Longevity of SARS-CoV-2 immune responses in hemodialysis patients and protection against reinfection.

Patients with end stage kidney disease receiving in-center hemodialysis (ICHD) have had high rates of SARS-CoV-2 infection. Following infection, patients receiving ICHD frequently develop circulating antibodies to SARS-CoV-2, even with asymptomatic infection. Here, we investigated the durability and functionality of the immune responses to SARS-CoV-2 infection in patients receiving ICHD. Three hundred and fifty-six such patients were longitudinally screened for SARS-CoV-2 antibodies and underwent routine PCR-testing for symptomatic and asymptomatic infection. Patients were regularly screened for nucleocapsid protein (anti-NP) and receptor binding domain (anti-RBD) antibodies, and those who became seronegative at six months were screened for SARS-CoV-2 specific T-cell responses. One hundred and twenty-nine (36.2%) patients had detectable antibody to anti-NP at time zero, of whom 127 also had detectable anti-RBD. Significantly, at six months, 71/111 (64.0%) and 99/116 (85.3%) remained anti-NP and anti-RBD seropositive, respectively. For patients who retained antibody, both anti-NP and anti-RBD levels were reduced significantly after six months. Eleven patients who were anti-NP seropositive at time zero, had no detectable antibody at six months; of whom eight were found to have SARS-CoV-2 antigen specific T cell responses. Independent of antibody status at six months, patients with baseline positive SARS-CoV-2 serology were significantly less likely to have PCR confirmed infection over the following six months. Thus, patients receiving ICHD mount durable immune responses six months post SARS-CoV-2 infection, with fewer than 3% of patients showing no evidence of humoral or cellular immunity.

High Prevalence of Asymptomatic COVID-19 Infection in Hemodialysis Patients Detected Using Serologic Screening.

BACKGROUND: Strategies to minimize the risk of transmission and acquisition of COVID-19 infection in patients with ESKD receiving in-center hemodialysis have been rapidly implemented across the globe. Despite these interventions, confirmed COVID-19 infection rates have been high in the United Kingdom. Prevalence of asymptomatic disease in an adult hemodialysis population has not been reported. Also, to our knowledge, the development of humoral response to SARS-CoV-2 has not been previously reported in this population. Although serologic testing does not provide information on the infectivity of patients, seroprevalence studies may enable investigation of exposure within dialysis units and hence, assessment of current screening strategies. METHODS: To investigate the seroprevalence of SARS-CoV-2 antibodies in a hemodialysis population, we used the Abbott IgG assay with the Architect system to test serum samples from 356 patients receiving in-center hemodialysis for SARS-CoV-2 antibodies. RESULTS: Of 356 patients, 121 had been symptomatic when screened before a dialysis session and received an RT-PCR test; 79 (22.2% of the total study population) tested positive for COVID-19. Serologic testing of all 356 patients found 129 (36.2%) who tested positive for SARS-CoV-2 antibodies. Only two patients with PCR-confirmed infection did not seroconvert. Of the 129 patients with SARS-CoV-2 antibodies, 52 (40.3%) had asymptomatic disease or undetected disease by PCR testing alone. CONCLUSIONS: We found a high seroprevalence of SARS-CoV-2 antibodies in patients receiving in-center hemodialysis. Serologic evidence of previous infection in asymptomatic or PCR-negative patients suggests that current diagnostic screening strategies may be limited in their ability to detect acute infection.

Severe COVID-19 is associated with endothelial activation and abnormal glycosylation of von Willebrand factor in patients undergoing hemodialysis.

