IntroductionThe crosstalk between immune cells through plasma extracellular vesicles (EVs) during SARS-CoV-2 infection may represent a significant determinant of clinical course in COVID-19 patients. EVs from SARS-CoV-2 virus-infected cells deliver their informational content to immune cells implicated in COVID-19 pathogenesis, thereby modulating pro-inflammatory immune responses during infection. γδ T cells are innate cells known for their pleiotropic properties spanning both innate and adaptive immunity and for their possible contribution to inflammation. This study aimed to characterize the biophysical profile and protein content of EVs derived from patients with severe and mild COVID-19, and to analyze their impact on the functional activity of Vδ2 T cells.MethodsPlasma samples from 42 COVID-19 hospitalized patients (17 severe and 25 mild) were enrolled at the National Institute for Infectious Diseases Lazzaro Spallanzani in Rome. Twenty-three healthy donors (HD) served as the control group. Plasma cytokines were quantified by an automated multiplex immunoassay. EVs were purified using nickel-based isolation (NBI) and analyzed by quantitative LC-MS proteomics. Data are available via ProteomeXchange with identifier PXD072061. Characterization of EVs was performed using multiparametric flow cytometry, as well as the Vδ2 T cell functional assays. Peripheral blood mononuclear cells from 10 HD were utilized for immunological assays.ResultsCytometric characterization revealed that EVs from severe COVID-19 patients were enriched in platelet components compared to HD and mild patients. Protein expression of EVs from severe patients clustered differently in PCA and heatmap analyses with respect to HD and mild patients. A volcano plot revealed several proteins that were differentially expressed between EVs from mild and severe patients. A significant induction of several processes, including platelet degranulation, complement, coagulation, and innate immunity, was observed in the pathway analysis. EVs from severe COVID-19 patients enhanced the responsiveness of Vδ2 T cells to phosphoantigen, increasing their activation and proinflammatory cytokine production (TNF-α).ConclusionsProteomic differential analysis reveals the expression/regulation of innate immune-related proteins in EVs from severe patients compared to mild patients/HD and supports their potential role in modulating innate immunity. Specifically, functional analysis of Vδ2 T cells suggests that EVs may contribute to the pathogenesis of severe COVID-19 by delivering molecular signals that exacerbate innate immune-driven inflammation.

Objectives: This study was designed to assess the safety and immunogenicity of the first dose of the TAK-003 dengue vaccine. The immune response profiles of vaccinated participants were compared among individuals who experienced or did not experience natural dengue infection in the past or as an acute infection. Methods: In this single-centre prospective observational study, subjects were stratified into three groups: Group1-dengue seronegative; Group2-dengue seropositive; Group3-acute dengue infection. The assessments of vaccine-induced immunogenicity included: DENV-2 neutralizing antibodies, monocyte and dendritic cell (DC) phenotyping and T-cell response at baseline (T0) and 3 months (T3) post-vaccination (Group1 and 2) or post-infection (Group3). Results: One hundred fifty subjects were enrolled at T0, and among them 80 subjects (median age 38 years, 50% male) were also evaluated at T3. Anti-DENV-2 neutralizing antibodies increased 26.9-and 9.19-fold in Group1 and 2, and 3.06-fold in Group3. Group1 showed increased monocytes and Group3 had reduced myeloid-DC and higher plasmacytoid-DC. Group1 and 2 exhibited DENV CD4 MP-induced T-cell responses similar to those observed in Group3. Notably, Group1 demonstrated a significantly greater T-cell response to the DENV CD8 MP than Group3. Conclusions: Preliminary data showed that TAK-0 03 vaccine is safe and immunogenic. The first vaccine dose elicits a functional antibody and a robust T-cell response. Further analyses on the current cohort are ongoing. (c) 2026 The Author(s). Published by Elsevier Ltd on behalf of British Infection Association. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Background: Torquetenovirus (TTV) viremia is increasingly recognized as a biomarker of host immune competence. We assessed the association between baseline TTV DNA levels and immune responses to the Mpox virus (MPXV) and dengue virus (DGV) vaccines in two prospective cohorts. Methods: A total of 248 individuals were enrolled, and TTV DNA was quantified before vaccination. Humoral and cellular responses to MVA-BN (for MPXV) and QDENGA (for DGV) vaccines were measured by using serology, neutralization assays, and interferon-γ ELISpot, and correlations with TTV viremia were investigated. Results: TTV DNA was detected in 81.2% of individuals, with a significantly higher prevalence and viral loads in the Mpox-Vac group than in the DGV-Vac group. Between both groups, the only significant association observed was an inverse correlation between pre-vaccination TTV load and DGV neutralizing antibody titers in the DGV-Vac group and was limited to the subset of TTV-positive individuals; no additional correlations with antibody and T responses were identified. For the Mpox-Vac group, stratified analyses in people living with HIV (PLWH) confirmed this lack of association. Conclusions: TTV viremia does not predict vaccine immunogenicity in immunocompetent or mildly immunosuppressed individuals. These results, which derive from within-cohort analyses and do not rely on direct comparisons between heterogeneous vaccine populations, support the role of TTV as a marker of immune status along a continuum of immunosuppression, with predictive value likely confined to populations with more severe immune impairment.

