Anti-factor H antibody and its role in atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) an important form of a thrombotic microangiopathy (TMA) that can frequently lead to acute kidney injury (AKI). An important subset of aHUS is the anti-factor H associated aHUS. This variant of aHUS can occur due to deletion of the complement factor H genes, CFHR1 and CFHR3, along with the presence of anti-factor H antibodies. However, it is a point of interest to note that not all patients with anti-factor H associated aHUS have a CFHR1/R3 deletion. Factor-H has a vital role in the regulation of the complement system, specifically the alternate pathway. Therefore, dysregulation of the complement system can lead to inflammatory or autoimmune diseases. Patients with this disease respond well to treatment with plasma exchange therapy along with Eculizumab and immunosuppressant therapy. Anti-factor H antibody associated aHUS has a certain genetic predilection therefore there is focus on further advancements in the diagnosis and management of this disease. In this article we discuss the baseline characteristics of patients with anti-factor H associated aHUS, their triggers, various treatment modalities and future perspectives.

The mechanism underlying extrapulmonary complications of the coronavirus disease 2019 and its therapeutic implication.

The coronavirus disease 2019 (COVID-19) is a highly transmissible disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that poses a major threat to global public health. Although COVID-19 primarily affects the respiratory system, causing severe pneumonia and acute respiratory distress syndrome in severe cases, it can also result in multiple extrapulmonary complications. The pathogenesis of extrapulmonary damage in patients with COVID-19 is probably multifactorial, involving both the direct effects of SARS-CoV-2 and the indirect mechanisms associated with the host inflammatory response. Recognition of features and pathogenesis of extrapulmonary complications has clinical implications for identifying disease progression and designing therapeutic strategies. This review provides an overview of the extrapulmonary complications of COVID-19 from immunological and pathophysiologic perspectives and focuses on the pathogenesis and potential therapeutic targets for the management of COVID-19.

Critical analysis of acute kidney injury in pediatric COVID-19 patients in the intensive care unit.

BACKGROUND AND OBJECTIVES: COVID-19 is responsible for the 2019 novel coronavirus disease pandemic. Despite the vast research about the adult population, there has been little data collected on acute kidney injury (AKI) epidemiology, associated risk factors, treatments, and mortality in pediatric COVID-19 patients admitted to the ICU. AKI is a severe complication of COVID-19 among children and adolescents. METHODS: A comprehensive literature search was conducted in PubMed/MEDLINE and Cochrane Center Trials to find all published literature related to AKI in COVID-19 patients, including incidence and outcomes. RESULTS: Twenty-four studies reporting the outcomes of interest were included. Across all studies, the overall sample size of COVID positive children was 1,247 and the median age of this population was 9.1 years old. Among COVID positive pediatric patients, there was an AKI incidence of 30.51%, with only 0.56% of these patients receiving KRT. The mortality was 2.55% among all COVID positive pediatric patients. The incidence of multisystem inflammatory syndrome in children (MIS-C) among COVID positive patients was 74.29%. CONCLUSION: AKI has shown to be a negative prognostic factor in adult patients with COVID-19 and now also in the pediatric cohort with high incidence and mortality rates. Additionally, our findings show a strong comparison in epidemiology between adult and pediatric COVID-19 patients; however, they need to be confirmed with additional data and studies.

The role of PD-L1 in the immune dysfunction that mediates hypoxia-induced multiple organ injury.

Hypoxia is a pathological condition common to many diseases, although multiple organ injuries induced by hypoxia are often overlooked. There is increasing evidence to suggest that the hypoxic environment may activate innate immune cells and suppress adaptive immunity, further stimulating inflammation and inhibiting immunosurveillance. We found that dysfunctional immune regulation may aggravate hypoxia-induced tissue damage and contribute to secondary injury. Among the diverse mechanisms of hypoxia-induced immune dysfunction identified to date, the role of programmed death-ligand 1 (PD-L1) has recently attracted much attention. Besides leading to tumour immune evasion, PD-L1 has also been found to participate in the progression of the immune dysfunction which mediates hypoxia-induced multiple organ injury. In this review, we aimed to summarise the role of immune dysfunction in hypoxia-induced multiple organ injury, the effects of hypoxia on the cellular expression of PD-L1, and the effects of upregulated PD-L1 expression on immune regulation. Furthermore, we summarise the latest information pertaining to the involvement, diagnostic value, and therapeutic potential of immunosuppression induced by PD-L1 in various types of hypoxia-related diseases, including cancers, ischemic stroke, acute kidney injury, and obstructive sleep apnoea. Video Abstract.

