Neutralization of the SARS-CoV-2 Delta and Omicron Variants in Previous Non-Responder Kidney Transplant Recipients After Short-Term Withdrawal of Mycophenolic Acid

Background: Response to COVID-19 vaccination is significantly impaired in kidney transplant recipients (KTR) even after three doses of an mRNA vaccine. Adaptive immunization strategies are urgently needed to ultimately protect these patients from COVID-19. Method(s): We determined the effect of an additional mRNA-1273 vaccine dose in 76 non-responder KTR with at least 3 previous vaccine doses. In 43 KTR with triple immunosuppressive therapy including a calcineurin inhibitor (CNI), mycophenolic acid (MPA), and corticosteroids (CS), MPA was withdrawn to investigate the effect of short-term MPA withdrawal on COVID-19 vaccine immunogenicity. Seroconversion was determined four weeks after vaccination. In addition, neutralization of the delta and omicron variants was determined using a live-virus assay. In patients with temporary MPA withdrawal, donor-specific antibodies (DSA) and donor-derived cell-free DNA (dd-cfDNA) were monitored before MPA withdrawal and at follow-up. Result(s): After vaccination, 24/69 (35%) KTR showed anti-spike S1 IgG antibodies above the predefined cut-off, excluding 7 breakthrough infections that occurred during follow-up. SARS-CoV-2 specific antibodies were significantly higher in patients where MPA was withdrawn (Figure 1A). Neutralization of the delta variant was significantly better compared to neutralization of the omicron variant (Figure 1B). Higher SARSCoV-2-specific antibodies were associated with better in-vitro neutralization of the delta and omicron variants (Figure 1C). In KTR with MPA withdrawal, no significant changes in S-creatinine, proteinuria or dd-cfDNA were observed. No acute rejection episode occurred during short-term follow-up. However, resurgence of pre-existing DSA was observed in 7 patients and the development of de novo DSA in one patient. Conclusion(s): MPA withdrawal seems reasonable to increase immunogenicity of SARS-CoV-2 vaccination. For safety reasons, this may only be offered to patients without current or previous DSA.

Humoral responses to single-dose BNT162b2 mRNA vaccination in dialysis patients previously infected with SARS-CoV-2

Background: Seroconversion rates following infection and vaccination are lower in dialysis patients compared to healthy controls. There is an urgent need for the characterization of humoral responses and success of a single-dose SARS-CoV-2 vaccination in previously infected dialysis patients. Methods: We performed a dual-center study with 43 dialysis patients after BNT162b2 vaccination and 25 dialysis patients after PCR-confirmed COVID-19. Single-dose vaccination was performed in 13 previously infected patients. Anti-S1 IgG, neutralizing antibodies, and antibodies against various SARS-CoV-2 epitopes were measured 6 weeks after the first vaccination or onset of COVID-19 and 3 weeks after single-dose vaccination. Results: Previously infected patients without vaccination showed a significantly higher neutralizing capacity than patients vaccinated twice (median (IQR) percent inhibition 88.0 (71.5-95.5) vs. 50.7 (26.4-81.0);P=0.018). After one single vaccine dose, infected individuals generated 15-to 34-fold higher levels of anti-S1 IgG than age-and dialysis vintage-matched patients after infection or two-time vaccination with a median (IQR) index of 274 (151-791) compared to 18 (8-41) and 8 (1-21) (for both P<0.001). With a median (IQR) percent inhibition of 97.6 (97.2-98.9), the neutralizing capacity of SARS-CoV-2 antibodies was significantly higher in previously infected patients compared to other groups (for both P<0.01). Bead-based analysis showed high antibody reactivity against various SARS-CoV-2 spike protein epitopes after single-dose vaccination in previously infected patients. Conclusions: Single-dose vaccination in previously infected dialysis patients induced a strong and broad antibody reactivity against various SARS-CoV-2 spike protein epitopes with high neutralizing capacity.

Plasma exchange to treat patients with severe COVID-19

Background: The clinical spectrum of coronavirus disease 2019 (COVID-19) ranges from asymptomatic infection to critical illness and death in up to 89% of mechanically ventilated patients. Therefore, new therapeutic strategies are needed. Recent evidence suggests a multi-level inflammatory syndrome in some of the most critically ill patients with overlapping features of other hyperinflammatory or autoimmune diseases. Thus, plasma exchange (PE) has become a subject of controversy as potential therapy in these patients. Here, we report the results of the so far largest cohort of critically ill COVID-19 patients treated with PE. Methods: All critically ill COVID-19 patients treated with PE at Heidelberg University Hospital were analyzed between April and December 2020. Disease course and outcomes were compared with a standard care control group matched for age, sex, and disease severity. Changes in laboratory and clinical parameters were studied longitudinally. Kaplan-Meier and Cox regression analyses were performed. Results: In total, 28 critically ill COVID-19 patients were treated with an average of 3 PE procedures per patient. No relevant complications occurred during PE therapy. Inflammatory markers and biochemical indicators of end-organ damage and endothelial activation were significantly reduced during PE. These laboratory changes were accompanied by normalization of body temperature, improved pulmonary function, and reduced vasopressor demand. Most importantly, the laboratory and clinical improvements were maintained after the last PE. In contrast, most parameters in the control group did not improve significantly over seven days, although baseline clinical and laboratory parameters were comparable in both groups. Kaplan-Meier analysis showed improved 30-day survival in the PE group compared to the control group (67.9% vs. 42.9%, p=0.044). In a multivariable analysis, the hazard ratio for death was 0.27 (95% CI 0.11-0.68, p=0.005) with PE versus standard care. Conclusions: Our data further suggest that PE represents a potential therapeutic strategy for a subset of severe COVID-19 cases. The observed PE-related effects appear to go beyond a purely artificial improvement in blood parameters and may indicate a reversal of the complex COVID-19 immunopathology. Randomized controlled trials are urgently needed.

