Human kidney is a target for novel severe acute respiratory syndrome coronavirus 2 infection

Abstract

It is unclear whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can directly infect human kidney, thus leading to acute kidney injury (AKI). Here, we perform a retrospective analysis of clinical parameters from 85 patients with laboratory-confirmed coronavirus disease 2019 (COVID-19); moreover, kidney histopathology from six additional COVID-19 patients with post-mortem examinations was performed. We find that 27% (23/85) of patients exhibited AKI. The elderly patients and cases with comorbidities (hypertension and heart failure) are more prone to develop AKI. Haematoxylin & eosin staining shows that the kidneys from COVID-19 autopsies have moderate to severe tubular damage. In situ hybridization assays illustrate that viral RNA accumulates in tubules. Immunohistochemistry shows nucleocapsid and spike protein deposits in the tubules, and immunofluorescence double staining shows that both antigens are restricted to the angiotensin converting enzyme-II-positive tubules. SARS-CoV-2 infection triggers the expression of hypoxic damage-associated molecules, including DP2 and prostaglandin D synthase in infected tubules. Moreover, it enhances CD68+ macrophages infiltration into the tubulointerstitium, and complement C5b-9 deposition on tubules is also observed. These results suggest that SARS-CoV-2 directly infects human kidney to mediate tubular pathogenesis and AKI.

Fig. 1. The histopathology of kidney tissues from COVID-19 post-mortem.

Sections from six cases of COVID-19 post-mortem, one representative hepatitis B virus-associated membranous nephropathy (HBV-MN) patient and one representative trauma victim were collected to stain by haematoxylin & eosin (H&E). Arrow indicates infiltrated leukocytes. Scale bars = 200 μm. Data represent one of at least three technical replication each.

Fig. 2. Detection of SARS-CoV-2 viral RNA and protein antigens in kidney tissues.

a RNA in situ hybridization (ISH) in serial sections of kidney tissues from COVID-19 post-mortem (case #2) showed reactivity for the presence of SARS-CoV-2 viral RNA and the positive control probe to the housekeeping gene peptidylprolyl isomerase B (PPIB). Scale bars = 100 μm. b The kidney tissues from COVID-19 post-mortem (case #2) were incubated with primary anti-SARS-NP (nucleocapsid protein) antibodies (clone ID: 019, rabbit IgG; Sino Biological), anti-SARS-NP antibodies (ab273434, mouse monoclonal 6H3, Abcam), anti-SARS-S (spike) antibodies (ab273433, mouse monoclonal 1A9, Abcam), or only incubated with mouse or rabbit IgG1 control antibodies, and the expression of indicated viral antigens were further analyzed by immunohistochemistry. Arrow indicates positive tubules. Scale bars = 100 μm. Data represent one of at least three technical replication each.

Fig. 3. SARS-CoV-2 protein antigens co-express with ACE2 in kidney tubules.

a Representative expression of angiotensin-converting enzyme-II (ACE2) in kidney tissues from COVID-19 post-mortem (case #2) was detected by immunohistochemistry. Scale bars = 100 μm. b The co-expression of ACE2 and SARS-CoV-2 NP (nucleocapsid protein) or S (spike) antigens in kidney sections from COVID-19 post-mortem (case #2), hepatitis B virus-associated membranous nephropathy (HBV-MN) and trauma victims. Arrow indicates positive tubules. Scale bars = 100 μm. Data represent one of at least three technical replication each.

Fig. 4. SARS-CoV-2 protein antigens co-express with hypoxic damage-associated molecules in kidney.

Immunofluorescent double staining was used to detect the expression of a SARS-CoV-2 NP (nucleocapsid protein) and DP2 in kidney tissues from COVID-19 post-mortem (case #2 and #5); b SARS-CoV-2 S (spike) and prostaglandin D synthase (PDS) in kidney tissues from COVID-19 post-mortem (case #2 and #5); c SARS-CoV-2 NP and DP2 or S and PDS in kidney tissues from hepatitis B virus-associated membranous nephropathy (HBV-MN). Here, sections only incubated with rabbit and mouse secondary antibodies were used as isotype controls. Arrow indicates positive cells. Scale bars = 100 μm. Data represent one of at least three technical replication each.

Fig. 5. Immunohistochemistry analyzed leukocytes and the complement C5b-9 in kidney tissues.

Immunohistochemistry was used to detect the expression of a CD68, CD8, and CD56; b C5b-9 in kidney tissues from COVID-19 post-mortem (case #2), hepatitis B virus-associated membranous nephropathy (HBV-MN) and trauma victims. Arrow indicates positive cells. Scale bars = 200 μm. Data represent one of at least three technical replication each.