Outcomes of COVID-19 in Solid Organ Transplant Recipients: A Propensity-matched Analysis of a Large Research Network.

BACKGROUND: Organ transplant recipients comprise an immunocompromised and vulnerable cohort. Outcomes of coronavirus disease 2019 (COVID-19) in solid organ transplant (SOT) recipients remain understudied. METHODS: We used a multicenter federated research network to compare clinical outcomes of COVID-19 in patients with SOT to a propensity--matched cohort of patients without SOT. RESULTS: We identified 2307 SOT recipients and 231 047 nontransplant patients with COVID-19. Transplant patients were more likely to be male individuals, older, have a body mass index >30 kg/m2, and have comorbid hypertension, diabetes, nicotine dependence, heart failure, and ischemic heart disease compared with the nontransplant group (P < 0.05). One-to-one matching was performed for diabetes, hypertension, chronic lung diseases, race, nicotine dependence, heart failure, ischemic heart disease, and gender. There was no difference in the composite outcome of intubation or mechanical ventilation at 30 days (risk ratio [RR], 1.04; 95% confidence interval [CI], 0.86-1.26) or 60 days (RR, 1.03; 95% CI, 0.86-1.24) between the 2 groups. Hospitalization rate was higher in the transplant cohort (30.97% versus 25.47%; RR, 1.22; 95% CI, 1.11-1.34). There was no difference in mortality at 30 days (6.45% versus 5.29%; RR, 1.22; 95% CI, 0.88-1.68) or 60 days postdiagnosis (RR, 1.05; 95% CI, 0.83-1.32). More patients in the SOT group developed acute renal injury compared with non-SOT cohort (24.73% versus 14.29%; RR, 1.73; 95% CI, 1.53-1.96). CONCLUSIONS: Patients with SOT have high COVID-19-related mortality; however, propensity-matched analyses reveal that this increased risk is secondary to higher burden of comorbidities. SOT status independently increases risk of hospital admission and acute kidney injury.

Favipiravir use in children with COVID-19 and acute kidney injury: is it safe?

BACKGROUND: The rising number of infections due to Severe Acute Respiratory Syndrome Coronavirus-2 (popularly known as COVID-19) has brought to the fore new antiviral drugs as possible treatments, including favipiravir. However, there is currently no data regarding the safety of this drug in patients with kidney impairment. The aim of this paper, therefore, is to share our experience of the use of favipiravir in pediatric patients affected by COVID-19 with any degree of kidney impairment. METHODS: The study enrolled pediatric patients aged under 18 years and confirmed as suffering from COVID-19 and multisystem inflammatory syndrome in children (MIS-C) with any degree of kidney injury, who were treated with favipiravir at the time of admission. RESULTS: Out of a total of 11 patients, 7 were diagnosed with MIS-C and 4 with severe COVID-19. The median age of the cases was 15.45 (9-17.8) years and the male/female ratio was 7/4. At the time of admission, the median serum creatinine level was 1.1 mg/dl. Nine patients were treated with favipiravir for 5 days, and 2 patients for 5 days followed by remdesivir for 5-10 days despite kidney injury at the time of admission. Seven patients underwent plasma exchange for MIS-C while 2 severely affected cases underwent continuous kidney replacement therapy (CKRT) as well. One severe COVID-19 patient received plasma exchange as well as CKRT. Serum creatinine values returned to normal in mean 3.07 days. CONCLUSIONS: Favipiravir seems a suitable therapeutic option in patients affected by COVID-19 with kidney injury without a need for dose adjustment.

Renal Morphology in Coronavirus Disease: A Literature Review.