OBJECTIVES:This study was designed to assess the safety and immunogenicity of the first dose of the TAK-003 dengue vaccine. The immune response profiles of vaccinated participants were compared among individuals who experienced or did not experience natural dengue infection in the past or as an acute infection. METHODS:In this single-centre prospective observational study, subjects were stratified into three groups: Group1-dengue seronegative; Group2-dengue seropositive; Group3-acute dengue infection. The assessments of vaccine-induced immunogenicity included: DENV-2 neutralizing antibodies, monocyte and dendritic cell (DC) phenotyping and T-cell response at baseline (T0) and 3 months (T3) post-vaccination (Group1 and 2) or post-infection (Group3). RESULTS:One hundred fifty subjects were enrolled at T0, and among them 80 subjects (median age 38 years, 50% male) were also evaluated at T3. Anti-DENV-2 neutralizing antibodies increased 26.9- and 9.19-fold in Group1 and 2, and 3.06-fold in Group3. Group1 showed increased monocytes and Group3 had reduced myeloid-DC and higher plasmacytoid-DC. Group1 and 2 exhibited DENV CD4 MP-induced T-cell responses similar to those observed in Group3. Notably, Group1 demonstrated a significantly greater T-cell response to the DENV CD8 MP than Group3. CONCLUSIONS:Preliminary data showed that TAK-003 vaccine is safe and immunogenic. The first vaccine dose elicits a functional antibody and a robust T-cell response. Further analyses on the current cohort are ongoing.

A previously healthy 39-year-old man developed highly symptomatic post-COVID-19 condition (also known as long COVID) marked by cognitive dysfunction, disabling fatigue, and autonomic symptoms unresponsive to multiple multidisciplinary interventions. Given the presence of markedly elevated serum autoantibodies against G protein-coupled receptors, high-dose intravenous immunoglobulin therapy was initiated at 400 mg/kg per day for 5 consecutive days. After 4 weeks, a maintenance dose of 500 mg/kg was administered for 1 day, followed by two further maintenance cycles consisting of 500 mg/kg per day for 3 consecutive days, each given at 4-week intervals. In parallel, the patient underwent a cognitive stimulation intervention. Neurological symptoms were assessed with the Fatigue Assessment Scale and the WHO Disability Assessment Schedule 2.0, and the immunological profile was longitudinally analysed during intravenous immunoglobulin treatment. Fatigue scores normalised, neurocognitive performance returned to normal value, and quality of life improved after the first infusion and fully recovered within 1 year. Immunological profiling revealed the presence of an inverted CD4 to CD8 T-cell ratio that persisted during the whole follow-up. We also identified a CD8+ T cell-monocyte complex and spontaneous IFNγ release. Intravenous immunoglobulin therapy was associated with a significant reduction of these complexes, spontaneous IFNγ and TNF production, markers of endothelial inflammation, and circulating autoantibody titres. This patient provides exploratory evidence that high-dose intravenous immunoglobulin was associated with sustained clinical recovery from long COVID over 1 year of follow-up, accompanied by immunological changes consistent with modulation of post-viral immune dysregulation, including a reduction in pathogenic T cell-monocyte synapses. Although causal inference cannot be established from a single patient, these findings suggest that this cellular interaction can contribute to long COVID and that immunomodulation could represent a rational therapeutic approach to be evaluated in selected patients.

