Poor immunological responders (PIR) are HIV-infected patients with virologic suppression upon antiretroviral therapy (ART) but persistently low CD4+ T cell counts. Early identification of PIR is important given their higher morbimortality compared to adequate immune responders (AIR). In this study, 33 patients severely lymphopenic at ART onset, were followed for at least 36 months, and classified as PIR or AIR using cluster analysis grounded on their CD4+ T cell count trajectories. Based on a variety of immunological parameters, we built predictive models of PIR/AIR outcome using logistic regression. All PIR had CD4+ T cell counts consistently below 500 cells/µL, while all AIR reached this threshold. AIR showed higher percentage of recent thymic emigrants among CD4+ T cells; higher numbers of sjTRECs and greater sj/βTREC ratios; and significant increases in thymic volume from baseline to 12 months of ART. We identified mathematical models that correctly predicted PIR/AIR outcome after 36 months of therapy in 77-87 % of cases, based on observations made until 2-6 months after ART onset. This study highlights the importance of thymic activity in the immune recovery of severely lymphopenic patients, and may help to select the patients that will benefit from closer follow-up or novel therapeutic approaches.

Pathogen-specific CD8 ⁺ T cell responses restricted by the nonpolymorphic nonclassical class Ib molecule human leukocyte antigen E (HLA-E) are rarely reported in viral infections. The natural HLA-E ligand is a signal peptide derived from classical class Ia HLA molecules that interact with the NKG2/CD94 receptors to regulate natural killer cell functions, but pathogen-derived peptides can also be presented by HLA-E. Here, we describe five peptides from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that elicited HLA-E–restricted CD8 ⁺ T cell responses in convalescent patients with coronavirus disease 2019. These T cell responses were identified in the blood at frequencies similar to those reported for classical HLA-Ia–restricted anti–SARS-CoV-2 CD8 ⁺ T cells. HLA-E peptide–specific CD8 ⁺ T cell clones, which expressed diverse T cell receptors, suppressed SARS-CoV-2 replication in Calu-3 human lung epithelial cells. SARS-CoV-2 infection markedly down-regulated classical HLA class I expression in Calu-3 cells and primary reconstituted human airway epithelial cells, whereas HLA-E expression was not affected, enabling T cell recognition. Thus, HLA-E–restricted T cells could contribute to the control of SARS-CoV-2 infection alongside classical T cells.

The importance of circulating immune cells to primary progressive multiple sclerosis (PPMS) pathophysiology is still controversial because most immunotherapies were shown to be ineffective in treating people with PPMS (pwPPMS). Yet, although controversial, data exist describing peripheral immune system alterations in pwPPMS. This study aims to investigate which alterations might be present in pwPPMS free of disease-modifying drugs (DMD) in comparison to age- and sex-matched healthy controls. A multicentric cross-sectional study was performed using 23 pwPPMS and 23 healthy controls. The phenotype of conventional CD4⁺ and CD8⁺ T cells, regulatory T cells (Tregs), B cells, natural killer (NK) T cells and NK cells was assessed. Lower numbers of central memory CD4⁺ and CD8⁺ T cells and activated HLA-DR⁺ Tregs were observed in pwPPMS. Regarding NK and NKT cells, pwPPMS presented higher percentages of CD56^dimCD57⁺ NK cells expressing NKp46 and of NKT cells expressing KIR2DL2/3 and NKp30. Higher disease severity scores and an increasing time since diagnosis was correlated with lower numbers of inhibitory NK cells subsets. Our findings contribute to reinforcing the hypotheses that alterations in peripheral immune cells are present in pwPPMS and that changes in NK cell populations are the strongest correlate of disease severity.