Renal biopsy is useful to better understand the histological pattern of a lesion (glomerular, tubulointerstitial, and vascular) and the pathogenesis that leads to kidney failure. The potential impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the kidneys is still undetermined, and a variety of lesions are seen in the kidney tissue of coronavirus disease patients. This review is based on the morphological findings of patients described in case reports and a series of published cases. A search was conducted on MEDLINE and PubMed of case reports and case series of lesions in the presence of non-critical infection by SARS-CoV-2 published until 15/09/2020. We highlight the potential of the virus directly influencing the damage or the innate and adaptive immune response activating cytokine and procoagulant cascades, in addition to the genetic component triggering glomerular diseases, mainly collapsing focal segmental glomerulosclerosis, tubulointerstitial, and even vascular diseases. Kidney lesions caused by SARS-CoV-2 are frequent and have an impact on morbidity and mortality; thus, studies are needed to assess the morphological kidney changes and their mechanisms and may help define their spectrum and immediate or long-term impact.

Mass Screening Is Associated with Low Rates of Acute Kidney Injury among COVID-19 Patients in Hong Kong.

INTRODUCTION: Renal involvement in COVID-19 is less well characterized in settings with vigilant public health surveillance, including mass screening and early hospitalization. We assessed kidney complications among COVID-19 patients in Hong Kong, including the association with risk factors, length of hospitalization, critical presentation, and mortality. METHODS: Linked electronic records of all patients with confirmed COVID-19 from 5 major designated hospitals were extracted. Duplicated records due to interhospital transferal were removed. Primary outcome was the incidence of in-hospital acute kidney injury (AKI). Secondary outcomes were AKI-associated mortality, incident renal replacement therapy (RRT), intensive care admission, prolonged hospitalization and disease course (defined as >90th percentile of hospitalization duration [35 days] and duration from symptom onset to discharge [43 days], respectively), and change of estimated glomerular filtration rate (GFR). Patients were further stratified into being symptomatic or asymptomatic. RESULTS: Patients were characterized by young age (median: 38.4, IQR: 28.4-55.8 years) and short time (median: 5, IQR: 2-9 days) from symptom onset to admission. Among the 591 patients, 22 (3.72%) developed AKI and 4 (0.68%) required RRT. The median time from symptom onset to in-hospital AKI was 15 days. AKI increased the odds of prolonged hospitalization and disease course by 2.0- and 3.5-folds, respectively. Estimated GFR 24 weeks post-discharge reduced by 7.51 and 1.06 mL/min/1.73 m2 versus baseline (upon admission) in the AKI and non-AKI groups, respectively. The incidence of AKI was comparable between asymptomatic (4.8%, n = 3/62) and symptomatic (3.7%, n = 19/519) patients. CONCLUSION: The overall rate of AKI among COVID-19 patients in Hong Kong is low, which could be attributable to a vigilant screening program and early hospitalization. Among patients who developed in-hospital AKI, the duration of hospitalization is prolonged and kidney function impairment can persist for up to 6 months post-discharge. Mass surveillance for COVID-19 is warranted in identifying asymptomatic subjects for earlier AKI management.

Complement Activation in Kidneys of Patients With COVID-19.

