Immune Response Gaps Linked to SARS-CoV-2 Infection: Cellular Exhaustion, Senescence, or Both?

The COVID-19 pandemic, promoted by the SARS-CoV-2 respiratory virus, has resulted in widespread global morbidity and mortality. The immune response against this pathogen has shown a thin line between protective effects and pathological reactions resulting from the massive release of cytokines and poor viral clearance. The latter is possibly caused by exhaustion, senescence, or both of TCD8+ cells and reduced activity of natural killer (NK) cells. The imbalance between innate and adaptive responses during the early stages of infection caused by SARS-CoV-2 contributes to the ineffective control of viral spread. The present study evaluated the tissue immunoexpression of the tissue biomarkers (Arginase-1, CCR4, CD3, CD4, CD8, CD20, CD57, CD68, CD138, IL-4, INF-α, INF-γ, iNOS, PD-1, Perforin and Sphingosine-1) to understand the cellular immune response triggered in patients who died of COVID-19. We evaluated twenty-four paraffin-embedded lung tissue samples from patients who died of COVID-19 (COVID-19 group) and compared them with ten lung tissue samples from patients who died of H1N1pdm09 (H1N1 group) with the immunohistochemical markers mentioned above. In addition, polymorphisms in the Perforin gene were genotyped through Real-Time PCR. Significantly increased tissue immunoexpression of Arginase, CD4, CD68, CD138, Perforin, Sphingosine-1, and IL-4 markers were observed in the COVID-19 group. A significantly lower immunoexpression of CD8 and CD57 was also found in this group. It is suggested that patients who died from COVID-19 had a poor cellular response concerning viral clearance and adaptive response going through tissue repair.

Role of Genetic Polymorphism Present in Macrophage Activation Syndrome Pathway in Post Mortem Biopsies of Patients with COVID-19.

COVID-19 is a viral disease associated with an intense inflammatory response. Macrophage Activation Syndrome (MAS), the complication present in secondary hemophagocytic lymphohistiocytosis (sHLH), shares many clinical aspects observed in COVID-19 patients, and investigating the cytolytic function of the responsible cells for the first line of the immune response is important. Formalin-fixed paraffin-embedded lung tissue samples obtained by post mortem necropsy were accessed for three groups (COVID-19, H1N1, and CONTROL). Polymorphisms in MAS cytolytic pathway (PRF1; STX11; STXBP2; UNC13D and GZMB) were selected and genotyping by TaqMan® assays (Thermo Fisher Scientific, MA, USA) using Real-Time PCR (Applied Biosystems, MA USA). Moreover, immunohistochemistry staining was performed with a monoclonal antibody against perforin, CD8+ and CD57+ proteins. Histopathological analysis showed high perforin tissue expression in the COVID-19 group; CD8+ was high in the H1N1 group and CD57+ in the CONTROL group. An association could be observed in two genes related to the cytolytic pathway (PRF1 rs885822 G/A and STXBP2 rs2303115 G/A). Furthermore, PRF1 rs350947132 was associated with increased immune tissue expression for perforin in the COVID-19 group. The genotype approach could help identify patients that are more susceptible, and for this reason, our results showed that perforin and SNPs in the PRF1 gene can be involved in this critical pathway in the context of COVID-19.

Association Between COVID-19 Pregnant Women Symptoms Severity and Placental Morphologic Features.

Since the beginning of the pandemic, few papers describe the placenta's morphological and morphometrical features in SARS-CoV-2-positive pregnant women. Alterations, such as low placental weight, accelerated villous maturation, decidual vasculopathy, infarcts, thrombosis of fetal placental vessels, and chronic histiocytic intervillositis (CHI), have been described. Objective: To analyze clinical data and the placental morphological and morphometric changes of pregnant women infected with SARS-CoV-2 (COVID-19 group) in comparison with the placentas of non-infected pregnant women, matched for maternal age and comorbidities, besides gestational age of delivery (Control group). Method: The patients in the COVID-19 and the Control group were matched for maternal age, gestational age, and comorbidities. The morphological analysis of placentas was performed using Amsterdam Placental Workshop Group Consensus Statement. The quantitative morphometric evaluation included perimeter diameter and number of tertiary villi, number of sprouts and knots, evaluation of deposition of villous fibrin, and deposition of intra-villous collagen I and III by Sirius Red. Additionally, Hofbauer cells (HC) were counted within villi by immunohistochemistry with CD68 marker. Results: Compared to controls, symptomatic women in the COVID-19 group were more likely to have at least one comorbidity, to evolve to preterm labor and infant death, and to have positive SARS-CoV-2 RNA testing in their concepts. Compared to controls, placentas in the COVID-19 group were more likely to show features of maternal and fetal vascular malperfusion. In the COVID-19 group, placentas of symptomatic women were more likely to show CHI. No significant results were found after morphometric analysis. Conclusion: Pregnant women with symptomatic SARS-CoV-2 infection, particularly with the severe course, are more likely to exhibit an adverse fetal outcome, with slightly more frequent histopathologic findings of maternal and fetal vascular malperfusion, and CHI. The morphometric changes found in the placentas of the COVID-19 group do not seem to be different from those observed in the Control group, as far as maternal age, gestational age, and comorbidities are paired. Only the deposition of villous fibrin could be more accentuated in the COVID-19 group (p = 0.08 borderline). The number of HC/villous evaluated with CD68 immunohistochemistry did not show a difference between both groups.