Glomerular filtration barrier dysfunction in an RNA virus-induced glomerulopathy resembles findings of common nephrotic syndromes

Background: Virally induced kidney dysfunction is highlighted by the alarming incidence of SARS-CoV-2 associated acute renal disease including nephrotic syndrome (NS). Plasma levels of soluble urokinase plasminogen activator receptor (suPAR) are elevated in COVID patients and provide prognostic insights. SuPAR is also involved in proteinuric kidney diseases such as focal segmental glomerulosclerosis in which podocytes effacement/injury is a common feature. Hantavirus-induced hemorrhagic fever with renal syndrome (HFRS) represents another RNA virus-induced disease with acute kidney injury and NS. The exact pathophysiology of proteinuria is, however, unclear. We hypothesized that hantavirus infection results in podocyte injury and a dysfunctional glomerular filtration barrier (GFB), similar to findings in common NS. Methods: Renal biopsy specimens were analyzed by light and electron microscopy. Urinary nephrin and serum suPAR were measured over time in 26 patients with HFRS and 18 healthy controls. Results: Hantavirus patients showed significantly increased urinary nephrin, immunoglobulin G (IgG), a1-microglobulin (a1-MG) and serum suPAR concentrations compared to healthy controls. Furthermore, nephrin and IgG levels were significantly higher in patients with severe than with mild proteinuria. Differences in a1-MG levels, however, disappeared after normalization to urinary creatinine. Urinary nephrin levels as a marker for podocyte damage correlated strongly with biomarkers of non-selective glomerular proteinuria. Interestingly, suPAR correlated significantly with urinary nephrin, IgG and albumin levels, suggesting suPAR as a potential pathophysiological mediator in GFB dysfunction in response to RNA virus infection. The main finding in microscopy analyses was a focal foot process effacement. Proteinuria and kidney dysfunction recovered autonomously in all patients. Conclusions: Hantavirus infection causes a podocyte injury leading to GFB dysfunction. A better understanding of transient virally induced proteinuria syndromes and their often self-limiting disease character may generate new therapeutic approaches for NS.

Plasma exchange in critically ill COVID-19 patients

Introduction: The spectrum of coronavirus disease 2019 (COVID-19) ranges from asymptomatic infection to respiratory failure and death of patients. Severely affected patients may develop a cytokine storm-like clinical syndrome with multi-organ failure and a mortality rate of up to 90%. Case Description: Here we report on five COVID-19 patients with a median age of 67 years who were treated at the intensive care unit due to respiratory failure. Prophylactic antibiotic, antimycotic, and antiviral/immunomodulatory therapy was initiated in all patients upon admission. During the course of the disease, patients developed circulatory shock and persistent fever together with increased interleukin 6-levels compatible with the cytokine storm-like clinical syndrome. In addition, all patients had multi-organ failure with acute respiratory-distress syndrome (ARDS, 4 severe, 1 moderate) and acute kidney injury of at least KDIGO stage 2. A single PE with a median of 3.39 L of fresh frozen plasma was initiated in all patients followed by one additional treatment in patients 1, 3, and 5. During the PE, striking reduction of inflammatory markers C-reactive protein (-47%, P=0.0078) and interleukin 6 (-74%, P=0.0078), as well as significant reduction of ferritin (-49%, P=0.0078), LDH (-41%, P=0.0078), and D-Dimer (-47%, P=0.016) were observed. Due to circulatory shock, four patients received vasopressor treatment at the start of the PE that could be substantially reduced during treatment (-71%, P=0.031). Biochemical and clinical improvement continued over the following days together with an increase in the oxygenation index in 4 out of 5 patients. These improvements were achieved with only 1 to 2 PE, which might be a possible indication of a direct pathophysiological influence of PE on the COVID-19-associated cytokine storm-like clinical syndrome. Three of the 5 most critically ill patients are alive, while a 71-year-old male and a 76-year-old female patient died after the therapy was limited due to persistent severe ARDS. Discussion: PE improved inflammation, microcirculatory clot formation, and hypotension, thereby improving clinical outcomes. Further studies to test whether (repeated) PE can alter the course of critically ill COVID-19 patients are clearly indicated.