[This corrects the article DOI: 10.3389/fcimb.2025.1612198.].

Introduction:Long COVID (LC) has been associated with hypothalamic-pituitary-adrenal (HPA) axis dysfunction, although findings from blood cortisol measurements remain inconsistent. We hypothesized that LC patients exhibit a disrupted diurnal cortisol rhythm and that salivary cortisol (SC) profiling may provide a more accurate assessment of HPA activity. Methods:This prospective, single-center, case-control study was conducted at a Long COVID clinic in Rome between February 2023 and March 2024 and included 96 participants evaluated at least 28 days after confirmed SARS-CoV-2 infection. LC was defined as one or more new or persistent symptoms and classified as severe when four or more of the following were present: fatigue, cognitive impairment, exercise intolerance, dyspnea, arthralgia, or dysautonomia. SC was measured at 8:00 AM, 3:00 PM, and 11:00 PM. Results:The cohort (mean age 58.1 ± 14.8 years; 60% female; all White) included 83 LC patients (80% moderate, 20% severe) and 13 asymptomatic post-COVID (APC) individuals. Compared with healthy controls, both LC and APC groups showed reduced morning SC (p<0.01), flattened diurnal variation, and elevated evening SC, indicating loss of the normal morning peak and nocturnal decline. Blood cortisol levels did not differ among groups, but LC patients had higher ACTH than APC (26 pg/mL vs 13 pg/mL; p<0.01), suggesting compensatory HPA activation. One LC patient (1.2%) was diagnosed with adrenal insufficiency. Discussion:These exploratory findings suggest a disrupted circadian cortisol rhythm in individuals after COVID-19, with altered HPA axis dynamics that may be associated with disease severity.

This prospective, single-center, case-control study investigated circulating autoantibodies (AAbs) targeting G protein-coupled receptors (GPCRs) in Long COVID (LC) patients to identify potential diagnostic biomarkers and therapeutic targets. Fifteen participants were enrolled at the LC clinic in Rome: eleven with severe LC-defined as >4 persistent symptoms (fatigue, cognitive impairment, poor exercise tolerance, dyspnea, arthralgia, or dysautonomic manifestations) >3 months post-infection-and four asymptomatic post-COVID (APC) individuals. Fatigue was assessed using the Fatigue Assessment Scale (FAS ≥ 22; severe ≥ 35). Auto-Abs against AT1R, endothelin receptor A, adrenergic (α1, α2, β1, β2), and muscarinic (M1-M5) receptors were quantified, along with blood cortisol and ACTH levels. SARS-CoV-2-specific T-cell responses to Spike and Nucleocapsid proteins were evaluated by ELISpot assay. In our small cohort, LC patients were younger, had fewer comorbidities (p = 0.03), fewer vaccine doses (p = 0.03), and higher FAS scores (33 vs. 12; p = 0.001). Mean GPCR AAbs levels were higher in LC than in APC (8.88 vs. 5.45 Units/mL; p = 0.17), indicating a coherent autoimmune signature in LC that correlates with symptom development. Morning cortisol was lower in LC (12.7 vs. 17 mg/dL; p = 0.01), and T-cell responses tended to be weaker. These findings suggest GPCR AAbs may serve as biomarkers and therapeutic targets for a subset of patients, guiding diagnosis and treatments with IV immunoglobulin or immunoadsorption.