BACKGROUND: A major clinical feature of severe coronavirus diease 2019 (COVID-19) is microvascular thrombosis linked to endothelial cell activation. Consistent with this, a number of studies have shown that patients with severe COVID-19 have highly elevated plasma levels of von Willebrand Factor (VWF) that may contribute to the prothrombotic phenotype. In the current study, we investigated the extent of endothelial activation in patients receiving hemodialysis who had either mild or severe COVID-19. METHODS: Plasma VWF, ADAMTS-13, angiopoietin-2 (Ang2), and syndecan-1 levels were determined by ELISA. The sialic acid content of VWF was investigated using a modified ELISA to measure elderberry bark lectin, specific for sialic acid residues, binding to VWF. RESULTS: Patients receiving hemodialysis with severe COVID-19 had significantly higher plasma levels of VWF and lower ADAMTS-13. VWF levels peaked and were sustained during the first 10 days after positive confirmation of infection. While Ang2 trended toward being higher in severely ill patients, this did not reach significance; however, severely ill patients had significantly higher soluble syndecan-1 levels, with high levels related to risk of death. Finally, higher VWF levels in severely ill patients were correlated with lower VWF sialic acid content. CONCLUSIONS: Severe COVID-19 in patients undergoing hemodialysis is associated with both acute and sustained activation of the endothelium, leading to alteration of the VWF/ADAMTS-13 axis. Lower VWF sialic acid content represents altered VWF processing and further confirms the disturbance caused to the endothelium in COVID-19.

Resuming Deceased Donor Kidney Transplantation in the COVID-19 Era: What Do Patients Want?

BACKGROUND: The rapidly evolving novel coronavirus 2019 (COVID-19) pandemic bought many kidney transplant (KT) programs to a halt. Integral to resuming KT activity is understanding the perspectives of potential transplant candidates during this highly dynamic time. METHODS: From June 1 to July 7, 2020, a telephone survey of KT candidates on the deceased donor waiting list at Imperial College Renal and Transplant Centre in West London was conducted. The survey captured ongoing COVID-19 exposure risks and patients' views on waitlist (WL) reactivation and undergoing transplantation. RESULTS: Two hundred seven responses were received. Of the respondents, 180 patients (87%) were happy to be reactivated onto the WL; with 141 patients (68%) willing to give consent to transplantation currently, while 53 patients (26%) felt unsure, and 13 patients (6%) would decline a KT. The vast majority of patients had no concerns. In the responses from those who were uncertain or who would decline a KT, concerns about COVID-19 infection and the need for reassurance from transplant units dominated. Universally patients wanted more information about COVID-19 infection risk with KT and the precautions being taken to reduce this risk. CONCLUSIONS: The majority of surveyed patients are in favor of reactivation and receiving a KT despite the ongoing COVID-19 pandemic. Reactivation of candidates cannot be assumed and should take an individualized approach, incorporating clinical risk with patient perspectives. Improved communication with KT candidates is highly requested.

Hirudin anticoagulation allows more rapid determination of P2Y12 inhibition by the VerifyNow P2Y12 assay.

VerifyNow (VN) P2Y12 is a point-of-care assay used to assess response to P2Y12 inhibitors. Sodium citrate (citrate) is the standard anticoagulant used for this assay but requires a pre-incubation period. Hirudin is an alternative anticoagulant for platelet function studies that maintains physiological divalent cation levels. We investigated whether hirudin anticoagulation might allow more rapid testing of P2Y12 inhibition at the time of percutaneous coronary intervention (PCI). Blood was collected from the arterial sheath of aspirin-treated patients undergoing elective, urgent or emergency coronary angiography±PCI and aliquots were anticoagulated with either citrate or hirudin. For each anticoagulant, VN P2Y12 was performed both immediately and after 20 minutes. A total of 98 patients were included in this study following pre-treatment with clopidogrel (n=88), prasugrel (n=6) or no P2Y12 inhibitor (n=4). PRU with hirudin immediately (PRU_H_Imm) and PRU with citrate 20 minutes post sampling (PRU_C_20) were very strongly correlated (R=0.95) though PRU_H_Imm tended to be lower than PRU_C_20 so that optimal correlation was estimated by the equation PRU_H_Imm=0.95xPRU_C_20 (p<0.001). Bland-Altman plots showed good agreement between PRU_H_Imm and (0.95xPRU_C_20). Platelet reactivity was more stable over the studied time course with hirudin as compared to citrate. We therefore conclude that VN P2Y12 with hirudin anticoagulation can be performed more rapidly and results are strongly correlated with delayed citrate measurements. Further studies are warranted to assess the utility of this method for improving clinical outcomes in patients undergoing PCI.