Most patients who became critically ill following infection with COVID-19 develop severe acute respiratory syndrome (SARS) attributed to a maladaptive or inadequate immune response. The complement system is an important component of the innate immune system that is involved in the opsonization of viruses but also in triggering further immune cell responses. Complement activation was seen in plasma adsorber material that clogged during the treatment of critically ill patients with COVID-19. Apart from the lung, the kidney is the second most common organ affected by COVID-19. Using immunohistochemistry for complement factors C1q, MASP-2, C3c, C3d, C4d, and C5b-9 we investigated the involvement of the complement system in six kidney biopsies with acute kidney failure in different clinical settings and three kidneys from autopsy material of patients with COVID-19. Renal tissue was analyzed for signs of renal injury by detection of thrombus formation using CD61, endothelial cell rarefaction using the marker E-26 transformation specific-related gene (ERG-) and proliferation using proliferating cell nuclear antigen (PCNA)-staining. SARS-CoV-2 was detected by in situ hybridization and immunohistochemistry. Biopsies from patients with hemolytic uremic syndrome (HUS, n = 5), severe acute tubular injury (ATI, n = 7), zero biopsies with disseminated intravascular coagulation (DIC, n = 7) and 1 year protocol biopsies from renal transplants (Ctrl, n = 7) served as controls. In the material clogging plasma adsorbers used for extracorporeal therapy of patients with COVID-19 C3 was the dominant protein but collectin 11 and MASP-2 were also identified. SARS-CoV-2 was sporadically present in varying numbers in some biopsies from patients with COVID-19. The highest frequency of CD61-positive platelets was found in peritubular capillaries and arteries of COVID-19 infected renal specimens as compared to all controls. Apart from COVID-19 specimens, MASP-2 was detected in glomeruli with DIC and ATI. In contrast, the classical pathway (i.e. C1q) was hardly seen in COVID-19 biopsies. Both C3 cleavage products C3c and C3d were strongly detected in renal arteries but also occurs in glomerular capillaries of COVID-19 biopsies, while tubular C3d was stronger than C3c in biopsies from COVID-19 patients. The membrane attack complex C5b-9, demonstrating terminal pathway activation, was predominantly deposited in COVID-19 biopsies in peritubular capillaries, renal arterioles, and tubular basement membrane with similar or even higher frequency compared to controls. In conclusion, various complement pathways were activated in COVID-19 kidneys, the lectin pathway mainly in peritubular capillaries and in part the classical pathway in renal arteries whereas the alternative pathway seem to be crucial for tubular complement activation. Therefore, activation of the complement system might be involved in the worsening of renal injury. Complement inhibition might thus be a promising treatment option to prevent deregulated activation and subsequent collateral tissue injury.

Acute kidney injury associated with COVID-19-Cumulative evidence and rationale supporting against direct kidney injury (infection).

Acute kidney injury (AKI) is a common complication, affecting up to 37% of hospitalized patients with SARS-CoV-2 infection and is proportional to its severity and portends poor prognosis. Diverse mechanisms have been proposed and studies reported conflicting results. Moreover, renal tropism of SARS-CoV-2 does not equate to its renal pathogenicity. For a virus to be pathogenic, in addition to its affinity (tropism) for specific tissue(s), host cells must allow viral entry, and discuss the important role played by transmembrane protease, serine 2 (TMPRSS2) and coexpression of both ACE2 and TMPRSS2 in the same cells is important to cause damage. Lack of coexpression of ACE2 and TMPRSS2 in the same cells of the kidneys is the limiting factor of SARS-CoV-2 direct effects in the kidney. We present the rationale and cumulative evidence supporting that AKI is secondary to hemodynamic and immunologic effects of SARS-CoV-2 infection than the direct injury or infection.

The Kidney Contains Ontogenetically Distinct Dendritic Cell and Macrophage Subtypes throughout Development That Differ in Their Inflammatory Properties.

BACKGROUND: Mononuclear phagocytes (MPs), including macrophages, monocytes, and dendritic cells (DCs), are phagocytic cells with important roles in immunity. The developmental origin of kidney DCs has been highly debated because of the large phenotypic overlap between macrophages and DCs in this tissue. METHODS: We used fate mapping, RNA sequencing, flow cytometry, confocal microscopy, and histo-cytometry to assess the origin and phenotypic and functional properties of renal DCs in healthy kidney and of DCs after cisplatin and ischemia reperfusion-induced kidney injury. RESULTS: Adult kidney contains at least four subsets of MPs with prominent Clec9a-expression history indicating a DC origin. We demonstrate that these populations are phenotypically, functionally, and transcriptionally distinct from each other. We also show these kidney MPs exhibit unique age-dependent developmental heterogeneity. Kidneys from newborn mice contain a prominent population of embryonic-derived MHCIInegF4/80hiCD11blow macrophages that express T cell Ig and mucin domain containing 4 (TIM-4) and MER receptor tyrosine kinase (MERTK). These macrophages are replaced within a few weeks after birth by phenotypically similar cells that express MHCII but lack TIM-4 and MERTK. MHCII+F4/80hi cells exhibit prominent Clec9a-expression history in adulthood but not early life, indicating additional age-dependent developmental heterogeneity. In AKI, MHCIInegF4/80hi cells reappear in adult kidneys as a result of MHCII downregulation by resident MHCII+F4/80hi cells, possibly in response to prostaglandin E2 (PGE2). RNA sequencing further suggests MHCII+F4/80hi cells help coordinate the recruitment of inflammatory cells during renal injury. CONCLUSIONS: Distinct developmental programs contribute to renal DC and macrophage populations throughout life, which could have important implications for therapies targeting these cells.