The first evidence that Orthopoxvirus induced the expansion in vivo and the recall of effector innate Vδ2 T-cells was described in a macaque model. Although, an engagement of αβ T-cells specific response in patients infected with human monkeypox (Mpox) was demonstrated, little is known about the role of γδ T-cells during Mpox infection. IFN-γ-producing γδ T-cells in the resistance to poxviruses may a key role in inducing a protective type 1 memory immunity. We analyzed the kinetics of Vδ2 T-cell response from the acute phase up to three months after Mpox infection. Fourteen MSM subjects (5 PWH, 35.7%) were enrolled in a longitudinal study from May to July 2022. Blood samples were collected in the early phase of infection (T1, T2) and at 3 months (T3M) post-symptom onset. Vδ2 T-cell profiles (CD45RA/CCR7), activation/exhaustion markers (CD38/HLA-DR/CD57/PD-1/TIM-3), cytokine production (IFN-γ/TNF-α) and CD107a expression were assessed by multiparametric flow cytometry. Ten healthy donors (HD) were used as a control group. At T1, Vδ2 T-cell frequency of patients decreased, and effector memory Vδ2 T-cells increased with respect to HD. Activation/exhaustion markers were higher than HD. Vδ2 functionality decreased at T1 related to HD, and it was associated with CD38 and HLA-DR higher expression as well as TIM-3. Vδ2 T-cells restored their profile at T3M. The presence of effector/activated Vδ2 T-cells in the early stages of Mpox infection and their capability to activate quickly, producing pro-inflammatory cytokines, may be useful to enhance the early adaptive response to human Mpox, maintaining a protective memory/effector T-cell response.

BACKGROUND:Variant-adapted vaccines are recommended in vulnerable populations to address the waning immunity and the emergence of immune-escaping SARS-CoV-2 variants, yet data about immune responses to such vaccines in people living with HIV (PLWH) are limited. We therefore aimed to assess long-term immune responses to an original-BA.4/5 mRNA booster in this population. METHODS:In this prospective longitudinal study, PLWH receiving either an original-BA.4/5 bivalent booster or an original monovalent booster and HIV-negative healthcare workers (HCWs) receiving a bivalent booster were enrolled and sampled before (T0), 1 month (T1), and 4-9 months (T2) after the vaccine administration. SARS-CoV-2-specific T and B cells, RBD-binding antibodies, and RBD-blocking antibodies against both wild type (WT) and omicron BA.4/5 virus were determined. RESULTS:The bivalent booster is able to transiently increase both humoral and polyfunctional T cell responses in PLWH, with humoral responses comparable to those observed in HCWs. While T cell responses are cross-reactive against viral variants and stable over time, humoral immunity is imprinted to the ancestral virus and wanes quickly. Furthermore, whilst previous SARS-CoV-2 infection does not affect the trajectory of vaccine-elicited immune responses, markers of HIV-related T cell dysfunction are associated with lower antibody peak responses and higher antibody waning. Lastly, the bivalent booster was superior to the monovalent one in inducing BA.4/5-reactive RBD-blocking antibodies. CONCLUSIONS:The original-BA.4/5 bivalent booster is highly immunogenic in PLWH and superior to the monovalent one in inducing humoral responses against the BA.4/5 virus, although HIV-related T cell dysfunction markers are associated with blunted and less durable antibody immunity.

Background: Torquetenovirus (TTV) viremia is increasingly recognized as a marker of immune competence. In the context of COVID-19, TTV viral load (VL) has been shown to predict anti-Spike antibody levels in severely immunocompromised patients. This study aimed to evaluate whether pre-vaccine TTV VL could predict humoral and cellular immune responses to SARS-CoV-2 mRNA vaccines in people living with HIV (PLWH) and healthy individuals (HP). Methods: TTV VL was measured via real-time PCR in serum samples collected before the second and third doses of mRNA vaccines in 93 PLWH and 48 HP (second dose) and 255 PLWH and 48 HP (third dose). Immune responses were assessed through anti-SARS-CoV-2 receptor-binding domain (RBD) IgG, neutralizing antibodies, and IFN-γ release. Statistical analyses included correlation studies between TTV VL and vaccine-induced immune responses. Results: TTV VL did not significantly correlate with anti-RBD IgG or neutralizing antibody levels in either cohort; highlighting its limited predictive value for humoral responses in relatively immunocompetent populations. However, a strong inverse correlation was observed between TTV VL and IFN-γ release after the third, but not the second, vaccine dose. These findings suggest that higher TTV VL, indicative of reduced immune competence, may impair T-cell-mediated immunity to vaccines. Conclusions: In virologically suppressed PLWH and HP, TTV VL is not a reliable predictor of humoral immune responses to COVID-19 vaccines. However, its inverse relationship with cellular responses warrants further investigation in more immunosuppressed populations. These results reinforce the continuum model of TTV VL as a biomarker, with predictive utility increasing alongside the degree of immunosuppression

