There is increased interest in using microRNAs (miRNAs) as biomarkers in different diseases. Present in body fluids, it is controversial whether or not they are mainly enclosed in exosomes, thus we studied if urinary miRNAs are concentrated inside exosomes and if the presence of systemic lupus erythematosus with or without lupus nephritis modifies their distribution pattern. We quantified specific miRNAs in urine of patients with systemic lupus erythematosus (n = 38) and healthy controls (n = 12) by quantitative reverse-transcription PCR in cell-free urine, exosome-depleted supernatant and exosome pellet obtained by ultracentrifugation. In control group, miR-335* and miR-302d were consistently higher in exosomes than in exosome-depleted supernatant, and miR-200c and miR-146a were higher in cell-free fraction. In lupus patients, all urinary miRNAs tested were mainly in exosomes with lower levels outside them (p<0.05 and p<0.01, respectively). This pattern is especially relevant in patients with active lupus nephritis compared to the control group or to the SLE patients in absence of lupus nephritis, with miR-146a being the most augmented (100-fold change, p<0.001). Among the exosomal miRNAs tested, only the miR-146a discriminates the presence of active lupus nephritis. In conclusion, urinary miRNAs are contained primarily in exosomes in systemic lupus erythematosus, and the main increment was found in the presence of active lupus nephritis. These findings underscore the attractiveness of exosomal miRNAs in urine, a non-invasive method, as potential renal disease markers.

There is limited information on severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) T‐cell immune responses in patients with coronavirus disease 2019 (COVID‐19). Both CD4+ and CD8+ T cells may be instrumental in resolution of and protection from SARS‐CoV‐2 infection. Here, we tested 25 hospitalized patients either with microbiologically documented COVID‐19 (n = 19) or highly suspected of having the disease (n = 6) for presence of SARS‐CoV‐2‐reactive CD69+ expressing interferon‐γ (IFN‐γ) producing CD8+ T cells using flow‐cytometry for intracellular cytokine staining assay. Two sets of overlapping peptides encompassing the SARS‐CoV‐2 Spike glycoprotein N‐terminal 1 to 643 amino acid sequence and the entire sequence of SARS‐CoV‐2 M protein were used simultaneously as antigenic stimulus. Ten patients (40%) had detectable responses, displaying frequencies ranging from 0.15 to 2.7% (median of 0.57 cells/µL; range, 0.43‐9.98 cells/µL). The detection rate of SARS‐CoV‐2‐reactive IFN‐γ CD8+ T cells in patients admitted to intensive care was comparable ( P = .28) to the rate in patients hospitalized in other medical wards. No correlation was found between SARS‐CoV‐2‐reactive IFN‐γ CD8+ T‐cell counts and SARS‐CoV‐2 S‐specific antibody levels. Likewise, no correlation was observed between either SARS‐CoV‐2‐reactive IFN‐γ CD8+ T cells or S‐specific immunoglobulin G‐antibody titers and blood cell count or levels of inflammatory biomarkers. In summary, in this descriptive, preliminary study we showed that SARS‐CoV‐2‐reactive IFN‐γ CD8+ T cells can be detected in a non‐negligible percentage of patients with moderate to severe forms of COVID‐19. Further studies are warranted to determine whether quantitation of these T‐cell subsets may provide prognostic information on the clinical course of COVID‐19.