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The apoptotic molecule Fas and its ligand FasL are involved in the process of T-lymphocyte death, which may lead to lymphopenia, a characteristic of severe coronavirus disease 2019 (COVID-19). In this study, we investigated the influence of polymorphisms in the FAS and FASL genes, FAS and FASL gene expression, and plasma cytokine levels on COVID-19 severity and long COVID occurrence. A total of 116 individuals with severe COVID-19 and 254 with the non-severe form of the disease were evaluated. In the post-COVID-19 period, samples from 196 individuals with long COVID and 67 from people who did not have long COVID were included. Genotyping and quantification of gene expression were performed via real-time PCR, and cytokine measurement was performed via flow cytometry. The AA genotype for FAS rs1800682 (A/G) and the TT genotype for FASL rs763110 (C/T) were associated with increased FAS and FASL gene expression, respectively ( p < 0.005). Higher plasma IFN-γ levels were associated with higher FAS and FASL gene expression ( p < 0.05). Among individuals with non-severe COVID-19, carriers of the AA genotype for FAS rs1800682 (A/G) had higher levels of FAS expression, more symptoms, and higher IFN-γ levels ( p < 0.05). No association of the evaluated markers with long COVID were observed. The AA genotype of FAS rs1800682 (A/G) and the TT genotype of FASL rs763110 (C/T) influence the levels of FAS and FASL gene expression. Higher gene expression of FAS and FASL may lead to greater inflammation in COVID-19 patients, with higher levels of IFN-γ and T lymphocyte death.

Yellow fever (YF) is an infectious disease considered a public health problem in tropical and subtropical areas. YF has many pathophysiological events that are correlated with the host immune response. In this study, the in situ Th22 cytokine profile was evaluated. Liver tissue samples were collected from 21 YFV-positive patients who died of the disease and five flavivirus-negative controls who died of other causes and whose hepatic parenchyma architecture was preserved. Immunohistochemical (IHC) analysis of tissues in the hepatic parenchyma of YF cases showed significantly higher expression of interleukin (IL)-22, IL-13, tumour necrosis factor-alpha, and FGF basic (FGF b) in YFV-positive cases than that in flavivirus-negative controls. These results indicate that the response of Th22 cytokines emerges as an alternative for a better understanding of adaptive immunity in the hepatic parenchyma, highlighting the role of cytokines in the repair and suppressive responses in the immunopathogenesis of YFV infection., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Yellow fever (YF), a non-contagious infectious disease, is endemic or enzootic to the tropical regions of the Americas and Africa. Periodic outbreaks or epidemics have a significant impact on public health. Programmed cell death, or apoptosis, is generally characterised by distinct morphological changes and energy-dependent biochemical pathways. In this study, we performed immunohistochemistry analysis to identify and quantify proteases and protein targets involved in the cascade that triggers apoptosis in YF virus (YFV)-infected human hepatocytes. Liver tissue samples were collected from 26 individuals, among whom 21 were diagnosed as YF-positive, and five were flavivirus-negative and died due to other causes. The histopathological alterations in YFV-positive cases were characterised by the presence of apoptotic bodies, steatosis, cellular swelling, and extensive necrosis and haemorrhage in the hepatic lobules. Additionally, we observed an abundance of inflammatory infiltrates in the portal tract. The expression of various apoptotic markers in the hepatic parenchyma, including CASPASE 3, CASPASE 8, BAX, FAS, FASL, GRANZYME B, and SURVIVIN, differed between YFV-positive cases and controls. Collectively, this study confirmed the complexity of YFV infection-induced apoptosis in situ. However, our data suggest that apoptosis in liver parenchyma lesions may significantly contribute to the pathogenesis of fatal YF in humans.

Yellow fever (YF) is a pansystemic disease caused by the yellow fever virus (YFV), the prototype species of the family Flaviviridae and genus Flavivirus , and has a highly complex host-pathogen relationship, in which endothelial dysfunction reflects viral disease tropism. In this study, the in situ endothelial response was evaluated. Liver tissue samples were collected from 21 YFV-positive patients who died due to the disease and five flavivirus-negative controls who died of other causes and whose hepatic parenchyma architecture was preserved. Immunohistochemical analysis of tissues in the hepatic parenchyma of YF cases showed significantly higher expression of E-selectin, P-selectin, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and very late antigen-4 in YFV-positive cases than in flavivirus-negative controls. These results indicate that endothelium activation aggravates the inflammatory response by inducing the expression of adhesion molecules that contribute to the rolling, recruitment, migration, and construction of the inflammatory process in the hepatic parenchyma in fatal YF cases.