Background: In response to the SARS-CoV-2 pandemic, a massive vaccination campaign was launched. Nonetheless, concerns arose regarding some peculiar groups of patients, including those affected by Systemic Lupus Erythematosus (SLE), because of the immune-suppressive drugs routinely administered to patients and the risk of possible disease flares. Since the effects of the third booster vaccination in SLE have been poorly assessed, this study aims to evaluate the immunogenicity and safety of the third BNT162b2 vaccine dose, together with the effects of immunosuppressive drugs. Methods: A monocentric SLE cohort and a cohort of age- and sex-matched healthy controls (HCs) (all vaccinated with three homologous doses) were consecutively enrolled 6 months (T1) after their third vaccine shot. Vaccine immunogenicity was evaluated by analyzing humoral and cellular immune responses at T1 and 12 months (T2). Vaccine safety was evaluated by assessing adverse events related to vaccination (T0) and comparing disease activity among T0, T1, and T2. Effects of immunosuppressive drugs were assessed by stratifying patients according to therapy at vaccination: (1) receiving (IS) or (2) not receiving immunosuppressive drugs (Non-IS). Results: At T1, the humoral responses were comparable between SLE and HC subjects, while the cellular response was significantly higher in HC (p = 0.01). No differences were found at T2 between cohorts. Similarly, both at T1 and T2, the immune responses of IS and Non-IS groups were comparable. Moreover, lupus disease flares were limited and mostly mild, and no life-threatening adverse events were reported. Conclusions: The booster BNT162b2 vaccine is safe and induces an immune response, which is persistent and not affected by ongoing immunosuppressive drugs.

Long COVID (LC) is characterized by a wide range of symptoms, the causes of which remain unclear. We investigated associations between inflammatory and coagulation factors, adaptive immune response to SARS-CoV-2, and LC. We enrolled 196 unvaccinated individuals with SARS-CoV-2 (March–June 2020). Blood samples were collected at three (T3M) and twelve (T12M) months post infection. Plasma concentrations of coagulation factors (D-Dimer, E-Selectin, ICAM-1, VCAM-1) and inflammatory markers (IL-6, IL-8, TNF-α, IL-1β) were measured by ELISA, and SARS-CoV-2-specific T-cell response was assessed by Elispot. LC occurred in 66/196 patients (34%); 77.8% had been hospitalized. Respiratory symptoms were present in 54%, fatigue in 30%, and neuropsychological symptoms in 14%. At T3M, hospitalized patients exhibited higher levels of ICAM-1, VCAM-1, and IL-6, along with increased immunoreactivity. LC patients exhibited elevated IL-8 and TNF-α and enhanced immunoreactivity at T3M, though these differences were not observed at T12M. Inflammatory and coagulation markers were altered at three months after acute infection, with some changes persisting at one year, suggesting a long-term immunological impact of SARS-CoV-2 on the inflammatory response. A SARS-CoV-2-specific T-cell response was still detectable at T12M, albeit at a lower level than at T3M, suggesting the persistence of protective memory T-cells beyond the acute phase.

