underwent a mild or asymptomatic infection;

-13 healthy donors without SARS-CoV-2 infection in the past.

-Even 3 months after infection, an elevated level of LDNs/PMN-MDSCs in blood;

-LDNs/PMN-MDSCs correlates negatively with CD8+ T cells;

-Higher levels of GM-CSF in the convalescent serum.

Immune-Based Prediction of COVID-19 Severity and Chronicity Decoded Using Machine Learning [21].

-29 controls, 26 Mild-Moderate COVID-19 individuals, 48 Severe COVID-19 individuals, and 121 with PASC symptoms.

-Increased of IFN-g, CCL5/RANTES, IL-2, IL-4, CCL3, IL-6,IL-10 and VEGF levels in PACS;

-Reduced CCL4 and GM-CSF production;

-Increased B cells and CD14+, CD16+, CCR5+ monocytic subset frequency;

-Reduced % CD4 and CD8 PD-1+ T-cells and T-regulatory cells;

-“PASC Score”: (IFN-g + IL-2)/CCL4-MIP-1b;

-Threshold of “PASC score”= 0.5.

Markers of Immune Activation and Inflammation in Individuals With Post Acute Sequelae of Severe Acute Respiratory Syndrome Coronavirus 2 Infection [22].

-121 participants in a SARS-CoV-2 recovery cohort at early (< 90 days) and late (> 90 days) time points.

-Individuals who went on to develop PASC had higher levels of cytokine biomarkers: TNF-alpha (1.14 -fold higher) and IFN-gamma-induced protein 10 (1.28 -fold higher);

- PASC patients there was higher IL-6 levels in late recovery (1.44-fold higher).

Long-term SARS-CoV-2 specific immune and inflammatory responses in individuals recovering from COVID-19 with and without post-acute symptoms [23].

-70 cohort patients between 14 and 90 days after onset of COVID-19 symptoms;

-Monthly visits until 4 months after illness onset; they are then seen every 4 months thereafter.

-Patients with PACS have a lower frequency of CD8+CD107a+ (a marker of degranulation) and a more rapid decline in the frequency of N-specific IFN-gamma producing CD8+ T cells.

Longitudinal Analysis of COVID-19 Patients Shows Age-Associated T Cell Changes Independent of Ongoing Ill-Health [24].

-Paired immunophenotyping at initial SARS-CoV-2 infection and convalescence (n = 40);

-Validated findings in 71 further convalescent patients;

-40 pre-pandemiccontrols.

-Persistent expansion of intermediate monocytes (HLA-DR+CD14+CD16+), effector CD8+,activated CD4+ and CD8+ T cells at 68 days;

-Reduced naïve CD4+ and CD8+ T cells at 68 days.

Alterations in T and B cell function persist in convalescent COVID-19 patients [25].

-Patients were examined during COVID-19 and at up to 6 months of convalescence;

-Controls were sampled, frontline workers.

-B cell subsets in acute COVID-19 patients were recovered in convalescent patients;

-The recovery of IL-10+ B cells was associated with the resolution of lung pathology;

-T cells from convalescent patients have persistence of a cytotoxic program in CD8+ T cells and elevated production of type 1 cytokines andinterleukin-17 (IL-17).

Refining “Long-COVID” by a Prospective Multimodal Evaluation of Patients with Long-Term Symptoms Attributed to SARS-CoV-2 Infection [26].

-30 patients with persistent symptoms (> 30 days) attributed to COVID-19;

-17 convalescent COVID-19 individuals without persistent symptoms as control.

-Multiplex cytokines and ultra-sensitive interferon-a2 measurements were similar between both groups;

-Only 50% of patients had cellular and/or humoral signs of a past SARS-CoV-2.

Establishing the prevalence of common tissue-specific autoantibodies following SARS CoV-2 infection [27].

-84 individuals previously infected with SARS-CoV-2, with acute or convalescent COVID-19.

-32 individuals were in the intensive therapy unit for non-COVID reasons.

-Higher frequency of autoantibodies in the COVID-19 group;

-The autoantibodies were found in the serum 3-5 months post COVID-19 infection.