Persistent viral shedding despite seroconversion in a kidney transplant recipient with severe extrapulmonary COVID-19.

Renal transplant (RT) recipients are at increased risk for infectious complications. The clinical course of COVID-19 has been described in several RT recipients with varying clinical outcomes. Most present with pulmonary manifestations, however extrapulmonary presentations are not uncommon. Also, the timing and efficacy of seroconversion in transplant recipients is not well known. This report describes the duration of viral shedding and timing of seroconversion in a young adult RT recipient with COVID-19 who presented with severe diarrhoea and acute kidney injury requiring dialysis. She developed anti-SARS-CoV-2 IgG antibody after 5 weeks despite persistently shedding the virus in the nasopharynx until 6 weeks after symptom onset. Further studies are needed to determine if immunosuppressed patients have prolonged viral shedding and are still contagious despite seroconversion.

Covid-19 and kidney injury: Pathophysiology and molecular mechanisms.

The novel coronavirus (SARS-CoV-2) has turned into a life-threatening pandemic disease (Covid-19). About 5% of patients with Covid-19 have severe symptoms including septic shock, acute respiratory distress syndrome, and the failure of several organs, while most of them have mild symptoms. Frequently, the kidneys are involved through direct or indirect mechanisms. Kidney involvement mainly manifests itself as proteinuria and acute kidney injury (AKI). The SARS-CoV-2-induced kidney damage is expected to be multifactorial; directly it can infect the kidney podocytes and proximal tubular cells and based on an angiotensin-converting enzyme 2 (ACE2) pathway it can lead to acute tubular necrosis, protein leakage in Bowman's capsule, collapsing glomerulopathy and mitochondrial impairment. The SARS-CoV-2-driven dysregulation of the immune responses including cytokine storm, macrophage activation syndrome, and lymphopenia can be other causes of the AKI. Organ interactions, endothelial dysfunction, hypercoagulability, rhabdomyolysis, and sepsis are other potential mechanisms of AKI. Moreover, lower oxygen delivery to kidney may cause an ischaemic injury. Understanding the fundamental molecular pathways and pathophysiology of kidney injury and AKI in Covid-19 is necessary to develop management strategies and design effective therapies.

Angiotensin-converting enzyme 2 (ACE2): COVID 19 gate way to multiple organ failure syndromes.

BACKGROUND: Globally, the current medical emergency for novel coronavirus 2019 (COVID-19) leads to respiratory distress syndrome and death. PURPOSE: This review highlighted the effect of COVID-19 on systemic multiple organ failure syndromes. This review is intended to fill a gap in information about human physiological response to COVID-19 infections. This review may shed some light on other potential mechanisms and approaches in COVID -19 infections towards systemic multiorgan failure syndromes. FINDING: SARS-CoV-2 intervened mainly in the lung with progression to pneumonia and acute respiratory distress syndrome (ARDS) via the angiotensin-converting enzyme 2(ACE2) receptor. Depending on the viral load, infection spread through the ACE2 receptor further to various organs such as heart, liver, kidney, brain, endothelium, GIT, immune cell, and RBC (thromboembolism). This may be aggravated by cytokine storm with the extensive release of proinflammatory cytokines from the deregulating immune system. CONCLUSION: The widespread and vicious combinations of cytokines with organ crosstalk contribute to systemic hyper inflammation and ultimately lead to multiple organ dysfunction (Fig. 1). This comprehensive study comprises various manifestations of different organs in COVID-19 and may assist the clinicians and scientists pertaining to a broad approach to fight COVID 19.