Background: Priming strategies that improve the functionality of MSCs may be required to address issues limiting successful clinical translation of MSC therapies. For conditions requiring high trophic support such as brain and spinal cord injuries, priming MSCs to produce higher levels of trophic factors may be instrumental to facilitate translation of current MSC therapies. We developed and tested a novel molecular priming paradigm using docosahexaenoic acid (DHA) to prime adipose tissue-derived mesenchymal stromal cells (ASCs) to enhance the secretome neuroregulatory potential. Methods: Comprehensive dose–response and time-course assays were carried to determine an optimal priming protocol. Secretome total protein measurements were taken in association with cell viability, density and morphometric assessments. Cell identity and differentiation capacity were studied by flow cytometry and lineage-specific markers. Cell growth was assessed by trypan-blue exclusion and senescence was probed over time using SA-β-gal, morphometry and gene expression. Secretomes were tested for their ability to support differentiation and neurite outgrowth of human neural progenitor cells (hNPCs). Neuroregulatory proteins in the secretome were identified using multiplex membrane arrays. Results: Priming with 40 µM DHA for 72 h significantly enhanced the biosynthetic capacity of ASCs, producing a secretome with higher protein levels and increased metabolic viability. DHA priming enhanced ASCs adipogenic differentiation and adapted their responses to replicative senescence induction. Furthermore, priming increased concentrations of neurotrophic factors in the secretome promoting neurite outgrowth and modulating the differentiation of hNPCs. Conclusions: These results provide proof-of-concept evidence that DHA priming is a viable strategy to improve the neuroregulatory profile of ASCs.

Commercial availability of serological tests to evaluate immunoglobulins (Ig) towards severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has grown exponentially since the onset of COVID-19 (Coronavirus Disease 2019) outbreak. Their thorough validation is of extreme importance before using them as epidemiological tools to infer population seroprevalence, and as complementary diagnostic tools to molecular approaches (e.g . RT-qPCR). Here we assayed commercial serological tests (semiquantitative and qualitative) from 11 suppliers in 126 samples collected from hospitalized COVID-19 patients, and from 36 healthy and HIV-infected individuals (collected at the pre-COVID-19 pandemic). Specificity was above 95% in 9 tests. Samples from COVID-19 patients were stratified by days since symptoms onset (21 days). Tests sensitivity increases with time since symptoms onset, and peaks at 16-21 days for IgM and IgA (maximum: 91.2%); and from 16-21 to >21 days for IgG, depending on the test (maximum: 94.1%). Data from semiquantitative tests show that patients with severe clinical presentation have lower relative levels of IgM, IgA and IgG at 21 days since symptoms onset the relative levels of IgM and IgG (in one test) are significantly higher in patients with severe clinical presentation, suggesting a delay in the upsurge of Ig against SARS-CoV-2 in those patients. This study highlights the high specificity of most of the evaluated tests, and sensitivity heterogeneity. Considering the virus genetic evolution and population immune response to it, continuous monitoring of commercially available serological tests towards SARS-CoV-2 is necessary.

Objective: To assess the peripheral immune system of newly diagnosed relapsing remitting multiple sclerosis (RRMS) patients and compare it to healthy controls (HC). Methods: Cross-sectional study with 30 treatment-naïve newly diagnosed RRMS patients, and 33 sex and age-matched HC. Their peripheral blood mononuclear cells were analysed regarding: i) thymic function surrogates [T cell receptor excision circles (TRECs) and recent thymic emigrants (RTEs)]; ii) naïve and memory CD4 ⁺ and CD8 ⁺ T cells subsets; iii) T helper (Th) phenotype and chemokine receptors expression on T cells subsets; iv) regulatory T cell (Tregs) phenotype; and vi) expression of activating/inhibitory receptors by natural killer (NK) and NKT cells. Analyses were controlled for age, sex, and human cytomegalovirus (HCMV) IgG seroprevalence. Results: Newly diagnosed RRMS patients and HC have equivalent thymic function as determined by similar numbers of RTEs, and levels of sjTRECs, DJβTRECs and sj/DJβTREC ratio. In the CD8 ⁺ T cells compartment RRMS patients have a higher naïve/memory ratio and lower memory cell counts in blood, specifically of effector memory and TemRA CD8 ⁺ T cells. Among CD4 ⁺ T cells lower blood counts of effector memory cells are found in patients upon controlling for sex, age and HCMV IgG seroprevalence. RRMS patients have higher percentage of naive Tregs comparing to HC. Percentages of immature CD56 ^bright NK cells expressing the inhibitory receptor KLRG1, and of mature CD56 ^dim CD57 ⁺ NK cells expressing NKp30 are higher in patients. No major alterations are observed on NKT cells. MS severity and time from relapse correlate with immune cells alterations. Conclusion: Characterization of the peripheral immune system of treatment-naïve newly diagnosed RRMS patients unveiled immune features present at clinical onset including lower memory T cells blood counts, particularly among CD8 ⁺ T cells, higher percentage of naïve Tregs and altered percentages of NK cells subsets expressing inhibitory or activating receptors. These findings might set the basis to better understand disease pathogenesis.