RESUMEN
BACKGROUND: Information regarding coronavirus disease 2019 (COVID-19) in haemodialysis (HD) patients is limited and early studies suggest a poor outcome. We aimed to identify clinical and biological markers associated with severe forms of COVID-19 in HD patients. METHODS: We conducted a prospective, observational and multicentric study. Sixty-two consecutive adult HD patients with confirmed COVID-19 from four dialysis facilities in Paris, France, from 19 March to 19 May 2020 were included.Blood tests were performed before diagnosis and at Days 7 and 14 after diagnosis. Severe forms of COVID-19 were defined as requiring oxygen therapy, admission in an intensive care unit or death. Cox regression models were used to compute adjusted hazard ratios (aHRs). Kaplan-Meier curves and log-rank tests were used for survival analysis. RESULTS: Twenty-eight patients (45%) displayed severe forms of COVID-19. Compared with non-severe forms, these patients had more fever (93% versus 56%, P < 0.01), cough (71% versus 38%, P = 0.02) and dyspnoea (43% versus 6%, P < 0.01) at diagnosis. At Day 7 post-diagnosis, neutrophil counts, neutrophil:lymphocyte (N:L) ratio, C-reactive protein, ferritin, fibrinogen and lactate dehydrogenase levels were significantly higher in severe COVID-19 patients. Multivariate analysis revealed an N:L ratio >3.7 was the major marker associated with severe forms, with an aHR of 4.28 (95% confidence interval 1.52-12.0; P = 0.006). After a median follow-up time of 48 days (range 27-61), six patients with severe forms died (10%). CONCLUSIONS: HD patients are at increased risk of severe forms of COVID-19. An elevated N:L ratio at Day 7 was highly associated with the severe forms. Assessing the N:L ratio could inform clinicians for early treatment decisions.
RESUMEN
IgA nephropathy (IgAN) is characterized by IgA immune complex-mediated mesangial cell proliferation. We have previously identified the transferrin receptor (TfR) as an IgA1 receptor and found that, in kidney biopsies of patients with IgAN, TfR is overexpressed and co-localized with IgA1 mesangial deposits. We also showed that IgA1 binding to TfR was strikingly increased when IgA1 was hypogalactosylated and of high molecular weight, both features found in IgA from IgAN patients. More recently, we showed that purified polymeric IgA1 (pIgA1) is a major inducer of TfR expression (3-fold increase) in quiescent human mesangial cells (HMC). In addition, sera from IgAN patients upregulate TfR expression in cultured HMC in an IgA-dependent manner. IgA1-induced HMC proliferation is dependent on TfR engagement and can be inhibited by both TfR1 and TfR2 ectodomains as well as by the anti-TfR mAb A24. Finally, activation of mesangial cells through pIgA1 binding to TfR induced secretion of IL-6 and TGF-beta from the cells, that could be involved, respectively, in the inflammatory and pro-fibrogenic events observed in IgAN. We propose that deposited pIgA1 or IgA immune complexes could initiate an auto-amplification process involving hyper-expression of TfR allowing increased IgA1 mesangial deposition. Altogether, these data unveil a functional cooperation between pIgA1 and TfR for IgA1 deposition and HMC proliferation, features which are commonly implicated in the chronic mesangial injuries observed in IgAN.