ABSTRACT
Background: After infection with SARS-Cov-2 or vaccination against COVID-19, some patients develop kidney diseases, including minimal change nephrotic syndrome and IgA Nephropathy (IgAN). Here we characterized renal injury and inflammatory response in biopsies from patients with new onset IgAN diagnosed promptly after COVID-19 disease or vaccination. Method(s): Eleven kidney biopsies from patients who developed IgAN after SARSCov-2 infection and 6 from patients with new onset IgAN after vaccination against COVID-19 were diagnosed at Dep. of Nephropathology, FAU Erlangen-Nuremberg. Biopsies from patients with IgAN who had no prior COVID-19 disease (n=10) and zero-time biopsies from transplants (ZB;n=6) served as controls. Serum creatinine was assessed and kidney injury by analysis of podocyte loss, detection of Pax-8 positive parietal epithelial cells on the glomerular tuft and IF/TA. Macrophages and granulocytes were detected by triple staining of CD68, CD163 and myeloperoxidase. Result(s): Significant podocyte loss, as assessed by nephrin staining, was observed in all three IgAN groups compared to ZB, as well as Pax8-positve parietal epithelial cells on glomerular tuft. The serum creatinine, as a marker of kidney function, was on average 1.8-3.5-fold higher in the IgAN groups compared to ZB, but did not reach significance level due to small sample numbers. IF/TA was below 20% in most investigated biopsies. No significant differences in renal function or injury were observed between different IgAN groups. While CD68+CD163+MPO+, CD68+CD163-MPO+ and CD68+CD163+MPO-(M2c-like macrophages) inflammatory cells were significantly increased in both COVID-19 IgAN groups, significant increase of CD68-CD163+MPO-cells compared to ZB control was restricted to IgAN w/o COVID-19 group (11.7+/-8.1 vs 0.8+/-0.9 cells / mm2). CD68+CD163-MPO-M1-like macrophages and CD68-CD163-MPO+ neutrophils tended to be higher in all IgAN groups but failed to reach the level of significance. Conclusion(s): Changes in kidney function and renal damage was comparable in all three investigated IgAN groups independent on experience of COVID-19 or vaccination. Renal macrophage and neutrophil invasion tended to by higher in COVID-19 IgAN groups. However, no significant differences in inflammatory were observed in direct comparisons of IgAN groups.