OBJECTIVES:The immunological signature of mpox Clade IIb was described in the early stages of infection. We aimed to characterize the kinetics of both humoral and cellular immune responses against mpox from the onset of symptoms up to one year later. METHODS:Sixty-nine patients with mpox infected with Clade IIb during the 2022 outbreak were included in a longitudinal study. Blood samples were collected during the first 3 weeks and 3-4 (T3-4M), 6-8 (T6-8M), and 12 months (T12M) after infection. Mpox-specific IgM, IgA, IgG, and neutralizing antibodies (nAbs) titres were measured by immunofluorescence assay and 50% plaque reduction neutralization test. Interferon-γ producing specific T-cells to Modified Vaccinia Ankara (MVA) peptides was assessed by ELISpot assay. CD4+ and CD8+ T-cells phenotypic markers (CD38/CD57/PD-1) were performed by flow cytometry. RESULTS:All the humoral markers were detected as early as 4 days and peaked at week 2 (IgG) or 3 (IgM, IgA, nAbs) from symptoms onset. At T3-4M from onset, the antibody levels decreased, and IgM was detected in only one patient; IgA in 50% (13/26), IgG and nAbs in 92% (24/26) of participants. Further decreases in IgG and nAb mean titres were observed at 6-8M. At T12M, IgM, IgA, IgG, and nAbs were detected in 4 (2/47), 48 (23/47), 93 (44/47) and 78% (37/47) of patients, respectively. MVA-specific T-cell response was detected early in the acute phase of infection, peaked at T3M and are maintained until T12M. DISCUSSION:These data provide evidence of persistence of humoral and cellular immune response 1 year after natural infection, suggesting the maintenance of adequate immune memory. Further study is needed to assess longer persistence of immunity and the cross-protection against different mpox clades.

The impact of anti-Spike monoclonal antibody (mAbs) treatment on the immune response of COVID19-patients is poorly explored. In particular, a comparison of the immunological influence of different therapeutic regimens has not yet been performed. Aim of the study was to compare the kinetic of innate and adaptive immune response as well as the SARS-CoV-2 specific humoral and T cell response in two groups of SARS-CoV-2-infected patients treated with two different mAbs regimens: Bamlanivimab/Etesevimab (BAM/ETE) or Casirivimab/Imdevimab (CAS/IMD). SARS-CoV-2-infected patients (n = 39) with mild/moderate disease were enrolled before (T0) and after 7 days (T7) and 30 day (T30) from mAbs infusion. Patients were divided in two groups on the basis of the mAb regimen: BAM/ETE (n = 15) and CAS/IMD (n = 24). The phenotype/function of immune cell subsets was evaluated by flow-cytometry and by ELISA. The Spike-specific T cell response (IFN-γ) and anti-Nucleocapside IgG were evaluated by chemiluminescence assay. SARS CoV-2 RNA in nasal swabs was evaluated by RT-PCR. Eleven out of the thirty-nine enrolled patients tested negative at T7, among which nine (81.8 %) had been treated with CAS/IMD regimen. A comparable increase in CD4 and CD8 T cells was observed in both treatment groups. Moreover, a reduction of CD38 expression on T (CD4, CD8 and Vδ2) and on NK cells was observed in both groups, as well as a reduction overtime of the perforin expression in T (CD8, Vδ2) and in NK cells reaching significance only in CAS/IMD-treated patients. The SARS-CoV-2-specific T cells response increased at T7 in BAM/ETE-treated patients and at T30 in CAS/IND group. Of note, at T30 SARS-CoV2-specific T cells was higher in CAS/IMD than in BAM/ETE group. Furthermore, the titre of anti-N IgG increased overtime in both groups with a faster kinetic in CAS/IMD group. The spontaneous production of inflammatory cytokines by monocytes and neutrophils was similar the two mAb regimens, as well as the level of plasmatic IL-6. Finally, patients were also analysed according to sex. The male group showed a higher frequency of activated CD4 T cells, NKG2A-expressing CD8 T cells and perforin-expressing Vδ2 T cells compared to female group. Moreover, a higher specific T cell response at T30 was observed in the male compared to female group. In conclusion, these results show similar effects of both mAb regimens in restoring T and NK cell homeostasis and in reducing inflammation. In contrast, CAS/IMD allows a better humoral and cellular SARS-CoV2 specific immunization.

BackgroundThe COVID-19 pandemic highlighted challenges in managing patients with multiple sclerosis (PwMS), as disease-modifying therapies (DMTs) can interfere with immune responses to infections and vaccines.ObjectiveThis study investigates the spike-specific T-cell response after the third dose of mRNA COVID-19 vaccines in PwMS undergoing DMTs, evaluating different cytokines, beyond IFN-γ, and exploring their potential association with SARS-CoV-2 breakthrough infections (BI).MethodsWe prospectively enrolled 31 PwMS and 27 healthcare workers (HCWs). The spike-specific T-cell response was evaluated by measuring Th1 cytokines (IFN-γ, IL-2, TNF-α) and IP-10 using an easy-to-use whole-blood assay.ResultsMost PwMS mounted a Wuhan spike-specific T-cell response by releasing Th1 cytokines (IFN-γ, IL-2, TNF-α) and IP-10, albeit with significantly reduced Th1 cytokine levels compared to HCWs. Fingolimod-treated patients showed the weakest response with significantly reduced IFN-γ and IL-2 levels compared to HCWs (both p<0.0001), as well as to ocrelizumab (p=0.0018 and p=0.0002, respectively) and cladribine/IFN-β-treated patients (p=0.041 and p<0.0001, respectively). Moreover, a cell-mediated response was observed against the Delta spike variant, and all cytokines correlated with each other. BI occurred in 38.7% of PwMS, with predominantly mild COVID-19 cases. Male sex (IRR: 4.05, p=0.017) and primary progressive MS (IRR: 3.65, p=0.052) were associated with a higher BI incidence rate. Spike-specific T-cell response did not associate with a higher protection against BI.ConclusionsThis study provides an in-depth immunological characterization of the spike-specific T-cell response in PwMS under DMTs, evaluating immunological biomarkers whose relevance may extend beyond COVID-19 for studying immune responses to other infections and vaccinations.

The immunity conferred by MVA-BN vaccination against mpox appears to wane over time, particularly in individuals without prior smallpox vaccination, highlighting the potential benefit of a booster dose. We evaluated both humoral and cellular immune responses elicited by an MVA-BN booster administered at least 2 years after the primary course in 37 individuals at risk for mpox. Our results show that the booster restores and enhances both neutralising antibodies and T-cell responses, supporting the immunological value of booster strategies for individuals at ongoing risk of mpox. Moreover, we observed significant increases in IgG titres against both MPXV clades IIb and Ib, suggesting cross-protection among Orthopoxviruses. These findings support the use of a booster dose two years after the MVA-BN primary cycle to strengthen immunity in high-risk populations. They may inform future vaccination guidelines and public health recommendations in the evolving epidemiological context. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by Italian Ministry of Health, Ricerca Corrente Line 2, project 4. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Mpox-Vac study was approved by the INMI Lazzaro Spallanzani Ethical Committee (approval number 41z, Register of Non-COVID Trials 2022). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors

Introduction:Polymorphonuclear-myeloid-derived suppressor cells (PMN-MDSC) are elevated in COVID-19 patients, playing a crucial role in suppressing the SARS-CoV-2 specific T-cell response and serving as an early marker for disease progression. In this study, we investigated the involvement of PMN-MDSC from COVID-19 patients in the formation of extracellular traps (ET). Methods:Fifty RT-PCR-confirmed severe COVID-19 patients admitted to the ICU and ten healthy donors were enrolled. PBMC were isolated from peripheral blood by density gradient centrifugation, and PMN-MDSC frequency was evaluated by flow cytometry. PMN-MDSC were isolated by immunomagnetic separation. ET extrusion was analyzed by immunofluorescence imaging. Apoptosis of pulmonary microvascular endothelial cells cultured with PMN-MDSC was measured by flow cytometry. Results:We found that platelet-rich plasma (PRP) from COVID-19 patients, unlike that from healthy donors, induced ET formation by PMN-MDSC. Furthermore, the PRP-induced ET was found to be independent of Toll-like receptor 4 (TLR4) signaling. Interestingly, the SARS-CoV-2 Spike protein itself can trigger ET formation via a TLR4-dependent pathway. Additionally, PMN-MDSC induced endothelial cell apoptosis through an ET-independent mechanism. Discussion:These findings highlight a previously unrecognized contribution of PMN-MDSCs to the thrombotic complications in severe COVID-19 cases, underscoring their detrimental impact on disease progression.